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The Journal of Comparative 


Neurology and Psychology 


C 


(Continuing the Journal of Comparative Neurology) 


EDITORS 
Cc. L. HERRICK, Socorro, New Mexico. 


C. JUDSON HERRICK, Manager, 


Denison University 


ROBERT M. YERKES, 
Harvard University 


ASSOCIATED WITH 


OLIVER 5S. STRONG, 
Columbia University 


HERBERT S. JENNINGS, 
University of Pennsylvania 


COLLABORATORS 


J. MARK BALDWIN, Johns Hopkins University 
FRANK W. BANCROFT, University of California 
LEWELLYS F, BARKER, University of Chicago 
H. HEATH BAWDEN, Vassar College 
ALBRECHT BETHE, University of Strassburg 
G. E COGHILL, Pacifie University 

FRANK J. COLE, University of Liverpool 

H. E. CRAMPTON, Columbia University 

Cc. B. DAVENPORT, University of Chicago 

WM. HARPER DAVIS, Lehigh University 
HENRY H. DONALDSON, University of Chicago 
LUDWIG EDINGER, Frankfurt a-M. 

5. I. FRANZ, McLean Hospital, Waverley, Mass. 
THOMAS H. HAINES, Ohio State University 

A. VAN GEHUCHTEN, University of Louvain 

h. G. HARRISON, Johns Hopkins University 

C. F. HODGE, Clark University 

S. J. HOLMES, University of Michigan 

EDWIN B. HOLT, Harvard University 

G. CARL HUBER, University of Michigan 
JOSEPH JASTROW, University of Wisconsin 

J. B. JOHNSTON, West Virginia University 


b, F. KINGSBURY, Cornell University 
FREDERIC S. LEE, Columbia University 
JACQUES LOEB, University of California 

E. P. LYON, St. Louis University 

ADOLF MEYER, N. Y. State Pathological Inst. 
THOS. H. MONTGOMERY, Jr., Univ. of Texas 
WESLEY MILLS, MeGill University 

C. LLOYD MORGAN, University College, Bristol 
T. H. MORGAN, Bryn Mawr College 

A. D, MORRILL, Hamilton College 

HUGO MUENSTERBERG, Harvard University 
W. A. NAGEL, University of Berlin 

G H PARKER, Harvard University 
STEWART PATON, Johns Hopkins University 
RAYMOND PEARL, University of Michigan 

C. W. PRENTISS, Western Reserve University 
C.S SHERRINGTON, University of Liverpoo! 
G, ELLIOT SMITH, Gov't. Medical Schoo}, Cairo 
EDWARD L. 'THORNDIKE, Columbia University 
JOHN B. WATSON, University of Chicago 

W. M. WHEELER, Am. Museum of Nat. History 
C. O. WHITMAN, University of Chicago 


VOLUME XIV. 


DENISON UNIVERSITY, GRANVILLE, OHIO 


1904. 


Viet journal of 


Comparative Neurology and Psychology 


CoNTENTS OF VOLUME XIV, 1904. 


Number 1, March, 1904. 


The Relation of the Motor Endings on the Muscle of the Frog to Neigh- 
boring Structures. By JOHN GorRDON WiLson, M.A., M.B. 
(Edin.) From the Hull Anatomical Laboratory of the University 
of Chicago. With Plates I and II. : 2 . ; 

Space Perception of Tortoises. By RoBerRT M. YERKES. From the Har- 
vard Psychologrcal Laboratory. ; 

A Note on the Significance of the Form ea Contents e the ‘Nucteuss in 
the Spinal Ganglion Cells of the Foetal Rat. By SHINKISHI 
Hatat. From the Neurological Laboratory of the University of 
Chicago. With Plates III and IV. ‘ : 

An Establishment of Association in Hermit Crabs, Eupagurus longicar- 
pus. By E. G. SpauLpinc, Ph.D. (Bonn). College of the City 
of New York. 

Editorial. : 

The Mid-Winter Micetnge. 

Literary Notices. 


Number 2, April, 1904. 


Physiological Evidence of the Fluidity of the Conducting Substance in 

the Pedal Nerves of the Slug—Ariolimax columbianus. By O. P. JEN- 
KINs and A. J. CARLSON. From the Physiological Laboratory of 
Leland Sanford, Jr., University. With one figure. 

The Nervous Structures in the Palate of the Frog: the Peripheral Net- 
works and the Nature of their Cells and Fibers. By C. W. PREN- 
Tiss, Zustructor of Biology, Western Reserve University. With 12 
figures. : : ; ; 

The Beginning of Social Reaetion in ‘Man and os er PAcitadle By CoE: 
HERRICK, Socorro, New Mexico. : 

Inhibition and Reinforcement of Reaction in the Boe. Rata dainitans: 
By Rosert M. YERKES. From the Harvard Psychological Labora- 
tory. 

On the Behavior and Reactions fof roeraie in pacls Stages of its Der ne 
opment. By RAYMOND PEARL. From the Zvuological Laboratory of 
the Universtty of Michigan. With one figure. 

Editorial. : é : : : : : ‘ : 

Recent Studies on the Finer Structure of the Nerve Cell. By G 
CoGHILL, Professor of Biology, Pucific University. 

Literary Notices. 


49915 


17 


27 


49 
62 
65 
70 


85 


93 


118 


124 


138 
165 


171 
203 


Number 3, June, 1904. 


An Enumeration of the Medullated Nerve Fibers in the Ventral Roots of 
the Spinal Nerves of Man. By CHARLES E. INGBERT. From the 
Neurological Laboratory of the University of Chicago. With 38 fig- 
ures in the text. 

Editorial. : ; : p 

Color Vision. By C. L. HERRICK. 

Literary Notices. 


\ 


Number 4, July, 1904. 


The Associative Processes of the Guinea Pig. A Study of the Psychical 
Development of an Animal with a Nervous System Well Medul- 
lated at Birth. By JEssIE ALLEN. With Plates V and VI and 12 
figures. 

Editorial. 

Literary Notices. 


Number 5, September, 1904. 


Retrograde Degeneration in the Corpus Callosum of the White Rat. By 
S. WALTER RANSON. (From the Neurological Laboratory of the 
University of Chicago and the Anatomical Laboratory of St. Louts 
University. With Plate VII. 5 3 ; : : 

The Early History ot the Olfactory Nerve in Swine. By EDGAR A. BED- 
FoRD, S. M. With 14 figures. ; : : : ; : 

The Relation of the Chorda Tympani to the Visceral Arches in Microtus. 
By Victor E. EMMEL. (from the Biological Laboratory of Pacific 
University.) 

Editorial. : ; : : . : : : ; 

Recent Contributions to the pone Mind Controversy. By C. L. HERRICK. 

Literary Notices. 


Number 6, November, 1904. 


The Behavior of Paramecium. By H.S. JENNINGS. With 17 figures. 
Editorial. Physiology and Pee 

Clarence Luther Herrick. By H. HEATH BAWDEN. 

Bibliography of C. L. Herrick. 


209 
271 
274 
281 


293 
360 


364 


SUBECT AND AUTHOR INDEX. 
VOLUME XIV. 


Author’s names are in small caps. References to subjects and 
authors of original articles are marked with an asterisk. 


BELSDORFF, G. and NAGEL, W. A. Circulation of blood in the retina 
and phenomena of Vision, 375. 

* Action, as a scientific category, 272. 
*Action-system, 441. 
Apams, C.S. Migration route of warbler, 379. 
AcaABow, A. Nerves of the sclera, 371. 
#ALLEN, J. The associative processes of the guinea pig, 293. 
Atuis, E. P. Nerves of Scomber scomber, 83. 
Amblyopsis, eyes of, 283. 
Amia calva, the natural history of, 282. 
Ammocetes, innervation of epidermis of, 208. 
Amphibia, sense organs of lateral line of, 433. 
Anastomosis, of nerves. SI. 
Anatomy, of nervous system, 364. 
Animal education, 70. 
Annelids, natural history of tube-forming, 285. 
Anniversary volume, to EDWARD LAURENS MARK, 281. 
Ant, crustacean-eating, 379. 
Ascaris, ganglion cells of, 368. 
* Association, in hermit crabs, 49. 
ee , In guinea pig, 293. 
Asymmetry, in lower organisms, 287. 


ARDEEN, C. R. Histogenesis of cerebro-spinal nerves of mammals, 369. 
*BAWDEN, H. H. Metaphysics in comparative psychology, 72. 

G0 oe ae , Obituary of C. L. HERRICK, 515. 

*BEDFORD, E. A. The early history of the olfactory nerve in swine, 390. 

Behavior, of Amia calva, 282. 

ee = , of Amphitrite, 285. 

eae , of the beach flea, 378. 

a , of the guinea pig, 293. 

eres or) Ne , of Limulus, 138. 

0S ee ee , of Paramecium, 441. 

BETHE, A. General anatomy and physiology of the nervous system, 364. 

Binet, A. L’année psychologique, 440. 

Blind vertebrates, eyes of, 283. 

*Body-mind, controversy, 421. 

Bone tissue, formation of, within brain substance, 434. 

BOURNEVILLE. Epilepsy, hysteria, and idiocy, 207. 

BRADLEY, O. C. Mammalian cerebellar fissures, 82. 

Brain, human, 432. 

hs ee) , of sheep, 433. 


Brain, of teleost, 289. 
Butterfly, phototropism of, 291. 


(Ges A.J. Physiology of the nervous system of the snake, 205. 
The rate of the nervous impulse in the hagfish, 204. 
Eee See JENKINS and CARLSON, 85. 
*Carnegie institution, station of experimental biology, Cold Spring Harbor, 272. 
Cerebral commissures, morphology of in vertebrates, 81. 
fa ees cortex, of man, 434. 
Cerebro-spinal nerves, of mammals, 369. 
Cerebrum, fissures of, 370. 
Cervical sympathetic, effect of joining with chorda tympani, 203. 
*Chorda tympani, in Microtus, 411. 
Ciliary movement, in relation to ions, 207. 
CLAPAREDE, E. The consciousness of animals, 74. 
Cocci1, A. Development of the lateral line organs in torpedo, 368. 
*COGHILL, G. E. Recent studies on the finer structure of the nerve cell, 171 
Cockroach, nervous cytology, 287. 
Color physiolog y, of higher crustacea, 435. 
Color vision, in frog, 372. 
*Color vision, theories of, 274. 
*Comparative method, in neurology and psychology, 271. 
*Comparative psychology, unemphasized aspects of, 360. 
Comparative psychology, metaphysics in, 72. 
*Conducting substance, fluidity of in the slug, 85. 
Conductivity, of the nervous system, 206. 
Consciousness, of animals, 74. 
*Corpus callosum, degeneration of in the rat, 381. 
Cortical areas, in man and mammals, 369. 
*Crabs, association in hermit, 49. 
CRAMER, W. _ Protagon, cholin, and neurin, 378. 
Cranial nerve, of selachians, 281. 
CusHING, H. Treatment of facial paralysis by nerve anastomosis, 81. 


| (eee pulex, reations to light and heat, 289. 

Davenport, C. B. Director of station of experimental biology, 273. 
Deepens in brain of tortoise, 203. 

, of corpus callosum in rat, 381. 

el ee at} Wallerian, 203. 

D#LAGE, Y. Movements of the eye, 378. 

*Development of medullation, in guinea pig, 293. 

peek , of mind in the guinea pig, 293. 

See , of the paraphysis in fowl, 369. 

DeExTeR, F. Development of the paraphysis in the common fowl, 369. 
Diopatra, natural history of, 285. 

DocieEL, A. S. Neural structures in the human skin, 208. 

DuccerscuHl, V. Audition in aquatic animals, 80. 


DINGER and WALLENBERG, Bericht, 81. 
EIGENMANN, C. H. The eyes of the blind vertebrates, 283. 
Elephant, neuroglia of spinal cord of, 369. 
*EmMMEL, V. E. Relation of chorda tympani to visceral arches in Microtus, 411. 
Encephalon, anatomy of in races, 369. 
Eyes, of blind vertebrates, 283. 
Eye, of pecten, 292. 


| Bi brain of, 289. 

en , eyes of blind, 283. 

FisHer, W. K. Habits of the albatross, 380. 
Fissures, in human cerebrum, 370. 


Fissures, cerebellar in mammals, 82. 

FLoyp, R. Nervous cytology of Periplaneta orientalis, 287, 
Fowl, development of paraphysis in, 369. 

: *Frog, inhibition and reinforcement of pees in, 124. 

2 , motor endings on muscle of, 

, nervous structures in palate of, 93- 

*Function, relation of concept of to that of structure, 63. 


“(( eivenocwsia of Paramecium, 484. 

Ganglion cells, of Ascaris, 36S. 

GEHUCHTEN, A. VAN. Degeneration in nerve, 203. 

*Geotropism, of Paramecium, 473. 

GoLpDscHMIDT, R. Ganglion cells of Ascaris, 368. 

GotcH, F. Photo-electric changes in the eyeball of the frog, 372. 
Gowers, W. R. Subjective sensations of sight and sound, 207. 
*Guinea pig, psychic development of, 293. 


H abits, of albatross, 380. 

an ee , of Amia calva, 282. 

ee , of Amphitrite, 285. 

eee we , of beach flea, 378. 

eee eee , of guinea pig, 293. 

_ ee , of salamander, 380. 

eee ie , of obera, 380. 

Hagfish, rate of nerve impulse in, 204. 

Hatt, G. S. and Smitru, T. L. Reactions to light and darkness, 376 
Harpesty, I. Neuroglia of the spinal cord of the elephant, 369. 
Harrison, R. G. Development of lateral line sense organs of Amphibia, 433. 
HaerrTL, J. The influence of water and salts on muscle and nerve, 372. 
*HATAI, S. Nucleus of spinal ganglion cells of the foetal rat, 27. 
Hearing, of water animals, 80. 

*Hermit crabs, association in, 49. 

HERRICK, C. ib Bibliography of, 529. 


eee Be , Editoral (L’envoi), 62. 
BPN , obituary and biography of, 515. 
amt ae =A 2 , Recent contributions to the body-mind controversy, 421. 
eRe , Social reactions in man and lower animals, 118. 
eae Se a , Theories of color vison, 274. 


His, W. Development of the human brain, 432. 

HoLMGREN, E. Nerve cells of Lophius, 370. 

beets , Spinal ganglion cells, 370. 

HUBSCHMANN, P. The medulla oblongata of Dasypus villosus, 208. 
Hype, I. H. The nerve distribution in the eye of Pecten irradians, 292. 


mitation in animals, 360. 

*INGBERT, C. E. Enumeration of medullated fibers, 209. 
*Tnhibition, in the frog, 124. 
Ions, relation of to ciliary movement, 207. 


ANET, P. See RAYMOND and JANET, 208. 
*JENKINS, O. P. and Carson, A. J. Physiological evidence of the fluidity 
of the conducting substance in the pedal nerves of the slug, 85. 
JENEED Ss H.S. Asymmetry in certain lower organisms, 287. 
cee , Behavior of Paramecium, 441. 


|) genes E. Visual organs, 371. 

KEEBLE, F. and GAMBLE, F. W. Color-physiology of crustacea, 435. 
Krrsow, F. Rate of nerve impulse in sensory nerves of man, 206. 
Kinematograph, use of in study of animal reactions, 439. 

*King crab, behavior and reactions of, 138. 


iii 


KSLLIKER, A. Development and significance of the vitreous humor, 371. 
Kormer, W. Vital staining in Corethra, 368. 
KRONTHAL, P. Leukocytes and nerve cells, 371. 


Gs 


| Bees J. N. Anastomosis of sympathetic with chorda tympani, 203. 
Lateral line, organs of in torpedo, 368. 

See , organs of in amphibia, 433. 

Life History, of Obera, 380. 

Lituiz£, R. S. Relation of ions to ciliary movement, 207. 

*Limulus, behavior and reactions of, 138. 

LinvILLE, H. R. The natural history of some tube-forming annelids, 285. 
Locy, W. A. A new cranial nerve in selachians, 281. 


Niece: cranial anatomy of, 83. 

Matt, F. P. Transitory or artificial fissures in the human cerebrum, 370. 
Mammals, histogenesis of cerebro-spinal nerves in, 369. 

MarENGHI, G. Neural structures in the epidermis of Ammocetes, 208. 

Mark, E. L. Anniversary volume in honor of, 281. 

MarsHALL, W.S. Marching of the larva of the maia moth, 379. 

McCartuy, LD. J. Formation of bone tissue within the brain substance, 434. 
Medulla oblongata, of Dasypus, 208. 

Meetings, of zodlogists and physiologists, 65. 

Meics, E. B. Mechanism of voluntary muscular contraction, 371. 

MeE.tus, E. L. Undescribed nucleus lateral to fasicularis solitarius, 370. 
MENDEL and JAcosson, Jahresbericht, 83. 

Mitts, C. K. Physiological areas and centersof the cerebral cortex in man, 434. 
apie eee , W. Neurones and the neurone concept, 208. 

*Motor endings, relation of to neighboring structures on muscle of frog, 1. 
Morora, Y. Conductivity of the nervous system, 206. 

*Muscle, motor endings on, I. 

MuskEns, L. J. J. Compensatory eye movements in Octopus, 378. 


[Nees W. A. Influence of pressure and electric current upon dark adapted 
eye, 374: 

and SCHAFER, K. L. Changes in the retina during adaptation to 
darkness, 372. 

Natural history of Amphitrite, 285. 

cow 2 RO , of Amia calva, 282. 

*Nature-study, 418. 

NEAL, H. V. The development of the ventral nerves in selachians, 285. 

*Nerve cell, finer structure of, 171. 

*Nerve components, doctrine of, 168. 

*Nerve fibers, medullated in ventral roots of spinal nerves of man, 209. 

Nerve impulse, conduction of in slug, 85. 

nature of, 206. 

eee , rate of, in sensory nerves, 206. 

*Nerve, olfactory, in swine, 390. 

*Nerves, in slug, 85. 

Same , ventral of selachians, 285. 

Nervous system, anatomy and physiology of, 364. 

ieee ae , of guinea pig, 293. 

ee ae , of snake, 205. 

*Nerve network, in palate of frog, 93. 

Neurone, concept of, 208. 

*Neurology, comparative method in, 271. 

*Nucleus, of spinal ganglion cells of foetal rat, 27. 


SSS SESSS ) 


(ye H. Rhythmical song of the wood pewee, 380. 
*Olfactory nerve, of swine, 390. 


ea nervous structures of in frog, 93. 
*Paramecium, behavior of, 441. 
Paraphysis, development of in fowl, 369. 
ParKER, G. H. The phototropism of the mourning cloak butterfly, 291. 
*PEARL, R. On the behavior and reactions of Limulus, 138. 
Pecten, eye of, 292. 
*Perception, of space in tortoises, 17. 
Periplaneta, nervous cytology of, 287. 
Phototropism, of butterfly, 291. 
___-----, of Daphnia pulex, 289. 
ais: ER sin man, 376. 
Eby, siology, of the nervous system, 364. 
5 eae , comparative method in, 271. 
2 ae ae Ee , and psychology, 511. 
Piper, H. Electro-motor changes in the retina of Eledone, 434. 
POLICE, G. Nervous system of scorpion, 37". 
Porter, J. P. Preliminary study of psychology of the English sparrow, 439. 
*PRENTISS, C. W. The nervous structures in the palate of the frog, 93. 
Psychology, comparative, 360. 
a , and physiology, 511. 


|Reeees encephalic anatomy of, 369. 
*RANSON, S. W. Degeneration in corpus callosum of white rat, 381. 
*Rat, degeneration in the corpus callosum of, 381. 
____, form and contents of nucleus in the spinal cord of, 27. 
____, psychology and growth of nervous system of, 70. 
Rate of impulse, in sensory nerves, 206. 
ee , in hagfish, 20 
RAYMOND, F. and JANE es “Pp. Les obsessions et la psychasthénie, 208. 
Pcero ators of Daphnia to light and heat, 289. 
Sd eee , of Limulus, 138. 
“4 , of Paramecium, 441. 


eS ae , social, in animals, 118. 

REIGHARD, J. The natural history of Amia calva, 282. 
*Reinforcement, of reaction in the frog, 124. 

Retina, changes in, 372, 374, 375, 434- 

*Rheotropism, of Paramecium, 468. 

Ritter, W. E. and Davis, B. M. Ecology, of enteropneusta, 380 
RITTER, W.E. Habits of Autodax lugubris, 380. 

Rossi, G. Fiber tracts in the brain of the tortoise, 203. 


Seno. habits of, 380. 

SARGENT, P. E. The torus longitudinalis of the teleost brain, 289. 
Scuiaprp, M. G. The microscopic structure of cortical areas, 369. 
Scomber, the skull and cranial nerves of, 83. 
Selachians, development of ventral nerves of, 285. 
af ee , a new cranial nerve in, 281. 

*Senses, of guinea pig, 293. 

= eee , lateral line in Torpedo, 368. 

Sensations, subjective of sight and hearing, 207. 
Sense organs, of lateral line in Amphibia, 433 
Sensory nerves, rate of impulse in, 206. 

Sight, subjective sensations of, 207. 

Skin, neural structures in, 208. 

*Slug, fluidity of conducting substance in pedal nerves of, 85. 
SMALLWOOD, M. E. The beach flea, 378. 

eo , W. M. Natural history of some nudibranchs, 440. 

Smell, 378. 

SmirH, G. E. On the morphology of the cerebral commissures, 81. 
Snake, physiology of the nervous system of, 205. 


Vv 


*Social life, of man and lower animals, 118. 

Sound, subjective sensations of, 207. 

*Space perception, of tortoises, 17. 

Sparrow, psychology of, 439. 

*SPAULDING, E. G. An establishment of association in hermit crabs, 49. 
Spinal cord, neurologia of in elephant, 369. 

*Spinal-ganglion cells, in rat, 2 

Ae ee ee , nerves, medullated fibers, 209. 

ae es , nerves in selachians, 285. 

SpitzKA, E. A. The encephalic anatomy of the races, 369. 

Staining, vital, in Corethra, 368. 

Statistical methods, in psychology, 76. 

STREETER, G. L, Anatomy of the floor of the fourth ventricle, 369. 
*Structure and function as correlative concepts, 63. 

Stuart, T. P. A. Mechanism of accommodation of the eye for distance, 378. 
*Swine, olfactory nerve in, 390. 


“T Hornpikeg, E. L. Educational psychology, 76. 
Tortoises, degeneration of fibers in brain of, 203. 

eee , Space perception of, 17. 

Torus longitudinalis, of teleost, 289. 


| peste J. von. Movements of the serpent star, 439. 


\ 7 anessa antiopa, phototropism of, 291. 
Ventricle, fourth, 369. 
Vision, theories of color, 274. 


W ATSON, J. B. Animal education, 70. 

cei ee 2 , Some unemphasized aspects of comparative psychology, 360. 
WepssTER, F. M._ Life history, habits, and relations of Obera, 380. 
WHEELER, W. M. A crustacean-eating ant, 379. 
WILDER, B. G. The brain of the sheep, 433. 
*WILSON, J. G. Motor endings on the muscle of the frog, 1. 
Wo LFF, M. Continuity of the perifibrillar neuroplasm, 370. 


OY ERKEs, R.M. Inhibition and reinforcement of reaction in the frog, 124. 
alee pe Be , Nature-study, 418. 

NS Aare , Physiology and psychology, str. 

_--_.---, Reaction of Daphnia pulex to light and heat, 289. 

fees , Space perception in tortoises, 17. 

* , Structure and function as correlative concepts, 63. 


UCKERKANDL, E. Fibers of the alveus, 371. 

ZUGMAYER, E. Sense organs in the tentacles of the genus Cardium, 371. 
ZWAARDEMAKER, H._ Sensations of smell, 378. 
sp es , and Quix, F. H. Sensitiveness of the human ear to tones, 378.. 


vl 


The Journal of 


Comparative Neurology and Psychology 


Volume XIV. 1904. Number 1. 


THE RELATION OF THE MOTOR ENDINGS ON 
THESMUSCLE OF THE FROG. TO NEIGH- 
BORING- STRUCTURES. 


By JoHn Gorpon Wirson, M.A., M.B., (Edin.) 
(From the Hull Anatomical Laboratory of the University of Chicago.) 


With Plates I and II, 


It is obviously a matter of some importance in the study 
of the relation of nerve excitability to muscle contraction, to 
determine the manner in which the peripheral part of the 
neurone is related to the muscle fiber. Nor has it been neg- 
lected ; it has long been a favorite subject for investigation and 
a prolific field for speculation and debate. At the present time 
renewed attention is being called to it by the recent works of 
of APATHY, RUFFINI, GRABOWER and others. In these writings 
special emphasis is being laid on the presence of fine fibrillae, 
called by RurFini ultra-terminal fibrillae, which are projected 
from nerve endings to various neighboring parts. 

From an historical standpoint it is extremely interesting 
to compare the results of KUHNE with those of RUFFINI, 
DociEL, Huser, SIHLER and others, and to observe that as 
methods and technique improve, a corresponding complexity 
can be shown in the relation of nerve to muscle. This is well 
exemplified in the ending of the motor neurone on the frog’s 
muscle. As regards this animal one must acknowledge that 
the remarks of APATHY on nerve endings in invertebrate mus- 
cles are not inappropriate :— 


“‘Wenn ich auch hier und da schlechthin von Nervenendigungen 
spreche, so will ich doch gleich hier von vorn herein betonon, dass ich 
eine Endigung der leitenden Primitivfibrillen nirgends mit Sicherheit 
constatiren konnte ; ich kann nur sagen, bis wie weit ich eine leitende 


2 Journal of Comparative Neurology and Psychology. 


Primitivfibrille, oft wohl bereits Elementarfibrille, an einer bestimmten 


Stelle meiner Praparate zu verfolgen im Stande bin.” ? 


In 1877 GERLACH described the nerve endings of the frog 
as branching dichotomously to form an intravaginal network 
which runs through the contractile substance of the muscle fiber 
in close relation to, if not in actual continuity with, the con- 
tractile fibrillae. He appears to have been influenced in his 
deductions by the fact that in staining with gold chloride, he 
obtained reactions from certain elements of the sarcous sub- 
stance which were similar to those obtained in nerve endings. 
In 1889 he repeated these investigations with methylene blue, 
and claimed that this method substantiated his previous views. 
Subsequent research by others has not confirmed his results 
nor upheld his deductions; nor can his own drawings be said 
to support the claims he attempted to establish. To one con- 
versant with zztra-vitam staining with methylene blue, it will 
appear a very doubtful procedure to base results on the simi- 
larity of staining reactions. By this zztva-vztam method one 
constantly sees fine blue-stained fibers in the intermuscular con- 
nective tissue which, taken alone, might simulate nerve fibrillae. 
At times one observes beautifully stained examples of myo- 
fibrillae either as very fine closely-arranged points or as continu- 
ous structures. On this ground alone, therefore, it is obvious 
that it would not be possible to deduce a nervous plexus either 
within or without the muscle-cell. In addition, there must 
be present an undoubted continuity of structure with an unmis- 
takable nerve fiber, together with any characteristic appearance 
which one is accustomed to find in corresponding terminals. 

In 1896 ApAtHy drew attention to the manner in which 
the axis cylinder divides in invertebrate muscle fibers. He de- 
scribes the primitive fiber as entering the muscle cell and there 
dividing into fine fibrillae (primary fibrils). These, however, 
do not form a plexus but either send comparatively thick 
branches (secondary fibrils) to adjacent muscle-cells there to 
form terminations from which it may be that further branches 


1 Mitheil. a. d. Zoolog. Station zu Neapel., Bd. XII, 1896, p. 505. 


Witson, Motor Endings of the Frog. 3 


(tertiary fibrils) may proceed to other muscle cells; or they 
divide repeatedly into ever finer fibrils till ultimately perhaps, 
elementary fibrillae result. He often saw very fine nerve 
fibrillae pass out of a muscle cell into the neighboring con- 
nective tissue and it might be, branch there. As to the ulti- 
mate fate of the finest fibrillae he is uncertain, but he declares: 
‘‘Ks kommt mir an wahrscheinlichsten vor, das sie mit anderen 
ahnlichen ein intermuskulares Elementargitter bilden.”’* 

The results of ApATHY led RUFFINI in 1900 to re-examine 
nerve endings in the human muscle which he had stained by 
his chloride of gold method. Here he found in some of his 
specimens fine fibers which he had not previously noted and 
which he now described under the name of ultra-terminal 
fibrillae. These are very fine, non-medullated fibrillae which 
pass out from the motor end-plate. ‘‘This fibrilla” (ultra- 
terminal), he says, ‘‘after an unbranched course, more or less 
long, may terminate in the same muscular fiber on which rests 
the plate from which it is derived, or, as is often the case, put 
itself into relation with one of the neighboring striated fibers. 
From it collaterals may at times come off.’ It may end ina 
swelling or in a second small plate (plaquette); in one case 
from a plaquette another fibre was seen to pass out, but its 
course could not be followed. Summing up the results of his 
examination, he says: ‘‘The motor plates in man do not rep- 
resent the true and real terminations of motor nerves, because 
beyond the plate there exists a well demonstrable anatomical 
continuity shown by non-myelinated nerve fibrillae of which we 
do not know the last relations.’’ * This is obviously a state- 
ment very closely akin to that given by APATHY in the sum- 
ming up of his results. 

Later PERoncITO, working with RuFFINI and using his gold 
chloride method, describes in Lacerta muralis and Lacerta 
viridis the ultraterminal fibrilla as separating itself from the 


1 Jbid., p. 695. 


? RUFFINI: Sulle fibrille nervose ultraterminale nelle piastre motrici dell’ 
uomo. ivista di pat. nerv. e ment., 1900, V. 5. 


4 Journal of Comparative Neurology and Psychology. 


nerve fiber at the point where it loses its medullary sheath and 
penetrates the motor plate; from here it may pass to end ona 
muscle fiber or in a neuromuscular spindle. 

In any discussion on nerve endings it is well to recognize 
the facts that are universally accepted. Thus it is well estab- 
lished that a motor nerve may branch repeatedly before ending, 
or to put it otherwise, the peripheral ending of a motor neurone 
is connected with many muscle fibers. This branching occurs 
at a node. Each branch is a medullated fiber smaller in calibre 
than the parent stem and it ultimately loses the medullary 
sheath and breaks up to form a nerve ending usually on one 
muscle fiber, to which it alone is attached. To this very gen- 
eral statement there are a variety of exceptions. Thus, two or 
more endings may go to one muscle fiber; or a non-medullated 
nerve may pass off from a node; occasionally, though more 
rarely, a non-medullated nerve may be seen leaving a medul- 
lated nerve where no node is apparent. To define concisely 
and yet accurately the term motor nerve ending, either from an 
anatomical or physiological standpoint, is in the present state 
of our knowledge by no means easy. For our present purpose 
a motor ending may be regarded as that peripheral part of the 
nerve which, on reaching a muscle fiber, loses its medullary 
sheath and breaks up into more or less numerous non-medul- 
lated! branches or end-twigs which enter into a more or less 
close relation to the muscle fiber. Having thus defined a motor 
ending, the significance of the term ultraterminal fibrilla is the 
better understood; this is a fine non-medullated fibril which 
passes from one of the twigs of the nerve termination to a re- 
gion beyond the primary ending. Here it enters into relation 
with the muscle fiber on which rests the ending from which it 
originally sprang, or with some adjacent muscle fiber or 
with a neighboring muscle spindle. 


1 DoGIEL has described a medullary sheath as occurring in the nerve end 
ing (Archiv f. mikr. Anat., Bonn, 1890, p. 314). This I have never seen, 
though the dye oozing from the axis cylinder at times gives a resemblance 


to such. 


Witson, Motor Endings of the Frog. 5 


The following investigations were undertaken by me to 
determine how the motor nerve endings on the muscles of the 
frog are related to other structures; and also to ascertain, as 
far as possible, how the terminal nerve fibrils finally break up 
and disappear. Especially did it appear necessary to compare 
the results observed by RurFini and others using gold chloride 
methods with the results obtained by the zz¢va-vitam methylene 
blue method. 

Method: The muscles of the frog used were either the M. 
sartorius, the M. peroneus or the M. tibialis anticus. Into 
these was injected with a hypodermic syringe, a very weak 
solution of methylene blue in various salt solutions, for this re- 
search has been carried on as a preliminary part of an investiga- 
tion on the effect of various salts and poisons on motor nerve 
endings. Grammolecular solutions of the following salts, among 
others, were used: sodium chloride, sodium carbonate, sodium 
ammonium phosphate, magnesium sulphate. Nerve endings 
can be obtained by a solution of methylene blue in distilled 
water, or with methylene blue in solution with any of the above 
salts; but the most constant and best results are obtained if 
sodium chloride is present in the solution. So far as the pres- 
ent paper is concerned, the following solution was constantly 


employed: 
Methylene blue (GRUBLER’S nach EHRLICH) 0.5% sol. I or 2 cc. 
Sodium chloride solution, 0.58% sol. 21CG; 
Aqua destil. 7 cc: 


This was found to be the most suitable strength of methylene 
blue to use, though one of half this strength often answers well, 
especially for sensory endings and sympathetic plexures on blood 
vessels. The largest and most complex endings were seen 
when the muscle was injected with the above solution after 
there had been added to it a few drops of a weak alkaline salt, 
such as sodium ammonium phosphate, and then a very weak 
faradic current passed through the nerve trunk for a few 
seconds. 

A few minutes after injecting the solution the muscle is 
cut out and exposed on a glass slide which has been moistened 


6 Journal of Comparative Neurology and Psychology. 


with normal salt solution. Within a varying time, usually 
about five minutes, the nerve endings begin to appear. As 
soon as these are well marked the muscle is fastened to cork 
and placed in ammonium molybdate solution (5%) at a tem- 
perature near freezing point. Temperature plays a very im- 
portant part in the subsequent treatment of the tissues. If it 
rise at any point of the procedure—e. g. when washing in 
water or passing through alcohol—the methylene blue dissolves 
out from the very fine fibrillae. If the tissue has to kept over 
night in molybdate it is well to place it, especially in summer, 
in a refrigerator. When passing through alcohol, the vessel 
should be surrounded by ice-cold water. 

The addition of HCl to the molybdate solution is not nec- 
essary; I have found it even a disadvantage for the finer results. 
BETHE in his recent work has abandoned its use. 

After removal from the molybdate, the muscle, if too thick, 
is cut in a freezing microtome, examined in water, and only that 
part kept which shows traces of nerve endings. The tissue is 
now passed through 95% and absolute alcohol, preferably, as 
stated above, at a low temperature; then from xylol into par- 
affin. It is important that it remain sufficiently long in xylol 
to remove the alcohol; otherwise the temperature of the melted 
paraffin will cause any alcohol present to remove the methylene 
blue from the fine fibrillae. It remains in paraffin for two 
hours. The thickness of the section varies with the object 
aimed at. To get long stretches of nerve endings, it is best to 
cut from 20 to 50 micra; if one wish to study the relation of 
the endings to the muscle cell, a thickness of from 5 to 10 
micra must be used. 

After numerous experiments with various dyes as a coun- 
terstain, the following was found most suitable, inasmuch as it 
dyed the muscle fiber an orange, the sheath of HENLE a rose- 
pink and the neurilemma a faint pink: 


Acid fuchsin Me (a 
Orange ‘‘G” Omg: 
Alcohol, absolute, 60 cc. 


Aqua destil. 240 cc. 


Witson, Motor Endings of the Frog. 7 


In the frog’s muscle the nerve ending has no ground plate 
in which the branches ramify. The ramifications are not local- 
ized but are spread over a relatively large and apparently vari- 
able area of the muscle fiber. Usually but one medullated 
nerve ends in a muscle fiber, though two medullated nerves 
may be seen at times and three have been described ; occasion- 
ally two medullated nerve fibers and one non-medullated and 
much finer fiber may go to the muscle fiber. When more than 
one nerve goes to a muscle fiber it is often possible to trace the 
origin of these to the same nerve stem. In no case was there 
even the suggestion of one of these fibers coming from a nerve 
whose course lay distinctly apart from the others. If more 
than one nerve go to the muscle fiber, the places where the 
nerves enter into contact with the fiber are, if not always, at 
least most frequently, in close proximity to one another. In 
short, on the muscle fiber the area to which the entering nerves 
apply themselves relative to the entire length of the muscle 
fiber is limited. 

Several varieties of motor endings have been described. 
Thus, there are the four or five types of Cuccati which RErzius 
would reduce to two; the one exemplified by the branching 
plate, the other by the broad band. At present, any classifica- 
tion must be but temporary; with equal justification several 
varieties may be classed as typical by one and rejected by 
another. For example, one might well wish to add to the 
types of Rerzius that more strictly localized variety which 
Doeiet has described and which occurs not unfrequently in cer- 
tain muscles—a variety which closely resembles the branching 
of mammalian nerve endings only without an end plate.! 

There is, however, one type which is generally recognized 
as predominating—das Stangen-gewerh of Ktune. In it the 
nerve after losing its medullary sheath divides more or less 
dichotomously and spreads itself along the length of the muscle 
fiber. The band variety is less common; one notes that the 
better stained the preparation the less frequently it appears. 


1 Arch. f. mikrosk. Anat., 1890, Bd. xxxv. 


8 Journal of Comparative Neurology and Psychology. 


In the frog the end-arborizations do not terminate neces- 
sarily on one muscle fiber. It is not unusual to find that, 
while the majority of the terminal fibers confine themselves to 
one muscle fiber and to a certain definite area, one or more fine 
non-medullated fibrillae pass far beyond the area or to a neigh- 
boring muscle fiber. So common is this that in well stained 
preparations one is ever expectant of finding at least traces of 
such fibrillae. They are often difficult to observe; but the 
cause of this is not so much that they do not readily stain, as 
that it is hard to fix the dye and easy to have it extracted dur- 
ing the stages subsequent to fixation. 

Such non-medullated fibrillae may be termed ultraterminal. 
A convenient way to describe them is to classify them accord- 
ing to the manner in which they end, so far, at least, as such 
can be traced at present. With this in view, we might describe 
them as follows: 

(1) Relatively thick, non-medullated fibers which pass to adjacent 
muscle fibers and divide into endings which resemble more 
or less closely, though much smaller, the dichotomously 
branching arborizations from which they spring. These come 
off very soon after the primary axial fiber loses its medullary 
sheath and begins to break up (Fig. 1; Fig. 4; Fig. 6). 

(2) Fine fibrillae which pass from the nerve ending into the inter- 
muscular connective tissue and there cease to be capable of 
being followed farther (Fig. 1; Fig. 3; Fig. 2). 

(3) Very fine non-medulated fibrillae which detach themselves at 
various points of the terminations and pass to end in adjacent 
muscle-fibers in one of the following ways: 

a) by getting so faint and so fine that it becomes impossible to 
follow them farther (Fig. 1; Fig. 2; Fig. 3). 

b) by terminating at what appears as a much thickened knob 
(similar to Fig. 1, B and C) 

c) by breaking up into a plexus from which some at least of the 
fibrillae disappear in the muscle fiber while others continue on 

Fig. 2 : 

d) s ee a plexus which enters into close relationship with 
a typical nerve ending (Fig. 3) 

e) by breaking up after a relatively long course to form a small 
localized ending, each termination of which is furnished with 
a knob (Fig. 6). 


Witson, Motor Endings of the Frog. 9 


At no time have I seen any appearance of an intermuscu- 
lar nerve plexus formed by these fibrillae. I am inclined to 
regard the motor fibrillae which pass into the intermuscular con- 
nective tissue and there disappear, as either broken fibrillae or 
fibrillae only partially stained. 

The relation of the nerve ending to the muscle fiber.—The re- 
lation of the nerve endings to the sarcolemma has been 
much disputed. Of recent writers who have discussed this 
question with reference to the muscle of the frog, the following 
only need to be referred to: HusBrer-DEWiIrT,’ after a caretul 
investigation, come to the conclusion that the terminals lie un- 
der the sarcolemma and are devoid of any sheath. SIHLER,? on 
the other hand, using a method which he finds particularly ap- 
plicable to this research, considers that the endings lie over the 
sarcolemma and that the end of fibrils are covered ‘‘down to 
their tips with the sheath of ScHwann ;”’ further that the sheath 
of HENLE is open (verwachst mit nichts) and does not cover the 
end fibrils, but that the nerves emerge from it as an arm from 
a sleeve (wie der Arm aus dem Aermel ); at the same time, he 
does not deny that there are points where the nerve substance 
and the muscle fiber may come into contact. 

In fresh muscle fibers in which the nerves have been stained 
by the zztra-vitam methylene blue method, I have found that, 
while the majority of the terminal branches lie in close relation 
to the muscle fiber, at times a terminal fibril is seen to rise 
some distance above the muscle fiber, and occasionally such a 
nerve fibril sends down to the muscle fiber little rootlets com- 
parable to those described by SrtHLER. But sooner or later 
even in such nerve fibrils the ultimate terminals come to lie on 
the muscle fiber. While the occurrence of such nerve fibrils 
may be held to prove that the larger fibrils may be epilemmal, 
there is nothing to show what the felation of the terminal fibrils 

1 HuBer-DEWITT: Nerve Endings in Muscles. /. Comp. Neurol., 1897, 
VIET ps 185- 


2 SIHLER: (a) The Nerves of the Capillaries with remark on Nerve End- 
ings in Muscles. /. Exp. Med., 1901, V, p. 511. (b) Neue Untersuchungen 
liber die Nerven, etc. Zeit. f. wiss. Zool., Leip., 1900, LXVIII, pp. 351 and 
375: 


10 Journal of Comparative Neurology and Psychology. 


to the muscle fiber may be. To investigate this a much higher 
magnification and a more differential stain are necessary than at 
present are available in the examination of fresh tissues. 

By means of the orange G acid fuchsin counterstain above 
referred to, I have found it possible to distinguish clearly be- 
tween the nerve fiber (blue), the sheath of HENLE (rose-pink), 
the faintly stained neurilemma (pink), and the muscle fiber 
(orange). In thin sections (5 to 7”) examined by the 1-12 
ZEIss oil immersion lens, where the medullated nerve was ob- 
served to lose its medullary sheath and divide into the primary 
branches, I often clearly saw the primary branches, especially 
when they were lying in the upper edge of the muscle fiber, 
enclosed by the neurilemma and by the sheath of HENLE. 
Moreover these sheaths could at times be traced for some dis- 
tance on the primary divisions of the ending. The differentia- 
tion of the two nerve sheaths was at times aided by the fact 
that one could distinguish the attachment of the neurilemma 
to the node, as described by Boveri and BeErHE,' while the 
sheath of HENLE had no such attachment but was continuous 
over the node. This condition was seen in the section from 
which Fig. 7 was obtained. Here the neurilemma attached 
itself to the node where the medullary sheath ceased, and thence 
was continued over the fibrils. For this research it was not 
necessary to determine whether at the node the neurilemma was 
or was not interrupted. Outside of this lay the sheath of HENLE. 
Each sheath could be followed separately to the muscle fiber, 
where together they applied themselves to the sarcolemma. 
When so applied to the muscle fiber, it was not possi- 
ble to distinguish with accuracy between the pale 
stained neurilemma and the strongly stained sheath of 
HENLE. But it was possible to see clearly that the sheath 
round the nerve was distinct from and was placed outside of the 
sarcolemma—a distinction which was aided by the fact that 
here the sheath of HENLE stained at times more strongly than it 
had previously done and appeared as if it were there thickened 


1 BETHE: Anatomie und Physiologie des Nervensystems, 1903, p. 50. 


> 


Witson, Motor Endings of the Frog. Il 


or compressed. As the fibrils subdivided each branch was sur- 
rounded by a sheath which became fainter as the nerve fibril 
became finer. 

Occasionally there coiled round a primary terminal branch 
of a nerve ending another nerve in no way related either to 
this nerve ending or to its muscle fiber. Thus in Fig. 5§ at (2) 
the nerve (3) curved round a primary terminal division of 
the nerve termination on muscle fiber A. This is only 
to be explained by one of two suppositions; either both 
nerves at that point were over the sarcolemma or under it. The 
latter supposition is open to many objections; the former will 
generally be acknowledged to be the more probable, and to me 
is a confirmation of what I have already stated. 

Attention was now directed to two points: 

(1) The relation of terminal fibrillae and of the end knobs 

to the sarcolemma ; 

(2) The relation of the ultraterminal fibrillae to a sheath. 

In sections where very fine fibrils were seen, one could 
trace the blending of the nerve sheath with the sarcolemma. 
In Fig. 9 the terminal nerve fibrilla rested on an apparently 
homogeneous substance which was not separated from the con- 
tractile muscle substance by any sarcolemma and which was 
covered by a cap formed by the blending of the nerve sheath 
with the sarcolemma. In short, it lay under the sarcolemma. 
When the section from which Fig. 9 was drawn, was carefully 
examined under the 1.5 mm. ZEISS apochromatic and Oc. 6, 
the sarcolemma appeared at (@) to split into very faint lines. 
Two of these were seen to project as at (@) and disappear in 
the covering cap. Similarly at (2) a line was seen to go off as 
delineated. The impression formed by the study of this and of 
other similar sections, was that though the cap over the termi- 
nal nerve fibrilla or end-knob was formed by the blending of 
the sheath which surrounded the nerve fibril with the sarco- 
lemma, the tissue which had principally to do with its formation 
was the sheath of the nerve fibril. 

The relation of the root-like knob to the muscle fiber was 
sometimes particularly interesting. It seems to lie more in the 


12 Journal of Comparative Neurology and Psychology. 


sarcolemma than under it, though at times a knob could be 
observed to penetrate deeper towards the fibrillated sarcous 
substance. It was noted that in every ending the fibrillated 
sarcous substance was sharply marked off, so that it was always 
easy to determine that the nerve terminals did not penetrate 
within or even as far as the fibrillated muscle substance. 

On the ultraterminal fibrillae a sheath could at times be 
seen. This sheath followed closely the convolutions of the 
nerve, and could be traced to the neighboring muscle to which 
the nerve was going; there it blended with the sarcolemma. 
The nerve terminals and end-knobs differed in no respect from 
the corresponding parts of the main nerve stem (Fig. 6). 

In short the primary divisions of the nerve ending lie over 
the sarcolemma, and are surrounded by both the neurilemma 
and the sheath of HENLE; the ultimate fibrils lie in a homo- 
geneous substance within the sarcolemma, and are covered by 
a cap formed by the blending of these sheaths with the sarco- 
lemma. The open condition of the sheath of HENLE, as described 
by SIHLER, was not observed. 


Conclusions. 


The so-called nerve ending of the frog is to be regarded 
in the first place as the peripheral separation of the contents of 
the axis cylinder, by which separation it is able to spread itself 
over a relatively wider area. Asa nerve fiber may attach itself 
to various muscle fibers, so the fibrillae of the ending may like- 
wise reach over to adjacent muscle fibers. Those fibrils which 
detach themselves near the central point of separation are, as a 
rule, larger and more easily stained than the more distal ones, 
and are comparable to the non-medullated fibers which may 
arise from the medullated nerve stem. One can note that the 
secondary endings to which they give rise are often comparable 
in form to the primary endings, though having a smaller num- 
ber of branchings; this would suggest that the amount of 
branching which is possible bears a relation to the diameter of 
the fiber. 

A plexus is often formed by the nerve terminations (Fig. 


Witson, Motor Endings of the Frog. 13 


5, Fig. 3, Fig. 6.). Whether this is merely an interlacing or a 
true anastomosis, it would be difficult to decide. The close 
approximation of some of the terminals and the way in which 
they run together (Fig. 6) suggest at least a very intimate re- 
lationship between them. By means of this plexus arrange- 
‘ment we can well understand how effective the nerve impulse 
may become. From this network fibrillae may pass to other 
muscle fibers (Fig. 3, Fig. 6). 

Not only in the fixed but in the unfixed preparations the 
larger branches of the endings are seen to lie over the sarco- 
lemma and even at some distance from it (Fig. 1, Fig. 7). 
In fresh preparations one occasionally sees a terminal lying over 
the paler stained yet clearly outlined muscle fiber, and sending 
down root-like structures to the muscle fiber. The neurone 
enters into intimate relationship with the muscle fiber either at 
the peripheral termination of the ending, where each termina- 
tion appears as a very fine fibrilla to which an end knob or bulb 
may be attached (Fig. 1, B& C, Fig. g) or at the terminal knob of 
each of those root-like structures which at times are projected 
from the fibrils of a nerve ending. The former termination, in- 
cluding both the terminal fibrilla and its knob, lies in homogene- 
ous substance under the sarcolemma ; it is covered bya cap into 
whose formation there enters both the nerve sheath and the 
‘sarcolemma, though chiefly the nerve sheath. The latter ter- 
mination is in close opposition to the sarcolemma and may be 
either in or under it. 


BIBLIOGRAPHY. 
Apathy, St. v. 

Kontraktile und leitende Primitivfibrillen.  A/zttez?. d. z00l. Stat. zu Nea- 
pel, 1892, Bd. 10, 355-375. 

Das leitende Element in den Muskelfasern von Ascaris. Arch. f. 
mikr. Anat., 1904, Bd. 43, p. 886-911. 

Das leitende Flement des Nervensystems und seine topographischen 
Beziehungen zu den Zellen. AM7ttezl. d. zool. Stat. zu Neapel, 1897, 
Bd. 12, p. 495-748. 

Ueber Neurofibrillen. Proc. of the inter. cong. of zool., Cambr., 1808, 
Sep. 


14 Journal of Comparative Neurology and Psychology. 


M. Heidenhain’s und mein Auffassung der kontraktilen und leitenden 
Substanz und iiber die Grenzen der Sichtbarkeit. Amat. Anz., 1902. 
Bd. 21; "p. Ol. 
Barker, L. F. 
The Nervous System and Its Constituent Neurones. Mew York, 1899. 


Bethe, A. 
Eine neue Methode der Methylenblaufixation. Amat. Anz., 1896, Bd. 12, 
p- 438. ; 
Die anatomischen Elemente des Nervensystems und ibre physiologische 
Bedeutung. SBrolog. Centralbl., 1898, Bd. 18, p. 843-974. 
Allegemeine Anatomie und Physiologie des Nervensystems. Le7fz., 1903. 
Cuccati. 
Delle terminazioni nervee nei muscoli addominali della Rana temporaria 
e della Rana esculenta. Jnternat. Monatsh. f. Anat. u. Phys., 
1888, V. 
Dogiel, A. S. 
Methylenblautinction der motorischen Nervenendigungen in den Mus- 
keln der Amphibien und Reptilien. Arch. f. mikr. Anat., 1890, 
XXXV. 
Ehrlich, P. 
Ueber die Methylenblaureaktion der lebenden Nervensubstanz. Svzolog. 
Centralbl., 1887, Bd. 6, p. 214-224. 
Ueber die Beziehungen von chemischer Konstitution, Verteilung und 
pharmakologischer Wirkung. v. Leyden-Festschrift, 1901, Bd..1, Sep. 
Gerlach. 
Ueber die Einwirkung des Methylenblaus auf die Muskelnerven des 
lebenden Froschen. Sztzber. a. math.-phys. Cl. d. k. bayer. Akad. d. 
Wiss., 1889, XIX. 
Grabower. 
Ueber Nervendigungen im menschlichen Muskel. Arch. f. mikr. Anat. u. 
Entwickl., 1902, Bd. 60, I. 


Kiihne. 
Ueber die peripherischen Endorgane der motorischen Nerven. Lezpzzg, 
1862. 
Krause. 


Uber die Endigung der Muskelnerven. Arch. f. rat. Med., 1863. Also 
several papers in the earlier numbers of the Jnternat. Monatsh. f. 
Anat. u. Phys. 
Huber-DeWitt. 
A Contribution on the Motor Nerve-endings and on the Nerve-endings 
in the Muscle-spindles. 7. Comp. Neur., 1897, v. 7, 169-230. 
Perroncito, A. 
Sur la terminaison des nerfs dans les fibres musculaires striées. Arch. 
Ital. de Btol., 1901, 36, 245-254. 
Ruffini, A., and Apathy, St. 
Sulle fibrille nervose ultraterminali nelle piastre motrici dell’ uomo. 
Riv. dt Pat. nerv. e ment., Firenze, 1900, Vv. 55 433, Sep. 


Witson, Motor Endings of the Frog. 15 


Ruffini, A. 
Le fibrille nervose ultraterminali nelle terminazioni nervose di senso e la 
teoria del neurone. iv. dz Pat. nerv. e ment., 1900, v. 6, 70-82. 
Sihler, Chr. 
Neue Untersuchungen iiber die Nerven der Muskeln mit besonderer 
Beriicksichtigung umstrittener Fragen. Zezt. f. wéss. Zool., 1900, 
LXVIII, 3, pp. 323-378. 
The Nerves of the Capillaries, with Remarks on Nerve Endings in Mus- 
cle. Journ. of Experimental Medicine, 1901, vol. 5. 


EXPLANATION OF THE DRAWINGS. 


Iam much indebted to Mr. LEONARD H. WILDER for the carefulness and 
accuracy with which he has prepared the drawings which illustrate this paper. 


PEALE a. 


Fig. 1. ZxE1ss D, Comp. occ. 4. The peripheral termination of a neurone, 
showing Terminal fibrillae with end knobs (1) and (2), Ultraterminal fibrilla 
ending in intermuscular connective tissue (3), Ultraterminal fibrilla ending 
on a separate muscle fiber (4). 

The medullary sheath, as sometimes happens, is faintly yet distinctly out- 
lined surrounding the continuous and well-marked axis-cylinder. There are 
three muscie fibers, A, Band C, to which go two medullated nerves, a and 4. 
The main stem of a breaks up on C at 5 into three primary fibrils. In its 
course there are given off to A two medullated branches, which lose their me- 
dullary sheath soon after leaving the main stem and which break up more or 
less dichotomously. From the one on the left, a non-medullated terminal branch 
(3) passes beyond the muscle fiber to disappear in the intermuscular connective 
tissue. The main supply of B is 4; but the medullated nerve, a, while passing 
over B gives off two very fine, apparently non-medullated branches, one of which 
ends on B, the other passing to endon C. The termination of the medullary 
sheath of a was close to the breaking up of the axis-cylinder at 5. One of the 
primary terminal branches on the right gives off a branch 4 which divides 
dichotomously on muscle fiber B. The others call for no special remark. 

fig. 7, Band C. ZEISs 1-12 oil immersion; Comp. occ. 4. Two forms of 
endings frequently presented at the terminals of very fine fibrillae. 

B. Drawn from (1), shows the fibrillae breaking up into a granular net- 
like structure. 

C. Drawn from (2), shows an elongated broadened club-like body with a 
marked central axis, imbedded in a well-defined granular mass and surrounded 
by a homogenous capsule, comparable to cap seen in Fig. 9. 

Fig. 2. Zeiss 1), Comp. occ. 4. Nerve ending with ultra-terminal 
fibrillae. 

The medullated nerve a loses its medullary sheath and breaks up on B at 
(1). It gives off at (2) a large non-medullated branch which also breaks up on 
B. The nerve endings send ultraterminal fibrillae to three muscle fibers. The 
terminal branches to the right could be traced to a distance twice as far as rep- 
resented. Several of these endings showed knobs similar to those repre- 


16 Journal of Comparative Neurology and Psychology. 


sented in Fig. 1, B and C. A separate non-medullated nerve (z) is shown 
which forms a small plexus on B, one fiber of which penetrates to a lower plane 
than the others and ends by forming under the sarcolemma a knob like Fig. 1, 
B; the other fibers pass on, one to end on B, the other on C. 

Fig. 3. ZrEtIss D, Comp. occ. 4. Three medullated nerves (a), (6) and (c), 
which pass to three separate muscle fibers, A, B and C, and which have ultra- 
terminal fibrillae and interlacing of endings. Muscle fiver B is seen only in 
part. 

Fig. 4g. ZxEIss D, Comp. occ. 4. The type of ultraterminal fibrillae seen 
most frequently. 

Fig. 5, A. ZEtss D, Comp. occ. 4. An ending forming a complex net- 
work on muscle fiber C. A nerve coiling round the primary terminal divisions 
of another nerve (compare page II on relation of nerve to sarcolemma). The 
nerve 2 goes to two muscle fibers, A and C. The nerve 3 on which no medull- 
ary sheath was seen divides into two branches; one of these ends undivided, 
the other separates into two branches which run close together and parallel. 
At (2) the upper branch coils round a primary fibril of the nerve ending on 
muscle fiber A; in addition it gives off a fibril which disappears in adjoining 
connective tissues. 

Fig. 5, B. Part of Fig. 5, marked (1), drawn with ZEIss oil immersion 
I-12 Comp. occ. 4. 


PLATE II. 


Fig. 6. ZEISS 1-12 oil immersion, Comp. occ. 4. Sections cut ‘10 M. 
Nerve endings shown only in part, with ultraterminal fibrillae (1), (2) and (3), 
one of these (1) with sheath. The main fiber is seen at x. From it a branch 
to the right passes off and soon divides ; one of these divisions has been cut by 
the sectioning, the other (1) passes to an adjoining muscle fiber, there to end 
ina small termination like an end-plate with end knobs. The nerve sheath 
could only be traced distinctly to the point where the nerve enters into contact 
with the muscle fiber. 

Fig. 7. Zetss 1-12 oil immersion, Comp. occ. 4. Section5 u. Stained in 
orange G, acid fuchsin. Part of nerve ending lying over sarcolemma. This 
dye colors the sheath of HENLE rose-pink, the neurilemma pink, and the 
muscle fiber orange. The medullary sheath was apparent at M just above, the 
node R, where the axis-cylinder divides into three branches which pass to the 
muscle fiber. The sheath of HENLE (H) is seen continued over R wituout at- 
tachment, and two of its nuclei (Hn) were distinctly outlined. Within the 
sheath of HENLE and closely applied to the axis-cylinder, lay the neurilemma 
N, attached to the node R. The primary terminal fibrils surrounded by the 
sheaths lie over the sarcolemma which is distinctly marked beneath the sheath. 

fig. 8. ZEISS apochomatic 1.5, Comp. occ. 6. Section7.5 uw. A primary 
terminal fibril with sheaths. H, HENLE’s sheath; N, neurilemma; S, sarco- 
lemma. . 

fig. g. ZEISS apochromatic 1.5, Comp. occ. 6, Section 54. <A terminal 
knob lying under the sarcolemma and covered by a cap which is chiefly com- 
posed of the nerve sheath. Fine fibers pass at (a) and (6) from the sarcolemma 
to blend with the nerve sheath in the cap. 


Journal of Comparative Neurology and Psychology, Vol. XIV. 


Plate |. 


L.A. WILDER 


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Journal of Comparative Neurology and Psychology. Vol. XIV. Pilate 


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SEACH SEE RCEPRION;, OF TORTOISES. 


By Ropert M. YERKES. 


(From the Harvard Psychological Laboratory, HUGO MUNSTERBERG, Director.) 


The Sense of Support in Animals. 


A number of investigators have noticed that the young of 
many animals possess a sense of support, and that their behavior 
is adapted to the spatial conditions in which they happen to be 
placed. It is this sense of support that saves the sightless kit- 
ten or puppy from falls; but in case of the young chick which 
similarly hesitates when it approaches the edge of a void visual 
stimuli apparently determine the reaction. These reactions to 
spatial conditions are controlled by a complex of sense impres- 
sions which is still unanalyzed. In certain animals visual im- 
pressions seem to be all-important; in others organic data are 
chiefly significant, and again in other organisms there are indi- 
cations of degrees of sensitiveness, if not modes of sense, of 
which we have no direct knowledge. And so, strange as it 
may seem, the ‘‘spatial worth” of sense data, as JAMES would call 
it, is no more a matter of accurate knowledge than is the de- 
velopment of the sense of space, or the modes of behavior in 
different spatial conditions exhibited by any animal. 

THORNDIKE (’99, p. 284), who has studied the behavior 
of young chicks with reference to spatial relations, says ‘‘If 
one puts a chick on top of a box in sight of :his fellows below, 
the chick will regulate his conduct by the height of the box.”’ 
A chick 95 hours old does not hesitate to jump off at heights 
of 1 to 10 inches; at 22 inches it often hesitates a long time, 
and at 39 inches it usually does not jump atall. Furthermore, 
immediately after hatching, young chicks are able to peck at 
objects with considerable accuracy, and they apparently esti- 
mate distances fairly well before they have had much experience 
outside the shell. 


18 Journal of Comparative Neurology and Psychology. 


The behavior of young pigeons, chicks, kittens and pup- 
pies in unusual spatial conditions has been studied most fully by 
Mitts (’98, p. 150), who in discussing the ‘‘sense of support”’ 
writes: ‘‘I have found in the case of all puppies, and several 
other kinds of animals examined, that even on the first day of 
birth they will not creep off a surface on which they rest, if 
elevated some little distance above the ground. When they 
approach the edge they manifest hesitation, grasp with their 
claws or otherwise attempt to prevent themselves falling, and, 
it may be, cry out, giving evidence of some profound disturb. 
ance in their nervous system. 

‘Tt would seem that there isno more urgent psychic neces- 
sity to young mammals than this sense of being supported. 
All their ancestral experiences have been associated with serra 
firma, so that it is not very surprising that when ¢evra firma seems 
about to be removed they are so much disturbed. To my own 
mind this is one of the most instructive and striking psychic mani- 
festations of young animals, though I am not aware that any 
attention has been called to it before ; and instead of referring 
to it under any of the usual divisions of sense, as the muscular 
sense, pressure sense, etc., I prefer to treat the subject under 
the above general heading (Sense of Support), for it seems to 
me that the feeling is a somewhat complex one. 

“Tt is interesting to note that a water tortoise I have had 
for a number of years will at any time walk off a surface on 
which he is placed. But this is not a creature that always is on 
terra firma in the same sense as a dog, but it frequently has 
occasion to drop off logs, etc., into the water. But again, I 
find this sense of support well marked in birds which drop 
themselves into ‘thin air’. Nevertheless, a consideration of an- 
cestral experiences throws light on most cases, and perhaps on 
this one also.” 

Concerning white rats, SMALL (’99, p. 93) states that ‘‘as 
early as the second day (after birth) they show an uneasiness 
when on the edge of a void—sometimes drawing back, some- 
times manifesting their dominant trait of curiosity by leaning 
over and sniffing. At the age of four or five days the presence 


YERKES, Space Perception of Tortorses. 19 


of this sense (the sense of support) is unmistakable, and is not 
due to experience, as I have found by trying rats that have had 
no such experience.’’ And Watson (’03, p. 40) remarks that 
a rat that wanted to get down from the top of the food box 
‘‘would usually stretch his head down two or three times, then 
pull himself back, as though he feared to attempt such a dan- 
gerous a feat.” 

The observations quoted indicate the possibility of inter- 
esting studies of the development of space perception in animals, 
and of such analyses of the sensory complex as shall exhibit 
. the ‘spatial worth’ of each kind of sense data. Partly for the 
purpose of making an approach to the comparative study of 
space perception, partly for the solution of the following specific 
problems I have observed the behavior of several species of tor- 
toises with respect to spacial conditions. The question which 
really led to the investigation was, What relation do the reac- 
tions of tortoises to space bear to their habits ? Does the water 
species behave in essentially the same manner as does the land- 
inhabiting form? The attempt to answer this question led to 
the study of the general behavior of different species, and of the 
importance of vision and the ‘sense of support’ in reactions to 
space. 


Relation of Reactions to Space to Habits in Tortoises. 


My method of experimentation was to place a tortoise in 
the middle of a board 30 cm. by 60 cm. which was elevated 
30 cm., gO cm. or 180 cm. abovea net of black cloth into which 
the animal fell when it crawled or plunged over the edge of the 
board. The fall was thus rendered harmless to the animals, 
and they gave no evidence, by increased hesitancy in crawling 
off, that it was disagreeable to them. The observer carefully 
noted the behavior of the tortoise while it was on the board, 
and recorded the time that it remained there. It would seem 
that the time from the noticing of the edge of the board till the fall 
should be recorded rather than the total time spent on the board, 
but as it was found that some species notice the spatial condi- 
tions while they are still in the middle of the board, whereas 


20 Journal of Comparative Neurology and Psychology. 


others give no evidence of perception of the height until they 
have reached the edge, it was necessary to make the record as 
described. Since in these experiments it was necessary that 
time as well as space should be considered, 60 minutes was fixed 
as the duration of the experiment, and in case the animal re- 
mained on the board longer than that period the test was re- 
corded as a failure. Failures in this case have positive value, 
to be sure, but they do not give us the accurate measurement 
of the time of reaction which indefinite prolongation of the 
period of observation would furnish. 

For detailed study three species were chosen: Chrysemys 
picta Schneider, as a representative of the water inhabiting 
forms; Nanemys guttata Schneider, to represent those species 
which spend part of their lives in water and part on land, and 
Terrapene carolina Linnaeus, as a strictly land inhabiting form. 

Several individuals of each of the species were studied. 
In the tables the results for four individuals of each are pre- 
sented. Each individual was given one trial a day at each of 
the three heights, 30, 90 and 180 cm. for ten days. In Table 
I we have a summary of the results, which are given in detail 
for the various individuals in Table II. From an examination 
of the records the following facts appear: (1) The time spent 
on the board is shortest for the water species, longest for the 
land species. This indicates that the hesitation in the presence 
of a void increases as we pass from the strictly water forms to 


TABLE Il. 


Reactions to Spatial Conditions of ‘Tortoises of Different Habits. 
Summary of Results. 


Chrysemys picta. Nanemys guttata. Terrapene carolina. 
Height. | Average |Failures ||Average | Failures. || Average Failures. 
Time. Time. Time. 
30 cm. 0.57’ fe) 2710" Il AZ S70 9 
go cm. 6.307 oO AQsI7 30 DA 33 
180 cm. 10.107 I 60.07 40 59.27 39 


YERKES, Space Perception of Tortotses. 2a 


TABLE II. 
Reactions to Spatial Conditions of 


Chrysemys picta. 


Subject No. 3. | No. 7. No. 8. No. 9. 


Height. Average] Failures|/Average |Fail- ||Average | Fail- Average | Fail- 
Tj 


ime. Time. ures. |; Time. ures. || Time. ures. 
20) cm. | (0.377 fe) 0.69% fe) 0.74 fo) 0.477 fo) 
i / 
go cm. | 12.80 fo) 4.807 oO Beton fe) 4.60 fo) 
180 cm. | 17.507 I 4.007 oO 25300 oO 16.607 fo) 


Nanemys guttata. 


Sabject No. 1. No. 2. No. 3. | No. 5. 
ZOlem) ||| 32.07 5 9.4’ fo) 38 57 5 | 30.4 I 
go cm 60.07 10 30.87 4 saia(ei 8 Bao 8 
180 cm] 60.07 10 60.07 10 60.07 fe) 60.07 10 

: Terrapene carolina. 
| 

Subject No. 1. INOS 2: Nos: 3: | No. <5. 
BOleme || 30.14 fo) Shoe | I | 5568 ial 41.47 I 
go cm.| 60.0% 10 40.77 4 56.37 60.07 10 

180 cm. | 60.07 10 56.87 9 60. 60,07 Sor as, Io 


those which are land inhabiting ; (2) Total inhibition of the re- 
action, i. e., failure to crawl over the edge of the board in the 
60 minutes, appears at a much less height for the land species 
than for the water-land and water forms. 

This quantitative expression of the amount of hesitation 
exhibited by different species of tortoises under the same spatial 
conditions clearly indicates a close relation between the de- 
mands of the natural environment of the species, so far as spa- 


22 Journal of Comparative Neurology and Psychology. 


tial relations are concerned, and the behavior of the animals. 
A land tortoise has cause to notice heights and to react to them 
in a manner different from that of a water form. The former 
plunges over a precipice and is dashed to pieces, the latter 
plunges into the water from an equal height without injury. 
It is interesting to note, too, that there are intermediate forms 
between the two extremes, for the ‘‘spotted”’ tortoise MV. gut- 
tata is more careful in its reactions to space than C. fpzcta, but 
less so than 7. carolina. 

We may now turn from the roughly quantitative facts of 
this study to the observations of the general behavior of the 
animals when placed in unusual spatial conditions. 

Of the three species of tortoises under consideration 
Chrysemys picta is the most active. Ata height of 30 cm. it 
usually plunges off without hesitation; at go cm. it frequently 
stops at the edge, looks about carefully, and sometimes draws 
back and seeks another part of the edge. There can be no 
doubt that it senses the spatial relations in visual terms. At 
180 cm. this species is manifestly afraid of the edge. Some in- 
dividuals hesitate for long intervals before pushing off into 
space; others rush off at once. Usually, however, at this 
height the edge of the board is carefully explored, and abortive 
attempts to push off are made repeatedly. There is no evidence 
that the unusual conditions are perceived until the animal 
reaches the edge of the board. 

Nanemys guttata hesitates even at the height of 30 cm. 
Most individuals carefully examine the board and look intently 
toward the net and surrounding objects before pushing off. 
They crane the neck over the edge to a greater extent than does 
C. picta. When go cm. or more above the net this species sel- 
dom approaches the edge without manifestations of fear. Fre- 
quently an individual pushes itself almost over, then stops sud- 
denly and draws back, or attempts to catch the edge with its 
claws to save itself from falling. This striking conflict of im- 
pulses sometimes occurs repeatedly before the animal finally goes 
over the edge. The tortoise is impelled by the narrowness of 
its confines on the board, and by its isolated and exposed posi- 


YERKES, Space Perception of Tortoises. 23 


tion to seek escape, and, in the case of the water tortoises, to 
seek the water, but as it is pushing over the edge the visual 
impressions of distance initiate a conflicting motor impulse 
which causes the animal to draw back. This species manifests 
fear much more markedly, frequently, and at a less height than 
does C. picta. On the whole we may say that its behavior to 
spatial relations would ordinarily be interpreted as indicative of 
more accurate space perception. 

At none of the three heights used in the experiments does 
| Terrapene carolina push over the edge without some hesitation 
and manifestations of fear. At 30 cm. almost all individuals 


TABLE III. 


ze \ Behavior much the same as that of 7. carolina. 
Became ETE There is careful inspection of the surroundings and 
Taylor long hesitation. One individual was found that 


plunged off directly at the height of 180 cm. 


Xerobates polpyhemus Examination of edge asin 7. éaurz. Hesitation at 
Daudin 30 cm., and great fear at 180 cm. 

Testudo vicina Not afraid to fall 30 to 50 cm. but careful when at 
Giinther greater heights. 


; his ecies shows greater hesitation than NV. 
Chelopus tnsculptus Eon eais sale 8 E ; oe 
guttata. At 30 cm. it examines the surroundings, 


Laconte and often fails to leave the board. 


In this species there is some hesitation at 30 cm. but 
seldom failure to go off. At 180 cm. there is marked 
Shaw fear as in WV. guttata, which it very closely resembles 


Emys meleagris 


in its behavior. 


Although this form carefully examines the edge and 
looks at the floor intently it seldom fails to go off. 
Its actions are very deliberate in most cases. 


Chelodina novaehollan- 


diae Dumeril et Bibron 


Many indiduals pay no attention to the edge it: 
tle hesitation even at 180 cm. Behaves much like 
Ga picia- 


Trachemys scabra 


Agassiz 


No hesitation, no fear at any height at which it was 
tried. Pays less attention to spatial conditions than 
any of the species studied. 


Podocnemis madagas- 


cartensts Grandidier 


24 Journal of Comparative Neurology and Psychology. 


will leave the board if given plenty of time. This species is 
more careful than the others in approaching the edge, and it 
cranes the neck over even more frequently than does C. pzcta. 
The inhibition of impulses frequently appears as in case of JV. 
guttata. Unlike the other species, 7. carolina notices the spatial 
relations from its position in the middle of the board, for when 
180 cm. above the net an individual is frequently afraid to move, 
and will remain for a long time just where the experimenter has 
placed it. 

This study of the reactions to space of the three species of 
tortoises already considered was supplemented by observations 
of the behavior of several other species at the heights of 30 and 
180cm. In Table III, a summary statement of the results is 
presented. J 

Without knowledge of the name of the species, but solely 
on the basis of the results of the experiments, I classified the 
species under the three categories Water, Land-Water, and 
Land Species in order to determine the. value of reactions to 
space as a sign of habits. 


Classification tn accordance with reactions to space. 


Water Species. Land- Water Species. Land Species. 
Chrysemys picta Emys meleagris Terrapene baurt 
Podocnemis mada- Nanemys guttata Terrapene carolina 

Se SCATLCIESES | Xerobates polyphemus 
: : | y 
Chelodina novachollandiae Testudo vicina 
Trachemys scabra | Chelops insculptus 
Polymedusa galeata 


This classification agrees fairly well with what is known of 
the habits of the forms, except that Chelopus insculptus is a land- 
water rather than a land species. 


The Spatial Worth of Sense Data. 


For the purpose of ascertaining the relative importance for 
reactions to space of the visual, tactual, muscular and organic 
sense impressions some experiments were made with blindfolded 
tortoises. The eyes, in these experiments, were covered with 
tin-foil caps which effectually excluded visual stimuli. 


YERKES, Space Perception of Tortotses. 25 


C. picta when blindfolded usually rushed off a surface at 
any height without the least hesitation. There is no evidence, 
from my experiments, that the tactual and muscular impressions 
received when the legs are stretched over the edge have any in- 
hibitory influence on the movement. From this it is clear that 
the hesitation of this species observed at heights of 180 cm. is 
due to visual impressions, not to the unusual organic impres- 
sions received. This species at first tries to remove the cover- 
ing from the eyes by rubbing the fore legs over the head, but 
failing it soon becomes accustomed to the blindfolded condi- 
tion. 

NV. guttata is much disturbed by the obstruction of its 
vision, and for long periods persistently tries to remove the cap. 
Most individuals after a time move about freely, but whenever 
they reach the edge of the board they turn back. Evidently 
the tactual and muscular impressions inhibit the tendency to 
move forward. Whereas in case of C. pzcta, we see the blind- 
folded animal risking falls which it would not have risked in its 
normal condition, in /V. gwttata we see exactly the reverse, for 
as a rule the animal when blindfolded does not leave the board. 

T. carolina does not struggle so persistently to remove the 
covering as do the other species, but it is inactive when blind- 
folded. It behaves in general much as it does when placed at 
a height of 180 cm. above the floor. This indicates that it de- 
pends upon vision for guidance in its movements to such an 
extent that it is not likely to move about much unless it can 
see Clearly. 

Visual impressions are of prime importance in the space 
perception of tortoises, and tactual, muscular and organic data 
occupy a position of secondary importance. Yet there are 
many reasons for believing that we often underestimate the value 
in the reactions of simple organisms of that complex mass of 
sense impressions which we are not as yet able to refer to spe- 
cific organs. James (’90, II, p. 150) has called attention to a 
fact that is significant in this connection; ‘‘Rightness and left- 
ness,” ‘‘upness and downness,”’ he says, ‘‘are again pure sensa- 
tions differing specifically from each other, and generically from 


26 Journal of Comparative Neurology and Psychology. 


everything else.”’ We are inclined to lose sight of the organic 
impressions, and to refer reactions to data received through the 
so-called special senses. Many experiments have already been 
made which show that the direction of turning, apart from 
vision, is extremely important in the motor habits of tortoises 
and frogs. 

I gratefully acknowledge my indebtedness to Mr. SAMUEL 
HeEnsHAW for suggesting to me the desirability of a comparative 
study of the space reactions of tortoises; to Mr. Tuomas Bar- 
BOUR for valuable assistance in many ways, and for the oppor- 
tunity of observing the behavior of several foreign species; to 
Mr. Wo. T. Hornapay, director of the New York Zoological 
Park, and to Mr. R. L. Dirmars, Curator of Reptiles, for the 
privilege of conducting experiments in the Park, and for many 
courtesies, andto Mr. C. W. Haun for the use of tortoises 
which were in his possession. 


REFERENCES. 
James, Wm. 
790. Principles of Psychology. New York. 
Mills, Wesley. 
798. The Nature and Development of Animal Intelligence. Lozdon, 
307 PP- 
Small, W. S. 
99. Notes on the Psychic Development of the Young White Rat. 
Amer. Jour. Psychology, Vol. 11, pp. 80-100. 
Thorndike, E. L. 
799. The Instinctive Reactions of Young Chicks, Psychological ke- 
view, Vol. 6, pp. 282-291. 
Watson, John B. 
703. Animal Education. Chicago, Universtty of Chicago Press. 106 pp. 


XX NOGEMON: THE -SIGNIFICANCE OF THE FORM 
AND CONTENTS OF THE, NUCLEUS IN THE 
SPINAL GANGLION:..GELLS OF THE FOETAL 
RAT. 


By SHINKISHI HAral. 
(from the Neurological Laboratory of The University of Chicago.) 
With Plates III and IV. 


In the course of an investigation on the growth changes 
in the nerve cells of the white rat, the writer noticed that the 
nucleus very often had a peculiar shape ; the shape being simi- 
lar to an amoeba exhibiting pseudopodia-like processes along 
one side. Careful observation revealed the fact that this pecu- 
liar form of the nucleus occurs normally during the period of the 
early growth and in attempting to explain it we meet several 
interesting questions of histological as well as physiological 
importance. The results here reported form a part of a series of 
observations on the growth changes in the developing nerve 
cells. 

For this investigation, the intrauterine embryos of cat, 
pig and white rat were used. The present description and 
drawings are, however, based entirely on preparations from 
white rat. Unless otherwise mentioned, the description 
also applies to the cat and pig. The tissue was preserved 
in a normal salt solution saturated with HgCl; in Carnoy’s so- 
lution and in GRaAr’s chrom-oxalic mixture. For the micro- 
chemical test for P. and Fe., however, the tissue was fixed ad- 
vantageously with 95 % alcohol. The paraffine sections were 
made 3 to 6 micra in thickness, and were stained with HEIDEN- 
HAIN’S iron-haematoxylin alone or sometimes followed by 1% 
aqueous solution of eosin and Bionpi-EHRLICH’s tri-color stain. 
Other sections were stained with toluidin blue and eosin. 


28 Journal of Comparative Neurology and Psychology. 


General characters of the spinal ganglion cells.—The 
spinal ganglion cells in embryos of the white rat, 10 to 13 mm. 
long, present a bipolar shape in most cases; one of the pro- 
cesses contains a large amount of the cytoplasm and is recog- 
nized easily because it stains more deeply than the other. The 
second process arises from the opposite side of the cell-body 
and stains faintly. It contains a very small amount of cyto- 
plasm and is hard to distinguish from the surrounding struc- 
tures. Only the former process is shown in the figures. The 
relation of these processes to the spinal cord will be described 
in a future paper. Hereafter, in this paper, the term process 
means the former branch, rich in cytoplasm. 

The nucleus is very large compared with the cell-body and 
presents a more or less oval shape. It contains a large number 
of the minute granules among which two different forms may 
‘be distinguished, not only by their size but also by their stain- 
ing reactions with iron-haematoxylin ; one form of the granules 
stains deep black while the other presents a grey tint. The 
granules which stain an intense black are very much larger in 
size and occur most abundantly along the nuclear wall and its 
vicinity ; the faintly staining granules, on the other hand, are 
very small in size and appear to form a fine network in the 
nucleus. This network is most condensed around the larger 
granules of the former group. The large granules are identi- 
fied with the basophile substance and the small granules with 
linin or oxyphile substance. This grouping is by no means 
satisfactory, for by using the BronpI-EHRLICH stain, as well as 
by applying the microchemical tests, it has been noticed that 
among basophile granules (larger form) there are several differ- 
ent kinds which stain with different intensities and similarly 
there are several different kinds of the oxyphile granules. So 
far, therefore, as color reactions are concerned, the oxyphile 
and basophile granules grade into one another and no sharp 
distinction can be drawn between the two. This fact is ex- 
tremely important in connection with the present investigation 
and will be discussed more fully later on. 

Among the large granules, sometimes one and in some 


Hata, Spinal Ganglion Cells. 29 


cases more than one, can be distinguished as exclusively com- 
posed of the basophile substance, but in many cases, the large 
granules contain both basophile and oxyphile substances. When 
this occurs and the basophile surrounds the oxyphile substance 
then such a granule may be regarded as a nucleolus of the adult 
nerve cells. 

Enlarged granules of this nucleolar type are shown in 
Figs. 1 and 2. The position of these granules is not constant 
but they lie in some cases along the nuclear membrane and in 
others they occupy the center of the nucleus (Fig. 1). 

Shape of nucleus.—Changes in the shape of the nucleus 
and the alterations of its position in the cell have been noted 
by a number of observers. The phenomena have been observed 
especially under experimental and pathological conditions. In 
the normal condition, however, they have been reported by 
only a few investigators. Several investigators observed a 
pocket formation along the nuclear surface in the spinal gang- 
lion cells of fish. These invaginations are repeated several 
times in one nucleus, some of them being deeper than the 
others, and thus the nucleus presents pseudopodia-like pro- 
cesses. Such an appearance is rather common in the nuclei of 
the nerve cells in spinal ganglia and ventral horn of lower ver- 
tebrates (HOLMGREN), but on the other hand, it is rarely visible 
in the cells of the higher mammalia, and when it occurs it is 
not so conspicuous as in the lower forms. The present writer 
had the opportunity to examine a large number of the prepa- 
rations of the nerve cells of the white rat at different ages, but 
failed to find the pseudopodia-like processes of the nuclei in ani- 
mals of one day or older. Asa rule, after the age of one day 
the shape of the nuclei is constantly ovoid or spherical and does 
not show pseudopodia-like processes. 

By examining the nuclei of spinal ganglion cells of em- 
bryos (10 to 13 mm.), the following appearances have been ob- 
served : 

As is shown in the figures, the nucleus of the embryonic 
spinal ganglion cells lies, as a rule, at one side of the cell body ; 
that is it lies eccentrically. Such an eccentric location of the 


30 Journal of Comparative Neurology and Psychology. 


nucleus also occurs in the cells of the adult animal. The shape 
of the nuclei is somewhat oval, the longer diameter being per- 
pendicular to the long axis of the protoplasmic process. On 
one side towards the center of the cell, the outline of the 
nucleus is more or less wavy. In some cases, the wavy out- 
line is not very marked (Fig. 5) but in most cases, it is con- 
spicuous and one is lead to compare it to the pseudopodia-like 
process of an amoeba (Figs. 1, 2, 4). 

The nuclei showing the pseudopodia-like processes have 
been observed by several investigators; in the egg nuclei of the 
insects and Coelenterata by KorscHE Lr (’89); in the spinning 
gland cells of a Swedish caterpillar and also in the spinal gang- 
lion cells of the fishes, frogs, etc., by HotmGreEn (’95-’00) ; in 
the developing ovum of the Nassa by HorrMann (’02); in the 
nuclei of the ventral horn cells of various vertebrates by Kor- 
STER (01); and the same thing is also shown in the illustrations 
accompanying a large number of papers in which, however, the 
authors do not describe this interesting phenomenon. Before 
going on to a further discussion of this appearance, I shall de- 
scribe more in detail the histological characters of the wavy 
outline together with the structure of the adjoining part of the 
cell body which contains the centrosome. 

The neuclear membrane which covers the pseudopodia is 
not completely continuous but is composed of separate portions 
when seen in thin sections; in other words, the surface of the 
nuclear membrane towards the cytoplasm is porous. A disap- 
pearance or dissolution of the membrane on this side of the nu- 
cleus has been observed by HormGreEn, and PuaGnart (98), but 
in the case of the white rat, it is always porous in character. 
This is clearly shown in Fig. 2. In many cases, however, the 
local dissolution of the nuclear membrane is not as conspicuous 
as in Fig. 2, but the outline appears varicose in structure owing 
to an accumulation of basophile granules around the pores 
(Bigs92,75): 

The nuclear membrane which lies towards the protoplasmic 
process is of uneven thickness. The thicker portions stain 
much more deeply than the rest of the membrane with the 


Haral, Spinal Ganghon Celts. 31 


basic dyes (Figs. 1, 5). This indicates that the thicker por- 
tions contain an accumulation of the nucleoproteid. This state- 
ment is supported by the fact that the preparations tested for 
iron show this area deeply stained (Fig. 2). The accumulation 
of the nucleoproteid along the part of the nuclear membrane 
which turns towards the process is a highly interesting phenom- 
enon since it bears on the problem of the cell metabolism. 
This point will be discussed later on in detail. An accumula- 
tion of the nucleoproteid is frequently visible along the outer 
surface of the nuclear membrane as is shown in Fig. 3. 

These pseudopodia-like processes of the nucleus are inti- 
mately related to the rays of the centrosome. The centrosome 
in nerve cells has been described by several investigators, and 
in the nerve cells of the white rat in both adult and young it 
has been described by the present writer (’01). Although some 
investigators deny the existence of the centrosome in the nerve 
cell, the structure is so definite and so clear that in properly pre- 
pared sections, its presence can not be disputed. The centro- 
some is especially clear in the case of the embryonic cells and 
every minute feature of the organ may be distinguished. Asa 
rule, the centrosome lies very near the nucleus and in the con- 
€avity, formed by it (Figs.1; 2) 3,4, 5). ~Ihe centrosome is 
composed of two minute central corpuscles surrounded by still 
more minute granules (centrosphere). These granules arrange 
themselves in straight lines which run from the center towards 
the periphery radially (astral lines). The astrosphere is clearly 
distinguished from both surrounding cytoplasm and centro- 
sphere, since it stains very lightly with iron-haematoxylin owing 
to a lack of the Nisst granules. By _ overstaining with 
acid dyes, however, astrosphere stains a more intense red than 
the surrounding substance. The minute structure of the cen- 
trosome in the nerve cells of the white rat has been reported 
already by the writer (’01) and therefore, with the exception of 
the astral structure, it need not be further described here. The 
astral rays which start from the centrospere run radially towards 
all parts of the cell body. Those rays which runs towards the 
nucleus extend not only as far as the nucleus but penetrate its 


32 Journal of Comparative Neurology and Psychology. 


membrane and become directly continuous with the linin net- 
‘work. This is shown in Figs. I, 2, 4, 5. As is shown in the 
figures, the protoplasmic lines pass through the pores of the 
nuclear membrane and run into the nucleus where they fuse 
with the linin network. Some of the rays fuse together with 
the linin network as soon as they enter into the nucleus, but 
others run quite a distance without losing their original charac- 
ter as rays. Ultimately, however, they fuse with the network 
and no rays can be seen near the periphery of the nucleus. 
The penetration of these rays was verified by careful examina- 
tions, many times repeated, all precautions being taken against 
possible mistake. Thus my observations on the spinal ganglion 
cells of the white rat show a direct continuation of the cyto- 
plasm and nuclear network by means of the rays of the cen- 
trosome. In addition to these observations, HoLMGREN (’99) 
noticed in adult nerve cells of Lophius piscatorius that the Nissi 
granules were hung along the astral rays and that these granules 
could be traced with them into the nucleus. From this fact 
HoxtmGREN concluded that the Nisst granules are formed by 
the migration of the chromatin out of the nucleus, and that the 
granules thus formed are again passed back into the nucleus by 
means of the rays. He, therefore, regards the rays as a path- 
way by which Nissv granules re-enter the nucleus. The present 
writer was unable to find any formed Nissi granules along the 
line of the rays within the centrosphere. Therefore the return- 
ing of the formed Nisst granules into the nucleus was not 
found in the nerve cells of the white rat. I will return to this 
point in general discussion. 

Distribution of the nuclear material.—At this stage of intra- 
uterine life, the nucleus of the nerve cell contains a large num- 
ber of the chromatic particles which are scattered through it. 
The particles vary in size from minute granules to comparatively 
large bodies. The larger granules do not exceed five in num- 
ber and may be composed exclusively of basophile subtances. 
Subsequent to the stage in which basophile and oxyphile gran- 
ules are distinct, the nucleolus appears. The minute granules 
as distinguished from large granules, mentioned above, stain 


Hata, Spinal Ganglion Cells. 33 


with iron-haematoxylin a deep black toa grey. The iron test 
shows in the same granules also varying amounts of the iron. 
These granules are hung along the linin net as is shown in all 
the figures. By using Bronpi-EuR Icu’s tricolor stain, these 
granules stain from a deep blue to a brownish red; thus all the 
staining methods employed show that these granules are chem- 
ically heterogeneous. This gradation in the staining capacity 
probably indicates gradations in the chemical constitution of the 
granules which range from a substance rich in nucleic acid to a 
substance poor in nucleic acid. These granules are found most 
abundantly along the nuclear membrane, especially at the two 
poles of the nucleus on the side toward the cytoplasmic process 
(Figs. 1, 4, 5). Itisa‘striking fact connected with the distri- 
bution of the granules that the appearance of the Nissi gran- 
ules in the cytoplasm is clearly correlated with the accumulation 
of the granules at the two poles of the nucleus. The Nissi 
granules first appear in the neighboring cytoplasm. This fact 
suggests that the Niss_ granules are derived from the nucleus. 
From facts similar to those just given, as well as from other 
evidence, Scotr (’98-’99) arrived at the conclusion that the 
Nissv granules are of chromatic origin and are produced by the 
migration of the basophile granules from the nucleus. The 
nuclear origin of the nuclein compounds which are seen in the 
cytoplasm has been maintained by several investigators from 
observations on glandular tissues as well as on the muscles. 
My own observations therefore indicate the nuclear origin of 
the Nisst granules and thus corroborate the observations of 
these previous investigators, HOLMGREN (’99) on the nerve cells 
of Lophius prscatorious and Rouve (’03) on the nerve cells of 
various vertebrates. 


1 The formation of the Niss_ granules in the nerve cells is comparable 
with the formation of the zymogen granules, muscle fibrils, and yolk granules. 
This is a highly important and fundamental problem in cellular biology and the 
subject is fully discussed and presented historically in WuiLson’s ‘Cell in De- 
velopment and Inheritance,” 2nd edition, 1900. 


34 Journal of Comparative Neurology and Psychology. 


Migration of the nucleoh.'—A migration of the nucleolus 
as well as other nuclear material from the nucleus to the cell 
body has been reported by several investigators. In the case 
of the nerve cells, RonDE (’96-’03) observed the migration of 
the nucleolus in the case of both lower vertebrates and mam- 
mals. In a recent paper on the nerve cells, RoHDE (’03) main- 
tains the migration of the basophile substance from the nucleus, 
where it exists in solution, into the cytoplasm. Levi (’96) 
believes the neurosomes in the cytoplasm to be derived from 
the nucleus. Levi showed this relation by the electrical stimu- 
laton of nerve cells. In the present work, I have noticed also 
the migration of the nuclear substance or accessory nucleoli 
from the nucleus to the cytoplasm. This is so often seen in 
the nerve cells at this stage of development that it cannot be 
regarded as an artifact. The migration is always towards the 
cytoplasmic process, no matter whether this process turns dis- 
tally or toward the spinal cord. If the dislocation of the large 
masses or accessory nucleoli were due to mechanical forces, the 
knife or gravitation, or to other mechanical factors, one would 
expect to see them moved towards the less resistant side, that is 
towards uncovered side of the nucleus, as in the case of path- 
ologically altered cells in which the nucleolus or intranuclear 
masses escape towards the side on which the cytoplasm is least 
abundant. Again, if such a migration were produced by the 
knife or gravitation, as Herrick (’95) showed to be the case 
in the ovarian cells of the lobster, one would expect to find the 
displacement always in the same direction in all the cells of a 
given section, but such is not the case. Moreover, the general 
appearance within the cells does not suggest a mechanical burst- 
ing of the nuclear membrane. For these reasons, I believe 
that the observations of ROHDE and others are correct and my 
own observations strongly confirm their statements. The fate 
of the extruded granules has still to be considered. In order to 


1 History of the observations on this subject in the tissue cells is given in 
‘detail by MONTGOMERY, T. H.—Comparative Cytological Studies witb especial 
Regard to the Morphology of the Nucleolus, Journ. Morphology, VOL. 15, No. 
2, 1808. 


Hatai, Spenal Ganglion Cells. 35 


understand their final destination it is necessary to describe the 
migration of the nuclear substance more in detail. Figures 4, 
5, 6, 7 and 8 illustrate this. The granules, for the most part 
accessory nucleoli, may be both larger and smaller than the other 
granules contained in the nucleus. They stain deep black with 
iron-haematoxylin and rather pinkish red with the tri-color 
method ; that is, their staining reaction resembles very closely 
that of the Nissi granules. These accessory nucleoli, there- 
fore, can be distinguished from the nucleolus since the latter is 
composed of the two substances, basophile and oxyphile. In 
each case I noticed only one granule migrating at a_ time, 
although I have seen once or twice several granules attached 
along the external surface of the nuclear membrane on the side 
toward the process (Fig. 3). This arrangement is very rare 
and cannot be regarded as typical. The migration always takes 
place towards the main protoplasmic process and in addition 
the granule is extruded in the neighborhood of the poles of the 
nucleus where the Nisst granules first appear. After migration 
I was unable to see these granules at any distance from the 
nucleus, though they were abundant near to it. From this we 
conclude that as soon as the granules migrate from nucleus, 
they disintegrate and their substance is mixed with the sur- 
rounding cytoplasm. If the corpuscles which have migrated 
out of the nucleus still continue their movement until they 
finally come out of the cell body, as is believed by Roupg, it 
would be possible to observe such corpuscles outside of the 
cell body, but I have not been able to find them. Therefore 
from at least three facts: (1) that the granule after migration 
is always found near the nucleus; (2) that the granule after mi- 
gration is not found in the cytoplasm at any distance from the 
nucleus and (3) that it is not found outside the cell body, the 
writer concludes that these granules have been disintegrated and 
mixed with the surrounding cytoplasm. If my hypothesis is 
correct the migration of the accessory nucleoli is another form of 
the extrusion of the minute granules; a second form of the 
nuclein formation in the nerve cell—the first or commonly rec- 


36 Journal of Comparative Neurology and Psychology. 


ognized method being the extrusion of very small granules. 
(See page 33). 

Judging from the staining reaction of the accessory nucleoli 
which contain both phosphorus and iron, they are composed 
of the same substance as the Nissi granules and therefore it 
may be safely concluded that the disintegrated substance was 
utilized for the formation of the Nissi granules. This observa- 
tion agrees with that of Roupeg, but with his further statement 
that some of the accessory nucleoli become the neuroglia 
nuclei, I cannot agree. So far as my observations on the nerve 
cells of the white rat go, there is no indication that the accessory 
nucleoli form the nuclei of the neuroglia cells. The migration 
of the accessory nucleoli was found only in the cells at the early 
stage of intra-uterine life here examined, and at more advanced 
stages I was unable to observe this phenomenon, although a num- 
ber of later. developmental stages were studied. [From this 
fact, we may conclude that extrusion of the nuclear substance 
into the cytoplasm occurs only in the very early stages of the 
developing nerve cells. 

Significance of the pseudopodia-like processes of the nucleus. — 
The observations of the previous investigators (HOLMGREN, 
Rouve and Scott), as well as those presented in this paper, 
furnish good evidence for believing that Nissx granules originate 
in at least two ways; namely (1) by the extrusion of small 
granules; (2) by the extrusion of accessory nucleoli. If all 
the materials which appear in the Nissi granules of the mature 
nerve cell are derived from the chromatin of the nucleus, then 
it is plain, since the nucleus at no time contains as much sub- 
stance as is presented by the Nissi. granules at maturity, that 
the chromatin of the nucleus must be continually built up by 
the material supplied to it from the cytoplasm. So far as I am 
aware no investigator except HoLtmGREN (’99) has attempted 
to explain this phenomenon. HotmGreEn found in the nerve 
cells of Lophius piscatorius that the Nissi granules are hung along 
the astral rays which run through the nuclear membrane and 
according to him this indicates the return of the Nissi granules to 
the nucleus by way of the astral rays. Thus, according to him, 


Hata, Spinal Ganghon Cells. 37 


there is a circulation of the Nissi granules between the nucleus 
and cytoplasm. In the general description of the nerve cell, 
my results agree with those of HortmGren in the following 
points: (1) the rays of the attraction sphere run into the nu- 
cleus where they become continuous with nuclear network, (2) 
the Nissi granules migrate from the nucleus either as minute 
granules or accessory nucleoli, (3) the nuclear membrane be- 
comes perforated along the surface which turns toward the 
cytoplasmic processes. However, I was tnable to see the 
basophile granules either within the centrosphere or along the 
astral rays in the cytoplasm. Therefore, HOLMGREN’s hypo- 
thesis of the return of the formed Nissi granules into the nu- 
cleus is not supported by the appearances in the nerve cells of 
the white rat. My own observation suggests that the Nissi 
granules which have migrated from the nucleus are utilized for 
the maintainance of the cell body and what remains of them 
after they are broken down, together with fresh material, is 
taken into the nucleus by means of the pseudopodia-like pro- 
cesses. For the above view, the following evidence may be 
presented : 

(1) The pseudopodia-like processes of the nucleus are di- 
rected towards the central corpuscles of the centrosome. Ac- 
cording to KorscHe tT (’91), HorrMann (’03) and others the 
pseudopodia-like processes are to be regarded as organs taking 
up nourishment from the surrounding cytoplasm. 

(2) In them, as well as in their vicinity, basophile granules 
are abundant. 

(3) Within the nucleus, the astral rays are surrounded by, 
or have attached to them, a large number of basophile granules. 

(4) Positive proof of the presence of iron and phosphorus 
was obtained in the granules along the rays, as well’ as 
within the centrosphere, although they did not give with 
HEIDENHAIN’S iron-haematoxylin nor with the tricolor methods 
reactions similar to that produced in the Nissi granules. This 
proves that the substances necessary for the formation of the 
nuclein bodies (Nissx granules) are present in the centrosphere 
as well as in its rays, in a peculiar form. 


38 Journal of Comparative Neurology and Psychology. 


As supplementary to the foregoing the following observa- 
tions may be added: (1) the pseudopodia-like processes of the 
nucleus as well as the migration of the accessory nuclei are 
present only at a very early stage in the development of nerve 
cells, at the time when the Nissi granules have not yet appeared 
or are found in very small amounts, and when the cell body 
needs an abundant supply of formative materials. The patho- 
logical as well as experimental studies give us still stronger evi- 
dence for the foregoing view. 

Pathological and experimental evidence.—The morphological 
completeness of the cell body is attained in an early foetal 
period when metabolic processes in the cell body are very active 
and we associate the formation of pseudopodia-like processes 
and the migration of accessory nucleoli and of the minute gran- 
ules, with the hyperactivity of the cell at this time. The ex- 
perimental studies of the nerve cells made by a large number of 
investigators (Hopce, 792; Mann, ’95; SJOvALL, ‘O3:- and 
others) show that when the nerve cell is stimulated with the 
electric current, the nucleolus becomes first swollen and later 
shrunken ; the outline of the nucleus becomes irregular, form- 
ing pseudopodia like processes (HonGE, see figures) ; accessory 
nucleoli migrate out of the nucleus (HOLMGREN); acidophile 
substance or neurosomes are sent from the nucleus into cell 
body (Levi); at the same time the Nissv granules are quickly 
disintegrated. These observations favor my hypothesis of the 
metabolic processes in the cell since they are similar to those 
changes which take place normally at an early stage in the his- 
tory of the cell body when it is actively growing. As a result of 
the electric and other stimulation the reserve materials of the 
Nissv granules are used up very quickly and for the mainte- 
nance of the cell a new supply of the substance is demanded. 
The migration of the nuclear contents and the quick absorption 
of the necessary materials from the cell body into the nucleus 
by means of the pseudopodia-like processes are both necessary. 
Notwithstanding that a large number of investigators have ex- 
amined the nerve cells under various conditions, the pseudopo- 
dia-like processes have been overlooked by most of them. 


Harat, Spinal Ganglhon Cells. 39 


SJOvALL (’03) has pointed out these structures in the human 
nerve cells, in a patient dying from tetanus. and gave many fig- 
ures showing different stages of the processes of the formation 
of the granules. SjoOvaLt showed further an accumulation of 
basophile granules along the nuclear membrane where the pro- 
cesses are covered. He concluded from these observations that 
‘‘Die gesehenen Veranderungen sind als von der tetanischen 
motorischen Erregung verursachte, innerhalb vollig physiolog- 
ischer Grenzen sich abspielende Aktivitatserscheinungen aufzu- 
fassen, und nur als solche. Zu dieser Ansicht komme ich: 
(1) Weil sie den experimentell hervorgerufenen Aktivitatsver- 
anderungen der Nervenzellen wesentlich gleich sind. Dies be- 
trifft ; (a) sowohl die friiher gesehenen Veranderungen, (b) wie 
die von mir gefundene Beziehung zwischen Kern und Proto- 
plasma, die mit den Befunden von HoLMGREN identisch ist, und, 
wie diese, sicher als einen Restitutionsvorgang des wahrend der 
Aktivitat in anspruch genommenen Tigroids zu deuten ist.”’ 

The writer had a chance to examine several preparations 
of the nerve tissue of rat, cat, dog and man under pathological 
as well as under experimental conditions and found always the 
pseudopodia-like processes at one side of the nucleus. This 
phenomenon was more clear when the nucleus was located 
eccentrically ; the pseudopodia being extended toward the main 
portion of the cell body. These observations show changes 
in the cell body and nucleus corresponding to those occurring 
during foetal life. 

Growth changes in the nerve cells. —As soon as the pseudo- 
podia-like processes have disappeared marked changes take place 
in the structure of the nucleus The most notable changes are: 
(1) the nucleus assumes a spherical or oval shape with a smooth 
outline ; this shape is maintained during life; (2) the chromatic 
granules (basophile) which existed abundantly along the nuclear 
membrane disappear and at the same time some of the granules 
move towards the center where they surround a cluster of the 
acidophile granules and form a permanent nucleolus; (3) most 
of the basophile granules are changed into oxyphile granules 
as is shown by the change in staining capacity, since the orig- 


40 Journal of Comparative Neurology and Psychology. 


inal basophile granules are now stained with acid-dyes; (4) fol- 
lowing the nuclear changes just described the cell body is 
filled with the basophile granules or the Nissi substance; (5) 
the astral rays of the centrosome are not as clearly shown as in 
the earlier stages. The nerve cells thus changed do not differ 
from the adult functional cells except in size and, therefore, it 
may be concluded that the morphological completion of the 
nerve cell of the white rat is attained during early intra-uterine 
life. In the case of man, MakINESCO (99) and Bierviiet (’00) 
noticed such fully formed Nissi granules in the ventral horn 
cells of the spinal cord at birth. This does not mean, however, 
that all the Nissi granules are formed in the cells at this stage, 
but that they are relatively as abundant as in the adult cells. 
Therefore it is clear that when the cell body increases in volume 
the amount of the stainable substances increases correspond- 
ingly. The explanation of the formation of the stainable sub- 
stance at the latter stage is not easy, since at this stage the 
structure of the nucleus is different from that of the earlier 
stage in which the nucleus resembles that which can be seen in 
the cells of the active glandular tissue. Before going into a 
further discussion of this point, it will be well to describe the 
main features of the nucleus in the adult nerve cells. 

The nucleus in the spinal ganglhon cells.—The nucleus in the 
spinal ganglion cells in an adult white rat is slightly oval in 
shape and is located at or near the center of the cell. The nu- 
clear membrane is very distinct and can be distinguished easily 
from the surrounding cytoplasm. The nucleolus appears nearly 
in the center of the nucleus, consisting as a rule of a single cor- 
puscle and staining an intense blue with toluidin blue and ery- 
throsin. Several endonucleoli are often distinctly visible with- 
in the nucleolus. These are composed of acidophile substance. 
The nucleolus is, therefore, composed of two different substances, 
acidophile substance within, the basophile substance without. 
The nucleus contains a Jinin network and a large number of the 
acidophile granules; the latter hung on the threads of the for- 
mer and most abundant along the periphery of the nuclear 
membrane and around the nucleolus. Thus, except the baso- 


Hata, Spinal Ganghon Cells. 4! 


phile covering of the nucleolus, no more chromatic substance 
can be demonstrated by using ordinary stains like toluidin blue 
and erythrosin. It is a well-known observation, not only in 
the early embryonic nerve cells but also in the cells of the active 
glandular tissues, that preceding the migration of the chro- 
matic substance from the nucleus to the cell body the substance 
appears at first along the inner surface of the nuclear membrane 
whence it passes by either diffusion or migration into the cyto- 
plasm. But as described above, the nucleus of the adult nerve 
cell does not show basophile or chromatic substance except as 
in a thin layer about the nucleolus. 

Very recenly, by applying ZIMMERMANN’s ‘‘Jodgrunfuchsin 
method” to the nerve cells in various animals, RoHDE (’03) 
arrived at the conclusion that ‘‘Das Enchylema ist farbbar und 
zwar durch Jodgriinfuchsin wei die Nukleinkérper. Es en- 
thalt demnach ebenfalls Nuclein, entweder gelost oder in dif- 
fuser Form.’’ This conclusion is correct also in the case of the 
white rat. I applied the iron and phosphorus reaction to the 
adult nerve cells and obtained always positive results from the 
enchylema which, however, does not stain by using ordinary 
histological technique. Figure 7 is a drawing of the ventral 
horn cells in an adult white rat treated by the method for de- 
tecting iron and phosphorus. As the figure shows, the Nissi 
granules are directly continuous with the dissolved nuclein in 
the nucleus. At the two poles of the oval-shaped nucleus, the 
dissolved nuclein is most abundant (Fig. 7) and from these 
poles it diffuses out of the nucleus into the cytoplasm. By 
using the technique for phosphorus and iron one is surprised to 
see the large amount of the nuclein which exists in a soluble 
condition. Thus one can easily imagine a cyclical interchange 
of the substances between the cell body and nucleus, since the 
material to be exchanged is in solution in the enchylema. The 
application of technique for the detection of phosphorus and. 
iron to the spinal ganglion cells in the adult rat shows the same 
results and therefore does not need to be especially described. 
These appearances suggest that in the adult and later stages the 
Nissx granules are formed in the cytoplasm from the nuclein 


42 Journal of Comparative Neurology and Psychology. 


which has diffused out of the nucleus. This hypothesis is 
favored by examining the adult nerve cell which has been 
stained either by toluidin blue and erythrosin or by HEIDEN- 
HAIN’S iron haematoxylin, followed by orange G. These stains 
show minute particles densely packed around the nucleus; 
especially at its two poles. This appearance is shown in figure 
8, which has been drawn from one of the adult ventral horn 
cells stained with iron haematoxylin. As is shown in the figure, 
densely packed minute granules appear around the nucleus. 
Some of the granules stain a deep black, while the rest of the 
granules are tinged grey. Now if we apply the test for phos- 
phorus and iron to such a preparation, the peripheral layer of 
the nucleus just within the membrane is found packed with 
a large amount of the dissolved nuclein, as is shown in figure 
7, but is not shown in figure 8. From these figures we con- 
clude that the dissolved nuclein which does not take up either 
toluidin blue or iron-haematoxylin has been modified into a 
stainable form on passing from nucleus. This change is due 
perhaps partly to the accumulation of the minute granules into 
comparatively larger granules and partly to a chemical trans- 
formation of the dissolved nuclein into the true Nissi granules. 
Scott (’99) was able to distinguish three different kinds of the 
nuclein compounds in the nerve cells; Nisst granules, baso- 
phile granules or covering substance of the oxy-center or the 
central mass of the nucleolus, and oxychromatin. According 
to him, these three nucleins were derived from the mitotic chro- 
matin of the primitive nerve cells (germ-cells). It must be 
kept in mind that all substances in the body are undergoing 
constant metabolic change. Further, the Nissi granules in- 
crease in proportion as the oxychromatin increases with the 
growth of the cell body. This means that a new formation of 
the Nissi granules takes place within the cell body constantly ; 
that is, katabolic and anabolic processes are going on incessant- 
ly. The play of these two processes within the cell body is 
beautifully described by Max. VeRworn (’99). He says ‘‘The 
cell receives certain substances from the outside ; of these some 
(a) upon meeting substances already present in the protoplasm, 


Hata, Speval Ganglhon Cells. 43 


undergo decomposition and synthesis. Of the substances re- 
sulting from these transformations some (b) are at once ex- 
creted as useless, others (c) remain in the protoplasm and are 
there employed further, while a third class (d) is passed on to 
the nucleus. The nucleus, moreover, obtains a portion of the 
substances (e) received from the outside and passed on un- 
changed through the protoplasm. The substances (de) enter- 
ing into the nucleus there undergo on their part certain trans- 
formations, from which again substances result; these in 
part (f) are given off to the outside without being changed by 
the protoplasm, in part (h) pass to the protoplasm to find there 
further employment, and in part (g) remain in the nucleus 
itself. If, now, we realize that every arrow represents a sum 
of substances, that the substances passing from the nucleus to 
the protoplasm undergo transformations as well as those enter- 
ing from the outside, and that the substances arising from these 
transformations are in part conveyed again to the nucleus, we 
obtain an approximate idea of how close the metabolic connec- 


sy 


tion of the nucleus with the protoplasm is. 


Text-figure 7. Scheme of cell-metabolism (VERWORN) 

All these changes illustrated by VERWoRN may be traced 
also within the nerve cells. It is, however, always difficult to 
correlate physiological phenomena with histological structure, 
but from the present studies on the nerve cells, sufficient evi- 
dence has been obtained to make some application of the his- 
tological facts to the physiological phenomena in the nerve cells. 


44 Journal of Comparative Neurology and Psychology. 


For instance, as I have already mentioned, in an earlier stage of 
the cell life, the first Nrsst granules are derived from the nucleus 
either by diffusion or extrusion, some of them changed, while 
others remain unchanged. The changed granules are utilized 
in part for the formation of the cytoplasm and in part during 
this process are returned to the nucleus or excreted as waste. 
While in the adult nerve cells, the dissolved nucleins are trans- 
formed into the Nisst granules, ground substance, pigment, 
oxyneutrophile granules (Marinesco, ’02), amphophile gran- 
ules (O_mER, ’O1), neurosomes (HELD, ’95), etc. All the 
structures given above differ from one another morphologically 
as well as chemically, thus indicating that the nucleins in the 
nucleus, after they have been brought into the cytoplasm are 
transformed there. This corresponds with the scheme of VER- 
WORN. 


SUMMARY. 


The following is a summary of the main facts given above : 

(1) Ata very early stage of the spinal ganglion cells of the 
~white rat, pseudopodia-like processes are formed from the nu- 
cleus and extend towards the protoplasmic process. The mem- 
brane of the pseudopodia is perforated. 

(2) Through these perforations the astral rays of the cen- 
trosome, which lies near the nucleus and is enclosed by the 
pseudopodia, penetrate into the nucleus and become continu- 
ous with the linin network. 

(3) The Nisst granules, when first formed, are derived 
either by the diffusion of the nucleins from the nucleus or by 
a migration of the accessory nucleoli into the cytoplasm. 

(4) The materials for the formation of the nuclein are ab- 
sorbed into the nucleus by means of the pseudopodia. These 
materials are collected from the periphery of the cell body to 
the center of the centrosome by means of the astral rays 
and then again through these rays they are conveyed toward 
the pseudopodia. 

(5) At an advanced foetal stage, as well as in the adult, 
the nucleins are enclosed within the nucleus in a dissolved con- 


Hata, Spenal Ganglion Cells. 45 


dition, as is shown by the technique for the detection of P. and 
Fe. These nucleins pass into the cytoplasm by diffusion. The 
diffusion occurs most actively from the two poles of the oval 
nucleus. 

(6) The changes in the nerve cells in pathological condi- 
tions or after excessive stimulation may be regarded as the re- 
sult of hyperactivity since similar changes are observed nor- 
mally in the cells during the period of most active growth. 

(7) A return of the Nisst granules as such from the cell 
body to the nucleus by means of the astral rays (HOLMGREN) 
was not observed in the case of the white rat. 

(8) A formation of the neuroglia nuclei from the migrated 
accessory nucleoli (ROHDE) was not observed. 

(9) There is not the slightest evidence to favor the recent 
theory presented by Krontuar, who believes that the nerve 
cells are built up from leucocytes. 


BIBLIOGRAPHY. 


Biervliet, J. Van. 
700. La substance chromophile pendant le cours du développement de 
la cellule nerveuse (chromatolyse physiologique et chromolyse expér- 
imentale). Nevraxe, Vol. I. 
Bihler, A. 
795. Protoplasmastruktur in Vorderhornzellen der Eidechse. Verhandl. 
ad. Phys. med. Ges. Wiirzburg. Bd. XXIX, T. 3-5. 
98. Untersuchungen iiber den Bau der Nervenzellen. Verhandl. a. 
Phys. med. Ges. Wirzburg, N. F. Bd. XXXVILI. 
Dell’lsola. 
700. Le modificazioni evolutive della cellula nervosa. /»termationale 
Monatschr. f. Anat. u. Physiol., Ba. XVII. 
Dumey, R. 
702. Rapports du cytoplasme et du noyau dans l’oeut de la Cytherea 
cione L. La Cellule. Tome XIX, F. 2. 
Eycleshymer, A. C. 
"02. Nuclear changes in the striated muscle of Necturus. Amat. Anz. 
Bd. XXI. 
Hatai, S. 
701. On the presence of the centrosome in certain nerve cells of the 
white rat. Journ. Comp. Neurol., Vol. XI, No. 1. 
701. On the mitosis in the nerve cells of the cerebellar cortex of the foetal 
cat. /Journ. Comp. Neurol., Vol. X1, No. 4. 


46 Journal of Comparative Neurology and Psychology. 


Hodge, C. F. 
792. A microscopical study of changes due to functional activity in nerve 
cells. Journal of Morphology, Vol. VII, No. 2. 
Hermann, F. 
788. Ueber regressive Metamorphose des Zellkerns. Anat. Anz , Bd. III. 
Herrick, F. H. 
795. Movement of the nucleolus through the action of gravity. Anat. 
Anz., Bd. X. 
Hoffmann, R. W. 
702. Ueber die Ernaihrung der Embryonen von MNassa mutadtlis, Lam. 
Zettsch. fiir Wiss. Zool., Ba. LXXII. 
Holmgren, E. 
799. Zur Kenntniss der Spinalganglienzellen von Lophius prscatorius, 
Lin. Anat. Hefte, Bd, XII. 
700. Studien in der feineren Anatomie der Nervenzellen. Anat. Heft., 
Bd. XV. 
Kolster, Rud. 
701. Ueber Centrosomen und Spharen in menschlichen Vorderhorn 
zellen. Deutsche Zettsch. fiir Nervenhewlk., Bd. XX. 
701. Ueber Centralgebilde in Vorderhornzellen der Wirbeltiere.  Azzat. 
FHeft., Bd. XVI. 
Korschelt, E. 
791. Beitraige zur Morphologie und Physiologie des Zellkerns.  Zoo/. 
Jahrb. Anat. u. Ontogente, Bd. IV. 
Kronthal, P. 
702 Von der Nervenzellen und der Zelle in Allgemeine. Jena. 
Levi. 
’96 Contributo alla fisiologia della cellula nervosa. ev. dt Pat. nerv. e 
ment. No. V. 
Macallum, A. B. 
95 On the distribution of assimilated iron compounds, other than hae- 
moglobin and haematins in animal and vegetable cells. Quar. Journ. 
of Microscp. Science. Vol. XXXVIII. 
798 On the detection and localisation of phosphorus in animal and veg- 
etable tissues. Proceedings of Roval Soctety of London. Vol. LXIII. 
Mann, G. 
795 Histological changes induced in sympathetic, motor and sensory 
cells by functional activity. Journ. Anat. Physiol. London, Vol. 
XXIX. 
702 Physiological histology, methods and theory. Oxford. 
Marlinesco, G. 
799 Etudés sur l’evolution et l’involution de la cellule nerveuse. ev. 
Neurol., No. 20. 
703 Réchérches sur les granulations et les corpuscles colorables des 
cellule du systéme nerveux central et périphérique. Zettsch. Alleg. 
Physiol., Bd. III. 


Haral, Spenal Ganghon Cells. 47 


Mathews, A. P. 
’99 The metabolism of the pancreas cell. /ourn. of Morphol., Vol. 
XV, Suppl. 
Montgomery, T. H. 
798 Comparative cytological studies with special regard to the morph- 
ology of the nucleolus. Journ. of Morphol., Vol XV, No. 2. 
Nelis, Charles. ; 
700 L’apparition du centrosom dans les cellules nerveuses au cours de 
Vinfection rabique. Mevraxe, Vol. I. 
Pugnat, C. 
798 Des modifications histologiques de la cellule nerveuse dans ses divers 
états fonctionnels. Bzbliographie anatomigue, T. VI. 
Rohde, E. 


795 Ganglionzellkern, Achsencylinder und Punktsubstanz. Arch. f. 
mikr. Anat. 
796 Ganglionzellkern und Neuroglia. Ein Kapital iiber Vermehrung 
u. Wachsthum von Ganglienzellen. Arch. mtkr. Anat. 
798 Ganglienzelle. Zeztsch, Wiss. Zool. 
703 Untersuchungen iiber den Bau der Zelle. 1. Kern und Kernkorper 
Zettsch. Wiss. Zool., Vol. LXXIII. 
scott, F. FH. 
798-’99 The structure, micro-chemistry and development of nerve cells 
with special reference to their nuclein compounds. 7vansactions of 
Canadtan Institute, Vol. VI. 
Sjovall, E. 
703 Die Nervenzellenverinderungen bei Tetanus und ihre Bedeutung. 
Jahrb. f. Psychiatrie und Neurologie. 
Verworn, N. 
799 General physiology. English translation, Te Macmillan Co. 


‘ 


EXPLANATION OF THE FIGURES. 


The following figures are free-hand drawings using Zeiss Oc. 4+Obj. 
1-12. 

a, centrosome ; 4, amoeboid processes ; ¢, basophile granules ; d, acidophile 
granules ; ¢, accessory nucleolus. 

Fig. 7 to Fig. 6, Spinal ganglion cells of foetal white rat. 

Fig. 7 and Fig. 8, Celis in ventral horn of adult white rat. 


PEATE, TM 


Fig. 7, Stained with BIONDI-EHRLICH’S tricolor. 

Fig. 2, Treated with Macai.Lum’s technique which shows the distribu- 
tion of iron. 

Fig. 3, Stained with BIONDI-EHRLICH’s tricolor. 

Fig. 4, Stained with HEIDENHAIN’s iron-haematoxylin. 


48 Journal of Comparative Neurology and Psychology. 


PLATE IV. 


Fig. 5, Stained with BlonDI-EHRLICH’s tricolor. 

fig. 6, Stained with BIONDI-EHRLICH’s tricolor. 

Fig. 7, Treated with MACALLUM’s technique which shows the distribution 
of phosphorus. 

Fig. 8, Stained with HAIDENHAIN’s iron-haematoxylin. 


Plate III. 


Journal of Comparative Neurology and Psychology, Vol. XIV. 


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Plate IV. 


Journal of Comparative Neurology and Psychology, Vol. XIV. 


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Fig. 7 


AN ESTABLISHMENT OF ASSOCIATION IN HERMIT 
CRABS, EUPAGURUS LONGICARPUS. 


By E. G. Spautpinc, Ph. D. (Bonn). 
College of the City of New York. 


Introductory. 


The experiments described in this paper are the result, 
first, of preliminary observations of a number of hermit crabs 
kept for some time in an aquarium at the Woods Hole Labora- 
tory, which showed them to be quite capable of profiting by 
experience. In fact, the results first obtained were in general 
quite confirmatory of those obtained by the subsequent more 
systematic investigation, the method for which they indicated. 

BeTHE' and YERKES’ have each made experimental studies 
of habit formation in the Crustacea, the former on the crab, 
Carcinus moenas, the latter on the crawfish, Cambarus affinis, and 
on the green crab, Carcinus granulatus. BrTHE at the end of his 
paper relates some experiments made to determine whether or 
not the crab possesses psychical processes, with the result that 
he asserts that it does not. This conclusion is not, however, 
necessarily to be accepted even from BETHE’s own experiments, 
for the reason that these at best serve to demonstrate the ab- 
sence of only one kind of psychical phenomena, viz., those of 
inhibition or control; other kinds may be present. BETHE 
himself does not recognize that the method he employed was 
defective in this respect, but an account of it will, we think, 


1 BETHE, A., Das Centralnervensystem von Carcinus moenas. Archiv f. 
mikr. Anat, Bd. 51, 1898. 


27 YERKES, ROBERT M. and HuGGins, Gurry E. Habit Formation in the 
Crawfish, Caméarus afinis. Harvard Psychological Studies, Vol. 1. 1903. 


YERKES, ROBERT M. Habit Formation in the Green Crab, Carcinus gran- 
ulatus. Biolog. Bulletin, Vol. I11. 1902. 


50 Journal of Comparative Neurology and Psychology. 


make evident the justification of our criticism. His frst ex- 
periment was to place a crab in a basin in the darkest corner of 
which there was an Eledone (a cephalopod). The crabs, be- 
cause of their instinct to hide, moved immediately into this 
corner and were seized by the E/edone. Freed from its grasp 
one crab returned repeatedly five times, another six, to the dark 
and the enemy, showing, as BeETuHE thinks, that it had not 
profited by experience. It is to be emphasized, however, that 
to have done this latter in the way Berue thought possible, it 
would have been necessary that the crab zz/zdz¢ its instinctive 
action. This inhibition could take place only if, first, a xepre- 
sentation of the pain of the seizure by the Aledone were present, 
and second (and essentially), if the representation were the 
‘‘stronger’’; the other possibility, that the representation should 
occur and yet be overcome by the instinct, is accordingly not 
disproved by BETHE’s experiment. The same criticism applies 
also to his second method that, notwithstanding maltreatment 
on each such occasion, the crabs repeatedly seize food when 
offered. 

The criticism above made is quite in agreement with that 
principle of method for comparative psychology which is in re- 
ality very simple, but not always observed, that in any instance 
where the question of the presence of consciousness in any 
species is admittedly to be decided by experimentation, this 
question must take a particular form, and our efforts must be 
directed to the establishment of the presence or absence of 
some definite kind of consciousness, e. g., associative memory 
between constructs of two sense fields, conceptual reasoning, 
CLG: 

YERKES in his experiments with the crawfish made use of 
the labyrinth method. The subject could escape from a box 
into the aquarium only by ‘‘choice of a certain passage.’’ The 
‘‘choice’’ consisted in or was manifested by learning (by repeat- 
ed experience) to avoid the blocked passage and gain the 
aquarium by the most direct path. Accordingly all conflict, 
requiring inhibition, between the two elements or ‘‘constructs” 
to be associated, viz., ‘‘correct path’ and ‘‘aquarium,”’ was ab- 


SPAULDING, Assoctation in Hermit Crabs. 51 


sent. ‘‘Correct path,’ as opposed to the incorrect, logically 
implies in these experiments ‘‘aquarium”’ ; and its selection, as 
shown by the ratio of improvement from day to day may, 
though not necessarily, imply the representation of the con- 
struct ‘‘aquarium,’’ but it does demand the admission that acts 
of recognition and discrimination, or even of what Lroyp Mor- 
GAN calls ‘‘perceptional inference’ take place. These in turn 
presuppose necessarily, as is well known, retention and pro- 
duction. 

Carefully excluding the possibility of the crab’s merely 
following a path by smell, taste, or touch (although if it did 
only this one could not account fora correct after an incorrect 
choice had once been made) YERKES found in one case that 
after 40, in another that after 250, experiences no mistakes in 
choosing were made. Ina number of cases the subject turned 
from, before it reached, the partition which blocked the pass- 
age, thus showing the important part played by weszon in direct- 
ing the animal in the absence of smell, taste, and touch. All 
of these, however, together with muscular sensations, YERKES 
concludes xormally play a part in the formation of labyrinth 
habits. These experiments therefore seem to show that upon 
the basis of the ‘‘constructs’’ which one sense alone, viz., vis- 
ion, give the crab, a consistent selection of the correct path is 
possible; but this is explainable it seems, even if it is consid- 
ered that only a recognition of each successive part of that path 
and consequently a discrimination between it and the incorrect 
is made, and yet that no sepresentation or ‘‘reconstruction’’ of 
“aquarium” takes place, although of course this latter interpre- 
tation is not excluded. 

A method of experimentation, however, which shows that 
in the formation of a habit, or in the learning of a motor reac- 
tion involving two sense fields, e. g., taste and vision, it is nec- 
essary to overcome an instinct or tropism in the opposite direc- 
tion, such a method, we think, would at least give more cogent 
grounds for accepting the presence of representation than one 
not doing this, although even here conservatism in making this 
claim would be the safer course. 


52 Journal of Comparative Neurology and Psychology. 
Some Characteristics of the Hermit Crab. 


The genus Zupagurus is easily found in the shallower waters. 
about Woods Hole and is represented by four species, /onxgz- 
carpus, annulipes, acadianus, pollicaris. k. longicarpus was se- 
lected for the present investigation on account of its convenient 
size (34-1% inches in length) for aquarium purposes, and be- 
cause of a manifestly greater brightness. Supplementary ex- 
periments show that #. pollcaris, e. g., learns with greater 
difficulty. 

Members of the entire genus inhabit, under normal condi- 
tions, the shells of gastropods, by which the abdomen is com- 
pletely protected, the cephalothorax alone protruding. This 
peculiar mode of life is correlated with a dextral asymmetry, 
which extends to almost all the organs of the entire body, and 
which shows a very nice adaptation. This favors the view that 
the asymmetry is a result of life in dextrally spiral: shells, ex- 
emplifying at the same time degeneration. 

The establishment of the fact that these Hermits learn is 
not surprising in view of the complexity and fineness of their 
physiological sense apparatus, which is essentially the same as 
that of all the Crustacea, so that it is very probable that any 
denial of this ability to any species of the group, even upon the 
basis of experiment, is due to incomplete or faulty methods 
of investigation. 
Sense Organs. 


The crab has only two general kinds of sense organs, viz., 
eyes and sense hairs, the latter of which are, however, differ- 
entiated as to their function. These hairs, which are found in 
all the extremities, are epithelial in nature, and are not pene- 
trated by a nerve, but rather this latter spreads out underneath 
each epithelial group and gives to each cell a fibril. These 


7h and 


epithelial sense cells lie in a support of ‘‘Matrixzellen,’ 
according to variations in their structure and especially position 


are respectively gustatory, tactile, and auditory or ‘‘equilibra- 


4 
1 vom RaTH, Orre. Zoologischer Anzeiger, No. 386, 1892. 


SPAULDING, Association in Hermit Crabs. 53 


tory.”’ The gustatory hairs, lie as two patches of ‘‘minute curi- 
ously flat organs” on the under surface of the outer filament of 
the antennules, the innermost appendages, which observation 
shows are kept moving constantly. There are no sense organs 
in the mouth.’ 

At the basis of each antennule is a little sac formed by an 
infolding of the chitinous integument, communicating freely 
with the water, and containing little sand grains or otoliths. 
Here are present a second kind of sensory hairs, connected 
with the central nervous system by branches of the antennulary 
nerve, and whose function is either that of audition or of equi- 
librium.?. The third class of hairs are tactile in function, and 
are especially numerous on the antennae, 1. e., the second pair 
of appendages, although there are some on the antennules, the 
other appendages, and the remaining integument. 

The two eyes of the crab are compound or facetted and are 
seated on movable pedestals. They are covered by a transparent 
chitinous cuticle, forming a cornea; this is divided into facets, be- 
neath each of which there is an ommatidium with two segments 
(a) an outer, which is vitreous and refractive, and an inner, a 
short retinula, which is sensitive, thus giving a structure analo- 
gous to rods and cones. These cones are surrounded and so 
separated from each other by a pigment; their apex is em- 
braced by elongated cells in the midst of which is a fibril of the 
optic nerve. Each facet functions as a single eye and therefore 
like the vertebrate eye gives no sensitive continuum but, rather, 
‘mosaic vision,” i. e€., various images in juxtaposition. The 
eye as a whole is supposed to give a vision of distinct objects 
and space relations. 

The brain is formed from the first three pairs of embryonic 
ganglia, and is therefore a ‘‘syn-cerebrum’’; it supplies the eyes, 
the antennules and the antennae with nerves. It is connected 


lvom Ratu, Orro. Zur Kenntniss der Hautsinnesorgane der Crustaceen, 
Zoologischer Anzetger, 365, 1891. 


4 HENSEN (Studien tiber das Gehoérorgan, Zeétsch. f. wiss. Zoolog., Bd. 13, 
1863) says they are auditory, while DELAGE, Archiv. d. Zool. Expér., 1887, (2), 
T, 5, says they are for position and qeuilibrium. (‘ited by vom RATH.) 


54 Journal of Comparative Neurology and Psychology. 


by two oesophageal branches with the central nerve cord, which 
is represented principally by a single large thoracic ganglion or 
concrescence of ganglia. The thoracic portion of the nervous 
system is, however, symmetrical. The mandibles, or the third 
pair of appendages, crushing jaws, the right of which is larger, 
the maxillae and the manillipeds all receive nerves. The nerv- 
ous system is therefore in general so constructed that it would 
seem at least reasonable to expect that associations might be 
formed. 


Experimental 


The systematic experiments by which the association be- 
tween the ‘‘constructs” of two sense fields, taste and vision, 
was eStablished, and a ‘‘reconstruction”’ or reproduction subse- 
quently shown possibly to take place, were preceded by various 
preparatory observations, some of which were made in the sum- 
mer of 1902. For instance, it was then shown that the Hermit 
is remarkably ¢hzgmotactic, for when a shell inhabited by a crab 
is suspended at the distance of about twice the diameter of the 
shell from the floor of the aquarium, the animal is thereby made 
decidedly uncomfortable, protrudes nearly its entire body, feels 
about, and usually leaves its shell, especially if there is a vacant 
shell near by. Suspended at the height of from eight to ten 
inches the crab will remain in the shell until it dies. They are 
also somewhat rheotactic. New shells thrown into the aquarium 
are soon examined and accepted at what would sometimes seem 
_to be a disadvantage. This constant ‘‘desire”’ for change, to- 
gether with both a great natural rapacity and pugnacity, are in- 
deed indications of a strenuous life even among Hermits. 

Both that series of observations upon which special empha- 
sis is placed in this paper, and that preliminary one which 
showed that the method adopted would probably lead to satis- 
factory results, were made with a very simple apparatus and in 
a very simple way. A number of crabs which had been kept 
in an ordinary laboratory glass jar aquarium about twenty inches 
in diameter, were made to go into a darkened portion of this 
that they might get their food, which consisted of a_ freshly 


SPAULDING, Association in Hermit Crabs. 55 


cleaned Fundulus held in place ona wire. The same portion 
of the aquarium was darkened each time just before feeding by 
setting down into the constantly running water a screen consist- 
ing of two thin boards fastened at right angles, leaving only an 
opening at each end of the vertical board wide enough for the 
crabs to go through one by one; around the outside of the 
aquarium from end to end of this portion set off by the screen 
was kept a piece of heavy brown paper to shut out the light 
coming from the other direction. The only light which could 
enter came therefore through the openings at each end. Sand 
was placed in the bottom of the aquarium, and all the condi- 
tions such as its position and that of the tap, with the exception 
of the putting in and taking out of the wooden screen, were 
kept constant during the entire series of experiments. 

These were conducted in detail as follows: to establish, 
first, an association and, second, present an occasion for possible 
‘‘reproduction” from the ‘‘after-effect’’ of one by the external 
stimulus of the other ‘‘construct.” 

Thirty-six crabs of the species Eupagurus longicarpus were 
placed in the aquarium on July 30th, and, first, allowed until 
August 6th to become accustomed to aquarium conditions ; 
during this period they were simply fed each day with a fresh 
Fundulus, no screen being used; they seized their food most 
eagerly, oftentimes fighting and driving each other away from 
it. The death of six selected the thirty most fit individuals. 
The crabs were, furthermore, observed to remain in the Aghtest 
part of the aquarium practically all of the time, i. e., they 
were positively heliotropic. The positive heliotropism was con- 
firmed by a number of control experiments with other lots and 
by that of Aug. 6th. Thescreen was inserted and all the crabs, 
30 in number, placed behind it. In 10 minutes 28 had gone 
through the opening into the light and 27 of these were near 
the point of its maximum intensity. 

Each day following this, the screen was inserted, a fish on 
a wire placed in the darkened portion, and the number of crabs. 
going into the dark through ether one of the entrances at the 
end within a given time, which was constantly shortened during 


56 Journal of Comparative Neurology and Psychology. 


the series, counted. A crab going in and coming out again 
was counted as zz, but in every case by far the greater number 
that had entered remained behind the screen as long as the food 
was there. Two stimuli to two different senses, taste and vis- 
ion were thus simultaneously and contiguously presented; and 


if this led to an association between the two ‘‘constructs, 


” 


“food” and ‘‘screen-darkness,”’ it would necessitate the over- 
coming of the natural positive heliotropism manifested at the 
start, and by contrast on this background the association would 


stand out more prominently. After the crabs were fed each 


EXPERIMENT I. > 


Lot 2, Eupagurus longicarpus. 


Total No. No. entering. Per cent. Time. Percent. ini14 

Ist day 30 3 IO 15/ .66 

2d day 30 14 46 2043 2/3 

3d day 30 15 50 7S .66 

4th day 30 20 66+ 1 4.4 

5th day 30 Done 83 BC 16.6 

6th day 30 27 90 54 18, 

7th day 2 26 96 Bo B32. 

8th day 20'* 28 97 Bi Ig.+ 


1 This long time was granted in order, if possible, that the crabs might 
ultimately find their way 77 as a result, perhaps, of merely wandering around 
in their evident endeavors to localize the source of the taste stimulus, which in 
every case caused considerable agitation. The varying length of time used 
throughout the series was a matter of dest adapting the means to the end. Thus 
it was quite justifiable to shorten the time later to 3% if the majority of the 
crabs went through the openings in that time, although to do this would give 
manifestly more favorable results than to wait longer. 

2. On this 5th. as well as on each successive day up to the gth. it was 
noticed that as soon as the screen was put in, and the fish was placed behind it, 
the crabs were much agitated and some started for the openings, 

3 The three that did not go in on the previous day had been removed for 
the purpose of determining if possible if there was already a certain perma- 
nency of habit among the twenty-seven entering; the result was confirmatory. 
The three were then returned. 

* One had died. 


day under these conditions, fish and screen were removed, and 
the latter was carefully washed with running sea water, as it 
was also each time just before using. After a few days of this 
treatment immediately upon the insertion of the screen the 


SPAULDING, Association in Hermit Crabs. 57 


crabs became most agitated, some hurrying and scurrying about, 
others making almost directly for one of the openings. A prefer- 
ence for the right-hand one seemed to exist and this may be con- 
nected with the right-handed asymmetry. No attempt however 
to investigate this matter systematically was made, and there 
were no ‘“‘landmarks”’ in the aquarium, such as stones, etc., where- 
by a path could be learned. The preceding tabulated results 
show, (1) the total number each day, (2) the number going 
into the dark within (3) a certain time, when fed under the con- 
dition named, (4) the per cent. entering, and (5) for compara- 
tive purposes, the per cent. entering in one minute. 


EXPERIMENT (CII. 


Lot 2. 
Total Number Per cent. Ti Per cent, 
number. entering. entering. aes in 17 
gth day 28 { eo \ 24 86 Baa W752 
roth day 28 22 79 ae Wee 
Iith day 28 26 93 5a 18.6 
12th day 28 25 $9 x 8 17.8 
13th day 27 25 93 a 31 
{ inand ) vie 
away, of 73 \ remained eae 3 Bes 
15th day 2 24 89 Be 29.6 
16th day 2 22 82 30 27e3 
17th day 27 22 82 3x S73 
18th day 27 22 82 BG 27e3 


' At the end of the 5’ the fish was put behind the screen in order that 
the association might not be broken up by the crabs entering and finding noth- 
ing there. When this was done all but one of the eight outside, four of which 
had gone in and come out again, entered within 2’. This was done each suc- 
cessive day. 

2 Then fed, and in 1’ all but one had entered. This shows again the con- 
stant improvement, the learning taking place in a surprisingly short period. 

3 In one minute after feeding all of the seven outside had entered. 

4 After feeding all entered in 114’. 

> After feeding all but one entered in 2’. 


Accordingly, after the 8th. day, evidence having been thus 
secured that an association between the two ‘‘constructs,’’ food 
and sense-darkness, had been established, its efficiency was 


58 Journal of Comparative Neurology and Psychology.” 


further tested by simply putting in the screen with no fish be. 
hind it, and the record of the crabs entering was taken in the 
same way as before. The results are tabulated above. 

These results, if confirmed by control experiments, must, 
we think, be accepted as showing conclusively that the Hermit 
crab of the species /oxgicarpus, firstly, forms an association be- 
tween two sense-constructs, which, secondly, can be interpreted 
as showing that the crab, subsequently, when only one stimulus 
is presented, reproduces an image of the other. The same reac- 
tion, entering the dark, which previously demanded two stimuli, 
is later secured with only ove stimulus; the other therefore 
must either be excited or reproduced. We may say perhaps 
that if, when only the screen is put in as in the second series, 
only visual perception or recognition takes place, then there is 
no reason why the crabs should not remain where they are, in 
the light, which is their natural preference. The screen, which 
they now recognize, has however through association come to 
mean for them other than something to be avoided; it means 
‘food,’ and this meaning is present when the food is not. The 
difference between YERKES’ experiments and these consists, 
therefore, in this, that YERKES’ crabs ‘‘acquired the habit” of 
going by a correct path from a place disliked to a place liked ; 
the Hermits on the other hand go from a place liked to a place 
naturally disliked, but ‘‘artificially” liked because of food either 
there or—may we say—‘‘expected” to be there. This must 
mean that an associative element at first external, i. e., physical, 
but now no longer ¢hat, is, nevertheless, now present as znfer- 
nal, and its internal presence must be due to either an excita- 
tion or a reproduction by the other stimulus. If the latter, 
then the Hermit may be said to remember vaguely, i. e., to 
veconsti uct. 

These conclusions are strengthened by the following con- 
trol experiments: 

EXPERIMENT III. 

Lot 4. Aug. 20th. Forty crabs in a similar aquarium ; 
the same screen was used, carefully washed each time. The 
previous procedure was reversed here, by placing the crabs be- 


SPAULDING, Assocation in Hermit Crabs. 59 


hind the inserted screen first, and feeding in the light. From 
the data already obtained it would be expected that in this a 
greater per cent. of crabs would from the start make their exit 
than had in the first experiment made their entrance. This 
proved to be the case as the following record shows: 


Number of crabs. Exit. Per cent. Time. Per cent. in I’ 
40 34 85. af 17. 
40 36 go. Re 30. 
40 35 87.5 Se 17.5 
40 35 85. se 17. 
40 34 85. Le 17. 


Comparison of this with Experiment I shows that not until 
the 5th. day was as high a ratio approximately obtained. In 
both cases of course the crabs are guided by taste; the two ex- 
periments together, therefore, serve to demonstrate the natural 
preference for the light, and the quicker results obtained when 
this works with than when against the feeding instinct. 


EXPERIMENT 1V. 


Lot 3. This same preference was demonstrated by a sec- 
ond control experiment. Twenty-four crabs were placed ina 
large rectangular aquarium directly next to a window witha 
northeast exposure. Half of the aquarium was darkened by 
holding down with a stone a box with one end taken out. Sand 
was placed over the entire bottom. 

Twenty observations failed to discover a single crab inside 
the ‘dark line® from j)edge to edge of: the box. ~The crabs, 
therefore, seem to prefer the light to the darkness, at least in 


the aquarium. 
EXPERIMENT V. 


Lot 6. A third very similar control experiment was also 
confirmatory. Thirty crabs, the aquarium jar and screen ex- 
actly as in Experiment I were employed. The question might 
arise, would not the crabs possibly ‘‘learn’’ to go behind the 
screen when this was inserted even though no fish was there, 
the necessary feeding being done at other times. Should they 
do this the conclusions from Experiment I would be quite 


60 Journal of Comparative Neurology and Psychology. 


worthless. The results were that they would not enter. Zen 
observations were made; in seven of these cases no crab (with- 
in 5’) went further than to the edge of the entrance, which had 


= My gs 


in no experiment been counted as ‘‘in’’; of the three other 
cases, within the period of 5 minutes, 5, 8 and 5, respectively 


entered, but there was no evidence of progress. 


ADDITIONAL EXPERIMENTS- 


Maze Experiment. Can the Hermit learn to go through 
a maze for its food? A simple maze was constructed of thin 
boards in such a way that it was necessary for the-crabs, 16 be- 
ing used, to enter at one end, go through to the other, enter 
the second passage, go back to the other end and enter the 
food compartment, The crabs were first given an opportunity 
to ‘‘become acquainted” with the maze by leaving it in the 
aquarium about two hours. The next day this was repeated 
with the result given in the first line of the table. The results 


are as follows: 


Total No. Successful. Per cent ‘*ins7? Time. Average in I” 
16 All 100 go” 9 
16 13 81 45/ 1.8 
16 16 81 Sint 1.47 
16 15 94 30° 3-13 
16 8 50 307 1.66 
16 15 94 45¢ 2.09 
16 14 85 30” 3.93 
14 (2 died) 13 93 307 2st 


This experiment was not conducted as carefully as it would 
be possible to make it; the crabs could not be watched all of 
the time, but only occasional observations and a record, as the 
above, at-astated time, made. The results showed, however, 
though perhaps not as clearly as might be desirable, that an im- 
provement had taken place, and they have a value, as being in 
general confirmatory of the first experiment. 


Conclusions. 


The Hermit Crab, Aupagurus longicarpns, is capable of 
puofiting by experience, in a rather short time, by associating 


SPAULDING, Association ir Hermit Crabs. 61 


the ‘‘constructs” of two ‘‘sense flelds,’’ vision and taste. The 
existence of this association is proved by its effectiveness in 
subsequently bringing about, with only one stimulus presented, 
the same reaction against a natural positive heliotropism, as pre- 
viously occurred with two stimuli present. The reaction here 
is therefore conditioned zzternally, as well as externally. The 
internal condition must be identical with either the excitation 
of, or with that and the reproduction from the ‘‘after-effect’’ of 
the second, the ‘‘taste-stimulus;” if there is only excitation 
then the internal event is only physiological ; if there is also re- 
production then it is psychical as well as physiological. 

Both interpretations agree equally well with the data ob- 
tained, for the reason that even in the second case there must 
be a physiological basis for the psychical events if present, and 
consequently, the two being quite compatible as ultimately reg- 
ular and uniform series of events, there is theoretically no cer- 
tain objective criterion for the presence here of consciousness. 

Practically there is, however, such an objective criterion 
which we make use of in our intercourse with other men, and 
if the above data are interpreted in as strict analogy to this as 
possible, it seems justified to consider that the Hermit Crab 
‘‘reproduces”’ or, if one will, remembers vaguely. 

The author, as a holder of one of its ‘‘research rooms’’ at 
Woods Hole wishes to acknowledge his indebtedness to the 
Carnegie Institution for the opportunities thus presented for the 
carrying on of this and other investigations. 

Jan. 12, 1904. 


EDITORIAL, 


L’ -ENVOI. 


The change recently announced and, by the appearance of 
this number, placed in process of realization means much to 
the writer. It means, among other things, the fulfillment of a 
cherished desire and the realization of hopes which led to the 
founding of the /ournal of Comparative Neurology at a time 
when the prospect of either scientific or material support 
seemed very small. The small but growing band of investi- 
gators in this country were much better than their promise in 
supplying material and in supporting the enterprise from the 
start. In spite of the fact that the specific purpose of the 
venture was realized only in part, a fact partly to be accounted 
for by the long-continued incapacity of the writer, it is believed 
that the thirteen years of the existence of the /ournal have not 
been entirely unfruitful. 

It seems not inappropriate that the writer should avail - 
himself of this occasion, apparently so full of promise for greater 
usefulness in the future, to express his personal gratitude for the 
unselfish toil which has been expended by the numerous col- 
laborators on the staff during a period of nearly ten years, dur- 
ing which care on his part has been impossible and his own re- 
sponsibility of the most perfunctory kind. To my brother, 
Professor C. Jupson Herrick, especially, who has carried the 
administrative and editorial responsibility, much of the time with 
little or no assistance, and on whom the financial burden has 
too largely fallen, the /owrnal owes its continued existence and 
the new lease of life to which we now look hopefully forward. 
Thanks are due also to the many others, both in this country 
and abroad, who have actively shared in the responsibilities 


Editorial. 63 


and have contributed from their original material, as well as to 
the numerous friends who at this emergency have contributed 
money to enable us to enlarge at once, pending the substantial 
increase in circulation which is already in progress. 

At the time the earlier numbers were issued there was 
little of that camaraderze and acquaintance among the widely 
scattered workers in this, as in many other lines, which now is 
one of the pleasant and encouraging features of scientific work. 
With a growth of this fellowship we note with gratification the 
almost entire disappearance of the acrid or acrimonious criti- 
cism that disfigured early scientific literature in America. It is 
now possible to admit differences of opinion or to detect errors 
in the work of another without establishing forthwith a breach 
of cordial relations among the workers. Goi HERRICK. 


Kok 
* 


Structure and function are correlative concepts; neither 
is complete without the other; as cause implies effect, so func- 
tion implies structure. These are trite statements, yet it would 
seem that we can not be reminded too often that the under- 
standing of life is dependent upon our ability to correlate struc- 
tural and functional facts. It is chiefly in the interest of such 
correlation that Zhe Journal of Comparative Neurology and Psy- 
chology is published. True, there is no more reason for consid- 
ing the psychic process a function of the nervous system, than 
for calling the brain a function of consciousness ; but, this aside, 
animal behavior and the functions of the sense organs and cen- 
tral nervous system are dependent upon neural structures, and 
it is these which most concern us. A survey of modern re- 
search literature shows clearly that those investigators have 
been eminently successful who have studied structure and func- ° 
tion at the same time. To the physiology of the senses vastly 
more is contributed by those who know form as well as func- 
tion, than by those who neglect anatomical conditions ; in anit- 
mal behavior, it is from the student who attends to anatomical 
and histological facts that a satisfactory account of the reactions 
of an organism is to be expected. 


64 Journal of Comparative Neurology and Psychology. 


Throughout the organic realm a correlation of structure 
and function is demanded. It is our aim, in Zhe Journal of 
Comparative Neurology and Psychology, to bring together 
anatomical, physiological and psychological facts in such a 
manner that their relations may appear. Thus, it is hoped, the 
specialists in structural work will be impressed by the import- 
ance of the functions of the organs which they study, while at 
the same time those whose chief concern is animal behavior 
will see more clearly that they cannot work to advantage unless 
they know wat is functioning. If we are to understand life 
we must consider the organism not as a structural unit, nor yet 
as a sum of activities, but as a functioning structure. 

R. M. YERKES. 


THE MID-WINTER MEETINGS. 


Though abstracts of the proceedings of most of the socie- 
ties, which met during convocation week have already 
been published, it may be of interest to enumerate ina single 
list the more important papers read which bear upon our prob- 
lems, as an aid to the annual invoice of scientific achievement 
which one naturally makes at this time of year. 

At St. Louis the zoological section of the American Asso- 
ciation and the Central Branch of the American Society of 
Zoologists held joint sessions at which the following papers of 
neurological interest were read: 

Further Observations on the Breeding Habits and on the Functions 
of the Pearl Organs in Several Species of LEventognatht, by JAcoB 
ReteHarp. The breeding habits of certain shiners and suckers were 
described and illustrated by instantaneous photographs. 

Phototaxis in Ranatra, by 8. J. Hotmes. Lanatra is positively 
phototactic and a great variety of reactions can be eee at will 
with mechanical precision. 

The Correlation of Brain Weight with Other Characters, by Ray- 
MOND PEARL. A statistical review of the data for the human brain. 

The Morphology of the Vertebrate Head from the View-point of the 
Functional Divisions of the Nervous System, by J. B. JoHnston. This 
paper will appear in full in this /owrna/ in the course of the current 
year. 

The Brain and Nerve Cord of FPlacobdella pediculata, by E. E. 
Hemrnaway. Wax models of the nervous system of this new leech 
were presented. The results in general confirm those of WHITMAN 
for Clepsine. 

The Mechanism of Feeding and Breathing in the Lamprey, by JEAN 
Dawson. The anatomical work was controlled by observations on 
the living animals which add to our knowledge of the habits of the 
species, notably the fact that the lamprey feeds on the soft tissues as 
well as the blood of its host. 


66 Journal of Comparative Neurology and Psychology. 


Some Reactions of Mnemiopsts leidyi, by G. W. Hunter. This 
paper will be published in this /owrnad. 

A Theory of the Fistogenesis, Constitution and Physiological State of 
Peripheral Nerve, by PoRTER E. Sarcent. To be printed shortly in 
full in this Journal. 

The Association of American Anatomists met in Philadel- 
phia. There were five neurological papers, aside from the 
memoir by Dr. WiLson which appears in our present issue. 

On the Origin and Destination of Fibers of the Occipito-temporo- 
pontine Bundle (Tiirck’s Bundle, Meynert), by E. Lixpoxn MELuuvs. 
In a circumscribed experimental lesion of the cortex of the 
temporal lobe in the monkey, involving the first and second temporal 
conyolutions projection fibers degenerated, passing by way of the sub- 
lenticular segment of the internal capsule to the pes pedunculi, where 
they occupy the external fifth (occipito-temporo-Briickenbahn, 
FLECHSIG ; sensory tract, CHARcoT and others). To reach the pes 
these fibers break through the inferior portion of the lenticular nucleus 
in small bundles, pass around the external geniculate body just above 
the point of exit of the optic tract and enter the pes external to those 
fibers which form the posterior extremity of the internal capsule as it 
passes between the thalamus and the lenticular nucleus. Instead of 
turning downward toward the pons, like the capsular fibers, they pur- 
sue a course obliquely backward and slightly downward and, after a 
very short course in the pes, disappear, apparently passing to the an- 
terior quadrigeminal body. 

The Brains of Three Brothers, by Epw. ANTHONY SPITZKA. 
Opportunities for demonstrating the influence of heredity in the con- 
figuration of the human brain are exceedingly rare; adult material 
of this kind has only once before been described and by the same 
writer before this Association three years ago in the case of the brains 
of the two distinguished physicians SeGury, father and son. It may 
be remembered that in the Sraurn brains there were found some no- 
table resemblances which could be attributed to hereditary transmis- 
sion. The writer again had the good fortune to test the question of 
encephalic morphological transmission in the brains of three brothers 
recently executed together in New York State. In the search for 
positive evidences of hereditary resemblance, only such parts of the 

cerebrum as are subject to great range of variation in different brains 
could be depended upon to support the proposition ; it was found, in 
fact, that peculiarities of anatomical configuration of this class, un- 
common enough in the general run of brains as they come to the 


The Mid-Winter Meetings. 67 


hands of anatomists, were similarly reproduced in the three brains. 
Illustrations were given. 

The Bimeric Distribution of the Spinal Nerves in Elasmobranchit 
and Urodela, by CHARLES R. BARDEEN. In those vertebrates in which 
a definite metameric segmentation is maintained in the body wall, 
both the cutaneous and the motor nerves of each segment reach their 
distribution through the myoseptum and supply structures both 
cephalad and caudad to their septum. Occasionally a single motor 
nerve fiber may be seen dividing and sending one branch to the 
myotom anterior to the septum and the other to the myotom posterior. 
Attention is called to the difficulty of reconciling these facts with a 
strict adherence to an extreme form of the neuro-muscular theory such 
as is maintained by some morphologists. 

A Description of the Gross Anatomy of the Adult Human Brain, by 
Bern Bupp GaLiauper. ‘The description was confined to the thal- 
mus and was based on forty adult brains. 

On the program of the Eastern Branch of the American 
Society of Zoologists, meeting at Philadelphia, the following 
titles, among others, were announced : 

The Physiology of the Lateral Line Organs in Fishes, by G. H. 
PARKER. ‘To appear in abstract in this /owrnal and in full in the 
Bulletin of the U.S. Fish Commission. 

A Fair of Giant Nerve Cells of the Squid, by LEonaRD W. WIL- 
LIAMS. 

The Nervous System of Lamellibranchs, by GILMAN A. DREW. 

The Origin and Function of the Medullary Sheaths of Nerve Fibers, 
by Porter E. SARGENT. To appear in full in this Journal. 

The Relation of the Size of Nerve Elements and Their Constituent 
Parts to Structural and Functional Conditions, by PORTER E. SARGENT. 

At the Philadelphia meeting of the American Physiological 
Society the following papers, of special interest to neurologists, 
were read: 

The Survival of Irritability in Mammahan Nerves after Removal 
from the Body, by W. D. Currer and P. K. Girman. Making use 
of the fact noted by other observers that the mammalian nerve re- 
tains its irritability for some time after removal from the body, the 
authors attempted to determine the duration of this survival, the vari- 
ations in irritability during the period of survival, and, lastly, the 
effect of prolonged anesthesia upon the phenomenon. Irritability 
was determined by measuring the action current of the nerve when 


68 Journal of Comparative Neurology and Psychology. 


stimulated by aseries of induction shocks. The experiments were made 
upon dogs, and the sciaties of both legs were taken for observation. 
One sciatic was removed as soon as the animal was anesthetized suff- 
ciently for the operation. ‘The nerve was placed at once in the moist 
chamber, and its action current was determined at intervals of half an 
hour, as long as a response could be obtained to stimulation. With 
the values of these ‘action currents as ordinates, a curve was con- 
structed, showing the duration and variations of irritability in the 
‘unanzesthetized nerve” during the period of observation. The other 
sciatic was left in the animal for a period of four to six hours, and 
during this time the animal was kept completely anesthetized by mor- 
phia and ether. At the end of this period, there was a considerable 
fall in rectal temperature (30°-31° C.). The anesthetized nerve was 
then removed, and galvanometric observations were made similar to 
those just described. The results obtained show that the nerve re- 
moved from the anesthetized (and cooled) animal survives for a longer 
period than that taken from the animal at the beginning of the period 
of anesthesia, the difference in time of survival being as much as four 
or five hours. A more marked difference, however, is that the 
‘‘anesthetized” nerve exhibits throughout a much greater irritability. 
The curves obtained were irregular; but that for the ‘‘unaneesthe- 
tized” nerve showsasmall increase in irritability occuring shortly after 
the excision, and soon followed by a steady decline to zero; while that 
for the ‘‘anzesthetized” nerve exhibits, as its most marked feature, a 
large and sudden increase in irritability coming on some hours after 
the excision, and followed by a more rapid fall to zero. 

The Condition of the Vaso-constrictor Neurones in ‘‘ Shock,” by W. 
T. Porter and W. C. Qurypy. The normal fall of blood-pressure 
produced by stimuli of uniform intensity applied to the central end of 
the depressor nerve was measured in the rabbit and the cat. In the same 
animals the shock was then brought on, arid the measurements repeated. 
The experiments make clear (1) that the normal percentage fall 
in blood-pressure may be obtained by stimulating the depressor nerve 
during shock ; (2) if during shock the blood-pressure be raised to nor- 
mal values by the injection of suprarenal extract or normal saline so- 
lution, and the depressor nerve be stimulated while the pressure is still 
high, the absolute fall in blood-pressure may be as great as it was in 
the same animal {before shock began. Exhaustion of the vaso-con- 
strictor neurones cannot therefore be the essential cause of the symp- 
toms termed shock. 


Demonstration of Rabbits Nerves, Showing the Effect of Ligation 


The Mid-Winter Meetings. 69 


upon Vital Staining, by 8. J. Metrzer. A single ligation of a nerve 
has no influence upon the staining of the nerve on either side of the 
ligature. When, however, two ligatures are applied, the section of 
the nerve between the ligatures remains free of color, while both ends 
are-stained. This is the case, even if the section between the ligatures 
comprises nearly the entire length of the nerve. 

The Lffect of a Subcutaneous Injection of Adrenalin on the Eyes of 
Cats whose Sympathetic Neive ts Cut, or whose Supertor Cervical Gang- 
lion ts Removed, by 8. J. Mevrzer. When the sympathetic is cut, a 
subcutaneous injection of adrenalin causes a retraction of the nictitant 
membrane, and no change is seen in the size of the pupil or the width 
of the palpebral fissure. When, however, the superior cervical gang- 
lion is removed, an injection causes a strong dilatation of the pupil, a 
considerable widening of the palpebral fissure, and a retraction of the 
nictitant membrane. 

The Delineation of the Motor Cortex in the Dog, by H. Cusine. 

Demonstration of Expressive Motions tn a Decerebrate animal, by R. 
S. Woopwortu. 


At the meeting of the American Philosophical Association 
at Princeton the paper, ‘‘An Establishment of Association in 
Hermit Crabs,” by Epwarpb G. SpauLpING, which we publish 
herewith, was read. ‘There was one paper on comparative psy- 
chology read at the meeting of the American Psychological As- 
sociation at St. Louis. | 

A Preliminary Paper on the Psychology of the English Sparrow, by 
James P. Porrer. Experiments were made with the food box, with 
SMALL’s complex maze and in other ways to determine the method of 
approaching the food, to investigate the so-called senses of number 
and of direction and the color preferences. 

A paper was read before the section of physics of the 
American Association at St. Louis, which is of some interest 
to physiologists, especially when taken in connection with the 
physiological experiments of NaGet on the rate of diffusion of 
odors and savors in water. 

The Rate of Propogation of Smell, by JOHN ZELENY. Attention is 
drawn to the extreme slowness of diffusion of odors in air tubes where 


convection currents are avoided. The time required for the diffusion 
of odors is roughly proportioned to the square of the distance. 


LIPERARY NOTICES: 


Animal Education.! 


Under this title Dr. Warson has published the results of a study 
of the white rat made for the purpose of correlating the psychical de- 
velopment with the growth of the nervous system. The work is natu- 
rally divided into three parts: (1) an experimental study of the 
psychical development; (2) an histological study of the central nerv- 
ous system, for the purpose of tracing the development of medullation, 
and (3) a correlation of the psychical facts with the neurological facts. 

Part I. The ability of the white rats at different ages to form 
simple associations was tested by various forms of the labyrinth method. 
The obtaining of food was employed as a motive. Usually the food 
was placed in a box and the animals were given a chance to get it by 
finding a hidden opening into the box, by opening a spring door, or by 
wending their way through a labyrinth. The observer watched the be- 
havior of the animals, and recorded the time required for the accom- 
plishment of a given act. The results of this psychological study 
include certain interesting points of difference between young and ma- 
ture rats which cannot be better stated than in the words of the author : 


t. No form of problem which the adult rat is capable of solving 
presents insurmountable difficulties to the rat of twenty-three days of 
age. 

2. a) The time of first success in solving problems conditioned 
chiefly upon physical activity is shorter for young rats than for adults. 

b) For the second solution of such a problem, adult rats do not 
require a longer time than young rats. 

c) Problems not so conditioned upon physical activity are solved, 
even the first time, more quickly by adult than by young rats. 

3. a) Young rats make many more useless movements than 
adult. 


1 Watson, JOHN B. Animal Education: An experimental study on the 
psychical development of the white rat, correlated with the growth of its 
nervous system. Chicago, The University of Chicago Press, 1903, 122 pp., 22 
Figs., 3 Plates. 


Literary Notices. ps 


b) After once associating the various parts of a problem, adult 
rats make only the movements necessary to attain the desired end, 
while young rats—owing to their superabundant physical activity and 
lack of muscular control—continue to make useless movements long 
after adult rats have discarded them entirely. 

c) There is a gradation in the number of useless movements made 
by rats at different ages. At thirty-five days of age, when physical 
activity appears to have reached its highest stage, the percentage of 
useless movements is largest. As the rats grow older this super- 
abundant activity disappears, and in its place comes direction of ac- 
tivity. 

Concerning the stages of memory the author writes : 

1. Until the rat has reached the age of twelve days, life to it is 
simply a matter of pure instinct. Certain movements are made, but 
these movements are dependent upon the ready-made adjustments of 
neural and motor elements with which the rat begins life ; intelligence 
plays little or no part. 

2. At twelve days of age memory is present in a simple form. 

3. From the twelfth to the twenty third day there is a, gradual but 
rapid increase in the complexity of the memory processes until at the 
latter age psychical maturity is reached. Development after this age 
is analogous to the development that takes place in a child of ten years 
as he gradually becomes more and more mature. 

Parts II and III. Having investigated the capacity of rats to 
learn simple associations, at different stages of development, the author 
proceeded to make a careful histological study of the changes which 
occur in the nervous system from birth to maturity in order that he 
might be able to correlate the psychical and neural conditions and 
definitely determine whether associations are dependent upon the me- 
dullation of nerve fibers. Asa result of this work Dr. Watson con- 
cludes: (1) that the ‘‘medullated fibers in the cortex of the rat are not 
a condttio sine qua non of the rat’s forming and retaining definite associ- 
ations, and (2) that the complexity of the psychical life increases much 
more rapidly than does the medullation process in the cortex, psychical 
maturity being reached when approximately only one-fifth of the total 
number of fibers in the cortex are medullated.”’ 

Instead of speculating about the general significance of medulla- 
tion the author very wisely confines himself to the discussion of his 
own particular facts. The experimental work is clear cut and decisive, 
and if one sometimes feels that fewer words might have sufficed and 
and space been saved by the condensation of results into tables, the 
excellent summaries more than compensate for the lengthiness of the 
descriptions. Dr. Watson has done a valuable piece of work ina 
field which has been open thus far for the theorizing of neurologists - 
and psychologists. ROBERT YERKES. 


72 Journal of Comparative Neurology and Psychology. 


Metaphysics in Comparative Psychology.! 


The first of these articles is a defence of the comparative method 
in psychology in general, but more particularly when based upon an 
identity theory of the relation of brain and consciousness. He criti- 
cizes that school-of comparative psychologists which attempts to reduce 
all forms of animal reactions to the type of mechanical tropisms, assert- 
ing that this tendency toward a mechanical interpretation is the direct 
product of false metaphysical assumption—that of psychophysical par- 
allelism. Instead of this, the author upholds a theory of identity 
which makes it possible for him to put ‘‘Seele” in parenthesis after 
“(rebinne’ 

The arguments with which he attacks the parallelistic doctrine are 
familiar enough and will perhaps pass muster ; at least they are the usual 
arguments wielded in current controversy. On a _ parallelistic hypo- 
thesis, when the one series is complex, the other should be complex, 
and vice versa: but this is not the case. The psychical sequence, 
which, on the parallelistic theory, ought to form a continuous whole is 
arbitrarily broken without any assignable cause, or the psychological 
causes which are assigned prove, on closer inspection, to be inadequate. 
Both of these arguments, in the opinion of the reviewer, can be met 
by the parallelist. But let it pass. More important for criticism are 
the positive arguments brought forward in support of the identity 
doctrine. 

The author points out that there are important brain centers which 
are inaccessible to present physiological experimentation and which 
seem to bear no direct relation to our ordinary consciousness. Con- 
sciousness corresponds to a comparatively limited phase of cerebral 
activity. Indirectly, however, the content of consciousness is influ- 
enced to a high degree by the activities of these centers. It is not 
astonishing, therefore, that the psychophysical law does not hold. 
(He does not say so, but presumably this is because of the inhibitory 
effect of competing stimuli originating in these centers.) 

Instead of regarding this as evidence simply of an unsuspected 
complexity in the conditions of that shifting area of tension which con- 


1A. FoREL. Die Berechtiging der vergleichenden Psychologie und ihre 
Objekte. Journal fiir Psychologie und Neurologie, Band I, Heft 1 und 2, pp. 
3-10 (1902); Beispiele phylogenetischer Wirkungen und Riickwirkungen bei den 
Instinkten und dem Kérperbau der Ameisen als Belege fiir die Evolutionslehre 
und die psychophysiologische Identitaitslehre. /dzd., Band I, Heft 3, pp. 99- 
110 (1902); Ants and Some Other Insects, Monzst, Vol. XIV, No. 1. Oct. 
1903; Jan. 1904. Tr. by W. M. WHEELER. 


Literary Notices. 73 


stitutes consciousness he, however, regards it rather as evidence of an 
infra-consciousness corresponding to, or rather he would say, constitut- 
ing these inaccessible cerebral activities. What more natural than to 
assume, he says, that every cerebral activity has its introspective or 
inner counterpart, if not in our ordinary upper consciousness, then in 
this lower consciousness. Here is the key to the author's point of 
view and to his identity theory, and the reader who has already 
threshed out the problems here involved will doubtless turn to more 
instructive reading. There is no fallacy which to a greater extent 
vitiates the arguments ordinarily brought forward in support of this 
theory than the doctrine of subconscious mental states. 


Under cover of this concept of a lower consciousness, the author 
finds it possible to attribute, not only consciousness but in some 
cases a high degree of consciousness to the lowest types of animals, 
e. g., tothe Arcellae described by ENGELMANN. He finds evidences of 
memory, perception, association, feeling, choice in ants and bees. He 
says that the domestication of certain insects proves their plasticity, and 
finds evidence of this trait even in worms and echinoderms. Obvious- 
ly, the significance of such statements must be interpreted in terms of 
his theory of unconscious mind. 

His second article treats more in detail of the habits of various 
species of South American ants—which, again, he makes corroboratory 
of his identity doctrine. That there is truth in some form of the 
identity theory is extremely probable. One will perhaps agree with 
the author when he says that logically there is no more direct connec- 
tion between my individual psychology and your individual psychology 
than there is between my individual psychology and the physiology of 
my brain. Hence actions, gestures, movements, attitudes, are as 
significant for psychology as sense-impressions. Human_ psychology 
is, and must be, comparative psychology. 

But when he says that environment influences brain (soul) through 
the sensory nerves, and brain (soul) influences the muscles, glands, 
etc. (and thus the environment) through the motor nerves, one begins 
to feel that the meanings of words are becoming confused. And this 
feeling is increased when he adds that the soul is the brain-activity re- 
flected in consciousness. One suspects that the concept of a lower 
consciousness is simply a screen behind which the author may slip un- 
noticed from one meaning of a word to the other according to the ex- 
igencies of the argument. 

But quite apart from this, it must be remembered that the brain- 
activity, which the author identifies with the soul-activity, cannot be 


74 Journal of Comparative Neurology and Psychology. 


isolated from the activities of the whole organism. It is probably true 
that the brain activity and the so-called mental activity are ultimately 
one, but it certainly is neither good biology nor good psychology to 
attempt to identify the latter with the former in any sense which op- 
poses these to non-nervous organic or to the extra-organic processes. 
The author unquestionably has hold here of an important truth, but it 
is a truth still in solution—still fluid, not yet precipitated in a form 
that is quite consistent. In truth, this is just the desideratum in the 
current controversy as to the nature of the relation existing between © 
the physical and the psychical—a statement of the law of the conditions 
of consciousness which will not violate the principle of continuity in 
nature. 

The article in the A/ontst on ‘‘Ants and Some Other Insects, ’ 
traslated from the German by Professor Witt1amM Morton WHEELER, 
is an ‘‘inquiry into the psychic powers of these animals with an ap- 
pendix on the peculiarities of their olfactory sense.” This is an ac- 
count of some very interesting experiments upon ants and bees, pre- 
faced, as in the case of the other two papers, by a metaphysical 
introduction. As in the former articles, he finds evidence of the 
possession in these insects of memory, association, will, etc. The ex- 
periments are certainly instructive even though one is inclined to regard 
the interpretation of results as infected detrimentally by the metaphys- 
ical standpoint. The standpoint here again, while suggestive, seems 
untenable. One is pleased with the statement that ‘‘we can therefore 
compare attention to a functional macula lutea wandering in the brain, 
or with a wandering maximal intensity of neurocymic activity’ (p. 36). 
But we are astonished then to be told that ‘‘if this assumption is cor- 
rect . . . we are not further concerned with consciousness. It does 
not at all exist as such, but only through the brain-activity of which it 
is the inner reflex. . . . Consciousness is only an abstract concept, 
which loses all its substance with the falling away of ‘conscious’ brain- 
activity” (37). In other words, the author adopts the identity theory 
and wholly rejects the parallelism. And the criticism, in a word, is 
this, that he has thus cast aside the very element that makes the iden- 
tity intelligible. H. HEATH BAWDEN. 


Claparéde on Animal Consciousness.! 


The present article is in large measure a revision, or restatement, 
of the author’s contribution to the subject in the Revue Philosopht- 


'EpOUARD CLAPAREDE. The Consciousness of Animals. The /nterna- 
tional Quarterly, Vol. VII{, pp. 296-315. Dec., 1903. Translated by WILLIAM 
HARPER Davis, Columbia University. 


Literary Notices. 75 


gue,’ worked over for the benefit of English readers. After a brief 
glance at the history of the problem, the present reaction of biologists 
against the anthropomorphic tendencies of the Darwinian period, and 
the attempts of Logs, BerHe and others, to reduce the activities of 
lower organisms to simple physico-chemical tropisms are discussed in 
detail... The question is pointedly asked, why are tropisms necessarily 
unconscious? In all probability they are a great deal more complex 
than they are assumed to be by these investigators, and in any case it 
is difficult to discover any difference in kind between tropisms, reflexes 
and voluntary acts. 

Any such objective tests of consciousness as Logs’s ‘‘associative 
memory”, or WATKINS’ ‘‘spontaneity” are quite beside the mark, for 
they overlook the fact that consciousness is and can be only subjective. 
The only legitimate point of view for approaching the problem is that 
of pyscho-physical parallelism, the principle which assumes that for 
every change in consciousness there is a parallel and corresponding 
change in the nervous system. Just what the relation is that subsists 
between the two is as yet undetermined, but at any rate we must look 
upon them as two distinct series, and therefore it does not make a par- 
ticle of difference, so far as the external series of acts is concerned, 
whether a biological process is conscious or not. If biologists would 
realize this fact, and cease trying to bring in the mind as a _ biological 
factor which exerts an influence on the body, much confusion would 
be avoided. So far as physical acts are concerned, consciousness is an 
epiphenomenon. 

BetHe and his associates have gone to the other extreme in their 
efforts to get a perfectly objective nomenclature for all reactions to 
stimuli. ‘They deny the possibility of psychic states in animals, or at 
least the possibility of gaining such knowledge of them as will furnish 
material for science, and hence they demand the suppression of com- 
parative psychology. But any such argument would apply to human 
psychology as well. Comparative psychology is here and cannot be 
suppressed. From the standpoint of psycho-physical parallelism there 
are two parallel methods of studying life activity: (1) the ascending, 
or physiological, beginning with the lowest organisms and going on to 
the highest, explaining everything on purely physico-chemical princi- 
ples; (2) the descending, or psychological, going down from man, and 
reasoning by analogy as to the mental life of animals. Both of these 


1 EDOUARD CLAPARNDE. Les animaux sont-ils conscients? Revue Philo- 
Sophigue, tome LI, pp. 481-498. 1901. 


76 Journal of Comparative Neurology and Psychology. 


lines of investigation are necessary, and they should not conflict, but 
should supplement each other. But as to the problem of the appear- 
ance of consciousness in the world, we must continue to say: /g7o- 
rabimus. J. CARLETON BELL. 


The Measurement of Mental Traits.! 


Those interested in the scientific study of education will welcome 
this book as a contribution to its methods. Professor THORNDIKE, fol- 
lowing the line of GaLron’s famous researches, undertakes to bring 
together in a brief space such of the reliable statistical methods as have 
already proved fruitful or promise fruitful results in the study of men- 
tal traits, especially of school children and college students. Per- 
haps the greatest value of the book, as the author himself foresees, 
will be to bring home to educators, more forcibly than heretofore, the 
untrustworthy character of the current generalizations on education, and 
to create a demand for inductive statistical study of the facts, such as 
those being carried on by Professor CaTTreLt, himself, and others, in our, 
own country. ' 

The implied assumption underlying the whole treatment in this 
book is that of the possibility of mental measurement ‘This does not 
mean an attempt to measure that timeless and spaceless, that incom- 
mensurable, abstraction that often goes by the name of the ‘‘mental” 
in discussions of the mind-matter problem. It means measurement of 
the behavior of an organism in terms of those reactions which have 
come to be called mental because of their relations to the so-called 
higher values in life—but essentially identical in principle with physi- 
cal or medical measurements. It is in this sense, apparently, that the 
author seeks ‘‘units of mental measurement” (p. 169), comparable to 
the inch, the ounce, the ohm, the ampere, the calorie, etc., in physical 
science. ‘The difficulty is a practical one only. ‘There is no inherent 
theoretical reason why such a unit may not be found and used. The 
variability of mental traits renders measurements approximate only. 
But this is true ultimately of all measurements; they are all anthropic 
at first. And approximate accuracy is better than the vagaries of cur- 
rent theory, while ‘‘the greater the number of measurements, the closer 
the approximation will be.” 

If education is to become a science, the physical and mental meas- 


1E. L. THORNDIKE, Educational Psychology (Library of Psychology and 
Scientific Methods, edited by J. MCKEEN CATTELL). Mew York. Lemcke and 
Biichner, 1903. 


Literary Nottces. PF, 


urements upon which its conclusions are based must be exact. We 
have a body of general but inexact knowledge about instincts, habits, 
memory, attention, interest, reasoning. We have descriptions of these 
in the literature of child-study and methods of teaching. We havea 
great many general ideas about the influence of inheritance, environ- 
ment and general mental development. But we have little or no ac- 
curate knowledge on these points. 


Not much value is attributed to those ‘‘ Broader Studies of Human 
Nature’ (Chapter XIV), carried on mainly by the guestionnatre method, 
which have emanated from the Clark University school of child-study. 
The possibility of a scientific study of the loves and hates, fears, inter- 
ests, ideals, habits, motives and opinions, influence of books, games, 
toys, etc., is not denied but doubt is cast upon the accuracy of the 
methods used and the reliability and importance of the generalizations. 
“Information about tooo people with respect to one trait is of far less 
importance than information about too traits in each of ro individu- 
als” (p. 161). 

After discussing the possibility of mental measurement (Chapter 
II), the author takes up the problem of ‘‘The Distribution of Mental 
Traits” (Chapter III). Is there any law of distribution of mental traits 
in groups of individuals ? As between the sexes? As between groups 
having different inheritance or different training? Can we treat cour- 
age, honesty, ambition, eminence, as we can treat color of eyes or 
hair or weight, statistically? The reply is in the affirmative. But we 
must beware of imagining ‘‘that nature has provided distinct classes 
corresponding to our distinct words, e. g., normal and abnormal, ordi- 
nary and exceptional,” genius and idiot, precocious and retarded, 
bright and dull, etc. (p. 22). 

In Chapter [V we have a discussion of ‘“The Relationships Be- 
tween Mental Traits.” Alteration of one function involves others. 
Educational problems involving this principle are the question of the 
disciplinary value of studies, arrangement of groups of electives, sys- 
tems of grading and promotion, tests of mental growth and condition. 
The relationships are often very different from what the educational 
literature would have us believe. ‘The striking thing is the compara- 
tive independence of different mental functions even where to the ab- 
stract psychological thinker they have seemed nearly identical’’ (p. 28). 
The mind is a dynamic, organic, functional whole; not a mechanical 
whole. It is like the nervous system—a hierarchy of relatively inde- 
pendent activities, ‘‘a collection of protoplasmic bands.” We _ have 
memories not memory, specific habits of attention not a general faculty 


78 Journal of Comparative Neurology and Psychology. 


of attention ; reason is a name for a host of particular capacities. ‘‘It 
follows that an individual’s status in any one function need not be 
symptomatic of his status in others.” Hence the fallacy of college en- 
trance examinations as accurate measure of mental traits, and the folly 
of using any one study, such as arithmetic, as the basis of promotion. 

In Chapters V and VI Professor THORNDIKE discusses the im- 
portant questions of ‘‘Original and Acquired Traits,” and ‘‘The Inher- 
itance of Mental Traits.’ ‘‘What ancestry does is to reduce the vari- 
ability of the offspring and determine the point about which they do 
vary” (p. 48). There is no theoretical reason why we may not meas- 
ure the variation and inheritance which determines family resemblance. 
The author starts, of course, from the work of GaLron, and discusses 
the small amount of really scientific work which has been done in this 
field. He does not mention the recent work on MENDEL’s law, which 
certainly has a bearing. Nor is there any reference to the doctrine of 
organic selection of OssporN, MorGAN and BaLpwin as offering a 
possibility of mediation between the extreme views of the transmission- 
ists and the non-transmissionists. 

Chapter VII is on ‘‘The Influence of the Environment.” Here, 
again, it is perfectly possible to measure the influence of change in 
climate, food, school-training, friendship, sermon, occupation, etc. 
But we must avoid the fallacy here ‘‘of attributing to training facts 
which are really due to original nature or selection.”’ The author 
would substitute for such vague and indefinite terms as culture, discip- 
line, training, practice, imitation, the conceptions of ‘‘(1) Furnishing 
or withholding conditions for the brain’s growth. and actions; (2) Fur- 
nishing or withholding adequate stimuli to arouse the action of which 
the brain is by original nature or previous action capable; (3) Rein- 
forcing some and eliminating others of those activities in consequence 
of the general law of selection in mental life” (p. 77). 


One of the most valuable Chapters in the book is Chapter VIII on 
‘‘The Influence of Special Forms of Training Upon General Abilities.” 
‘‘Does the study of Latin or of mathematics improve one’s general rea- 
soning powers? Does laboratory work in science train the power of 
observation for all sorts of facts 2?’ In other words, ‘‘How far does the 
training of any mental function improve other mental functions ?”’ (p. 
80). There is no doubt that there is some influence. The question 
is, ‘“To what extent and how” does this take place? ‘‘Learning to do 
one thing well has much less influence upon one’s other abilities ’ than ed- 
ucational theorists would have us think. The general conclusion from 
his own experiments is ‘‘that a change in one function alters any other 


Literary Notices. 79 


only in so far as the two functions have as factors identical elements”’ 
(p. 80). ‘‘Improvement in any single mental function need not im- 
prove the ability in functions commonly called by the same name. It 
may injure it” (p. 91). There is no ‘‘general ability.” Upon this the 
author repeatedly insists. The present reviewer thinks that Professor 
THORNDIKE carries his idea of the independence of the mental func- 
tions to a point which threatens the unity of the mental life. One won- 
ders how a mind such as the author describes ever could perform such 
a synthesis as that involved, for example, in writing book on Educa- 
tional Psychology. He says that ‘‘the mind must be regarded not as a 
functional unit nor even asa collection of a few general faculties which 
work irrespective of particular material, but rather as a multitude of 
functions, each of which is related closely to only a few of its fellows” 
(p. 29). ‘‘The mind is really but the sum total of an individual’s feel- 
ings and acts” (p. 30). ‘This view is in harmony with what we know 
about the structure and mode of action of the nervous system. ‘The 
nervous system is a multitude of connections between particular hap- 
penings in the sense organs and other particular events in the mus- 
cles? (p. 30). 

These unguarded statements surely must be accounted for as the 
result of a violent recoil from the extremes to which the ‘‘abstract psy- 
chological thinker” has carried the faculty psychology. It cannot be 
that Professor THORNDIKE means to deny the important structural and 
functional unities found in the nervous system and in conscious pro- 
cess. 

Chapter X treats of ‘‘Changes in Mental Traits with Age,’ 
and Chapter XI of ‘‘Sex Differences in Mental Traits.” No mention 
is made of Professor HELEN BRADFORD THOMPSON’S recent work on 
“«Psychological Norms in Men and Women.” Chapter XII is on ‘‘Ex- 
ceptional Children,” especially defective children. A brief concluding 
chapter puts the ‘‘Problem of Education as a Science.” An Appendix 
contains an ‘‘Index of Tests,” of ‘‘Common Measures,” and ‘‘Sugges- 
tions for Investigations in Educational Science.” 

The author is rather cavalier in his treatment of educational the- 
ory. But most of his readers will probably forgive him for that. As 
before remarked, the book is chiefly valuable as setting the task and 
suggesting the methods of a scientific study of education. It can 
scarcely be said that it adds much of positive value in the way of con- 
clusions from data already studied. There are very few of the general- 
izations contained in this book which it would be safe to adopt without 
further vindication of their truth. But it certainly will stimulate more 


8o Journal of Comparative Neurology and Psychology. 


exact methods of study of mental traits in relation to education, and 
this is more than justification for its appearance at this time. 
H. HEATH BAWDEN. 


Are Sounds, Made in the Air, Audible in the Water? 


In their works on the sense of hearing in fishes and crustacea, 
KREIDL, BEER and PARKER have laid more or less emphasis on the 
reflection of sound waves in the air from the surface of the water. 
PARKER says (basing his statement to some extent upon experiment), 
“the plane separating air and water is, under ordinary circumstances, 
an almost impenetrable one for most sounds, whether they are gene- 
rated on one side or the other of it, and many of the negative results 
obtained by previous investigators on the sense of hearing in fishes 
may have been due not so much to the absence of hearing in the ani- 
mals experimented upon as to their inaccessibility to the sound, or at 
least to sound of an intensity sufficient to stimulate.” 

Interesting experimental evidence on this question is furnished by 
Dr. V. Duccescut,' of Naples, in a recent number of the A7zvista 
d’ tala. Struck by the fact that some boys, diving along the shore, 
were able to repeat, on emerging from the water, the words called to 
them by their comrades while they were still beneath the surface, he 
secured the services of an expert diver, provided himself with a boat 
and some simple apparatus, and set out to test the matter experiment- 
ally. ‘Trials were made at various depths up to seven meters. The 
length of time that the diver remained under water was about ro seconds. 
At 5 meters the diver could hear distinctly, and repeat on coming to 
the surface, every word called to him from the boat. At 6 meters he 
could distinguish between the sounds of two glass bells of different 
sizes, a whistle and a small trumpet, all sounded in the air, could tell 
how many times each one was sounded. and in what order. At 7 
meters the diver was able to distinguish the sounds with much less cer- 
tainty, and sometimes not at all. The high tones were found to be 
much more difficult to distinguish than the low. 

The same set of experiments was tried when the water was some- 
what rough, with the result that the sounds were perceived with slightly 
less accuracy. It is true that in all these experiments the possibility of 
the sound being communicated through the boat to the water is not ex- 
cluded. Moreover Duccescut thinks it may be a question whether 


1V. Duccescul. Gli animali aquatici possiedono il senso dell ’udito? 
Rivista a’ Italia, Anno VI, pp. 958-966, Dec., 1903. 


Literary Notices. SI 


the sounds were perceived through the ears or through the bones of 
the head, as stopping the ears with vaseline did not seem to affect the 
perception. ; J. CARLETON BELL. 


Edinger and Wallenberg’s Bericht.' 


We heartily welcome the appearance of this ericht printed as a 
Separit of convenient form. Six hundred and twenty-eight titles are 
noticed in two hundred and seventy-two small pages. About one-tenth 
of the work is devoted to vertebrates below the mammals. The 
greater part of the whole work is now done by WALLENBERG. 

Jn Bop 
Substitution of Function after Nerve Anastomosis. 


Some interesting side lights on the plasticity of the associational 
paths within the human cerebral cortex are thrown by a recent sur- 
gical case* in which, after traumatic destruction of the facialis root 
and resultant paralysis, the central end of the spinal accessory nerve 
was sutured on to the peripheral facialis and a successful union effected. 
There resulted total permanent paralysis of the trapezius and sterno- 
mastoid muscles and almost perfect restoration of facial symmetry both 
at rest and (less perfectly) in the facial movements. 

The account of the case is illustrated by numerous photographs 
taken before the operation for anastomosis and at various stages during 
the restoration of the function. The case brings into unusually sharp 
prominence the problem involved in the resultant alterations in the 
central associational paths and suggests a plasticity of cortical paths 
quite at variance with some of the current theories. Ge is He 


The Cerebral Commissures Again.’ 


Professor G. ELLtor SMITH takes as his text a remarkable aberrant 
commissure found only in the forebrain of Sphenodon and the true 
lizards and subjects the commissures of the hippocampal region of 
amniote vertebrates to a critical comparative examination. ‘This 
aberrant commissure he finds to be ‘‘a bundle of fibers derived from 


! Bericht iiber die Leistungen auf dem Gebiete der Anatomie des Central- 
nervensystems in den Jahren 1901 und 1902. Von Prof. Dr. L. EDINGER und 
Dr. A. WALLENBERG. Le?pzig, Verlag von S. Hirzel, 1903. 

2? CUSHING, HARVEY. The Surgical Treatment of Facial Paralysis by Nerve 
Anastomosis. <Aznals of Surgery, XXXVII, 5, May, 1903. 

’Smiru, G. ELLioT. On the Morphology of the Cerebral Commissures in 
the Vertebrata, with special Reference to an Aberrant Commissure found in the 
Forebrain of Certain Reptiles. Zvrans. Linn. Soc. London, 2 Ser., VIII, 12, 


July, 1903. 


82 Journal of Comparative Neurology and Psychology. 


the caudal portion of the hippocampus, and therefore homologous (in 
part) with the psalterium of the Mammalia. But its behavior presents 
a marked contrast to that of the Mammalia: for, instead of pursuing 
an extensive forward course to cross over in the lamina terminalis, it 
avails itself of the primitive direct connection between the caudal lip 
of the cerebral hemisphere and the optic thalamus, and in this way 
reaches the roof of the third ventricle directly.” Examination of cer- 
tain amphibian brains leads the author to conjecture that here the 
aberrant commissure is represented, not in the dorsal commissure of 
the lamina terminalis, but in the superior commissure of OsBorn ! 
Apparently there is here an interesting problem in cerebral morphology 
which remains to be worked out in the Ichthyopsida. CS, nate 


The Homologies of the Cerebellar Fissures. 


Professor O. CHARNOCK BRADLEY! attacks this intricate problem 
using a combination of the methods of comparative embryology and 
comparative anatomy, building upon the foundations laid by Srroup 
and KuirHan. He recognizes that we must not» begin by secking 
homologues of the human fissures in lower animals; but that, beginning 
with the smoothest and least complicated cerebellum, the fissural pat- 
tern should be worked out in the ascending series of mammalian com- 
plexity. 

The paper opens with a description of the developmental stages 
of the cerebellar surface in the rabbit, after which comparison is made 
with other simple adult cerebella; viz., the hare, shrew, hedgehog, 
mole, rat, water-vole, bat and squirrel. The second part of the paper 
includes a similar description of the development of the pig, with com- 
parison with the marten, badger, dog, fox, cat, goat, sheep, cow, 
horse and donkey. This is followed by a provisional application of 
the results to the subdivision of the human cerebellum in the light of 
the comparisons made. The paper is illustrated by numerous outline 
figures. 

In a later paper Professor G. ELLIoT SMITH’ controverts the author’s 
position regarding the relations of the flocculus, paraflocculus and 
vermis, concluding that his views in this regard rest upon insuffi 
cient data, in fact upon a (presumably anomalous) hare’s brain and are 


' BRADLEY, O. CHARNOCK. On the Development and Homology of the 
Mammalian Cerebellar Fissures. Journ. Anat. and Physiol., XXXVII, Jan. 
and June, 1903. 

2 Notes on the Morphology of the Cerebellum. /ourn. Anat, and Physvol., 
XXXVIE , July, 1903. 


Literary Notices. $3 


not consistent with the data of comparative anatomy generally. And 
this is followed by a more extended series of notes' supplementary to 
the same author’s paper, ‘‘The Primary Subdivision of the Mammalian 
Cerebellum,” in Journal of Anatomy and Physiology for 1902, and illus- 
trated by a large number of figures, including a useful diagrammatic 
schema. CS ica He 


Mendel and Jacobsohn’s Jahresbericht.’ 


The sixth issue of this admirable annual is similar in plan to its 
predecessors and equally indispensable. It contains 1333 pages, in- 
cluding 61 pages of author’s and subject indexes. (ORME Ms 


Allis on the Anatomy of the Mackerel.” 


This splendid memoir (which has appeared as yet only as an au- 
thor’s separate) follows closely along the lines of the same au- 
thor’s well-known monograph on the cranial anatomy of Ama. In- 
deed it dates from about the same period, haying been finished and 
submitted for publication in July, 1899, and now published without 
alteration. It is characterized by the same accuracy, thoroughness 
and beauty of illustration and will doubtless prove a standard of refer- 
ence for the teleost as the earlier work has done for the ganoid, though 
one cannot repress a shade of disappointment that it has not been 
possible for the author to revise the work at the time of publication 
so as to correlate the findings with the changed conceptions of cranial 
nerve morphology which the last five years have brought about. For 
instance, the full significance of the following criticism of GORONO- 
WITSCH (p. 249) comes out much more clearly now, I opine, than 
when this was written in 1899: ‘‘That a careful study of the course 
and ultimate distribution of the cranial nerves of fishes can, in the 
present state of the literature of the subject, have but little morpho- 
logical importance, and that all important results are to be obtained 


'Smiru, G. ELtior. Further Observations on the Natural Mode of Sub- 
division of the Mammalian Cerebellum. Azat. Anz., X XIII, 14-15, 1903, pp, 
368-384, 

* Jahresbericht iiber die I.eistungen und Fortschritte auf dem Gebiete der 
Neurologie und Psychiatrie. VI. Jahrgang. Bericht iiber das Jahr 1902. 
Berlin, S. Karger, 1903. 

3 ALLIS, EDWARD PHELPs, JR. The Skull and the Cranial and First Spinal 
Muscles and Nerves in Scomber scomber. Reprint from the /ournal of Mor- 
pholosy, XVIII, Nos. 1 and , April, 1903. 


84 Journal of Comparative Neurology and Psychology. 


only by a study of the central origin of the fibers, seems to me certain- 
ly an error. To know where a nerve goes, and what it does, is abso- 
lutely necessary in all attempts to establish its homologies, and is hence 
equally as important as to know where it comes from, what character 
of fibers it contains, or how it is developed. Its peripheral distribu- 
tion should, in fact, be, first of all, definitely known.” By way of 
practical illustration of this contention, Mr. ALuts has here for another 
type carried the study of peripheral distribution as far as the most re- 
fined dissection methods can do and in some of the cases (such as the 
relations of the post-vagal nerves) whose interpretation has still baffled 
him the subsequent microscopical study of these nerves has already 
solved the problem. OC. 22k 


The Journal of 
Comparative Neurology and Psychology 


Volume XIV 1904 Number 2 


ria SOLOGICAL EVIDENCE OF FHE PLUIDIFY OF 
ik CONDUCTING SUBSTANCE. VIN. Tite 
PEDAL NERVES OF THE SLUG—ARIOLIMAX 
COLUMBIANUS. 


By O. P. JENKINS and A. J. CARLSON. 
(From the Physiological Laboratory of Leland Stanford, Jr., University.) 


In measuring the rate of the nervous impulse in the slug 
Artolimax columbianus ‘ the fact of the remarkable extensibility of 
the pedal nerves, which were used for the pupose by us, was 
a matter of constant observation, as it gave us no little trouble 
in making the determinations. This slug reaches a large size, 
individuals being frequently met with which, when extended in 
the act of crawling, are 25 centimeters in length. 

A workable distance of 8 cm. or more of the pedal nerve 
can be obtained in such slugs. Now this nerve in the unin- 
jured living animal is extended during its act of crawling and 
contracted during its time of rest and during these changes it, 
obviously, remains functional. We found that when the pedal 
nerve is freed from its ganglia and allowed to contract without 
hindrance it would shorten to about one-half the length main- 
tained in it when the animal was fully extended in the act of 
crawling. Ina muscle-nerve preparation made as described in 
the paper referred to, this nerve could be repeatedly stretched 
to this extent and allowed to contract and at each of these posi- 
tions and at intermediate ones, normal contractions were ob- 
tained. Thus the stretching of the nerve through these limits 


1 JENKINS, O. P. and Cartson, A.J. American Journal of Physiology, 
1903, Vol. VIII, p. 251-268. 


86 ournal of Comparative Neurology and Psychology. 
SD y) ee 


does not appear to affect its functional activity. If, however, 
the nerve was stretched one or two centimeters in excess of the 
length it reaches in the animal fully extended by its own act of 
crawling, this excess of stretching itself acted as a stimulus and 
both the elasticity and irritability of the nerve were speedily 
lost not to be subsequently regained. It became a matter of 
interest to determine what is the effect of stretching the nerve 
on the rate of conduction of the nervous impulse. 

In the time from August, I9g01, to May, 1902, the muscle- 
nerve preparations of 25 individuals, in connection with other 
work, were tested on this point, and all these showed without 
exception an increase in the latent period following the exten- 
sion of the nerve from the contracted state, the height and 
rapidity of the muscular contraction remaining fairly constant. 
In order to determine more accurately the relation of the amount 
of extension of the nerve to its rate of impulse we took a series 
of records obtained from stimulating the central and peripheral 
points chosen on the pedal nerve in the contracted condition 
and in the extended condition. From these records rates for 
different amounts of extension in the same nerve were deter- 
mined, allowing comparisons to be made. This series of ex- 
periments was carried on at the Hopkins’ Seaside Laboratory 
at Pacific: Grove in, June, 1902. , Except “for theialtemate 
stretching and relaxation of the nerve, the apparatus and method 
of experimentation were the same as used in the previous work 
on the slug. The muscle-nerve preparations from 16 large 
individuals in good condition were used and it will be seen from 
the summary in table IV that several pairs of records both in 
the extended and contracted condition of the nerve were usu- 
ally obtained from each preparation. 


Fig. 1. Artolimax columbianus. Four pairs of successive records obtained 
on stimulating peripheral and central points in the stretched and relaxed condi- 
tion of the pedal nerve in the same individual. c. curve from central, £. 
curve from peripheral point of stimulation. 

No. 1. Stretched, length of nerve, 8 cm. rate, 36.8 cm. 


No. 2. Relaxed GG |e “c  4 cm. rate, 36.4. cm. 
? are) 

INOW 3s stretched, (7 cs =: se 8'cm. rate, 33.6) cm. 

No. 4. Relaxed, BG te 4-em: rate, 30:5 cm. 


Relaxed 


4. 


Stretched 


li 


Relaxed 


5 ee 
ie} xe] 


PX 


Stretched 


He 


—__————— 


Ann 


An 


Anny 


AI AANA AAA AAAI AAA AAA 


te 


nanny 


| 
| 


P, 


88 Journal of Comparative Neurology and Psychology. 


To make sure that the point of peripheral stimulation was 
the same in the extended and the contracted condition of the 
nerve the point of union of one of the branches with the main nerve 
trunk was chosen and this point marked with a bit of carbon 
from the drum which adhered firmly through the experiments. 
Since the central point of stimulation was in every case nearer 
the pedal ganglion it was easily kept the same in the two con- 
ditions. Although in each of these 16 slugs the nerve was 
stretched to about twice the length exhibited in the contracted 
state, in no case was the nerve stretched sufficiently to give rise 
to an impulse, and it is therefore probable that the degrees of 
extension of the nerve were within the range employed by the 
animal in its normal movements. After a second or third repe- 
tition of the stretching, the nerve did not always contract to the 
length first assumed, although freed as much as possible from 
the restraining force. This was probably due mainly to the 
viscid mucus in the body cavity which stuck to the nerve more 
or less and by slightly hardening on exposure to the air, offered 
some resistance to its contraction. 

Of the sixteen experiments three typical ones are given in 
detail, the remainder only in summary. In this summary (table 
IV), the ‘length of nerve,” the ‘‘transmission time’ and the 
“rate’’ represent the averages calculated from the individual pairs 
of records in the stretched and contracted condition of the 
nerve. Fig. I gives a typical series of the tracings obtained 
from four successive pairs from alternately extended and con: 
tracted condition of the same nerve respectively. 

A study of these tables shows that there is practically no 
difference in the actual rate of the nervous impulse in the 
stretched and the contracted condition of the nerve; the in- 
crease in the latent period of the stretched nerve is caused by 
the additional length of the nerve. In nine of the experiments 
(Table IV, Nos. 1, 2, 4, 5, 6, 7, 9 and 12) the average rate in 
the stretched nerve is slightly less than that in the contracted 
nerve, but, as will be seen from Table I, in these series, indi- 
vidual pairs of records are found which show the reverse. In 


JENKINS AND CARLSON, Conducting Substance. 89 


TABLE I: 


Detail of experiment No. 8, Table IV. June 20, 1902. Temp. 18°C. 


Condition of Total latent time in Transmission| Length of | Rate in 
seconds. ; : . 
nerve. — time In sec. nerve incm., cm. 
Central | Peripheral 
Relaxed 0.230 | 0.136 0.094 4.5 47.7 
Stretched 0.428 0.184 0.2 10.5 43-5 
Relaxed 0.302 0.160 0.142 5.0 35-0 
Stretched 0.524 0.220 0.304 11.0 35-2 
Relaxed 0.340 0.200 0.140 6.0 42.6 
Stretched 0.580 0.230 0.350 Ete5 34.0 
Relaxed 0.400 0.200 0.200 7.0 35.0 
Stretched 0.590 0.220 0.370 11.5 31.05 
Relaxed 0.405 0.180 0.225 8.0 B52 
Stretched 0.595 0.200 0.395 11.5 28.75 


Average rate, relaxed: 38.9 cm. 
es coe stretched: 3455) 1em: 


TABLE EAI: 


Detail of experiment No. 13, Table IV. June 23, 1902. Temp. 21°C. 


Condition of Total latent time in Transmission | Length of | Rate in 
seconds. ; : f 
nerve time in sec. | nerve in cm. cm. 
Central. | Peripheral. 
| 
Stretched 0.314 0.140 0.174 6.0 34.2 
Relaxed 0.220 0.104 0.116 Bez 27.52 
Stretched 0.360 0.140 0.220 7.0 27.0 
Relaxed 0.268 0.120 0.148 3.5 23.45 
Stretched 0.380 0.160 0.220 7.0 27.0 
Relaxed 0.304 0.134 0.170 4.0 24.0 
Average rate, relaxed: 24.9 cm. 
ue ‘¢ stretched: 29.4 cm. 


TABLE TU: 


Detail of experiment No. 16, Table IV. June 24, 1902. Temp. 20°C. 


Condition of Total latent time in Transmission | Length of | Rate in 
seconds. : . ; 
nerve. time in sec. | nerve in cm. em. 
Central. Peripheral. 

Stretched | 0.470 0.200 0.270 8.0 29.6 
Relaxed 0.320 0.178 = OnnA2) 4.5 28.4 
Stretched 0.740 0.300 0.440 8.5 19.29 
Relaxed 0.460 0.220 0.240 5-5 22.50 


Average rate, relaxed: 25.4 cm. 
Ee Se stretcheds:s5 24-4scme 


gO Journal of Comparative Neurology and Psychology. 


TABLE IV. 


Summary of 16 experiments on the effect of stretching the nerve 
on the rate of the nervous impulse in the pedal nerve of Arzolimax 
columbianus. 


| 
No. of No. of pairs} Length of | Transmission time Rate in 
of records | nerve in cm. | IneSeC; cm. 
experiment 

Stra lRel-aiiotcy | Wels Str | Rel. Str Rel 

I 8 2 $:0) 9455 0.225 0.105 36.0 44.5 

2 2) 3 75 4.5 0.225 0.126 B32 35.6 
2 iB 2 G10 ad a7, 0.302 0.166 30.8 30.25 
4 I 2) 7.0 3°5 0.220 0.094 21.78 \— BOuTs 

5 4 4 9.0 4.5 0.240 0.108 37-0 41.5 

6 B 5 | 8.16| 4.7 0.286 0.146 28.2 22:0 

7h ) 4 | 8.66] 4.0 ©.201 0.096 32.78) 44.5 

8 5 5 | 12>) “Ger 0332 0.160 34.5 38.9 

G 3 AW eQes | 457, 0.336 0.139 28.0 36.0 

fe) I Ty |6.0" |) «320 0.080 0.040 75-0 75.0 

II I T |(10,0 5.0 0.344 0.170 29.0 29.0 

12 4 4 | 8.1 4.1 0.249 0.120 32-6 36.0 

13 8 a | 6.66 | 3.5 0.207 0.144 20.4 24.9 
14 2 Boy OsO 2.6 Os155 0.079 Boe 34.28 
15 4 3 | 73 3.8 0.216 0.126 R407 30.33 
16 2 2 8.25] 5.0 0.355 0.161 24.44| 25.42 

Average rate in the stretched nerve: 34.6 cm. per sec. 
oe ve eee pyelaxed ec s)6 637-1 cm. per Sec. 


five experiments (Table IV, Nos. 3, 10, 11, 14 and 16) the 
rate of the impulse in the two conditions in the nerve is identi- 
cal, and in two experiments (Table IV, Nos. 13 and 15) the 
rate in the stretched condition is slightly higher than that in the 
relaxed or contracted condition. The average rate of all the 
sixteen slugs is 35 cm. per sec. for the stretched nerve, and 37 
cm. per sec. for the contracted nerve. But these differences 
are slight when one considers the difficulties in applying the 
peripheral electrodes to exactly the same point of the nerve 
throughout the successive alternations, and the difficulties in 
obtaining exact measurements of the length of the nerve, be- 
cause of the necessary shifting of both pairs of electrodes, not 
to mention the difficulties in obtaining comparable tracings, due 
to the unequal relaxations of the muscular part of the prepara- 
tion. The records leave no doubt in regard to the uniformity 


JENKINS AND Carson, Conducting Substance. gI 


‘of the rate in the nerve in the different states of extension and 
contraction within the limits indicated. In the pedal nerves of 
Ariolimax, stretching the nerve within physiological limits in- 
creases the transmission time for the whole nerve while contrac- 
tion or shortening of the nerve decreases it, but in each change 
of length of the nerve the velocity in a unit of length is the 
same, that is the rate is the same in the two conditions. 

It is obvious that if the change of the length of the nerve 
was due to the straightening out or the formation of folds and 
kinks either in the nerve as a whole or in elements in individual 
nerve fibers the transmission time between two constant points 
of the nerve would be the same, and the rate would appear 
greater in the stretched condition as compared to that of the 
contracted condition. But the fact that the transmission time 
between any two points increases with the stretching of the 
nerve seems to show that the stretching is accompanied by act- 
ual extension of the conducting substance, whatever that may 
be. And the fact that the actual rate remains the same in the 
two conditions of the nerve seems to prove that this rearrange- 
ment of the conducting substance does not change the rate of 
the conducting process. Furthermore, this rearrangement of 
the molecules of the conducting substance within the wide limits 
represented by extending the nerve to twice in length does not 
appear to effect the functional properties of the nerve either in 
the above experimental conditions or in the normal conditions 
of the animal. 

These facts are certainly evidence on the side of the view 
that the conducting substance in this nerve is in a liquid con- 
dition or at least in a semi-liquid condition. 

These experiments also confirm measurements of the rate 
of the nervous impulse in the pedal nerves of Avzohmax report- 
ed by us in which the average rate was found to be 40 cm. per 
second. These records show an average rate of 36 cm. per 
second, the slightly lower figure in the latter case being in all 
probability due to the greater number of records used from each 
preparation, as it will be seen from Tables I, II and III that the 
rate decreases rapidly during the course of an experiment. 


92 Journal of Comparative Neurology and Psychology. 


They also show that the particular amount of stretching of the 
nerve within the physiological limits does not need to be re- 
garded as a source of error in determining the rate of the nerv- 
ous impulse in this slug. 


THbeNERVOUS SERUCTURES IN THE PALATE OF 
THE FROG: THE PERIPHERAL NETWORKS 
AND THE NATURE OF THEIR CELLS AND 
FIBERS. 


By C. W. PReENTIss, 
Instructor of Biology, Western Reserve University. 
With 12 figures. 


On account of the doubts which have recently been thrown 
upon the neurone theory by the researches of APATHY, BETHE 
and others, especial attention has been drawn to the networks 
of cells and fibers which apparently form an important part of 
the peripheral nervous system in most Metazoa. 

In his recent book on the nervous system BETHE (:03) 
discusses at some length the comparative histology and physi- 
ology of these structures. According to his own investigations 
and the observations of Hesse (’95), the brothers HERtwic 
(78), and Eimer (’79), the nervous system of the Medusae is 
composed largely of nerve cells and fibers which are united 
into a diffuse network. The neurofibrillae of this network form a 
basketwork about the nuclei of the cells, and are connected 
both with muscle-fibers and with sensory organs in the epi- 
thelium of the sub-umbrella. Smipr (:02) describes a sub- 
epithelial plexus in mollusks ; both he and BerHE demonstrated 
its connection with sensory organs, and according to the physi- 
ological experiments of the latter it also sends motor fibers to 
the muscles. , 

Among the arthropods similar structures were first ob- 
served by HotmGren (’95). Later Berue (’96) described 
peripheral networks in Crustacea, and his observations were 
verified by HotmGren (’98) and Nusspaum and SCHREIBER 
CoT): 


94 Journal of Comparative Neurology and Psychology. 


In the nervous system of vertebrates networks of cells and 
fibers have been studied chiefly in connection with the blood 
vascular system. They have been described by Dociet (’93, 
’98), LeontowitscH (:01), CavaLig (:02), BretrHe (’95, :03) 
and others. BETHE states that such networks are present 
throughout the whole integument of the frog. They form a 
close network about the blood vessels and a wide-meshed sub- 
epithelial plexus. Docier (’98) and Lreonrowirscu (:01) have 
carefully studied the networks in the human skin. They assert 
that connections exist between these structures and the medul- 
lated fibers, but their figures do not convince one of this. Their 
statements have, however, been verified by Brrue (:03) who fig- 
ures a medullated fiber continuous with a wide-meshed sub-epi- 
thelial plexus. In the vertebrate heart also, Doct (’98), Hor- 
MANN (:02) and BEruHe (:03) have observed independently a net- 
work of cells and fibers surrounding the muscle bundles. This net- 
work resembles closely the diffuse nervous system of the Me- 
dusae and BETHE maintains that the structures he has seen are 
undoubtedly of a nervous nature. 

It has been stated even recently by certain investigators, 
that both the cells and fibers composing these networks are non- 
nervous structures. BARDEEN (:03), among others, has ex- 
expressed his doubts as to their nervous character ; he criticises 
LrEonTowiITSCH and suggests that the whole network described 
by the latter may be composed entirely of connective tissue. 
Even if the fibers are nervous structures the cells may be mere- 
ly sheath cells. 

It is important both to the teacher and student of neurology 
that these doubts be either confirmed or entirely removed. If 
networks of true nerve cells and fibers really exist in the integu- 
ment of vertebrates, then the idea that the peripheral nerves 
originate only from ganglion cells in or near the central nervous 
system must be abandoned. If, however, the networks are 
proved to be nothing more nor less than connective tissue struc- 
tures, the opponents of the neurone theory have lost one of 
their strongest arguments. 

My research was begun in the Physiological Institute of 


PreENTIss, Peripheral Networks. 95 


the University of Strassburg, where I was studying as PARKER 
Fellow of Harvard University. While demonstrating with 
methylene blue the innervation of the frog’s heart, I obtained 
several interesting preparations of the nervous elements in the 
palate, which led me to a further investigation of their structure. 
This investigation has enabled me not only to verify several 
points which have been hitherto in doubt, but also to observe 
new structures which other investigators have either overlooked 
or have failed to demonstrate. 

In the present paper I shall first give evidence from prep- 
arations of the normal palate to show that the fibers of the net- 
works described are true nervous structures. And, secondly, 
from degeneration preparations I shall endeavor to show whether 
the cells present in these networks are sheath cells or are as 
truly nerve cells as those of the brain and sensory ganglia. 


ie THE NERVOUS) STRUCTURES OF THE, PALATE: 


Preparations were obtained by injecting 1% cc. of a1 % so- 
lution of methylene blue (in normal salt solution) into the 
abdominal vein of the frog. The animals were either rendered 
passive by the subcutaneous injection of curare, or tied out im- 
movable on the wooden frame shown in figure 8, p. 107. With- 
in five or ten minutes after the appearance of the stain in the 
integument, the palate with its nerves and vessels was dissected 
from the roof of the mouth—an easy task, thanks to the lymph- 
sinus lying beneath the integument. The preparation was then 
placed epithelial side down, in a flat watch crystal and the ex- 
posed surface moistened with the animal’s blood while the 
progress of the stain was watched under the microscope. When 
the right degree of staining was judged to be obtained, the blood 
and mucus were rinsed away with normal salt solution and the 
tissue fixed with ammonium picrate. The preparations were 
first usually mounted in glycerin, studied in the fresh condition, 
and important details sketched with the camera lucida. They 
could then be quickly washed in water, refixed in ammonium 
molybdate and mounted in balsam. The molybdate method 
gives much clearer mounts, but has this disadvantage, that the 


gO Journal of Comparative Neurology and Psychology. 


finer details are often lost by the washing out of the stain in 
running the preparations up through the alcohols. By study- 
ing preparations by both methods I thus did away with the dis- 
advantages of each. Many mounts were made between two 
cover glasses, allowing the use of an oil immersion from both 
sides. This is a distinct advantage when whole mounts are em- 
ployed. 

The frog’s palate is innervated chiefly if not exclusively by 
the Ramus palatinus of the seventh cranial nerve (facialis). 
Each palatine branch (Fig. 1) passes down to the roof of the 


R. comm. R. comm. 
c. R. pal.-nas. ec. Ophthalm, 


Ductus Gl. 
intermax. 
Vomer 


R. praechvan. 
R. postchoan. 


R. pal.-nas. 


b 
R. comm. V, 2. 


M. lev. bulbi 


R. palatinus, 
(VIL.) 


‘ R. lat. Rr. postorb. 


Fig.7. The roof of the frog’s mouth with the integument dissected away 
to show the course of the palatine nerves. &. fa/atinus, palatine nerve; X. 
comm. V. 2, Ramus communicans of the trigeminal nerve; a, 6, points at which 
nerve was severed. (After GAUPP). 
mouth immediately anterior to the lateral process of the basi- 
sphenoid, runs nearly straight cephalad and then, bending sharp- 
ly laterad, joins the Ramus communicans of the trigeminus. 
Along its course the nerve gives off many lateral twigs, the 


fibers of which interlace to form an intricate plexus of medul- 


Prentiss, Pertpheral Networks. 97 


lated fiber-bundles over the whole inner surface of the palate. 
From this plexus fibers pass off to the epithelium. According 
to BETHE each medullated fiber divides into four branches and 
each branch innervates a different sensory organ, the number 
for each: organ being but two. This peculiar and definite 
method of innervation, he points out, is the most natural ar- 
rangement by which each end organ may receive a distinct 
nerve supply at the expense of the smallest number of nerve 
fibers—a separate nerve supply for each sensory organ being 
requisite for the localization of tactile stimull. 

My preparations confirm the general conclusions of BETHE, 
but the distribution of the sensory fibers is not as simple as he 
supposed. It is true that usually only two or three large fibers 
innervate each sensory organ; these break up into numerous 
fine fibrils, which, after a tortuous course, end between the epi- 
thelial cells. The sensory organs in which these fibers end 
project slightly above the surface of the palate and are most 
numerous at the sides. BrTHE counted an average of 210 end 
organs but only 70 fibers in the palatine nerve; if each fiber 
branches into four, as BETHE asserts, this would allow an aver- 
age of between two and three branches for each sensory spot. 
But in addition to these branches I find numerous bundles of 
fibrillae given off from each medullated fiber. These divide 
into still smaller fibrils which form a network of fine neuro- 
fibrillae and probably connect the different sensory organs. This 
network has not to my knowledge been observed in the integu- 
ment of the frog, but Srameni (:02) and Rurrini (:01) have 
recently described structures apparently identical to it in the 
skin of man. In the frog the fibrillae composing the network 
are very difficult of demonstration. In the great majority of 
methylene blue preparations they are but incompletely stained, 
and of good preparations I obtained but two or three out of 
perhaps a hundred trials. The network lies directly beneath 
the epithelium and is composed entirely of non-medullated fibril- 
lae (Fig. 2). Strands of these are given off from the medullated 
fibers as seen in the figure at a and a’. The strands divide and 
their fibrils are apparently continuous with each other in a fine- 


98 


Journal of Comparative Neurology and Psychology. 


k te) 
i ey 
# F Sy 
: i 
} } 
f él y, i 
« vi i, 
i 7 of 
f RR 
SN KN 
RW fl f \ 
= ate 5 


. MY. 5, 
TH se i S86 isn 
5 es SEA YY (pend: U; Ss 
Wes = oy 


Prentiss, Perepheral Networks. 99 


meshed irregular network ; for under a high magnification some 
of the meshes were found to be formed of a single fibrilla, and 
it is absolutely impossible to say where one fiber ends and an- 
other begins. Certain fibrils from this network end in the sen- 
sory spots of the epithelium (Fig. 2, 4, 0’); others terminate 
freely in the regions between the sensory organs. There 
is thus a diffuse sensory nerve supply throughout the epithelium 
of the palate. 

From certain preparations in which the fibrils of this net- 
work were incompletely stained, I was able to trace a single 
fibrilla from one medullated fiber into another without loss of 
continuity (Fig. 3). This connecting fibril appears to be homo- 
geneous in structure throughout its entire length. It is very 
possible that such a condition may be produced by the over- 
lapping of two fibrils. I myself have concluded after a careful 
study of these networks that they are formed by such an over- 
lapping of two fibrils and not by the direct union of fibrils from 
different ‘‘neurones.”’ In either case it is impossible to say 
that the fibril belongs to one neurone or to the other. 

The presence of fibrillar networks throughout the integu- 
ment is what we should expect from the physiological facts as 
to tactile sensations. The whole surface of the skin is more or 
less sensitive to tactile stimuli but the localization and acuteness 
of the sensations depend upon the presence of special recep- 
tive organs. If two stimuli are applied to a region between 
sensory spots only one sensation is felt, as the stimulus is dif- 
fused and affects equally a number of neurones. If, however, 
the two stimuli are so far apart as to affect different sensory 
spots, innervated by distinct nerve fibers, each of these will be 
strongly stimulated, and two distinct sensations will be the 
result. 


Fig, 2. A subepithelial network of neurofibrillae from the palate of the 
frog; a, a’, strands of fibrillae from medullated fibers; 4, #8,  fibrillae 
which apparently end in the sensory spots; c, ¢’, two sensory spots. 
The network is viewed from the epithelial side of the palate, and the termina- 
tions of the sensory fibrils among the cells of the epithelium are indicated by 
knob-like enlargements. X 330; details with Lrirz 1-12 oil immersion. 


100 Journal of Comparative Neurology and Psychology. 


In addition to this meshwork of sensory fibers there are 
present in the palate of the frog networks of cells and non- 


Fig. 3. A portion of a network similar to that shown in figure 2, with two 
medullated fibers which are apparently directly connected by a fibril. > 1000. 


Prentiss, Peripheral Networks. 101 


medullated fibers; these have been observed by BrTueE (’95) 
and are probably identical with the structures described by 
Doaiet (’98) and Leronrowitscu (:01). For convenience of 
description a perivascular and subepithehal network will be dis- 
tinguished. The perivascular network lies deep in the tissues of 
the palate and extends wherever blood vessels are abundant. 
Its meshes are large and the cells comparatively few in number 
except about the arteries ; here a close nework is formed by the 
fibers and many cells are present (Fig. 4). I have observed 


Fig. g. A nerve network about the walls of an artery (frog); a medullated 
fiber is seen to be connected with this network. 380. 


similar structures in the floor of the mouth, in the upper part of 
the oesophagus, and in the wall of the intestine. BETHE states 
that they may be found in all parts of the integument. In 
many cases medullated fibers may be directly connected with the 
mesh-work about the arteries. A connection of this kind is 
shown in figure 4. 

I have never been able to make out special endings in the 
perivascular networks. Thenerve fibrils may often be observed 


102 Journal of Comparative Neurology and Psychology. 


in contact with the circular muscle fibers of the arteries, but 
no end organs were ever seen at these points. 

The network which I have designated as subepithelial is 
found, as its name implies, directly beneath the epithelium It 
consists of a rather fine-meshed plexus of cells and non-medul- 
lated fibers; a portion of this network is shown in figure 5. 


Fig. 5. A subepithelial network of cells and non-medullated fibers from 
the palate of the frog; the network is continuous with a medullated fiber. x 380. 
The fibers seem to radiate from beneath the sensory organs, 
and at these points from 3 to 6 cells are usually found grouped 
together (Fig. 11, a, a’). Into the sensory organs fibers pass 
from the network, while others are given off at points between 


Prentiss, Peripheral Networks. 103 


the sensory spots, and end freely in the epithelium. I have 
never observed fibers from this network innervating the capil- 
laries, but such may be the case. It is, however, connected 
with the perivascular plexus; medullated fibers also frequently 
unite with itas may be seen in figure 5. The true nature of these 
structures has been called into question by many neurologists ; I 
may state here that when I first saw them in my preparations I did 
not believe that they were nervous structures. After studying 
them carefully, however, I gathered the following evidence: (1) 
specific stains for elastic fibers and connective tissue do not 
demonstrate these networks ; (2) as already observed, the fibers 
of the networks are continuous with branches from medullated 
fibers; (3) neurofibrillae may be distinctly observed in well dif- 
ferentiated preparations of these networks and the fibers have 
the varicose appearance characteristic of nerves. Inthe face of 


Fig. 6. A group of three cells from the subepithelial nerve network, show- 
ing the course of the neurofibrillae, and the connection of a large fibril with a 
medullated fiber; the fibril branches close to the first nucleus, but no network is 
formed in any of the cells by the neurofibrillae. 700. 
these facts there can be no doubt that the fibers of both the 
perivascular and subepithelial networks are nerve fibers. As to 
the nature of their cells, the histological evidence is no means 
conclusive. My preparations of the frog’s palate do not sustain 
the observations of BeTHE (:03) as to the presence of a neuro. 


, 


104 Journal of Comparative Neurology and Psychology. 


fibrillar network about the nucleus of each cell. On page 85 
he figures two cells showing such perinuclear networks and states 
in the text: ‘‘Von der Existenz glatt durch die Zellen hin- 
durch passierender Neurofibrillen habe ich mich allerdings an 
diesem Object [palate of frog] nicht mit Sicherheit iberzeugen 
konnen. Es ist aber doch sehr wohl moglich dass auch hier 
solche vorkommen, doch ist ihre Zahl sicher nicht gross.”’ To 
me it seems evident both from Berrue’s figures and my own 
preparations that most of the fibrillae do pass directly through 
the cells. The doubtful point is in the existence of a perinuc- 
lear network. The structures figured by BrETHE could easily 
be accounted for by the adhesion of the fibrils at their points of 
division. Brtue’s figures show plainly that the main portion 
of each fibril passes through the cell. It is only small side 
branches which show the semblance of a network. Of this I 
am sure, that in all my preparations of these cells the fibrillae 
do not form a network about the nucleus. The usual condition 
found in these cells from the palate of the frog is shown in fig- 
ure 6. The fibrils often divide in the region of the nucleus, 
but the branches which thus arise are not continuous with each 


Fig. 7. A single cell from the subepithelial network in the palate of /Vee- 
turus; most of the fibrillae run straight through the cell but in the region of the 
nucleus there is apparently evidence of a network. X I000. 
other. It is possible that the network figured by BreTHE may 
not have been stained in my preparations; but as the fibrillae 
passing through the cells were clearly demonstrated, it seems 
strange that some trace of the network, if present, could not 


Prentiss, Peripheral Networks. 105 


be discovered. In the palate of Mecturus there was some evi- 
dence of a fibrillar basket-work about the nuclei of certain cells 
(Fig. 7). Only a few meshes were observed and these may have 
been formed by the crossing of fibrillae; by far the greater num- 
ber pass directly through the cell without branching, as may be 
seen in the figure. I therefore maintain that these cells, if 
nervous structures, are to be compared, not as BETHE would 
have us, to the ganglion cells of invertebrates (in which a com- 
plete basket work is formed by the fibrillae), but rather to the 
central nerve cells of vertebrates, through which, as a rule, 
most of the neurofibrillae pass entirely independent of each 
other. 

In the palate of the frog the cells of the networks are usually 
located centrally with reference to the fibrillae, the nucleus being 
surrounded by the latter. It is difficult to see how such nuclei 
can be interpreted as belonging to sheath cells. Often, how- 
ever, a cell lies eccentric to the fiber, the fibrillae all passing 
to one side of the nucleus; or two nuclei may be found in close 
proximity to each other, the one surrounded by fibrillae, the 
Gener being eccentric in position, The form of the 
nuclei also varies with their location. If surrounded by 
fibrillae the nucleus may be of spheroidal or pyramidal shape; 
if lying eccentric they are usually flattened and elongate in form. 

I have described in some detail these networks of cells and 
fibers both because my observations substantiate more or less 
completely the results of DoGcieLr, BETHE, and LeonrowitTscu, 
and in order that the significance of the following degeneration 
experiments might be more easily understood. From the 
histological evidence one must conclude that the non-medullat- 
ed fibers of all these networks are true nervous structures, and 
not connective tissue as has been maintained. They are com- 
posed of neurofibrillae, are connected with medullated fibers, 
and are not demonstrated by specific connective tissue stains. 
The presence of neurofibrillae about the nuclei of some of the 
cells would indicate that they also are of nervous character, as 
BETHE and LEONowITSCH assert. The evidence as to the pres- 
ence of neuro-fibrillar networks in these cells is not conclusive, 


106 Journal of Comparative Neurology and Psychology. 


and those eccentrically located might well be sheath cells. The 
nature of these cells therefore is not definitely settled, and is a 
problem of great importance. For if it is conclusively proved 
that they are nerve cells, the structural independence of the 
neurone and its genesis from a single ganglion cell can no longer 
be maintained. By a series of degeneration experiments I have 
attempted to solve the problem. 


2. THE RESULTS OF DEGENERATION EXPERIMENTS. 


If all of the nerve fibres in the palate of the frog are proc- 
esses of the nerve cells situated either in the brain or in the sen- 
sory ganglion of the seventh cranial nerve, they should, when 
isolated from these cells for some weeks, degenerate completely, 
being separated from their only trophic centers. If, how- 
ever, there are peripheral nerve cells in the palate, these 
as well at the fibers connected with them should remain 
histologically unchanged. To determine which of these as- 
sumptions is correct the following method suggested itself: 
To sever the palatine nerves from all connection with their 
central cells, and after the expiration of a period sufficient 
for complete degeneration, to attempt the demonstration of 
the peripheral networks by means of methylene blue. The 
chief difficulty connected with this method lies in the well known 
fickleness of the stain, a factor which might lead to negative re- 
sults. I therefore experimented with normal animals until I 
was able to obtain regularly a good percentage of successful 
preparations. It was found that the subepithelial and perivas- 
cular networks take the stain very quickly as they are in close 
proximity to the blood vessels and capillaries, through the 
walls of which the stain passes to the other tissues. The chief 
point in getting good preparations therefore, is the removal and 
fixation of the tissues as soon as possible after the stain has 
passed through the capillaries. If one waits until the larger 
nerves are impregnated, the color will have disappeared from 
most of the finer elements. 

As is well known, methylene blue is a specific stain for 
degenerated myelin, and BETHE has proved that the neuro- 


PRENTISS, Pertpheral Networks. 107 


fibrillae, when degenerate, lose their power of taking up the stain. 
In methylene blue preparations it is therefore easy to distinguish 
between normal and degenerate nervous structures. 


Fig. 8. Photograph showing operating frame, the method of tying the 
frog and the point at which the root of the palatine nerve was exposed. About 
yy nat. size. 


The palatine branch of the seventh nerve passes, as we 
have already seen, to the roof of the mouth directly anterior to 
the lateral process of the basisphenoid bone (Fig. 1, page 96). 
Lateral to the eyeball it is connected with the maxillary branch 
of the fifth cranial nerve by the Ramus communicans, although, 
as far as I have been able to discover, no fibres from the trige- 
mus innervate the palate. To make sure however, that the 


108 Journal of Comparative Neurology and Psychology. 


palatine nerve is completely isolated from the brain and sensory 
ganglia, it must be severed at the points a and 0. 

The operation is simple and may be performed in the fol- 
lowing manner. The frog is tied out back down upon a wood- 
en frame nine inches long, shaped as shown in figure 8. In 
each of the five extremities of this frame a vertical slit has been 
cut. Three small blunt hooks attached to ten inch lengths 
of thread were provided. The mouth of the frog is opened, a 
hook caught into the upper jaw and the string drawn taut 
through the anterior slit, as seen in the figure. By means of 
a second hook the lower jaw is drawn back against the sternum 
and the cord fastened in one of the posterior slits. The animal 
is thus held motionless with mouth wide open. With small 
scissors an incision one-fourth inch long is made along the 
median line of the palate. One edge of the cut is then care- 
fully lifted with forceps and hooked to one side, the string be- 
ing drawn through one of the lateral slits. This exposes the 
palatine nerve at the point where it enters the roof of the 
mouth. (Fig, 1. a; Fig. 8). Next a small hooked needle 
may be passed under the nerve, the blood-vessels separated 
from it and a portion of the nerve removed. Both palatine 
nerves may thus be severed by making but one incision, and if 
the operation is carefully performed, without the loss of a drop 
of blood. Ina similar manner the Ramus communicans may 
be cut at the point 6 (Fig. 1) by making two small lateral 
incisions. It is not necessary to sew up the incisions; in fact 
the thread used in the stitches was found to irritate the animals 
and in most cases the edges of the wounds were simply drawn 
together. 


Degeneration Experiments. 

Series 1. This series of operations was practically nega- 
tive in its results. Eight animals were operated on during the 
last week in June, 1903. Six died, before the expiration of 
two weeks, of a skin disease which developed upon all the frogs 
kept in the laboratory at the time. Of the two surviving indi- 
viduals only one took the stain, and in this case very incom- 


Prentiss, Peripheral Networks. 109 


pletely. In the fresh preparation there was some evidence of 
the subepithelial network, but after fixation the stain was too 
faint to demonstrate clearly the difference between degenerate 
and non-degenerate nerves. I was encouraged, however, to 
make further attempts. 

Series 2. During the first week in October 1903, twelve 
frogs were operated upon. Of these three survived twenty-one 
days and were injected with methylene blue. Again only one 
palate took the stain well. In this preparation a network of 
non-medullated fibers was clearly demonstrated, and there was 
some evidence of it in one of the other preparations. BETHE 
(:03) has shown that when the peripheral nerves of winter frogs 
are cut distal to their cells, the neurofibrillae of the axis cylinders 
lose their affinity for stains after the expiration of from twenty- 
one to twenty-four days. This he proves to be due to the disap- 
pearance of the organic substance (Fibrillensaure) which is a con- 
stituent of all normal neurofibrillae and which, combining with 
certain dyes gives the primary fibrillar stain of both nerve cells 
and fibers. The fibrillae lose this acid substance, and refuse to 
stain long before myelin sheaths of medullated nerves show 
signs of degeneration In these preparations of the palates in 
which the nerves have been cut for three weeks, the myelin 
sheaths had almost completely broken down, showing constric- 
tions and vacuolations throughout the course of the fibers. This 
does not agree with results of BErHE and MONKEBERG ('99) who 
found complete degeneration of the medullary sheaths in the 
frog only after a lapse of 102 days, although the neurofibrillae 
had lost their specific staining power within three weeks. I 
therefore conclude that the process of degeneration must either 
proceed much more rapidly in the nerve fibers of the palate 
than in those of the sciatic nerve, or that the period of nerve 
degeneration is much shorter in the autumn than during the 
winter months. To make sure that degeneration was complete, 
a third series of frogs was operated upon. 

Series 3. On November 3rd, 1903, the palatine nerves of 
six individuals were severed. Three of these frogs were kept 
alive for thirty-five days and two good preparations of the pal- 


110 Journal of Comparative Neurology and Psychology. 


atine nerves were obtained. The stain was unusually complete 
for methylene blue preparations; the trunk and branches of the 
palatine nerve, the plexus of medullated fibers, and the branch- 
es running from this plexus to the sensory organs, were all 
demonstrated. But, while in methylene blue preparations of 
normal nerves the myelin sheaths are colorless and the axis 
cylinders (especially at Ranvrer’s nodes) are deeply stained 
(Fig. 3), in these degenerate nerves it is exactly the reverse. 
The stain is limited entirely to the myelin substance, and the 
axis cylinders are not demonstrated, a characteristic staining 
reaction for degenerated nerves. This is the case not only in 
the larger branches of the palatine nerve but also in single per- 
ipheral fibers (Figs. 9 and 10). Even without high magnifi- 


ESs-ag 


FIG. 9 FIG. 10 

Fig. 9. A portion of a medullated nerve trom a frog’s palate, the nerves 
of which had been severed 35 days before the preparation was made; the dark 
granules are the remains of the myelin sheaths; the axis cylinders of the fibers 
are not demonstrated. XX 360. 

Fig. ro. The distal portion of a single medullated fiber from the same 
preparation as Fig. 9; the myelin sheath is broken up into irregular segments 
which are deeply stained.  X 700. 
cation it may be seen that the disintegration of the myelin 
sheaths is complete (Fig. 9). The myelin has broken up into 
short segments which are deeply stained, the nuclei of the 
sheath have apparently disappeared and the nodes of RANVIER 
cannot be recognized. Comparing a single degenerate fiber 
from one of these preparations (Fig. 10) with a normal medul- 
lated fiber (Fig. 3) the difference can be seen at a glance. Not 
a single normal medullated fiber was found in the large nerve 


Prentiss, Pestpheral Networks. pig 


branches supplying the palate. Furthermore the endings of 
the medullated fibers in thé sensory spots of the epithelium 
were not demonstrated, endings which, under normal  con- 
ditions, are almost always stained. 

It is clear from such preparations that isolation from the 
central nervous system was completely accomplished by the 
operation. For the medullated fibers of the palatine nerves 
were not only wholly degenerated, but also stimulation of the iso- 
lated region failed to call forth any response. According to 
BETHE the myelin substance does not begin to undergo degen- 
eration until some time after the axis cylinders have lost their 
staining properties, and it follows that the latter have been de- 
generate for a considerable period. Butis this the case with 
the non-medullated fibers of the peripheral networks which 
BETHE and others have asserted to be directly connected with 
true nerve cells? 

In every degeneration preparation of the palate methylene 
blue failed to stain the fine network of the sensory fibrillae 
which I have described and shown in figure 2. This result was 
to be expected, as the network consists only of non-medullated 
fibrillae, all branches of medullated fibers, and goes to show that 
the degeneration of the latter is complete. Butin both cases in 
which the palatine nerves had been isolated for five weeks the 
subepithelial and perivascular networks were beautifully stained. 
Neither fibers nor cells showed the least trace of degenerative 
changes. In regions where the stain was well differentiated 
the neurofibrillae could be easily made out, proving that these 
elements were in a normal condition, and that the staining of 
the fibers was not alone due to the impregnation of the peri- 
fibrillar substance. 

A portion of the subepithelium network from one of the prep- 
ations of servzes 3 is shown in figure 11. It will be noted that 
a number of cells are grouped together at the points a anda’. The 
spot where such a group of cells occurs is in every case im- 
mediately beneath a sensory organ, and the fibers radiate out 
from these regions. Certain fibrils pass from the cells and 
apparently end in the sensory organs. I was not able to settle 


112 Journal of Comparative Neurology and Psychology. 


this point definitely but there are other fibrils which end in the 
epithelium between the sensory spots. From this it is evident 
that a part at least of the fibrillae of this network are sensory in 
function. And it is not clear to me why the cells should be 
grouped together beneath the sensory organs unless they have 


some connection with them. 


fig. rz. A portion of a subepithelial network from a degeneration prep- 
aration (period of degeneration five weeks); the cells and fibers apparently show 


normal structure, and were normally stained. a, a’, groups of cells beneath 


sensory organs; 4, 6’, degenerated medullated fibers of which 4 is connected 
with the network; c, a medullated fiber continuous with the network and show- 
ing normal structure for a short distance at its distalend. XX 225. 


Prentiss, Peripheral Networks. 113 


It has already been shown that certain of the fibers of the 
subepithelium network are directly continuous with medullated 
nerves. In the figures two such cases are seen; at times such 
fibers could be traced a considerable distance along the degener- 
ate nerves of the medullated plexus. These fibers showed all 
the normal characteristics of medullated nerves, but were never 
observed in the large nerve trunks. Other medullated fibers 
connected with the subepithelial network showed degenerative 
changes up to the point where they lost their myelin sheaths. 
As far as observed the only normal medullated fibers to be 
found in these degeneration preparations, were those connected 
with the subepithelial network. This network was found stained 
in all parts of the palate. The perivascular networks were not 
so completely demonstrated, but this was probably due to 
incomplete staining rather than to the degeneration of the net- 
works about the vessels. For these networks are never com- 
pletely stained in normal preparations. When stained in the 
degeneration preparations, neither fibers nor cells of the perivas- 
cular network show histological differences when compared with 
normal preparations (Fig. 12). As far as structure and staining 
qualities go, the one cannot be distinguished from the other. 


Fig. 72. A portion of a nerve network about the walls of a small vessel, 
from the same preparation as figure Il. XX 360. 
These series of degeneration preparations’ prove therefore 
that the peripheral networks of fibers and cells will retain their 
normal structure after five weeks of isolation from the central ner- 


114 Journal of Comparative Neurology and Psychology. 


vous system. The objection may be raised that the period which 
elapsed was not long enough, that the degeneration was simply 
incomplete, that the distal endings of the fibers form the net- 
works and that these were still in their normal condition. But 
we have already seen that the distal endings of most of the 
medullated nerves, the terminal fibrillae in the sensory organs, 
have completely degenerated. Why do the fibers of the net- 
works alone fail to show similar changes? 

It has been shown in the first part of this paper that the 
fibers of these networks are nerve fibers. It cannot be main- 
tained therefore that they do not degenerate because they are 
non-nervous structures. The only explanation of their immunity 
from the degenerative changes which affect the isolated medul- 
lated nerves is that the cells of the network exert upon them a 
distinct trophic influence. The cells are then something more 
than sheath cells or connective tissue cells as BARDEEN and 
others have asserted. The medullated fibers of the palate are 
well supplied with sheath cells but this does not prevent their 
degeneration when separated from their ganglion cells. We 
can only conclude that the cells of these networks are true 
nerve cells in that the integrity of the fibers is dependent upon 
them. This is in strict agreement with the conditions which 
we find in the nervous system of the Jower animals, and_ sub- 
stantiates the conclusions of BETHE and LEONTOWITSCH. 

As to whether these networks of nerve cells and fibers 
will retain their integrity indefinitely when severed from all con- 
nection with the central nervous system, we do not know at 
present. Experiments are in progress to determine whether 
they also will degenerate in the course of a few months, or 
whether they possess the power of regenerating new fibers. 
BETHE (:03) maintains that the sheath nuclei are modified nerve 
cells and still retain their primitive function of neurogenesis. It 
might be expected that these peripheral nerve cells possess a 
similar function. Our present data are not sufficient however 
to warrant the assumption of Leonrowitscu that there is a con- 
stant process of physiological regeneration going on in the 
skin, and that the subepithelial network is transformed into the 


Prentiss, Pestpheral Networks. 115 


peripheral portion of a neurite from a sensory ganglion cell. It 
seems to me rather that in these networks of nerve cells and 
fibers we have to do with primitive nervous structures more or 
less independent of the central nervous system, structures which, 
as BETHE points out, correspond to the diffuse nervous system 
of many invertebrates, and which are connected, on the one 
hand with the integument, and on the other hand with the non- 
striated musculature. 


SUMMARY. 


1. The palatine branch of the seventh cranial nerve forms 
a plexus of medullated fibers in the palate of the frog; from this 
plexus fibers pass, to end by branching in the sensory organs 
of the epithelium. 

2. The innervation of the sensory organs of the palate is 
not as diagrammatic as has been asserted; a diffuse network of 
neurofibrillae connects different sensory neurones, and puts the 
sensory organs into communication. 

3. A network of cells and non-medullated fibers extends 
throughout the deeper layers of the palate and forms a close 
meshwork about the walls of the vessels. 

4. Immediately beneath the epithelium is found another 
network of cells and fibers; sensory fibrils from it end in the 
epithelium, and it is also connected with the perivascular 
network. 

5. The fibers of the networks are nervous structures for 
(a) they are not demonstrated by specific stains for elastic and 
connective tissue; (b) they are composed of neurofibrillae; (c) 
they are often directly continuous with medullated nerves. 

6. Neurofibrillae are present in the cells of the networks, 
but most of them pass through without forming a_ basket- 
work about the nucleus. 

7. When the nerves of the palate are isolated from their 
ganglion cells the medullated fibers which end in the epithelium 
degenerate at the expiration of 25 to 35 days; the myelin 
sheaths disintegrate, and the axis cylinders fail to stain. 

8. Under the same conditions both the cells and fibers 


116 Journal of Comparative Neurology and Psychology. 


of the subepithelial and perivascular networks stain ina normal 
manner and show no degenerative changes in their structure. 

9. Some of the cells of the network are therefore true 
nerve cells and exert a trophic influence upon the fibers con- 
nected with them. 

10. The networks are comparable to the diffuse nervous 
system of certain invertebrates, and their existence is incom- 
patible with the idea that the nervous system is composed of 
of distinct cellular units. 


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:03. The Growth and Histogenesis of the Cerebrospinal Nerves in 
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Bethe, A. 
795. Die Nervendigung in Gaumen und in der Zunge des Frosches. 
Arch. f. mtkrosk. Anat., Bd. 44, p. 185-203, Taf. 12-13. 
796. Ein Beitrag zur Kentniss des peripheren Nervensystems von Astacus 
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:03. Allgemeine Anatomie und Physiologie des Nervensystems. Lezp- 
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THE BEGINNINGS OF SOCIAL REACTION IN MAN 
AND LOWER ANIMALS. 


By G. ly (Merrick, 


Socorro, New Mexico. 


It seems to be easy to employ the word ‘‘social”’ in a very 
slip-shod manner and it may very well be that greater care in 
its definition would remove several bones of contention that are 
being worried from time to time in the journals. 

When we admit that human experience ‘‘polarizes’’ (to 
use Professor BALDWIN’s expression) into ego and alter extremes, 
it becomes necessary very carefully to guard what is meant by 
the social self or social consciousness. CLIFFORD, and other 
writers since, have written of a tribal conscience or tribal self. 
Such expressions may easily be interpreted as though society 
were possessed of a consciousness in the same sense that the in- 
dividual is. Now this is, of course, nonsense, or rather, a fre- 
quently exposed fallacy. 

When we speak of the social self we mean the social re- 
flected in the individual or else we mean an abstraction of common 
elements in the individual selves constituting the society, which 
common factors we may thereafter use, like an algebraic ex- 
pression, as though it had an independent existence. It would 
be of immense advantage in simplifying philosophical and an- 
thropological inquiry if some sort of an agreement could be 
reached as to the use of words in this connection. Ought we 
not carefully to distinguish the two elements just referred to ? 
Let us, for example, call the first the ‘‘socius consciousness, ”’ 
meaning thereby all that portion of our conscious acts which in- 
volves the recognition of other-in-self and self-in-other, or if the 
line cannot be drawn, our conscious acts in so far as this impli- 
cation is under consideration. Let the second element be 


‘HERRICK, Soczal Reacton. 119 


b 


termed ‘‘society consciousness,’’ meaning thereby the common 
elements in the consciousness of the constituents of society or 
the consensus of society. In this way we avoid the ambiguity 
of the term social consciousness, or, if that term must be used, 
then by all means limit it to the social reactions within the indi- 
vidual consciousness and use the necessary circumlocutions to 
express the consensus idea. 

Professor BALDWIN, in his genetic series, lays great stress 
on the ‘‘bipolar self.’’ He shows that development of the ego 
goes pari passu with that of the alter; that self is social from 
the start. But this is only a phase of the general psychological 
law that self is reflexive. The wave of effort is met by an in- 
flowing wave of resistance. Without both of these elements 
experience would be impossible. Just as the simplest form of 
subjectivity is coupled necessarily with an objectivity (substance), 
so the most rudimentary personality involves the social ele- 
ment. 

For ethical purposes it is necessary to note that every 
moral act or thought has a social implication. This is part of 
the meaning of Kanvt’s well-known rules of morals. But psy- 
chology has, or ought to have, something to say as to the ori- 
gin of the social faculty. Much of this has been interpreted by 
Professor BaLDWIN in his description of the projective and 
ejective stages of social development. 

Perhaps, however, some attention should now be given to 
the condition back of the projective activity, namely to the con- 
tinuum habit, or, negatively expressed to fit its more common 
manifestation, the /zatus effect.’ If the equilibrium theory of 
consciousness be true, the elements in the equilibrium may be 
roughly classified into relatively constant, and variable elements, 
the a, b, c, series and the x, y, z series respectively. 

By a process of familiarization, one of the variables may 
be converted into a constant and become a part of the usual 
furniture of consciousness. The process of assimilation causes 
the stimulus or group of stimuli increasingly to participate in 


1 The law of dynamogenesis is implied throughout. 


120 Journal of Comparative Neurology and Psychology. 


the self group. A wooden leg or a thorn in the flesh may as- 
similate itself closely to the self of normal experience, self be- 
ing, of course, a relative or variable term the center of which 
alone is fixed. 

Now let any circumstance deprive us, let us say, of any 
“‘a’’ in the series of constants and there at once arises what we 
may call a feeling of hiatus. If this is true of stimuli in gen- 
eral, it is no less true of many stimuli that are called social. 
The habitutal reaction to the expected resistance is a large part 
of our daily activity and holds the germ of social response. If 
the very trivial nature of the following illustrations can be for- 
given they will illustrate what is meant better than psycholog- 
ical discussion. 

The writer has two horses which for years have been 
driven, housed and fed together. All habitual activities have 
been coordinated by necessities growing out of their environ- 
ment. Originally the animals (mares) regarded each other with 
distrust and even hostility. Even after years, their intercourse 
is always aggressive. One steals the other’s feed and is at- 
tacked for it. There is a continual ‘‘nagging.”’ Usually one 
acquires the ascendency and all that is necessary is a show of 
teeth on the part of one to cause flight or submission on the 
part of the other, which, nevertheless, is in a state of constant 
rebellion. 

Now should one animal be left in the stable with a manger 
full of hay and the other driven away, the stay-at-home is rest- 
less and uneasy, declines to eat and neighs continually. The 
animal driven away strives to turn back, is nervous and neighs 
and starts out of the road on coming in view of any horse in the 
distance. Each, as we say, ‘‘misses’ the other. What is the 
explanation? Evidently the simplest explanation is that a 
large segment has been knocked out of self. A whole group 
of activities (resistances and the like) have been removed. The 
equilibrium of habitual activity has been disturbed. For weeks 
every act has been tacitly or by unconscious implication put 
forth in view of a presence which could be relied upon to react - 
in certain ways. Hitherto the horse never ate, drank or pulled 


Herrick, Soczal Reaction. EAT 


in harness without expecting a certain set of counter actions. 
These may have been unpleasant reactions. When she drank 
she expected to be shoved aside, when she pulled she expected 
to be tweaked by her fellow. But, whatever the character of 
these acts, they have ceased; to the action the wonted response 
is wanting. 

One gets this sense of hiatus in an elementary form when, 
in climbing a ladder in the dark, a rung is discovered to be 
missing. Again, we return to the home after sending the fam- 
ily away on a picnic, thinking ‘‘how pleasant it will be to have 
a quiet day in the study” and find that the unwonted quiet 
sends us wandering through the empty house seeking we know 
not what that has gone from our life and the working equilib- 
rium is not soon restored. This is the ‘‘feeling of hiatus.” It 
is not confined to animate objects. The writer was once dis- 
turbed to find that he could not work well—things were not 
going as usual—there seemed to be a kind of mental unbalance 
and he discovered the cause in the fact that he had forgotten to 
put on collar and tie. This hiatus filled, the typewriter seemed 
to have as free a play of thought as ever. Certain fussy au- 
thors and artists have found it impossible to compose except in 
full court dress. (I fancy a disembodied spirit would have some 
difficulty at first with his ‘‘hiatus.’’) 

The infant, when passed from the arms of the nurse to 
those of a stranger, notices the difference and shows fear or dis- 
comfort. A strange room also disturbs the equilibrium of ex- 
perience. The sphere of experience created by every individual 
is normally a ‘‘continuum.’”’ When this continuum is disturbed 
the ensphering environment is left incomplete and one has the 
same sensation he has when the support beneath him is knocked 
out. It is not necessary that there should be any intellectual 
status in the intercourse. 

The above seems to be the most elementary condition of 
social existence. It consists in the enlargement of the sphere 
of experience by the admission of more and more elements 
which acquire a value to my being asa part of the equilibrium 
quite independent of any moral element in it. Its removal pro- 


122 Journal of Comparative Neurology and Psychology. 


duces an emotional reaction growing out of the feeling of loss 
—hiatus in self—solution of individual continuity. * We here 
have the elementary mechanic of social life. 

It is only after this relation is percetved as mutual that a 
moral element enters. When the child was about to leave 
home for a long visit he visited the cow, the chickens, and the 
cat to say farewell, and his regret in parting was greatly en- 
hanced by the feeling of how great the grief of these fellow 
creatures must be in losing him. He even paid a visit to famil- 
iar spots and took leave of them with all the feeling of re- 
ciprocity that he experienced in the case of living things. These 
things formed a real part of his experience, he must also form 
a part of theirs. This feeling of participation is a second step 
and a moral one. ‘This phase of social feeling is never entirely 
obsolete. ‘‘Who shall smoke my meerschaum pipe’ and ‘ ‘these 
dear spots shall see me no more’’ illustrate this fact. 

Add the further idea of dependence and a high social status 
is reached. ‘‘Really, I ought not to go away, for the servant 
will forget to feed the animals.’’ Obligation has arisen because 
of the feeling of participation. I find that I form a necessary 
segment in their lives, and, as they form a part of my sphere— 
of ‘‘me’’—of my larger or social self, I am obligated by that 
fact, i. e., by an enlargement of the law of self-preservation, to 
care for these animals. This is an obligation having a different 
kind and more intimate sort of compelling force than would be 
possible in the case of an inanimate and so non-participating 
thing. It may be that in reality the animals do not know that 
they are dependent on me for their sustenance, but it suffices 
that I imagine them so to feel. This mutuality feeling makes 
the obligation moral in a different sense from that growing out. 
of fear that I might perhaps suffer a pecuniary loss by neglect. 

It is customary to say that the social self is ejective, i. e., 
that we project our own feelings and experiences into others 
and act in view of them. Another and in some respects a truer 
way of expressing it is that the self is constantly enlarging to 
embrace new elements. It is not simply that someone else feels 
as I do—that might be an interesting fact, but it would have no 


Herrick, Soczal Reaction. siete 


compelling power. It is rather that I affect the other who par- 
takes with me in feeling. My affecting him makes him partner 
in my feeling. It is the element of participation or recognition 
of self in other which creates obligation. The mere fact that 
men in Mars feel as we do would not awaken moral response 
unless it could be showed that we affected them in some way. 

Professor Fiske has indicated that the long period of help- 
lessness on the part of the human infant is a very important 
factor in the intellectual superiority of the individual human be- 
ing. Still more important to the race is the effect of long-con- 
tinued dependence on the development of society. The tie 
that binds early societies is to a very large extent this same 
helpless period of infancy. In most lower animals this period 
being very short, the family relation covers a very limited 
period, while in the human family under ordinary circumstances 
this dependence is a continuing state and the family (and so 
eventually the tribe) becomes a permanent element to be reck- 
oned with in all dealings with men.’ It is not necessary to point 
out the many and far-reaching results of this fact. 


1 Note that social insects likewise pass through a helpless stage, requiring 


active ‘‘nursing.”’ 


INHIBITION AND REINFORCEMENT OF REACTION 
IN THE FROG .KANA CLAMITANS: 


By Rosert M. YERKES. 


(From the Harvard Psychological Laboratory, HUGO MUNSTERBERG, Derector.) 


GENERAL PROBLEMS AND METHODS. 


An investigation of the time relations of neural processes 
in the frog, which began with the determination of simple reac- 
tion-time (YERKES, '03, p. 598 et seq.), has now been extended 
to a study of the influence of complication of stimuli on time 
of reaction. In this report an attempt will be made to present, 
in summary, certain results which contribute somewhat to 
our knowledge of inhibition (Hemmung) and reinforcement 
(Bahnung).’ 

Attention was called, in the paper referred to above (p. 
627 et seq.), to the inhibition, by visual stimuli, of visible 
motor reactions to auditory stimuli, as well as to the apparent 
reinforcement, by an auditory stimulus (tuning-fork sound), of 
reactions to visual stimulation by a moving red disc, These 
observations led to a more detailed and systematic study of the 
influence of complication of stimuli, so far as reaction-time is 
concerned. 

The work thus far done includes studies of (1) the effect 
of stimulation by increase in light intensity upon reaction-time 
to electric stimulation of the skin, (2) the effect of an auditory 
stimulus upon electric reaction-time, (3) the effect of visual 
stimulation by the appearance of a moving finger, (a) when 
shown almost simultaneously with the giving of the electric 
stimulus, and (b) when shown a considerable interval (at least 


1 This work will be published in detail, in connection with other results, in 
Volume 2 of the Harvard Psychological Studies. 


YERKES, /x/ubition and Reinforcement. 125 


one second) before the giving of the electric stimulus, (4) the 
effect of visual stimulation by a moving red disc, shown in one 
series of experiments 0.1’, and in another 0.5”’ before and until 
the electric stimulus was given. 

In all cases the reaction-time to electric stimulation of the 
skin was studied with special attention to the influence of other 
stimuli which were given in definite temporal relation to the elec- 
tric stimulus. The general method of the investigation was the 
same as that described in my earlier paper (p. 601). A Hipp 
chronoscope, controlled by a Cattell’s falling screen, served as 
a time measuring apparatus. The other essentials of the appa- 
ratus were a reaction-box, and devices for giving the stimuli 
and indicating the reaction. Onthe bottom of the reaction-box 
a series of wires were so placed that an electric stimulus could 
be given to the frog resting upon them by the closing of a key 
in the hands of the experimenter. In preparation for each ex- 
periment the frog was placed upon these open circuit wires in 
such a position that the weight of its body pressed upon a deli- 
cate spring in the floor of the box, thus causing the chronoscope 
circuit to be completed. The forward jump of the frog in re- 
sponse to stimulation caused the breaking of this circuit by the 
release of the spring upon which the animal rested. When all 
was in readiness for an experiment the chronoscope was started, 
and a key closed which simultaneously gave an electric stimulus 
to the frog and completed a circuit which caused the chrono- 
scope record to begin. The stimulus consisted of a current 
from one or more ‘‘Mesco”’ dry batteries. The motor reaction 
of the frog broke the chronoscope circuit, thus causing the 
chronoscope record to stop. It was then possible for the ex- 
perimenter to read from the dials of the chronoscope the time, 
in thousandths of seconds, intervening between stimulus and 
reaction (reaction-time). In case of additional stimuli in con- 
nection with the electric, various simple devices were intro- 
duced to meet the demands of the experiments. These will be 
described in connection with the statement of results in each 
case. 


126 Journal of Comparative Neurology and Psychology. 


RESULTS OF EXPERIMENTS. 
1. Electric Stimulation and Light. 


The following specimen records leave no room for doubt 
as to the inhibitory influence of increase in light intensity on 
the electric reaction. In these tests the visual stimulus was 
given from I to 2 seconds before the electric by the turning on 
of a 16-candle power electric light which was placed 30 cm. in 
front of the animal in one series, and 15 cm. above it in another. 

The laboratory records appended are self-explanatory. 


TABLE I. 


Title of investigation. . . . Electric-Visual Series (Red Light). 
Experimented on. . . . Green Frog No. 4. 
l 8 a 
Harvard Psychological Laboratory. . . 9.15 A. M., Feb. 28, 1902. 
! § k 9-15 ; ’ 
Chronoscope control average 1896'. . . Electric stimulus, 1 Cell. 
Red light, 16 c. p., 2 seconds before and until electric stimulation. 


Number of Experiment. Reaction-time. 
I ; ; : : : P : 1446} 
2 192 
3 587 
4 No reaction. 
5 ; E : : : : : No reaction. 
6 Reaction to second stim. 
” No reaction. 
8 : ; 3 : F ; : No reaction. 
9 . : : : : ' ity) 
10 : ‘ ‘ : : ; : No reaction. 
II ; ' ; : 4 : : No reaction. 
12 , : : - F : , No reaction. 
@ : : : : : : : No reaction. 
14 4 , ; : 4 : F 1190 
15 : : 3 Z : 4 : No reaction. 
16 z : : : : } : No reaction. 
17 : : : : oe ee F No reaction. 
18 . : : , : ‘ : No reaction. 
19 : : : ; : : : No reaction. 
20 . No reaction. 


Table I indicates the lack of response to a I cell electric 
stimulus when accompanied by an increase in light intensity, 
and Table II proves conclusively that the light is the cause of 
the inhibition of reaction. 


1 All reaction-times are given in thousanaths of a second, indicated by 6. 


YERKES, /uhibition and Reinforcement. 027; 


TABLE II. 
Title of investigation. . . Electric-Visual (Red Light). 
Experimented on. . . . Green Frog No. 4. 
Harvard Psychological Laboratory. . . 9.40 A. M., Feb. 28, 1902. 
Chronoscope control average, 189 6. . . . Electric stimulus, 1 Cell. 
No LIGHT. 
Number of Experiment. Reaction-time. 
I 1526 
2 145 
3 221 
4 327 
5 263 
6 271 
7 329 
8 215 
9 225 
10 : : A 216 
LIGHT BEFORE ELECTRIC STIM. 
II : F 3 : ‘ F ‘ No reaction. 
12 : : 5 F : : ; No reaction. 
13 : : : : : : ; No reaction. 
14 : ; : : : 5 : No reaction. 
15 : 5 4 : : : . No reaction. 
No LIGHT. 
16 , ; : ; 3 ‘ : 216 


The inhibitory influence of lightin this case depends upon the 
intensity of the electric stimulus. Even a very strong light will 
not cause much retardation of reaction to a 3 or 4 cell current. 
As the strength of the electric stimulus decreases the delay of 
reaction increases, until finally there is complete inhibition. At 
this point, an electric stimulus to which the frog would react 
almost invariably when there is no disturbing condition, will 
fail to cause reaction in the presence of a sudden increase in 
light intensity. 

MERZBACHER (00, p. 253) states that the leg reflex of a 
frog, so placed that its legs hang free in the air, is greater in 
response toa given cutaneous stimulus in darkness than in 
daylight.’ 


1 «Blendung oder blosse Lichtentziehung erhéht die Erregbarkeit fiir me- 


chanische Reize.” (p. 253.) 


128 Journal of Comparative Neurology and Psychology. 
2. Electric Stimulation and Sound. 


Inasmuch as the experiments here described were con- 
ducted in a laboratory where noise and jar are unavoidable, it is 
worth while at this place to offer reasons for the belief that 
sounds did not to any considerable extent affect the time of re- 
action to other stimuli. 

As tests of the influence of loud sounds on the electric re- 
action-time, an apparatus was arranged whereby an electric bell 
rang for a certain interval before the electric stimulation. The 
bell was placed 40 cm. from the frog, and for one series of 300 
reactions it rang 0.1 second before the electric stimulation, for 
another 1.0 second before. The reactions were taken in pairs, 
first a reaction to the electric stimulus alone, then one to the 
electric stimulus preceded by the auditory, at the rate of one a 
minute. The results may be summarized, without mention of 
other values than the means, thus: 

Average of 300 reactions to 2 Cell Electric Stimulus Alone, 172.0 6 
peries 1. Average of 300 reactions to 2 Cell Electric Stimulus, when preceded 


for 0.1 second by Auditory Stimulus, 176.5 6 


Average of 300 reactions to 2 Cell Electric Stimulus Alone, 144.7 6} 
Series II. Average of 300 reactions to 2 Cell Electric Stimulus, when preceded 


for 1.0 second by Auditory Stimulus, 150.2 6 


In each of these series there is evidence that the sound 
caused slight inhibition or delay of reaction, but when we con- 
sider, as will be made clear later, that the probable error of the 
averages is greater than the apparent delay, it is at once evi- 
dent that we can not safely argue from these results to the in- 
hibitory influence of sound. Indeed most observations on rec- 
ord tend to show that audition is not very important in the frog, 
at least when it is out of water. 

3. Electric Stimulation and Moving Object. Preliminary Experi- 
ments. 

For the purpose of determining the effect upon reaction- 
time to an electric stimulus of stimulation of the eye by a 


1 The conditions were not precisely the same for the two Series, as the frogs 
had become inactive. 


YERKES, /nfhibition and Reinforcement. 129 


rapidly moving object, experiments were made in which, as in 
the case of sound and electricity, reactions to the electric stim- 
ulus alone and to visual and electric were alternated. Thus in 
case of each pair of reactions it was possible to note whether 
the visual stimulus lengthened or shortened the reaction-time. 
The visual stimulus was given by quickly bringing a finger be- 
fore a window in the reaction-box. 

Asa preliminary test two series of 20 pairs of reactions 
each were taken with two frogs (Nos. 5 and 6). In the first 
series the finger was suddenly moved over the window, and the 
electric stimulus was given either simultaneously or a small frac- 
tion of a second later. It was of course impossible to arrange 
for an accurate measurement of the temporal relations of the 
stimuli in this case. In case of the second series the finger was 
moved: back and forth before the opening for an interval of not 
less than a second before the electric stimulus was given. 

These experiments yielded results which were surprising 
in view of the previous work. When the stimult were given 
almost simultaneously the visual reinforced the electric, t. e., short- 
ened the time of reaction. As appears in the upper part of Ta- 
ble III, the average time of 40 reactions (20 for each frog) to 
the electric stimulus was 148°, and to the electric when it fol- 
lowed upon the visual, 1286. Furthermore, an examination of 
the pairs of reactions shows, as the table indicates, that there 
were 27 cases in which the visual stimulus caused reinforcement 
to 13 in which it caused inhibition. When the visual stimulus 
preceded the electitc by a considerable interval (1 second, see the 
right side of the table) exactly the reverse effect appeared, there 
was marked iniubition of reaction, The averages are 150 © for 
electric stimulation alone, and 1786 when it was preceded by 
the visual stimulus. In this series there were 25 cases of in- 
hibition to 14 of reinforcement. 


% 


130 Journal of Comparative Neurology and Psychology. 
TABLE III. 


Reaction-time to Electric Stimulation Alone, and to the Same when 
Preceded for 0.1, 0.5 or 1.0 Second by Visual Stimulus. 


nas e Ses : 
So : z O82 : 5S 
> 0 as) £ oa a) s 
e Ceo |) sone: Alaa Y "28 |} e2 1] oe] & 
orien =, o) G sre te _ See ; 
Y Ee a 2 eae ou ora i Sie cy Qe aire 
an of a5 else =e 3 o 8 55 fete aq as 
° o Oo Dn gra oat 35 o oo ano oa 3°O 3 
5 ra bn arene Seen a 1 rai ace oe = fs my 
ce Aq |Fa | 4H | 44 | 4248 || ax ,ea | ae 24 | 4a 
* 


Preliminary Series. Visual Stimulus Moving Finger. Averages for 20 reactions. 


No. 5. [179-16] 158-61 6 14 fo) 1636 | 206-6] 14 6 fo) 
No. 6. |116 98 9 13 fo) 136+] 150 II 8 I 
rad 148 | 128- | 13 27 | fe) 150- | 178- | 25 | 14 I 
Visual Stimulus Moving Red Disc. 
Visual 0,1’ before electric. | Visual 0.5” before electric. 
Series I. Averages for Bs reactions. 
INO. 554) 077 163- | 10 15 fe) 170-++| 255- 15 9 I 


No. 6.| 148-++| 112+ 6 19 


| 
| 
| oO T15— | 178— 18 7 fe) 


Series II. Averages for 25 reactions. 


No. 5. | 135-+| 120+ 18 oO 155+ 259-4 24 I fe) 
No. 6.| 128—- |] 111- | 6 19 oO 137.1 227+ 17 if I 


“I 


bo 


reer 147 126 29 fi | fe) | 


ma [ae 


In Table IV I have given the probable errors, standard 
deviations and coefficients of variation of the means, except in 
case Of, Series LL. 


4. Electric Stimulation and Moving Red Disc. 


The indications of the importance of the temporal relations 
of stimuli, so far as reaction-time results are concerned, fur- 
nished by these crude preliminary observations led me to un- 
dertake a more accurate study of the subject. To this end a 
revolving disc, which moved at the rate of one revolution per 


Yerkes, /uhibition and Reinforcement. 131 


minute, was so arranged that at a certain point it closed an 
electric circuit in which I had placed a magnet. This magnet 
attracted a steel arm at the end of which a disc of red card- 
broad 12 mm. in diameter was suspended. With the making of 
the circuit the steel arm was drawn downward suddenly and the 
red disc, by reason of the vibrations of the arm moved rapidly 
back and forth in front of a window in the reaction-box. In 
this way the moving object was exposed to view about Io cm. 
to the right and 3 cm. in front of the right eye of the frog. 
The revolving disc, a fraction of a second later, completed the 
electric stimulus circuit. Thus both stimuli were given auto- 
matically, at such an interval apart as the experimenter desired. 
In the two series of results now to be described the intervals 
were O.1 and 0.5 second respectively. 

These series consisted of 25 pairs of reactions each, with 
two animals. The results of the series are presented separately 
because the experiments which constitute them were separated 
by a period of three weeks, during which time the conditions 
of the frogs changed noticeably ; they became less active and 
less sensitive to stimuli. 

The lower half of Table ILI contains a simple statement 
of the results of these series. It is to be noted that these re- 
sults agree fully with those of the preliminary series. The vis- 
ual stimulus of a moving red disc, given 0.1 second before a 2 cell 
electric stimulus, reinforces the electric reaction, t. e., tt shortens the 
tame of reaction. The same visual stimulus given 0.5 seconds be- 
fore tends to inhibit the electric reaction, t. e., it lengthens the time 
of reaction. 

Table IV contains the various values determined for the 
results of these series. The general averages for the results of 
the Preliminary Series and those of Series I are as follows: 


132 Journal of Comparative Neurology and Psychology. 


Mean, with Standard Deviation, | Coefficient of 


timulus Probable Error. | with Probable Error. | Variation 


Elect. Alone. . 
180 reactions. 150.54 5.48.6 38.55+ 4.09.6 25.68 


Elect. with Visual 0.1’” 


before. 133.0+ 4.93. BA. 32. 43.23 26.84 
go reactions. 


Elect. with Visual 0.5” 


or 1.0” before. 197.0+ 14.19. IOI.44+ 10.03 50.74 
go reactions. 


Concerning the statistical values given in connection with 
this work certain important facts should be noted. First, the 
reactions are very variable. In fact the variability is so large 
that, were it not for the analysis of the pairs of reactions, the 
results could not be presented as conclusive evidence of the in- 
hibitory or reinforcing influence of stimuli. But the fact that 
two times in three a visual stimulus almost simultaneous with 
electric stimulation of the skin shortens the time of reaction to 
the latter, whereas the same visual stimulus when given half a 
second before the electric lengthens the reaction-time in at least 
two-thirds of the cases, justifies us in putting confidence in the 
averages of the series despite the large probable errors and 
coefficients of variation. 

The standard deviation of the electric reaction-time is un- 
usually large because, in averaging, no selection was made from 
among the results. The apparatus was such as to permit reflex 
reactions, and as some of these (40% to 70%) are included in 
the series, as well as delayed reactions, the range is often from 
40% to 5006. Arbitrary selection of reactions by limitation of 
the range did not seem advisable, and I have therefore pre- 
sented the results as they were taken. Indeed, when we work 
with voluntary modifiable reactions, instead of with those that 


are forced, we must not expect either small errors or small 
variabilities. 


YERKES, /uhibition and Reinforcement. 


133 


TABLE IV. 


Reaction-time to Electric Stimulation Alone, and to the Same when 
Preceded by a Visual Stimulus. 


Electric Stimulus Alone. 


Electric Stimulus when Preceded 
for a Short Interval (0.1/) by 
Visual Stimulus of Moving Finger. 


Coeffi- | Coeffi- 

Standard cient : 3 ient 

1 Standard ten 
ee AGE Deviation. | of War- 2S ee Varia_ 

iation. tion. 
No. 5. | 179+ 6.95 67/46.09+ 4.926] 25.75 || 158+ 6.826 |45.21+ 4.826] 28.61 
No. 6. | 116+ 4.49 |29.75+ 3.18 | 25.65 98+ 5.07 |33.57+ 3-58 34.26 
Electric Stimulus when Preceded 

Electric Stimulus Alone. for a Long Interval (1.0) by 

Visual Stimulus of Moving Finger 
No. 5.} 163+ 4.17 | 27.66+ 2.95] 16.97 || 206+ 9.29 eet eer | 29.87 
No. 2 136+ 5.71 | 37-88+ 4.04] 27.85 || 150+ 9.66 | 64.02+ 6.83] 42.68 
seri or Ses : Visual Stimulus of Moving Red 
Series I. Electric Stimulus Alone. Dice ir” Betore Blackie Sumaalus 

| 

INO Senay 474) | 25eh22= 3-35, |) 14sL0) ||) TOs 3857) |) 26:45 2.52 16.23 
No. 6.| 148+ 6.37 | 47.25+ 4.51 | 31.92 || 112+ 4.27 | 31.65+ 2.02 28.26 


Series I. Electric Stimulus Alone. 


Visual Stimulus of Moving Red 
Disc 0.5” Before Electric Stimulus 


Nol 5: | 1702: 5-05 | 37-45 5-29 
Noi 6.) Tt5s: 6.37 47254 4.51 
Aver- 
age of 


Ai 150.5+5.48 6/38.55+ 4.096 


22.03 


41.09 


25.68 


255 21-47 Ronee 62.43 


178+ 16.34 |121,09+ 11.54] 67.97 


General Ave. of all 0.1” een 


133+ 4.936 |34.22 + 3.23 6| 26.84 


Gen. Ave. of all .5 and 1” Interval. 


197+ 14.19 [101.46 + 10.03 50.74 
1 Values were determined by use of the following formulae : 
; (o} 
Mice eyes ivef) Probable) Hrror of Mean) — 32 :6745———— 
aes 
S a, A Set) ee eee see 6 
Standard Deviation = Wa Coefficient of Variation = Wiest 
n Med 


Probable Error of S. D. = + .6745 


2 Probable Error. 


G == Sq 10) 


2n 


134 Journal of Comparative Neurology and Psychology. 


The fact that the variability of the reaction-time to an elec- 
tric stimulus in connection with a nearly simultaneous visual 
stimulus is slightly less than that for the electric reaction-time 
is worthy of note, but it must be admitted that the difference is 
not sufficiently large to justify us in laying much stress upon 
the fact until further work furnishes additional evidence on the 
point. Clearly enough the greater variability when the visual 
stimulus precedes the electric by an interval of 0.5’ to 1.0” is 
due to the increase in the number of delayed reactions, which 
in turn we may suppose to be the result of the visual stimulus. 
For these reactions, moreover, the range is greater than for the 
electric reaction-time, and a graphic representation of the dis- 
tribution of the results shows that the mode is much nearer the 
500 ° extreme than in case of the simultaneous stimuli series. 

So far as my observations go (and it must be remembered 
that this research deals primarily with voluntary reactions) the 
statements thus far made concerning the influence of visual stim- 
uli upon electric reaction-time hold for reflex reactions (by 
which is meant reactions in from 40 © to 706) as well as for the 
slower more deliberate reactions. If further investigation 
should confirm the suggestion which my results furnish it would 
lend additional support to work already done on the nature of 
the reflex ; for MERZBACHER, not to mention the results of sev- 
eral other investigators, found that visual stimulation of the eye 
of the frog with a colored paper screen increases the extent of 
the reflex in response to cutaneous stimulation, or in other 
words, causes reinforcement of the reaction (’00, p. 250). As 
he has not studied the phenomenon with reference to the tem- 
poral relations of the stimuli, no comparison of his results with 
those of this paper are possible. 

The literature of inhibition and reinforcement consists al- 
most entirely of papers on the reflexes of animals, or on the volt- 
tional process of man, and in no instance have I been able to 
find any accurate statements concerning the significance of the 
temporal relations of the stimuli. Wuwnpr (03, III, p. 443) 
states, as his belief, that the interference of unlike 
stimuli is greater than that of stimuli of the same qual- 


YERKES, /rhibition and Reinforcement. 135 


ity. One sound delays the time of reaction to another, 
according to his findings, 45°, while a visual stimulus 
causes a delay of 78° in the auditory reaction. Apparently, 
in the researches thus far made, complication of stimuli more 
commonly causes inhibition than reinforcement. In the light of 
the results which have been considered in this paper it is of in- 
terest to inquire whether this may not be due to the fact that 
the temporal relation has not been considered. Possibly any 
two stimuli may be given in such relation that they will now in- 
hibit, now reinforce one another. 

An investigation by BowpircH and WarREN (’g0) is of 
special interest in this connection, since they studied the influence 
on knee-jerk of various stimuli, given at different intervals with 
respect to the tendon blow. As appears from the following 
summary statement (p. 60-61) of their results there is striking 
agreement between their findings for this reflex and mine for 
the frog: 

‘“(1) In the majority of individuals experimented upon a 
voluntary muscular contraction occurring simultaneously with 
the blow upon the knee increases the extent of the knee-jerk, 
but with the prolongation of the interval between the reinforce- 
ment signal and the blow this effect is reversed ; the knee-jerk 
becomes much reduced in extent and may even entirely disap- 
pear. With a still further prolongation of the interval the knee- 
jerk gradually returns to its normal value. The interval at 
which the effect changes from positive to negative varies with 
different individuals from 0.22” to 0.6”. The interval at which 
the knee-jerk returns to its normal value is 1.7’-2.5’. In two 
individuals the effect of muscular contraction on the extent of 
the knee-jerk was wholly positive. 

‘“(2) The effect of a sudden auditory stimulus on the ex- 
tent of the knee-jerk was, in the three subjects of experiment, 
almost wholly positive, though great individual differences were 
observed. The maximum effect was produced when the inter- 
val between the sound and the blow was o.2”’-0. 3”. 

‘*(3) The effect of a sudden visual stimulus upon the ex- 
tent of the knee-jerk was with two of the three subjects of ex- 


136 Journal of Comparative Neurology and Psychology. 


periment almost wholly positive, the maximum being reached 
when the interval between the flash and the blow was o.1’- 
0.3”. With the third individual a positive phase having its 
maximum when the interval was zero gave place rapidly toa 
negative phase reaching its maximum at 0.4”-0.8”. 

‘*(4) The effect of a sudden stimulus of the conjunctiva 
by an air blast was in general similar to that of a visual stim- 
ulus, except that the positive phase in all three individuals 
reached its maximum when the interval between the blast and 
the blow was 0.1”, and the negative phase in the individual 
who manifested this phenomenon had its maximum at o.8’- 
LeOle 

The effects of sudden stimulation of the nasal mucous 
membrane with a blast of air and of stimulation of the skin of 
the neck were very similar to those stated. 


SUMMARY AND CONCLUSIONS. 


1. Increase in light intensity from 1” to 2” before electric 
stimulation of the skin of the frog causes delay of reaction to 
the latter stimulus. If the electric stimulus be intense the in- 
hibitory influence, as indicated by the time of reaction, is 
slight, if it be weak the inhibition is marked, and reaction may 
fail entirely. 

2. Auditory stimuli give contradictory results. Some- 
times they appear to inhibit, sometimes reinforce, the electric 
reaction. In case of the sound of an electric bell introduced 
(a) 0:17 ‘before the electrie-stimulus; and((b) mo" before, (the 
average for 300 reaction-times indicate a slight inhibitory in- 
fluence. 

3. Visual stimuli either inhibit or reinforce electric reac- 
tions according to the temporal relation of the two stimuli. (a) 
The visual stimulation of a moving object when given 0.1” be- 
fore electric stimulation of the skin causes reinforcement of the 
reaction, i. e., shortens the reaction-time. (b) When given 
O.5'” 
ulus causes inhibition, i. e., lengthens the reaction-time. 


or 1.0” before the electric stimulus the same visual stim- 


4. The experiments described prove that it is of import- 


YERKES, /xhibition and Reinforcement. 137 


ance to consider the temporal relation of stimuli in any study 
of the relations of complexes of stimuli to sensory or motor 
processes. To say that two stimuli were given ‘‘nearly simul- 
taneously” or ‘‘within a short interval of one another’ does not 
suffice, for this unmeasured interval may make all the difference 
between the conditions necessary for reinforcement and those for 
inhibition. 

5. If the meaning of the above statements in terms of the 
neural processes is demanded, only a speculative reply can as 
yet be given. Of theories of inhibition there are already 
enough; what we need is methods by which the neural process 
may be studied. Until we have more definite knowledge of 
what occurs in the organism in case of the mutual interference 
or reinforcement of stimuli it may be well for us to experiment 
much and speculate little. 

A clear statement of what the neural changes which condi- 
tion inhibition and reinforcement say be is to be found in a re- 
cent article on inhibition by McDovgatt ('03). So far as this 
paper is concerned it matters little whether inhibition be ‘‘as- 
similation,’’ ‘‘drainage,’’ ‘‘competition,”’ or something yet un- 
named. 


References. 


Bowditch, H. P. and Warren, J. W. : 
’90. The Knee-Jerk and Its Physiological Modifications. /vur. of 
Phystol., Vol. 9, pp. 25-64. 
‘McDougall, Ww. 
03. The Nature of Inhibitory Processes Within the Nervous System. 
Brain, Part 102, pp. 153-191. 
Merzbacher, L. 
*oo. Ueber die Beziehungen der Sinnesorgane zur den Reflexbewegungen 
des Frosches. Arch. f. die ges. Physiot., Bd. 81, pp. 222-262. 
Wundt, Wilhelm. 
03. Grundzuge der physiologischen Psychologie. Funfte Auflage, 
Leipzig. 
Yerkes, Robert Mearns. 
°03. The Instincts, Habits and Reactions of the Frog. Harvard Psycho- 
logical Studies, Vol. 1, pp. 579-638, (Psychological Review Mono- 
graph Series, Vol. 4.) 


ON THE, BEHAVIOR AND: REACTIONS “OF “LINUE 
EUS IN~EARLY “STAGES OF 10S “DEV EEOL 
MENT.’ 


By RayMonpD PEARL. 


Introduction. 


In morphological research two modes of procedure are 
usually followed in investigating the significance of some par- 
ticular structure of an organism. First the form, position, re- 
lations and otaer characteristics of the structure in the adult 
organism are studied. Then the embryological history is 
worked out for the purpose of ascertaining how the structure 
develops to the complex condition of the adult. In this way, 
of course, has been gained the complete explanation of many 
organs and structures which were inexplicable when the adult 
condition alone was considered. Indeed, embryological study 
has come to be considered an absolutely necessary part of 
almost any morphological investigation which aims at complete- 
ness. The ontogenetic history of an organ is regarded as of 
prime importance in elucidating the adult condition. 

It is evident that the same thing may be true when the 
problem under consideration is one in animal behavior, instead 
of in animal morphology. As we go up the scale from the 
lower to higher forms, the behavior becomes more and more 
complex, and less easily resolvable into simple component 
factors. To be sure, the increase in physiological complexity 
does not run exactly parallel to the increase in morphological 
complexity, yet one does not have to go far before the analysis 
of the behavior of the adult organism becomes extremely diffi- 


! Contributions from the Zoological Laboratory of the University of Michi- 
gan, Ann Arbor, Mich., No. 71. 


PEARL, Reactions of Limulus. 139 


cult of accomplishment. For some time before the present 
piece of work was begun it was the opinion of the writer that 
valuable aid in the analysis of the behavior of higher organisms 
might be gained by following the plan of the morphologist and 
studying the development in the individual of the characteristic 
features of the behavior. Just as the morphologist studies the 
ontogeny of an organ as an aid to the understanding of the 
adult condition, so might the comparative psychologist study 
the ontogeny of a reaction. It seemed reasonable to suppose, 
in view of the close relationship which JENNINGs and others 
have shown to exist between structure and type of behavior in 
lower forms, that in higher forms the behavior would be sim- 
pler in character during embryonic or larval life when the struc- 
ture is simpler. Of course we know in a general way that this 
is true; but does it hold in detail for single complex reactions 
and reflexes? So far as is known to the writer, very little 
systematic work on behavior has been done from this point of 
view, except on some of the mammals and birds (cf. notably 
the work of Mriits, Liroyp MorcGan and Sma tt). In these 
forms the behavior has evidently a considerable psychical ele- 
ment in it. It was with the idea of determining whether anything 
_ of importance might be gained by studying the ontogeny of re- 
actions primarily reflex in nature that the present piece of work 
was undertaken. 

The form chosen for study was the king-crab Lzmulus 
polyphemus. The reasons for this choice were two-fold; in the 
first place, I was: already familiar with the behavior and reac- 
tions of the adult organism, and in the second place, Lzmulus is 
a form in which the behavior is quite complex, and yet at the 
same time the different reflexes are strikingly definite and ma- 
chine-like in character. The adult Lzmulus is an almost ideal 
form for physiological work, on account of its tenacity to life 
after most extensive operations have been performed upon it, 
and because of the definiteness of its responses. Something of 
the complexity as well as the definiteness of its behavior can 
be gathered from the excellent account which PaTTeEN (’93) has 
given of the gustatory reflexes, for example. 


140 Journal of Comparative Neurology and Psychology. 


The behavior of the adult Lzzulus is principally made up 
of the following movements and reflexes: the respiratory move- 
ments of the abdominal appendages, the swimming movements 
of the abdominal and thoracic appendages, various ‘‘gill clean- 
ing” reflexes of the abdominal appendages and the sixth legs, 
walking movements, and the reflexes of gustation and degluti- 
tion. Furthermore, it responds to temperature stimuli very 
strongly and characteristically, also to certain sorts of tactile 
stimuli, to disturbances of its equilibrium, to chemical stimuli, 
and is thigmotactic and phototactic. The original plan of the 
present work was to make a thorough detailed study of the be- 
havior and reactions during every stage of development from 
the time the embryo left the egg membranes till it attained the 
adult condition, in its behavior at least. It was hoped that in 
this way steps in the development of the reactions and reflexes 
could be traced. 

The work was begun in the U. S. Fish Commission La- 
boratory at Wood’s Hole, in July, 1go0o0, and continued through- 
out the summer. In that time the behavior was studied and 
the work finished from my point of view (with the exception of 
the phototactic reaction) up to the stage at which the first 
moult occurs (end of the so-called ‘‘trilobite’’ stage). During 
the following fall a preliminary statement of the results obtained 
was published in Sczence.' It was expected at that time that 
the work would be taken up again the next summer and older 
stages studied. This, however, proved to be impossible and at 
no time since have I been able to take up the work again. As 
it is uncertain when I shall be able to go on with this problem 
it has seemed desirable to publish the results so far obtained. 
I wish to put on record the complete statement of the facts 
made out in the two developmental stages which have so far 
been investigated. 

It gives me pleasure to make acknowledgement at this 
point to those who have in one way or another aided in this 
work. To Professor Wm. PatTeN, my friend and former 


UN. S. Vol. XII, No. 311, pp. 927-928, 1900. 


( 


PEARL, Reactions of Limulus. I4! 


teacher, I am indebted, not only for the material on which the 
work was done, which he very kindly furnished me, but also 
for many helpful suggestions freely offered as the work pro- 
gressed. When the work on Lzmulus embryos was begun I 
had already been engaged for two years on a study of the phys- 
iology of the brain of the adult animal, under his direction. 
Without the thorough knowledge of the adult behavior thus 
gained the present study would hardly have been possible. To the 
authorities of the U.S. Fish Commission, and especially to Dr 
H. C. Bumpus, I am indebted for the numerous facilities which 
were freely placed at my disposal at the Wood’s Hole Labotra- 
tory. 
Material and Methods. 


The material used consisted of several hundred developing 
Limulus eggs which were given me by Dr. Patren. When re- 
ceived they were nearly all at about the stage of development, 
designated as Stage I, by KiNnGsLey (’92). At room tempera- 
ture development proceeds quite rapidly, but owing to the fact 
that there is a great deal of variation in the rate of development, in- 
dividuals in widely different stages of development may be found 
at any time in the same batch of eggs. The eggs and embryos 
were kept in shallow glass dishes in sea-water which was changed 
at intervals, usually once in twenty-four hours. In this way 
the embryos were kept in good condition for a period of nearly 
two months. 

The results of the present work will be discussed under 
two headings: first the behavior and reactions before the em- 
bryo leaves the egg membrane (‘‘vicarious chorion,’ K1NGs- 
LEY’s Stage I), and second, the behavior up to the time of the 
first moult after the animal begins its free existence (the so-called 
‘trilobite’ stage, KinGs.Ey’s Stage K). © General accounts 
with figures of the morphological development of Lzmulus are 
given by KrinGsLey ('85 and 'g2). 


The Behavior before the Embryo begins its Free Existence. 


Stage of Development.—The earliest stage at which definite 
results could be obtained regarding the movements and reac- 


142 Journal of Comparative Neurology and Psychology. 


tions of the Lzmulus embryos was shortly before the time of 
hatching.’ At this stage the embryo has a distinctly limuloid 
appearance in nearly all respects. Ail the appendages are 
formed, and are movable, with the exception of the long telson 
characteristic of the animal in later stages. The legs are formed 
on the same plan as those of the adult female, the secondary 
sexual modifications of the chelae of the first pair of walking 
legs in the male, not yet appearing, In this and the succeed- 
ing stages the embryos have a general, superficial resemblance 
to a trilobite which has led to the designation of these as the 
‘‘trilobite stages’ in the development. The embryo lies in the 
“vicarious chorion” (cf. PACKARD ’72, and KiNnGsLey, '85, p. 
525) surrounded by fluid. The ‘‘vicarious chorion”’ is consid- 
erably greater in diameter than any dimension of the embryo, 
so that there is considerable free space on all sides of the latter. 
The embryo at this stage is about 4 mm. in length. The fol- 
lowing account of the behavior within the ‘‘vicarious chorion”’ 
applies to embryos at any time within a week before hatching. 
Closer time relations than this, as will appear from the account, 
cannot be fixed in the development of the reactions of this or- 
ganism. . 

Normal Position of the Embryo.—The embryo lies at the 
bottom of the hollow sphere formed by the ‘‘vicarious chorion,” 
with its neural side uppermost. This position is simply the re- 
sult of the action of gravitation, the embryo sinking to the 
bottom of the sphere because of the fact that its specific gravity 
is greater than that of the surrounding fluid. The reason for 
its lying with the neural surface uppermost is to be found in the 
fact (to be brought out in detail in another connection) that it 
is unable, under the circumstances in which it finds itself, to 
get into and retain any other position in which it is in stable 
equilibrium. 

Movements within the ‘‘ Vicarious Chorton.’’—In the descrip- 


' T shall speak of the developing organisms throughout as ‘‘embryos.’”’ The 
rupturing of the ‘‘vicarious chorion’’ and beginning of free larval life, will be 
termed the ‘“‘hatching.”” These expressions are used merely for verbal con- 
venience. 


PEARL, Reactions of Limulus. 143 


tion of the movements of the embryo within the ‘‘vicarious 
chorion” the abdominal appendages will be considered first, as 
the phenomena here are relatively simple in character. 

The abdominal appendages (operculum and gills) begin 
characteristic, rhythmical respiratory movements at least five 
days before hatching. It is probable that in reality such move- 
ments begin even earlier than this, but I have no observations 
going farther back. The ordinary respiratory movements when 
first observed are precisely like the same movements in the 
adult Limulus. They consist of a rhythmical, up-and-down 
beating of the gills, each gill book being opened during the 
phase of expansion, or ‘‘inspiratory’’ phase, to adopt the term- 
inology of Miss Hype (’94). 

There is, however, one significant difference in the respira- 
tory movements of embryos and adults. This is in the 
rate. In the adult the normal rate is about twenty-five to 
thirty beats per minute. In the embryos the rate is markedly 
more rapid, the average number of beats from my observations 
being sixty per minute. The range of variation is from 55 to 
60 beats per minute. The rhythm of the beats is quite as per- 
fect in the embryos as in the adults. 

These respiratory movements are the only movements 
which the abdominal appendages perform before the embryo 
leaves the ‘‘vicarious chorion,’’ so far as I have observed. I 
was mever able to detect any tendency towards swimming move- 
ments of the gills before the time of hatching, although the 
embryos were under observation for six or more hours every 
day, and especial attention was paid to this point. This absence 
of swimming movements is rather remarkable in view of the 
fact that all the embryos begin swimming immediately after 
hatching. 

In addition to the swimming movements the complex 
‘‘gill-scraping”’ reflexes are absent, according to my observa- 
tions, in embryos prior to the time of hatching. Certain of these 
reflexes have been described by Miss Hype (lI. c. p. 432, and 
Fig. 3). There also occur in adult Zzmu/z, under certain con- 
ditions, complex gill-scraping movements of the sixth legs. I 


144 Journal of Comparative Neurology and Psychology. 


have never seen these in the embryos before the time of hatch- 
ing. 

The intervals of rest in the respiratory movements, which 
in the adult occur frequently and may last for an hour at atime, 
are much Jess frequent in their occurrence in the embryos, and 
do not continue for such long periods. 

For some time before hatching the thoracic appendages 
can be seen to be making active movements almost continu- 
ously. These movements vary greatly in force in different in- 
dividuals, and at different times with the same _ individual. 
When they first appear they are usually very weak and increase 
in violence as development proceeds. At first it was thought 
that these movements were entirely random and aimless in char- 
acter. They appeared to consist entirely of mere wavings and 
stretchings of the legs. Closer observation showed, however, 
that they were rather more definite than at first appeared. It 
was seen that they were the cause of the curious translatory 
movements of the egg as a whole. As the time of hatching 
approaches one notices very frequently that a particular egg 
lying by itself on the level, smooth bottom of a glass dish will 
suddenly begin to move, and slowly roll along the bottom, usu- 
ally in a straight line. Frequently an egg will roll several cen- 
timeters in this way, although usually it does not cover more 
than from one to two centimeters. 

These translatory movements of the egg as a whole are 
caused by the movements of the thoracic appendages in the 
following way. As the animal lies in the bottom of the ‘‘vicar- 
ious chorion,”’ in the manner already described, the anterior and 
lateral margins of the cephalothorax are in fairly close contact 
with the inner surface of the ‘‘vicarious chorion.” At this. 
stage the chelae of the walking legs end in very sharp points. 
As a result of these two conditions, when the legs are extended 
the points of the chelae catch on the inside of the ‘‘vicarious 
chorion.” The legs are usually directed somewhat forward 
when they are extended, and as a consequence of this and of 
the normal anatomical position of the legs it follows that the 


PEARL, Reactions of Limulus. 145 


chelae catch at points lying on the anterior’ hemisphere of 


b) 


the ‘‘vicarious chorion.” Evidently then if the legs are ex- 
tended, or in other words, the chelae are strongly pushed away 
from the body, when they are caught in the ‘‘vicarious chorion,” 
a movement of the embryo or of the ‘‘vicarious chorion” will 
be caused. Which of the two shall move, will depend on the 
circumstances. If the ‘‘vicarious chorion” is held in any way, 
the embryo is moved within it, in the following manner. The 
anterior edge of the cephalothorax is pushed more and more to- 
wards the lowest part of the hollow sphere in which the embryo 
lies, until finally the whole embryo is nearly or quite in a verti- 
cal position, resting on the anterior margin of the cepha- 
lothorax. If the legs still continue their kicking against the in- 


yy” 


side of the ‘‘vicarious chorion’”’ the embryo is completely 
turned over and falls back to the lowest position of the sphere, 
with the haemal side uppermost. 

On the other hand, if the ‘‘vicarious chorion” is not held 
in any way, the same action which in the previous case caused 
the embryo to turn over within it, causes the egg as a whole to 
roll slowly over the substrate. That this must be the case is 
evident if it is remembered that the weight of the embryo tends 
to maintain the latter in a constant position with reference to 
the center of the earth, while the hollow sphere, against the in- 
side of which it is pushing, is rotated about it. On account of 
the fact that the embryo lies in a fluid in the ‘‘vicarious chor- 
ion’”’ there is practically no internal friction to hinder this rota- 
tion of the sphere about it. It will be seen that, from the point 
of view of mechanics, whether the ‘‘vicarious chorion’ asa 
whole shall rotate or not, depends on the relation which hap- 
pens at the time to prevail between the weight of the embryo 
and the external forces hindering any movement of the sphere. 
If the weight of the embryo overbalances the external forces 
the sphere will rotate, while on the other hand, if the external 


' Of course the terms anterior and posterior are here used to refer to the por- 
tions of the ‘‘vicarious chorion’’ nearest, at any given time, to the anterior and 
posterior ends of the embryo. 


146 Journal of Comparative Neurology and Psychology. 


hindrances are great enough to overbalance the weight of the 
embryo, the latter will turn over within the sphere. 

In the movements of translation of the eggs as a whole 
the direction of the movement is usually such as to keep the 
abdomen of the embryo in advance. This is a mechanically 
necessary result if the movements are produced in the manner 
just described. Of course, circumstances will sometimes pre- 
vent the egg from moving in a perfectly straight line, and again, 
the pressures exercised by the legs on the two sides of the body 
are not equal in amount. That they are about equal in the 
long run is shown by the fact that in the great majority of cases 
when free movement of the egg for some distance occurs, this 
movement is very approximately in a straight line. In cases 
where the movement is somewhat irregular the longitudinal axis 
of the embryo may not lie exactly in the path of motion, yet 
in no case have I ever seen the anterior end of the embryo in 
advance in the free translatory movements of the egg. The 
movements are always either somewhat sidewise with reference 
to the embryo, or, much more commonly, with the abdomen 
in advance. 

In the behavior just described there is no definite co-ordi- 
nation in the movements of the legs. Each leg acts by itself, 
and there is no rhythmic order in which the different legs move, 
as is the case, for example, in the gustatory reflexes of the 
adult Lemulus (cf. PATTEN, ’93, Pp. 7-9). 

The behavior when the ‘‘vicarious chorion”’ is held so that 
it cannot move offers some points of interest. The embryo is 
seemingly unable to maintain itself with the haemal side upper- 
most even after it attains that position in the manner described 
above. This is apparently a consequence of the fact that the 
organism after getting into the upright position does not stop 
the movements of the legs. When the legs are extended with 
the animal in an upright position the whole body is of course 
raised till its haemal surface is nearly in contact with the 
uppermost part of the sphere. When the embryo is in this 
position, if the effective pressure of the legs becomes greater on 
one side than on the other, as invariably happens, it forthwith 


PEARL, Reactions of Limulus. 147 


topples over and rolls down till it lies in the usual position in 
the bottom of the ‘‘vicarious chorion’ with the haemal side 
up. I have seen this series of actions repeated time after time 
by the same embryo. It usually takes several minutes of stren- 
uous labor for the embryo to get righted in the ‘‘vicarious 
chorion,’ and then within a few seconds of the time it attains 
that position, it suddenly loses its balance and falls back to the 
point from which it started. Then the same series of events 
begins again. There is nothing in the behavior which would 
in the least suggest any process of ‘‘learning by experience,”’ 
or of perfecting a reaction by practice. 

The stimulus which induces these almost continuous leg 
movements in the embryo is probably of the same sort as that 
which causes the righting reaction in the adult Lzmulus. If adult 
Limult are placed in water so that the haemal side is in contact 
with the bottom, they immediately give a characteristic reaction 
which brings them into the normal position. Froma long series 
of observations and experiments on the adult animals it appears 
that this apparent *‘equilibrium sense” is primarily due to a strong 
positive thigmotaxis of the neural surface of the body, together 
with anegative thigmotaxis of the haemal surface. A similar con- 
dition of affairs has been shown to be the cause of the righting 
reaction in other organisms (cf. PEakL, :03 for Planaria). It 
seems to me probable that the leg movements of the embryos 
when they are in an inverted position are thigmotactic responses. 
The only essential difference between embryo and adult in re- 
spect to this thigmotaxis would then be that the definite, 
purposeful reaction with which the adult meets and solves the 
difficulty has not yet developed in the embryo. Instead the 
embryonic thigmotactic reaction is simply a generalized response 
to a general stimulus. The reaction becomes specialized and 
better adapted to the accomplishment of its end as development 
proceeds. 

The movements of the thoracic appendages which have 
been described are the only ones which I have observed before 
the time of hatching. None of the complex, coordinated re- 


148 Journal of Comparative Neurology and Psychology. 


flexes of the legs, such as the gustatory and swimming move- 
ments, appear at this early stage. 

Reactions to Stimult.—It is rather surprising to find that 
before the time of hatching the embryos are extremely sensitive 
to mechanical stimuli applied to the external surface of the 
‘‘vicarious chorion.’’ If the surface of the ‘‘vicarious chorion” 
be touched very gently with a needle the embryo stops all 
movement at once, draws the legs back as far as possible into 
cephalothorax and strongly flexes the abdomen, so as to make 
practically a right angle between it and cephalothorax. These 
positions are maintained as long as the stimulus is continued. 
In a short time after the stimulation ceases the abdomen is ex- 
tended, and the respiratory and leg movements begin again. 


Fig. ¢.—Diagrams showing appearance of Zzmulus embryo immediately 
after hatching. A. Haemal side. 4. Neural side. (After KINGSLEY). 


This is the same reaction as that given in response to 
mechanical stimuli after hatching. It is somewhat remarkable 
that the organism should respond in the same way to the press- 
ure of a needle point when in one case this pressure has first to 
be transmitted by the surrounding fluid to the embryo, and in 
the other case the needle point touches the surface of the body 
directly. 

Hatching. —The behavior at the time of leaving the ‘‘vicari- 
ous chorion” I have not been able to observe. In the material 
which I had all the hatching occured during the night. 


PEARL, Reactions of Limulus. 149 


The Behavior after Hatching. 


Appearance of the Organism.—In general form the embryo 
at this stage closely resembles the adult Lzmu/us except for the 
absence of the elongated telson. The appearance of the em- 
bryo in dorsal and ventral aspects is shown in Fig. 1, A and B. 
This stage is KrNnGSLEy’s (loc. cit.) Stage K. 

Movement of Abdominal Appendages ; Respiratory Move- 
ments.—The respiratory movements continue after hatching in 
the same characteristic manner as has been described above for 
the preceding stage in development. The only difference in 
them is found in the rate, which becomes somewhat more rapid. 
According to my observations the rate of the beat after hatch- 
ing stands in about the ratio of 5 to 4 to the rate while the em- 
bryo is within the ‘‘vicarious chorion.’”’ During some experi- 
ments in which the embryos were taken from the water and 
placed on moist sand, with the haemal side uppermost, it was 
observed in several cases that the respiratory movements con- 
tinued in the normal manner, while the embryo was out of 
water. This was a rather unexpected finding, for the reason 
that adult Lz never perform continued, normal rhythmical 
movements except in the water. The only explanation for the 
case of these young embryos which has suggested itself to me 
is that possibly at this stage of development the gills are less 
sensitive to changes in the surrounding medium than they are 
to the adult. This, however, does not seem very probable, in 
view of the fact that the general tactile sensitivity of the em- 
bryo at this stage is greatly in excess of that of the adult. 

Swimming.—Immediately after the embryo leaves the ‘‘vi- 
carious chorion” characteristic swimming movements begin. 
So far as the abdominal appendages are concerned these move- 
ments are precisely the same in embryo and adult. They con- 
sist of strong extensions and flexions of the gills ' with refer- 
ence to the abdomen. They are rhythmical, and are essentially 


1 Throughout the paper where statements aré made concerning the perform- 
ance of swimming movements by the ‘‘gills’’ it will be understood that the gill 
covers and the operculum are the organs to which reference is made. The term 
‘¢gills” is used merely to avoid circumlocution. 


150 Journal of Comparative Neurology and Psychology. 


like the respiratory movements except that the amplitude and 
force of the beats are much greater in the swimming than in 
the respiratory movements. On account of the fact that the 
gills are extended so as to form nearly a right angle with the 
body at the beginning of each beat a considerable portion of 
the effective force of the stroke is directed nearly straight back- 
ward. 

There is a very marked and fundamental difference be- 
tween the swimming movements of the embryo and the adult 
with respect to the thoracic appendages. In the adult Lzmulus 
all the walking legs beat strongly back and forth in time with 
the gills during the swimming. As the gills are raised the legs 
are extended and thrown far forward in the cephalothorax, and 
as the gills strike backwards the legs accompany them in this 
movement. In the embryo of the stage under discussion, how- 
ever, the legs take no part whatever in the swimming move- 
ment. Whenever the gills begin swimming motions the legs 
are extended as much as possible and thrown forward until they 
touch the antero-lateral margins of the cephalothorax. Then 
they are held rigidly in this position as long as swimming con- 
tinues. The appearance in swimming is as if the legs became 
temporarily paralyzed and held in a ‘‘forced”’ position while the 
gills were performing swimming movements. 

A very interesting course of development is to be observed 
in connection with the ability of the embryo to direct its move- 
ments when swimming. The usual position of tne embryo, if 
lying by itself in the dish, is the same as its position in the 
‘‘vicarious chorion,’ namely, lying on the bottom in an inverted 
position. As has already been stated, swimming movements 
begin at once after the embryo is hatched. For some time 
after these movements begin, however, the embryo is not able 
to rise from the bottom. The gills beat most energetically, but 
the only result is to cause the embryo to slide along the smooth 
bottom of the dish. It has not acquired the faculty of so bend- 
ing the abdomen with reference to the cephalothorax as to 
make the force of the swimming raise it from the bottom. 
That this failure to rise is not due to lack of power in the gill 


PEARL, Reactions of Limulus. 151 


strokes is certain, from evidence to be presented later. To such 
an extent is the organism unable to direct its movement in 
these early stages that, instead of tending to swim up from the 
bottom, it actually tends at times to swim downward. In many 
cases I have seen the beating of the gills become so forcible as 
to raise the abdomen and send the embryo skimming along the 
bottom on the antero-haemal surface of the cephalothorax. If, 
under these circumstances, the anterior margin of the cephalo- 
thorax happens to meet an obstacle in its path the embryo will 
in many cases turn completely over on its anterior end as a 
pivot, and come down with the haemal surface uppermost. 
The ‘‘summersault”’ in such cases is caused solely by the con- 
tinued violent swimming movement of the gills while the an- 
terior end is held. 

How then does the embryo get up from the bottom at this 
stage, so as to swim freely through the water? This is done 
in one of two ways, during the earliest stages after hatching. 
The first of these methods is purely accidental so far as the or- 
ganism is concerned. If an embryo which is sliding along the 
bottom as the result of the violent swimming movement of the 
gills happens to strike squarely a very small obstruction in its 
path, the anterior end of the body will in some cases slide up 
onto the obstruction. This, of course, gives the body asa 
whole an upward tilt and if the swimming movements continue 
the embryo will rise clear of the bottom and swim freely through 
the water. Sand grains and pieces of cast egg membranes usually 
serve as the means for starting the animals upward in this way. 
Rising in this manner only occurs infrequently, since it is not 
often that all the necessary conditions will be fulfilled together. 
After the embryo gets started in this way it is able to sustain 
itself in the water for as long as a minute even in very early 
stages of its free existence. Such cases show that the ordinary 
inability of the embryo to rise from the bottom is not due to 
lack of force in the swimming movements. 

The second and more usual method by which very young 
embryos rise from the bottom is by first turning over from the 
usual position with the haemal side down, and then starting to 


152 Journal of Comparative Neurology and Psychology. 


swim from the upright position. As will be described in detail 
later, the embryos are able under certain conditions to right 
themselves after hatching. It very frequently happens with 
the youngest embryos that an individual in the upright position 
(i. e., with the neural side down) will suddenly start violent 
swimming movements with the gills. When this happens the 
embryo immediately moves forward and upward away from the 
bottom. For a short distance (varying in different cases) it 
maintains the upright position while free in water, but in a very 
short time after starting in every case it topples over and falls 
into the normal position for swimming, that is with the haemal 
side down. It then continues swimming in quite the normal 
way. 

As development proceeds the swimming becomes better 
controlled and the embryo gains the power of rising from the 
bottom by swimming without first turning over. The earliest 
stage at which I have seen embryos do this was about forty- 
eight hours after hatching. Even at this time the embryos do 
not rise directly from the bottom, but first slide along the bot- 
tom for a distance of from three to five centimeters and then 
sradually veer upward. In about a week after hatching the 
swimming is under perfect control in all cases. The animals: 
rise at once from the bottom, and direct the movement quite as 
well as does the adult. Apparently the only difference between 
embryos of this stage and adults with respect to the swimming 
is in the fact that the legs remain quiet in the case of the em- 
bryo. 

A problem in connection with the swimming movements 
in the embryo in which I was especially interested was this: 
Why is it that swimming movements of the gills appear imme- 
diately after hatching, while before that time no indication of 
such movements are to be observed? The most probable ex- 
planation seemed to be that the swimming was a purely reflex 
movement which needed the stimulus of the normal sea-water 
on the sense organs of the gills to set it into action. In other 
words, the reflex mechanism was complete in the embryo be- 


PEARL, Reactions of Limulus. 153 


fore hatching and swimming would have gone on there if the 
proper stimulus had been given. 

In order to get further evidence on this hypothesis experi- 
ments were tried on hatched embryos, with a view of determin- 
ing whether the chemical composition of the water influenced 
the swimming movements. Embryos were put in solutions of 
the following compositions : 

A. Fresh sea-water I part 
——Nacl 1 « 
Bb. Fresh sea-water I part 
Rain water Te mace 

The results so far as the swimming movements were con- 
cerned were essentially the same with the two solutions. There 
was practically no swimming in the concentrated sea-water, and 
very little in the diluted solution. Individuals would occasion- 
ally make spasmodic beginnings of swimming movements but 
these usually continued only for a few beats. The swimming 
movements were better in the diluted than in the concentrated 
sea-water, but in both series the total amount of swimming 
done was very greatly reduced in comparison with what goes 
on under normal conditions. Control series in normal sea-water 
demonstrated that these results could not be due to light or 
temperature effects. Other movements than swimming (walk- 
ing, respiration, etc.) were not affected in solution B, and in so- 
lution A only after the experiments had continued for over 48 
hours. The sensitiveness of the embryos to chemical stimula- 
tion was not apparently affected in either solution. 

These experiments, so far as they go, give confirmation to 
the view that the necessary stimulus for the swimming reflex is 
afforded by normal sea-water. It was impossible, on account 
of lack of time, to absolutely prove that this is the case, but I 
think we are justified in concluding that there is a considerable 
degree of probability that this is the explanation of the fact 
that swimming movements do not occur while the embryo is 
within the ‘‘vicarious chorion,” 
hatching. 


but begin immediately after 


(54 Journal of Comparative Neurology and Psychology. 


The proportionate amount of time spent by the embryos 
in swimming movements as compared with aimless leg move- 
ments or in walking movements, becomes progressively greater 
as development proceeds, during the ‘trilobite’ stage. Dur- 
ing the period immediately following hatching the embryos ap- 
pear to become quickly exhausted by violent swimming move- 
ments. As development proceeds they get stronger until dur- 
ing the week immediately preceding the first moult after hatching 
nearly all the time is spent in swimming. 

I have never seen in embryos at this stage any indication 
of the ‘‘forced”’ gill cleaning reflexes of the gills themseves 
which occur in the adult, and have been described by Miss 
Hype (loc. cit.). 

Movements of the Thoracic Appendages.—When the em- 
bryos are lying in an inverted position at the bottom the legs 
are practically continuously in motion. Immediately after 
hatching these movements are of the same character as those 
within the ‘‘vicarious chorion.’’ The hatched embryo, how- 
ever, has nothing for the chelae to engage and consequently 
the movements accomplish no purpose. These leg movements 
are probably still to be regarded as an incipient righting reac- 
tion (cf. above). Throughout the whole of the ‘‘trilobite”’ 
stage the embryos do not develop a definite, immediately pur- 
posive righting reaction like that of the adult. These young 
embryos right themselves in a great variety of ways and in 
nearly every case it is a long and tedious process. The most 
usual way is for one embryo to rather indefinitely push against 
or crawl over a second individual or a cast ‘‘shell’’ or some bit 
of debris in the water till it gets righted. The nearest approach 
toa definite righting reaction which I have seen in these very 
young individuals is a combination of swimming and leg move- 
ments. As has been described above violent swimming move- 
ments of the gills sometimes serve merely to raise the abdomen 
of an inverted embryo without causing the animal as a whole 
to rise from the bottom This results in making the embryo 
practically ‘‘stand on its head” (i. e., rest on the extreme an- 
terior margin of the cephalothorax), Not infrequently when 


PEARL, Reactions of Limutus. | 155 


an embryo has reached this position it will suddenly release the 
legs from the cramped position into which they are thrown 
when the gill swimming begins, and start scratching with the 
chelae against the bottom in front of the anterior margin of the 
cephalothorax. The evident purpose in this act is to help out 
the gills at the critical moment, with the legs. The result usu- 
ally is that the embryo immediately gets over into the normal 
upright position. This reaction is of interest as indicating the 
greater strength of the positive thigmotaxis of the chelae as 
compared with the tendency for the legs to be held in a forced 
position during the gill swimming. The tips of the chelae 
when the legs are in the forced position during the swimming 
project in front of the margin of the cephalothorax. When 
the posterior end of the embryo is raised far enough the chelae 
will evidently touch the bottom, and this stimulus is sufficiently 
strong to overbalance the tendency for the legs to hold the 
cramped position, and to cause them to kick against the bottom. 

The stimulus which calls forth all these attempts of the 
embryo (the same is also true of the adult) to right itself, comes, 
I believe, primarily, from the strong positive thigmotaxis of the 
neural surface of the body, and especially of the margin of the 
cephalothorax and the tips of the chelae, together with a nega- 
tive thigmotaxis of the haemal surface. 

As the time of the moult which terminates the ‘‘trilobite”’ 
stage approaches a very definite and curious reaction of the 
thoracic appendages develops. In its typical form this reaction 
is as follows: let a needle, or any other object of similar size, 
be held parallel to the long axis of the body so that the ends 
of one or more of the chelae touch it in the course of their 
movements. Immediately all the legs will close over the needle 
and, in a way, hug it up to the body. At once the embryo 
begins to crawl along on the needle held in this way. Even if 
the needle is held so as to be perpendicular to the bottom of 
the dish the embryo will crawl up on it as far as the surface of 
the water, and even in some cases rise partly out of the water. 
So firm a grasp do the legs have on a smooth needle that with 
moderate care an individual may be raised entirely out of the 


156 Journal of Comparative Neurology and Psychology. 


water by lifting the needle. This reaction cannot be induced 
immediately after hatching, and only reaches its greatest per- 
fection towards the end of the ‘‘trilobite” stage. It is a very 
definite and striking piece of behavior and may be induced 
with perfect certainty at every trial in late ‘‘trilobite’’ embryos. 
It can apparently only be classified as a form of thigmotactic 
reaction, and seems to me to be significant chiefly in indicating 
the degree of coordination in leg movements which has de- 
veloped since hatching. What, if any, significance such a re- 
action can have in the life of the embryo under the normal con- 
ditions of existence Iam unable to conjecture. It seems to be 
merely a reaction very perfectly adapting the embryo to the 
business of climbing up slender sticks or needles, and, so far as 
I know, there are no natural demands in the normal existence 
of the animal at this stage of development which would make 
such a reaction either necessary or even useful. I observed 
this reaction as first occurring about one week prior to the time 
of the moult which ends the ‘‘trilobite’”’ stage. 

Walking Movements.—I\mmediately after hatching the 
walking movements are very irregular. There is apparently 
little codrdination between the different legs, and as the animal 
progresses it rocks and sways from side to side and frequently 
falls over on one side. As development proceeds the move- 
ment becomes somewhat better coordinated. This form of loco- 
motion is, however, even in the adult, a poorly coordinated 
one, the organism being much better adapted to swimming 
than walking. The embryos got on better when walking on a 
rough surface like the sand bottom, than on a smooth ‘surface 
like glass. 

Avoidance of Obstacles in the Path.—Neither when walking 
nor when swimming do embryos show any perception of an ob- 
stacle in the path before they strike it. 

If a very young embryo when walking strikes an obstacle 
like a needle heid in its way, no attempt is made to get around 
it. Instead, the embryo will continue to walk straight ahead 
pushing the anterior margin of the cephalothorax against the 
obstacle. This action will be continued till, by chance, in the 


PEARL, Reactions of Limulus. 157 


unsteady walking movements the body gets pointed in a new 
direction such that the obstacle no longer completely stops the 
progressive motion. Then, of coure, the embryo is able to push 
around, and continue on its way. A large number of observa- 
tions were made on this subject to determine whether older 
embryos developed any distinct purposeful reaction to enable 
them to get around obstacles. I was unable to convince my- 
self that there was any real progressive development in this 
matter. Sometimes older embryos will stop walking when they 
strike an obstacle, fall back perhaps half the length of the 
body, and then start forward again in a path at an angle to the 
former line of motion. This will take them by the obstacle at 
once. This behavior, however, does not occur with sufficient 
frequency to warrant considering it a typical reaction. The 
typical behavior throughout the ‘‘trilobite’’ stage seems to be 
essentially that first described. 

Burrowing Reaction.—lf Limulus embryos in the ‘‘trilo- 
bite’’ stage are taken out of water and put‘on moist sand they 
will usually in a short time burrow into the sand so as to be 
completely buried. This behavior is of a character which would 
warrant it being characterized as instinctive. Analysis shows, 
however, that it is capable of explanation in another way. 
When an embryo is placed on the sand it starts walking in the 
usual way. This continues until some obstacle in the path 
stops further movement ahead. Then, as has been described 
in the preceding section, the animal pushes against the obstacle. 
Now when this action takes place on sand the sand grains are 
pushed out from below the embryo as a result of the action of 
the legs. The violent movements of the legs tend to raise the 
abdomen, and the anterior end gets pointed more and more 
down into the sand. As walking movements of the legs con- 
tinue more and more sand is thrust from below the animal, and 
the whole body is thrust downward and forward. In this way 
the burrowing is brought about. Any sort of obstacle in the 
path will induce the burrowing when the embryo is on sand, so 
far as I have observed. A needle held in front of the animal 


158 Journal of Comparative Neurology and Psychology. 


will start the burrowing; a small pebble or a few projecting 
sand grains in the path produce the same result. 

The burrowing reaction is then evidently started primarily 
as a result of the strong positive thigmotaxis of the margin of 
the cephathorax. This thigmotactic tendency is so pronounced 
that the mere catching of the anterior margin of the cephalo- 
thorax on a few sand grains is sufficient to start the animal 
pushing ahead into the sand. I have frequently seen the bur- 
rowing started in this way. 

The reflex nature of the burrowing reaction is well shown 
in some cases I have observed in which an embryo which had 
started burrowing and had succeeded in burying perhaps half 
the body, would, by the violence and lack of good coordina- 
tion of the leg movements, accidentally lift the anterior end out 
the hole which it had excavated. Such individuals, in every 
case observed, did not return to the burrowing but walked off 
over the sand in whatever direction they were pointed, until 
they chanced again to get the anterior margin of the margin of 
the body caught by some obstruction. | 

Complex Reflexes.—During the stage of development un- 


” 


der consideration the ‘‘gill scraping’ reflexes of the sixth legs 
appear. These consist in complete extensions and flexions of 
the sixth legs with the surface of the abdominal appendages. 
The reflex is a very characteristic one and its apparent purpose 
is to free the outer surface of the gills of any material which 
might prove injurious. These movements appear at once in 
their perfect form, so far as I have been able to observe. There 
is no process of gradual perfection by practice, or learning. 
The action is performed for the first time by the embryo in 
quite the same manner that it is by the adult. 

Reactions to Stimul.—The reaction of embryos in the ‘‘tri- 
lobite’”’ stage to tactile stimuli of all but the weakest intensities 
is precisely the same as that described above for the preceding 
stage. It consists in a strong contraction of all the flexor mus- 
cles of the body. This state of contraction persists as long as 
stimulation is continued. There are no differentiated responses 
to localized tactile stimuli. The same effect is produced what- 


PEARL, Reactions of Limulus. 159 


ever part of the body is stimulated. The reactions to very 
weak tactile stimuli applied to the tips of the chelae have been 
described above (p. 155). 

The characteristic gustatory reflexes of the adult Lzmzulus 
(cf. PATTEN, ’93) I have not been able to induce in embryos of 
the ‘‘trilobite”’ stage. Repeated experiments were made on 
this point with the substances which produced prompt and 
strong chewing movements in the adult, but always with nega- 
tive results. No distinct reactions of the legs are produced 
when clam juice is dropped on the coxal joints. The absence 
of these reflexes is probably correlated with non-development 
of the sense organs which are stimulated by edible substances. 

The adult animal is very sensitive to weak thermal stimuli, 
responding promptly and in a characteristic way to a puff of 
warm air, or to the warmth of the hand laid on the margin of 
the carapace (cf. PATTEN, '93). The embryos fail to show this 
sensitiveness to thermal stimulation. They will only respond 
to a strong temperature stimulus such as is given by holding a 
red-hot needle very close to the body, and then the reaction is 
a general one, like that given in response to tactile stimulation. 
The absence of characteristic temperature reflexes is again prob- 
ably to be explained as due to the non-development of the 
proper sense organs at this stage. 

Several years ago Logs (’93) gave a brief account of the 
reactions of Lzulus embryos in the ‘‘trilobite’” stage to light. 
The essential results of this author’s work are given in the fol- 
lowing sentences (loc. cit., pp. 98-99). (1) ‘‘Die Larven von 
Limulus polyphemus sind nach dem ausschlipfen auf dem Ei 
positiv, spater negativ heliotropisch.”” (2) ‘‘Die positiv helio- 
tropischen Bewegungen werden stets schwimmend, die negativ 
heliotropischen stets kriechend ausgefihrt.’’ Throughout the 
course of the present work considerable attention was paid to 
the subject of phototaxis, and a large number of experiments 
along this line were performed. It very soon appeared that 
there were other factors present in the reactions to light, be- 
sides those enumerated by Logs. The case is not by any 
means as simple as his account would indicate. The conditions 


160 Journal of Comparative Neurology and Psychology. 


under which the present work was done made it practically im- 
possible to carry out a thorough and complete investigation of 
the phototaxis of the embryos, so that in several particulars 
my results are incomplete. For this reason it seems preferable 
not to publish my observations in detail at this time. For the 
sake of indicating the general trend of the results as far as they 
go I will briefly summarize them. I was unable to get any 
evidence that the first reaction to light to appear after hatching 
was positive in sense. On the contrary it was clearly negative, 
regardless of whether the embryos were swimming or walking. 
Later there appeared a strongly marked positive reaction shown 
only by relatively few individuals. These individuals when re- 
sponding in the positive sense to the direction of the incident 
light were, so far as my observations went, always swimming in 
a very violent manner. In the same dish at the same time, 
with all the embryos of approximately the same age, many in- 
dividuals were negatively phototactic, fewer positively photo- 
tactic, and still fewer apparently indifferent to light. This ap- 
plies to light of the intensity of diffuse sunlight. The negative 
phototaxis is apparently associated with a strong positive thig- 
motactic tendency. 

It seems very desirable that the reactions of Lzmulus to 
photic stimuli in any or all stages of its development be thor- 
oughly investigated under proper conditions for experimenta- 
tion. I know of no form which seems likely to give more in- 
teresting and significant results in this field than this organism. 


Discussion of Results. 


With he detailed results now in hand it is possible to 
make a direct comparison between the behavior of Lzzu/us in 
its earliest larval stages and in the adult condition. In order 
make the comparison easy of comprehension the following 
table has been arranged. In parallel columns are stated the 
conditions with respect to certain definite features of the be- 
havior in the two stages of the life history. 


PEARL, Reactions of Limulus. 161 


Tabular Résumé of the Behavior of Lzulus in the Earliest 


Stage of its Free Existence, and in the Adult. 


Respiratory 
Movements. 

Swimming 
Movements. 


Walking 
Movements. 


Righting 
Reaction. 


Burrowing 

§# Reactions. 

Gustatory 
Reflexes. 

Temperature 
Reflexes. 

“*Gill-scraping 
Reflexes of 
Sixth Legs. 

“* Cleaning” 
Movements 


of Gills. 


Embryo. Adult. 


Same in character in embryo and adult. 


Gills only beat rhythmically. Legs and gills both 
Legs held in fixed position. beat rhythmically 
Gill movements the same in and _ synchronously. 


character as in the adult. 

Control of swimming move- 

ment poor immediately after 

hatching. Improve with prac- 

tice. 

Essentially the same in character in embryo and adult. 
Not so well coérdinated and directed in embryo as in 
adult. Improve with practice in embryo. 


Present from beginning but Definite, immedi- 
not well coérdinated. Not as ately purposive reac- 
definite in type as in adult. tion. 


Probably same in embryo and adult. 


Complex and highly 
codrdinated. 
Definite and pur- 
poseful reflexes. 


Absent. 


Absent. 
Essentially the same in embryo and adult. 


Absent. Present). -(cf. “ HivnE; 
loc. cit.) 


From this comparison it appears at once that, with a sin- 
gle exception, all the items of behavior presented by the adult 
are, in the case of the embryo, either entirely absent or pres- 
ent in essentially the same condition as in the adult. In other 
words, the embryo does not in general have simple types of be- 


162 Journal of Comparative Neurology and Psychology. 


havior, which during development give way to more complex 
types leading up to the condition found in the adult. This 
seems to be a matter of some importance, for the reason that 
it indicates that it will be nearly or quite useless to look to lar- 
val stages for help in analyzing the adult behavior in forms like 
Limulus. It seems likely from what we know of the general 
correlation between type of behavior and general type of body 
form, that the same thing will be true in most cases where the 
general form relations of the body are closely similar in larval 
and adult stages. In Lzmulus this similarity in body form is 
very close, and the present paper shows how similar in essen- 
tial features the behavior is in the two stages. 

The single exception to the general rule of essential simi- 
larity in type of behavior between adult and embryo in Lzmulus, 
is found in the swimming movement. In the embryo the legs 
take no active part in this movement, while in the adult they 
beat synchronously with the gills. So far as the legs are con- 
cerned we evidently have here a simpler type of behavior in the 
embryo than in the adult. The holding of the legs in a cramped 
position as described must be regarded as a definite action, just 
as any movement would be, only it is simpler in character than 
a rhythmical movement. The difference here in behavior be- 
tween embryo and adult is without doubt associated with a 
morphological difference in the nervous mechanism. 

In the case of swimming and walking movements, and the 
righting reaction the study of the embryos give indubitable 
evidence that there is improvement with practice. The embryo 
performs these movements better—that is, with steadily increas- 
ing purposiveness—the more it practices them. At the time 
of hatching it is endowed, so to speak, with an ability to per- 
form certain acts, but is unable to perform them in such a way 
that they serve any purpose at all well. The latter ability 
comes with practice. Shall we call this ‘learning through ex- 
perience” how to do certain things? It seems to the writer 
that one who maintains that it should be so called will occupy 
a practically impregnable position, yet he will be totally unable 
to prove that this necessarily involves any psychical element. 


PEARL, Reactions of Limulus. 163 


On the other hand, the phenomena in a case like the one under 
discussion appear objectively analogous to certain phenomena 
in the inorganic world. For example: one gets a complicated 
piece of machinery fresh from the factory. If energy is put 
into it it will do certain things. But on account of the new- 
ness the parts do not work smoothly together. There is an un- 
due amount of friction between the parts. As the machine is 
used the bearings get worn a little and we say that as a whole 
the machine ‘‘ works better.”” The continued functioning im- 
proves the general coordination as a result of the interaction of 
the parts. Objectively very much the same sort of change ap- 
pears to take place in the behavior of a Lzmulus embryo. Is 
there any more of a psychical element in the one case than in 
the other? This we obviously do not know, and it seems idle 
to discuss the question, since no amount of @ prorz reasoning 
will settle it and @ postertore evidence is not to be had. 


Literature Cited. 


Hyde, Ida H. 
’94. The Nervous Mechanism of the Respiratory Movements in Limulus 
polyphemus. Jour. Aforph., IX, pp. 431-448, Pl. I-III, 1894. 
Kingsley, J. S. 
85. Notes on the Embryology of Lzmulus. Q. J. Micr. Sct., N.S., 
XXV, pp. 521-576, Pl. XXXVII-XXXIX, 1885. 
’92. The Embryology of Lemuu/us. Jour. Morph., VII, pp. 35-68, PI. 
V-VI, 1892. 


93. Ueber kiinstliche Umwandlung positiv heliotropischer Thiere in 
negativ heliotropisch und umgekehrt. <Avch. /. d. ges. Physiol., 
54, pp- 81-107, 1893. 
Packard A. S., jr. 
72. The Development of Limulus polyphemus. Mem. Boston Soe. Nat. 
fizst., 11, pp. 155-202, Pl. II-V, 1872. 


164 Journal of Comparative Neurology and Psychology. 


Patten, W. 
93. On the Morphology and Physiology of the Brain and Sense Organs 
of Limulus. Q. J. Micr. Sct., N.S., XXXV, pp. 1-96, Pl. 1-5, 
1893. 
Pearl, R. 
:03. The Movements and Reactions of Fresh-water Planarians: A Study 
in Animal Behavior. @Q. /. Micr. Sct., N.S., 46, pp. 509-714 
1903. 


EDIMORTAL: 


Since the days of GERLACH’s reticulum there has been a 
growing tendency among neurologists of all schools to lay great 
stress on the functional importance of the neuropil, or felt- : 
work of finest non-medullated nerve terminations. It would 
appear that here some of the most characteristic nervous reac- 
tions take place, and that the peripheral fibrillar networks are 
not less important. Just what these reactions are it is still too 
early to affirm with confidence, but the problem is being at- 
tacked from several sides and with a fair prospect of immediate 
success in some of its phases. 

Anatomical interest centers now on neurofibrillae and 
enough facts have already been gathered in to justify the pre- 
diction that we shall not have to wait much longer for an accu- 
rate knowledge of what the structure of the neuropil really is. 
Physiological experimentation, too, is daily adding new facts 
and developing new points of view. Undoubtedly both of 
these classes of evidence must be greatly enlarged before we 
shall be in a position to determine just how far the newer con- 
ceptions of nervous function can be cast in the mold given by 
the terminology of the neurone as current in the decade just 
closed. Certain it is that we are not yet ready to throw away 
that terminology ; for even a contracted and defective mold is 
better than none so long as it turns out fruitful hypotheses and 
promotes clear analysis and accurate expression, provided only 
one does not make a fetish of it and in the end perhaps come 
to venerate its very defects. Practically, even the most strik- 
ing of our latest physiological experiments on the functional 
differentiation of the nervous elements can still be expressed 
more conveniently in terms of the neurone doctrine than in any 
other way. 


166 Journal of Comparative Neurology and Psychology. 


This much, at least, is clear, that the nervous system is 
not made up of structural elements (neurones) in the same sense 
that a house is built up of bricks or even that the liver is made 
of cells. The functional unit of the nervous system is the con- 
duction path or functional system of neurones, and for aught 
that we know to the contrary, the same neurone may bea 
member now of one functional circuit, now of another totally 
different. This is suggested, not only by the familiar anato- 
mical connections of the associational centers and simpler re- 
flex stations of the brain, but also by some more recondite 
phenomena, such as the vicarious functioning of one cortical 
area after injury to another. 

Still more striking in this connection are the cases of sub- 
stitution of function after peripheral nerve anastomosis, such as 
that recorded by CusuinG and referred to in our last issue. 
After traumatic destruction of the facialis root and resultant 
paralysis, the central end of the spinal accessory nerve was 
sutured on to the peripheral facialis and a successful union 
effected. There resulted total permanent paralysis of the 
trapezius and sterno-mastoid muscles and almost perfect restora- 
tion of facial symmetry both at rest and (less perfectly) in the 
facial movements. | 

Experimental cross-suturing has long been practiced on 
lower animals and LANGLEy has recently been reporting in the 
Journal of Phystology a series of such operations, especially 
upon the cervical sympathetic. In a case reported upon in 
February of this year the fifth cervical nerve in a kitten was 
sutured to the cervical sympathetic and functional union re- 
sulted. After 187 days, stimulation of the fifth cervical nerve 
caused the usual effects produced by stimulation of the cervical 
sympathetic. Since the fifth cervical root contains no pre- 
ganglionic sympathetic fibers it follows that ‘‘certain somatic 
nerve fibers are capable in favorable circumstances of making 
functional connection with sympathetic nerve cells.”’ 

It is evident that such remarkable changes in peripheral 
connections must result in profound changes in the central con- 
duction pathways, and that too probably without the loss of 


Editorial. 167 


any central neurones. This plasticity of the central organ, 
then, seems to be functional largely, not merely regenerative or 
structural. And this again will have an application in any at- 
tempt to define the value of the neurone. 


* OK 
* 


Some progress has been made with the functional analysis 
of the neurone. VAN GEHUCHTEN’S law of the polarization of 
the neurone (the dendrite being cellulipetal, the neurite celluli- 
fugal), while certainly not universally applicable, is neverthe- 
less quite generally true in higher vertebrates. The selective 
action of certain drugs on parts of the neurone is well known. 
Thus, curare will paralyze the terminal arborization (motor end- 
plate) of peripheral somatic motor neurones without destroying 
the functional integrity of the remainder of the neurone, and it 
is probable that nicotine acts in a similar way upon the terminal 
arborization of the pre-ganglionic sympathetic neurones. And, 
still more recently, LANGLEY has made it very probable that the 
difference between vaso-constrictor nerves and_ vaso-dilator 
nerves lies in the mode of the ending upon the unstriated muscle 
cells of the arteries of the post-ganglionic sympathetic neurones 
involved, and not upon the general character of these neurones 
or their central connections. 

Of much greater importance is the differentiation within 
the neurone of neurofibrils and a more fluid plasma—apparently 
a conducting substance and its nutrient stroma. And the 
further differentiation within the latter of Nissi bodies, we are 
taught, is a device for the distribution of a modified nuclear 
chromatin to facilitate rapid metabolism in the cytoplasm. 

We hear much recently about neo-vitalism in biology. In 
the minds of some the mechanical theory of life is on the de- 
cline. It is asserted that physics and chemistry have not ex- 
plained organic phenomena as was anticipated by the defenders 
of the mechanical theory fifty years ago. Many biological facts 
are not as yet capable of satisfactory explanation in terms of 


168 Journal of Comparative Neurology and Psychology. 


any known physical or chemical laws. To ask whether, when 
we have arrived at a complete knowledge of the organic world, 
the biological phenomena will be found to be explicable in 
terms of the laws of the inanimate world, is to miss the true 
significance of the problem. The truth is that both vitalism 
and the mechanical theory are undergoing transformation. 
Each is being interpreted in terms of the other. The reason 
that the mechanical theory today is inadequate to explain all 
the biological facts is that this theory was formulated upon the 
basis of too narrow a range of phenomena. If it is to remain 
the working hypothesis of the physiologist it must be allowed 
that development which, as itself an organic phenomenon, 
every working hypothesis exhibits. To take the mechanical 
theory as a rigid concept, as it was fixed by thought half a cen- 
tury ago, is logically as vicious as to push recklessly forward 
to an unwarranted vitalism. In so far as the neo-vitalism is a 
protest against the static character of this mechanical theory, it 
may well be that the truth lies, for the time being, in this swing 
of the pendulum towards vitalism. It behooves the defenders 
of the mechanical theory to look to the vitality of the mechan- 
ical theory itself. 


There are no neurological researches which American stu- 
dents can claim as their own with greater propriety than those 
centering about the functional analysis of the peripheral 
nervous system. The recent phase of this movement may 
be said to date from the suggestion of OsBorn in 1888 of 
the possibility of an anatomical correlation of certain components 
of the peripheral nerves and their end organs with corresponding 
centers within the brain, a correlation of which we had at that 
time only vague hints. This suggestion was taken up and first 
worked out in a concrete case for the cranial nerves by 
STRONG in 1895, and since that date has dominated most of the 
really valuable morphological work on the peripheral nerves ; 
in fact it is safe to say that no investigators in this field who 
have neglected to take account of this point of view have been 


Editorial. 169 


able fully to enter into their own data. Already some dozen 
researches have appeared in this country largely inspired by 
this point of view, which has, however, been generally ignored 
abroad save for the admirable studies of Cote of Liverpool. 

We may, then, claim for the doctrine of nerve components 
as comparatively studied that it is distinctly an American con- 
tribution to neurological science. It is not necessary in this 
place to enter into an exposition of what that doctrine is, for 
this has been done zz extenso in the address printed in our issue 
for last December. What we wish here to emphasize is that, 
apart from its great morphological value in determining 
homologies and critically defining the proper use of the cranial 
nerves in attacking such problems as the segmentation of the 
vertebrate head and its relation to the trunk, etc., perhaps its 
chief interest and value lie in the fact that it opens a very at- 
tractive avenue for the study of the physiological subdivision 
and interpretation of the entire nervous system, both central 
and peripheral. 


In fact the whole point of this series of researches from 
the beginning has been the accurate demarcation of functional 
systems of neurones as the real units of the nervous system. 
Starting at the periphery where the functions of the terminal 
organs of the nerves are either well known or open to direct 
experimental determination, the conduction pathway is followed 
proximally into the brain and through its devious ramifications 
within that organ. Ultimately when each such functional sys- 
tem is exhaustively known we shall have the anatomy and 
physiology of the central, as well as the peripheral, nervous 
system well outlined and, when this knowledge is made com- 
parative, the materials for a complete phylogeny of the nervous 
system. 

The great problems of evolution, when finally solved, 
must be stated in functional terms. It is the problem of evolu- 
tion to determine not merely what has been the history of the 
structural metamorphosis of organs and species, but what have 
been the dynamic factors which have shaped that metamorphosis, 
what influences of environment and internal organization have 


170 Journal of Comparative Neurology and Psychology. 


been operative at each successive evolutionary stage to deter- 
mine the next step to be taken. 

In the doctrine of nerve components as it is now being 
wrought out we have a concrete illustration of the correlation 
of structural and functional data and methods in the solution of 
some of the greater problems of vertebrate descent, and espe- 
cially in the interpretation of the human nervous system, the 
culmination of that evolutionary history. We shall be able to 
present from our contributors illustrations of the practical work- 
ings of this principle in detail within a few months. 


RECENT STUDIES ON THE FINER STRUCTURE OF THE 
NERVE CELL. 


By G. E. CoGHIL1, 
Professor of Biology, Pacific University. 


The finer structure of the nerve cell remains the object of study 
for numerous investigators. Interest centers here from many points of 
view. From the physiological view-point there is sought the correct 
differentiation of the protoplasm from the metaplasm and the determi- 
nation of the relation which each of these, in its various aspects, holds 
to the activities of the cell. The pathologist demands, further, the 
structural basis and explanation of the various morbid activities as dis- 
tinguished from each other and from the normal. And for the mor- 
phologist the subject presents a variety of problems which may be 
approached by both comparative and embryological methods. 

In a field of so varied interests and in which at the same time 
there is much diversity of opinion, the results from various sources 
must undergo frequent critical analysis and synthesis. In no other 
way can the general trend of facts be discovered and progress in the 
subject as a whole be measured and made useful. With this thought 
in mind I have undertaken to study such recent papers and mono- 
graphs relating to the structure of the nerve cell as were available 
and to bring together synthetically the opinion of different authors 
under topics which appear to hold important place in the minds of 
investigators. 

The discussion is arranged according to the following plan: 

Ground Substance and Neurofibrillae 

The Moniliform Condition of the Dendrites 
Golgi’s Endocellular Net 

The Gemmules 

Golgi’s Pericellular Net 

Intracellular Canaliculi 

The Nucleus 

The Nucleolus 

The Centrosome 

The Tigroid Substance and Chromatolysis 


172 Journal of Comparative Neurology and Psychology. 
The Ground Substance and Neurofibrillae. 


‘ 

The challenge which came to the neurone theory through the 
works of Ap<tHy and BETHE has awakened new interest in the finer 
structure of the cytoplasm of the nerve cell. That there are structures 
in the properly fixed and stained neurone, especially of invertebrates, 
which accord with the neurofibrillae of these authors can no longer be 
doubted. But the exact relation which these fibrillae hold to the pro- 
toplasm of the living cell, to the inter-relation of neurones, and, there- 
fore, to the conduction paths of the nervous system, is not satisfactorily 
explained. Is the neurofibril a protoplasmic thread or is it a derived 
substance of the protoplasm as PuGNat and others argue? If it is a 
derived substance, it may well pass beyond the limits of the cell and 
form extra-cellular nets in the neuropil, as BerHe and ApATrHy and 
their followers describe. But if the fibril is protoplasmic its nature ex- 
cludes the possibility of such nets since the limits of the cell would 
coincide with the limits of the protoplasm. But if the fibril be proto- 
plasmic, are there stuctural features of the cytoplasm by which the 
origin, development and final behavior of the fibril can be explained? 
Towards the answer of such leading questions, some of the following 
works contribute in a positive manner. 

HouMaren (’99), in his monograph upon the spinal ganglion cells 
of Lophius, does not commit himself to adefinite statement regarding 
the ultimate structure of the cytoplasm. He describes however, a cer- 
tain radial appearance about the nucleolus in its migration from the 
nucleus into the cytoplasm which he considers suggestive of the alve- 
olar structure. Yet his figures and descriptions in general do not 
seem to sustain this interpretation throughout. In his beautifully ex- 
ecuted drawings (Taf. IX-X, Fig. 3) he represents the cone of origin 
as marked with stripes which are directed from the axone into the 
cell body. In the more distal part of the cone these stripes seem to 
form elongated and very narrow meshes. As the structure recedes 
into the cell body the meshes become shorter and broader, and _ es- 
pecially is this true in the peripheral region of the cell where the 
meshes become very irregular in shape and size. Though HOLMGREN 
does not discuss this structure in detail as related to the structure of 
the cytoplasm his figures are strongly suggestive of the cytoplasmic 
reticulum as described by Harat and others. 

In a later work upon the structure of the nerve cell HoLMGREN 
(oo) finds more positive data on this feature of the neurone. 
He demonstrates a fibrillar structure which he considers identical with 
the fibrillar substance of FLemmMinG. The fibrillae of the cytoplasm are 


CocuiLt, Structure of the Nerve Cell. 173 


continuous with those of the axone, but none of them anastomose. 
They follow an undulating or somewhat spiral course through the cell 
body, with a tendency to be more nearly parallel in the peripheral 
zone. ‘The interfibrillar substance is homogeneous. 

But the fibrils of this net, it is important to notice, are to HouLm- 
GREN the neurofibrillae. In both vertebrates and invertebrates they 
may enter or leave the neurone at any point in the periphery of the 
perikaryon or of the processes. Furthermore, Holmgren says, ‘‘die 
wabige, pseudowabige oder spongioplasmatische Structur, wie man sie 
auch nennen will, die ich bei Zophius, die RAMON-yY-CAJAL, LENHOs- 
sk, VAN GEHUCHTEN u. A. beschrieben haben, nur einem accidentellen 
Aussehen der resp. Zellen entspricht, im besten Falle durch einen 
gewissen physiologischen Zustand hervorgerufen.” That is to say, 
the ‘‘filare Substanz” of FLEMMING is resolved by HOLMGREN into the 
neurofibrillae of Ap<rHy and Berne, and the structural parts of the 
ground substance, such as granules, trabeculae etc., of many authors 
are interpreted as functional or artificial modifications of FLEMMING’s 
amorphous ‘‘interfilare Substanz.” 

KoLsTer’s monograph upon the nerve cell of Petromyzon con- 
tains an interesting demonstration of certain features of the ground 
substance. Korster has made an exhaustive study of unstained 
preparations of the nerve cell mounted’ in media of various refractive 
indices, and also of unstained osmic acid preparations. In none of 
his mounts made by these methods has he found anything akin to a 
fibrillar or reticular structure. But in cells preserved in FLEMMING’S 
solution for several months or even for more than a year, and subse- 
quently stained in saffranin and differentiated in a 20% tannin solu- 
tion followed by absolute alcohol, he discovers very fine lines running 
through all the cytoplasm. These lines are made up of a single row 
of dark red granules which the author treats as microsomes. In some 
of his figures these lines seem to form a net with relatively large, ir- 
regularly shaped meshes, but the author believes that anastomoses be- 
tween the lines are relatively rare. In thick sections these granules 
appear large, but thinner sections show that these relatively large 
granules are made up of short rows of exceedingly small granules run- 
ning in all directions. The whole structure, then, is resolved into a 
network of microsomes in linear arrangement. Furthermore, KoLSTER 
demonstrates that this net is concentrated into a dense granular mass 
directly around the centrosphere, where a granular effect is given in 
unstained preparations. From this central mass rather thick rays ex- 
tend in different directions, and these fray out into the fine lines of 


174 Journal of Comparative Neurology and Psychology. 


microsomes. KoOLsreEr interprets this structure as different from any- 
thing that had been previously described, but it would seem to 
be indistinguishable from the neurosomic net met with by other 
authors. 

According to BocHENEK (or) a fibrillar net may be beautifully 
demonstrated in the nerve cells of Hedix by the gold chloride method. 
In the body of the cell the meshes of the net are triangular or poly- 
gonal but in the axone hillock they elongate. The fibrillae which 
course independently through the axone are continuous with the fibril- 
lae of the net. The author finds it impossible, however, to distin- 
guish between the motor and sensory fibrils. He finds, also, that the 
net in He/ix is much more dense than it is in the nerve cells of Lwm- 
bricus. He interprets this as indicating a higher state of organization 
in Helix, which would be, in respect to the degree of differentiation of 
the intracellular net, intermediate between ZLuwmébricus and the verte- 
brates. BocHENEK treats this net as ‘‘un réseau protoplasmatique.” 

Van GEHUCHTEN, in his earlier work (97) upon the internal or- 
ganization of the nerve cell, took the position that the ground  sub- 
stance of the cytoplasm consists of a fibrillar net suspended in an 
amorphous fundamental substance. This net extends into the process 
in the form of elongated meshes which superficially give the appear- 
ance of distinct fibrils. These two elements are considered by VAN 
GEHUCHTEN ‘‘le véritable protoplasme de la cellule nerveuse.” The 
net or organized part he homologizes with the ‘‘masse filaire” of 
Fuiemmina. Ina later work (98), published jointly with NELIs, VAN 
GEHUCHTEN quotes FLEMMING as coinciding perfectly with this 
interpretation as given in 1897. The authors, however, proceed at 
once to modify their interpretatation in certain details. They found 
certain spinal ganglion cells of the rabbit which, because of the absence 
of chromatic substance in the peripheral region, gave excellent ad- 
vantages for studying the achromatic structure. In these cells, by the 
use of toluidin blue and erythrosin, they found the net to be made 
up of granules united together by thin trabeculae of the same sub- 
stance. But they add: ‘‘Le reseau protoplasmatique qui existe indu- 
bitablement dans toutes nos preparations différe totalement des fibrille 
courtes, flexueuses, irréguliéres et independantes decrétes et figurées 
par FLemmina.” He believes also that the net differs clearly from 
the net described by Doater and that it is much more regular than that 
figured by MARINESCO. 

In regard to the cone of origin, also, the authors have changed 
their views slightly. Instead of the comparatively thick and regular 


CoGHILL, Structure of the Nerve Cell. 175 


fibrillae which most authors describe, VAN GEHUCHTEN and NELIs 
find a delicate, granular striation which they fail to connect certainly 
with the cytoplasmic net. The granules of the striae are so arranged 
as to give in some cases a cross-striated effect. 

Paton (oo), in his studies of the neurofibrils of the cerebral cor- 
tex of the pig, finds that the fibrillae of the axone run independently 
of each other into the cell body, where they enter into a most intricate 
net-work. He holds that the fibrillae of this net are continuous with 
those of a pericellular reticulum, which he interpets as identical with 
Go.ar’s pericellular net. 

PAToN believes that the fibrils are very quickly affected by post- 
mortem granular disintegration which begins at the center of the cell. 
He believes this fact may account for the view of certain authors that 
fibrils exist only in in the apical process of the cell. 

PRENTISS has recently published in this Journal his latest results 
upon the neurofibrillar structures in Avudo and Asticus. As tothe gen- 
eral arrangement of the fibrils in the cell body he confirms APpATHY’s 
position. He concludes, however, that ‘‘Neither in vertebrates nor 
in crustacea do the neurofibrillae of the nerve cells show any marked 
correlation in size and function.” He believes that the differences in 
size which ApAruy observed are due to incomplete impregnation of the 
fibrillae and perhaps to the cleaving together of smaller fibrillae in the 
cell process. As to the relation of the fibril to the cell and its pro- 
cesses PRENTISS supports BETHE’s view that fibrils may enter one pro- 
cess and leave by another or by a collateral without coming into rela- 
tion with the perikaryon itself. In //vwdo he finds a very limited fibril- 
lar network in the neuropil. Such nets are more extensive in Astacus 
but they are not diffuse in their relation. They put relatively few fib- 
rillae into communication with each other. Prentiss considers that 
his preparations tend to confirm Brrne’s theory that the cells are not 
the centers of nervous activity, and that the fibrillae are continuous 
from cell to cell. 

Puewnat, in his recent review on the finer structure of the nerve 
cells, comes to the conclusion that the formed substance of the cyto- 
plasm is a net, in some cases of fibrillae, in others of trabeculae, and 
that this net is continuous with the fibrillae of the processes of the cell. 
The relation which this net holds to the life aud function of the cell, 
he thinks, can best be explained upon Barp’s theory of ‘derived 
substance.” Although PuanatT does not accept the sharp chemical 
and physical distinction between the protoplasm and the derived sub- 
stance as BarD proposed, he believes that fibrillae are a product of the 


176 Journal of Comparative Neurology and Psychology. 


protoplasm, that they are the conducting element and are therefore 
the seat of katabolic processes, while the protoplasm and nucleus are 
the seat of the anabolic process. How the fibrillae are repaired by 
the protoplasm, PUGNAT says, we are absolutely ignorant. Through 
this theory of derived substance PuGNAT attempts to bring the neurone 
theory into harmony with the results of ApAruy and BETHE and their 
followers. He thinks that whether the fibrillae as derived products 
of the cell are continuous or not from cell to cell, the nerve cell itself 
may be considered as an anatomically distinct unit. He would, in 
other words, place the neurofibrillae in the same category with the 
fibrillae of the muscle or connective tissue cell. However, before such 
a compromise of the neurone theory is conceded Harar’s methods, by 
which he has received such brilliant pictures of the finer structures of 
the nerve cells and of the axone terminals, must be given a thorough 
test. The results which he has recently published are remarkably 
convincing. p 

In the afferent neurones of the electric lobe of Zorfedo Hatal 
(or) demonstrates fine fibrillae in enormous numbers, crowding the 
cell processes and the perikaryon. By serial sections through one of 
these large cells he shows the behavior of the fibrillae within the cell 
body. Upon emerging from the process into the cell body they di- 
verge in clusters. Some sweep around the nucleus to form here a 
dense net, others pass to various processes of the cell in such a man- 
ner that there is direct fibrillar connection established between each 
dendrite and every other dendrite and between the axone and all the 
dendrites. By this coursing of the fibrillae from the dendrites into the 
axone there is a beautiful spiral configuration given to the ground sub- 
stance of the cone of origin. Superficially HaTar’s figures in this case 
have a striking resemblance to the familiar drawing of the fibrillar 
elements in the nerve cell by MAX SHULTZE. 

HarTAl, however, makes an important step in advance by demon- 
strating that these same fibrillae in the electric neurones of Zorfedo 
can be resolved into rows of neurosomes. Furthermore, he asserts 
that these neurosomic fibrils in reality are a modified reticulum. It is 
only in thicker sections and under lower magnification that the struct- 
ure gives the fibrillar appearance. 

Harat has demonstrated the reticular structure more exhaustive- 
ly in the nerve cells of the white rat. He has studied these cells (03) 
by the methods of Berne and Docren, but finds no such fibrillar 
structures as they describe. On the other hand, he demonstrates by 
other methods a neurosomic reticulum which is modified into a pseudo- 


CoGHiLy, Structure of the Nerve Cell. 177 


fibrillar structure. The fibrillae are made up of rows of neurosomes 
connected by slender protoplasmic filaments. Generally, around the 
periphery of the cell body the meshes are larger than in other regions. 
Around the nucleus and in the cone of origin they become more nar- 
row and very much elongated. A more pronounced modification of 
this character is found in the axone so that the reticular condition is 
difficult to see. In the axone, however, the neurosomes stain brighter 
than elsewhere. Especially is this true of the neurosomes of the axone 
terminals, where they are also larger than in other parts of the cell. 
The dendrites contain a relatively small amount of the ground sub- 
stance and the neurosomes stain more faintly than in theaxone. This 
fact enables Harat to differentiate the finest dendritic branches from 
the contiguous terminals of the axone. Even in the gemmules he 
demonstrates the neurosomic reticulum as continuous with that of the 
rest of the cell, but he finds that its neurosomes differ both in size and 
staining reaction from those of the axone terminals. He concludes that 
there is no continuity of the so-called fibrillar structures between the 
nerve cells. 

Now Harat finds that a number of these neurosomic filaments 
may mat together into thicker strands and that several of these strands 
in some cases form a complicated network around the nucleus. Such 
a network does not appear in the cone of origin or in the periphery of 
the cell body. He homologizes this network with the intracellular 
anastomosing fibrils of ApATHy and also with the endocellular network 
of Goter. Thus Harat resolves the neurofibrils of ApATHy into the 
protoplasmic elements of the cell and denies that they pass continuous- 
ly from cell to cell. The diffuse nets in the neuropil and_ pericellular 
nets also may be resolved into the reticulum of axone terminals which 
would be strictly protoplasmic and not extra-cellular, derived 
substance. 


Moniliform Condition of the Dendrites. 


Since Doatev’s discovery of the dendritic varicosities in the cells 
of the retina this feature of the nerve cell has held an important place 
in neuro-cytology. Among the most comprehensive contributions upon 
the subject are those of SoukHANOFF. ‘This author made four exper- 
ments by ligature of the abdominal aorta, three upon guinea pigs 
which died from the experiment in from one-half to twenty-four hours, 
and one upon a rabbit which was killed after twenty-four hours. In 
these experiments he found that the diminished blood supply had_pro- 
duced a very rapid modification in the nerve cell, varying directly in 


178 Journal of Comparative Neurology and Psychology. 


intensity with the duration of the anemia. The modifications of least 
intensity consisted in the appearance of swellings along the dendrite 
which made its contour irregular. As this condition became more in- 
tensified the swollen regions of the dendrites became fusiform and 
then spherical. During this process the connecting regions between 
the enlargements of the dendrites became more attenuated till a final 
beaded or moniliform condition resulted. This modification he con- 
sidered pathological. 

In another article (98) upon the modification of the dendrites 
under the influence of narcotics SOUKHANOFF reports in considerable 
detail the results of nine experiments upon mice, rabbits and guinea 
pigs. These animals had been subjected to the vapor of ether, chloro- 
form or aleohol for various periods of time. Two of the experiments 
were made by injection of trional. As a result of these experiments 
and of a critical review of the work of other investigators, SOUKHA- 
NOFF draws the following conclusions: (1) The moniliform condition 
may occur in certain dendrites under normal conditions, a conclusion 
reached by practically all authors; (2) under the influence of ether, 
chloroform or alcohol there is not a very appreciable increase in the 
moniliform condition; (3) injection of trional causes a moniliform con- 
dition of nearly all the dendrites of the cerebral cortex; (4) this change 
is accompanied by a more or less complete loss of the gemmules; 
(5) a loss in weight in guinea pigs subjected to trional injections can 
be attributed only to profound nutritive derangement. ‘This suggests 
that the moniliform condition of dendrites may be ‘‘une degeneres- 
cence sui generis” manifested whenever nutrition is severely affected. 

A third contribution by SOUKHANOFF (’98) deals with the varicose 
atrophy of the dendrites in the cerebral cortex under pathological con- 
ditions. His pathological studies were checked by examination of a 
normal specimen. From an exhaustive study of the latter case he 
concluded that the moniliform condition of the dendrites is oceasional- 
ly found under normal conditions, but that it is very slight and not 
to be compared with that found in cases of poisoning. From nine ex- 
periments upon guinea pigs which had been subjected to arsenic poison 
in varying degrees for periods of from six to thirty-three days, he con- 
cludes that in acute and subacute poisoning by arsenic there occurs a 
moniliform degeneration of the dendrites of the cerebral cortex. This 
is very slight in some eases, but very marked in others. This differ- 
ence cannot be accounted for by difference in the duration of the pois- 
oning. Its cause is more likely to be found in individual differences 
in the specimens as regards resistive power and general health. 


CoGuILt, Structure of the Nerve Cell. 179 


SOUKHANOFF’S experiments include also poisoning by rabies and 
tuberculin and a ease of thyroidectomy. Ina rabbit infected with rabies 
during eighteen days and fatally, the varicose degeneration of the 
dendrites was slight. The experiment upon the influence of tubercu- 
lin was performed upon a dog that had some time previously been 
inoculated with tuberculin for immunization. It was then inoculated 
with an emulsion of the Bacillus of Kocu. From his study of this case 
SOUKHANOFF concludes that the varicose condition occurs in many 
dendrites of the cerebral cortex but that this is due to derangement in 
nutrition. In the case of thyroidectomy, upon a dog which lived a week 
after extirpation of the thyroid gland, profound changes were observed 
in both large and small dendrites of the cerebral cortex. This also 
SOUKHANOFF attributes to nutritive derangements which are known 
to follow thyroidectomy. 

In general SOUKHANOFF concludes that although some dendrites 
in the normal nervous system are found in the varicose condition, the 
large numbers found changed under certain conditions are indicative 
of a morbid process; and that all poisonings which cause profound de- 
rangement in general nutrition cause a pronounced varicose degenera- 
tion of the dendrites. 

The condition of the dendrites in the spinal cord of the rabbit has 
been studied by SouKHANOFF and CZARNIECKI ('02). The spinal 
cord of two specimens, which were killed quickly with chloroform 
were treated by the Gotar method. To bring about quicker penetra- 
aion of the fluid incisions were made along the cord. The authors 
find that the cells of the cord show very pronounced differences in the 
form of the dendrites. The cells of the anterior horns differ strikingly 
in this respect from all other cells in the cord. Some of the dendrites 
of the anterior horn cells have comparatively regular contour, others 
are in a distinct varicose condition while the majority are in a condi- 
tion intermediate between the two extremes. On the other hand, the 
dendrites of many of the small cells of the cord were found in a very 
marked varicose condition. 

GEIER (or) reports a series of experiments which are especially 
noteworthy for their thoroughness. They were made upon mammals and 
birds killed with chloroform or ether, and involved an examination of 
at least an entire cerebral hemisphere in each case. He describes each 
case in detail and draws the general conclusion that anesthesia by chlo- 
roform or ether does not of itself cause a moniliform condition of the 
dendrites, but that such a condition must be considered as the expres- 
sion of a morbid or fatigued state of the cell. He holds also that the 


180 Journal of Comparative Neurology and Psychology. 


moniliform condition is not an expression of the plasticity of the cell 
as certain authors have claimed. 

In a later contribution GEIER (02) presents important data upon 
the development of the protoplasmic processes as well as upon their 
form in the adult. He has studied by the Gouar method the cells of 
the spinal cord of rabbits of different ages; one day, two weeks and one 
month; and of kittens at birth and at three days, seven days, one 
month and two months old. The two series of experiments lead to 
the same conclusions: the protoplasmic processes of the anterior horn 
cells are less regular in outline in the new-born than in the adult. As 
the animal grows the outline of the processes become more regular and 
the process straightens. In the new-born the dendrites have a more 
regular contour in the region of the cell body than in the distal region, 
and the process of straightening progresses from the cell body outward. 
As for the dendrites of the posterior horn, Grier finds it difficult to 
determine whether there is any such change accompanying growth as 
he describes for the anterior horn cell. ‘This difficulty arises from the 
fact which he demonstrated in his earlier work and which his pres- 
ent investigation confirms, that the dendrites of the posterior horn of 
the adult are normally very irregular in outline as compared with the 
dendrites of the anterior horn cells. He finds, however, that there 
are certain cells in the anterior horn which have very irregular den- 
drites. He considers them commissural cells. In his youngest speci- 
mens he found the varicose condition of the dendrites very conspicu- 
ous, but less marked in the older specimens. The condition tends to 
disappear as the animal grows. 


Golg?’s Endocellular Net. 


SouKHANOFF (’02) has made a specific study of Gonat’s endocel- 
lular net in the cells of the cerebral cortex of mammals by modifica- 
tions of the Gora method. He finds this net only in a zone around 
the nucleus, although it does not lie directly upon the nucleus. Sur- 
rounding the net is a zone of protoplasm which is noticeably clearer 
than the rest. Some of the filaments of the net are fine, others are 
coarse, still others are ribbon-like. Often they are of irregular contour. 
In some small cells the net consists of only a few curls of the filaments, 
and it is a much simpler structure in the cortical cells than it is in the 
cells of the cord and spinal ganglia. In general form the net conforms 
rather closely to the shape of the cell. Sometimes one branch of the 
net, sometimes two or three, pass out into the process. 

In the intepretation of the endocellular net SOUKHANOFF speaks 


CoGHILL, Structure of the Nerve Cell. 181 


positively on three points: it isa strictly endocellular structure ; it has 
nothing to do with the neurofibrils of ApArHy and BEerHE; it is not 
identical with the canaliculus HotmMGREeN. Regarding its relation to 
“état spiremateau” of Newis, he could not at the time of writing offer 
a positive opinion. 

As already stated in the discussion of the structure of the ground 
substance, Hara (’03) resolves the net in question into a modified 
protoplasmic reticulum. His position upon this point is strongly sup- 
ported by almost every feature of the net which SouKHANOFF empha- 
sizes,—the lack of uniformity in size and the irregularity in contour of 
the fibrils, the restricted perinuclear position of the net, its conformity 
in shape to the shape of the cell and its relation to the processes of the 
cell. In all of these features the net has a striking resemblance to the 
filaments which Harari describes as formed by the matting together of 
numerous fibrillae of the neurosomic net. But it will be remembered 
that Harai considers that the neurofibrils of APATHY are identical with 
this modified reticulum. ‘The interpretation would place him in direct 
opposition to SoUKHANOFF when the latter says that the Gonc1 endo- 
cellular net has nothing to do with the neurofibrils of Ap<rHy and 
BETHE. 

By Harars work, therefore, another of the manifold structura 
elements of the nerve cell is explained upon the basis of the funda 
mental structure of the protoplasm. 


The Gemmules. 


The structures which BERKELEY called ‘‘gemmules”’ have received 
various names by other investigators: ‘‘épines” by RamOn-y-CaJAL; 
‘appendices piriformes” by MLLE. STerFANowsKA; and ‘‘appendices 
collatereaux” by others. As treated by many authors they may vary 
in form from short club-shaped to spindle-shaped or even filamentous 
structures. In his study of the cellular changes in the cerebral cortex 
under experimental anemia, SOUKHANOFF (’98) finds that as the symp- 
toms become more acute the gemmules become modified and ulti- 
mately disappear. In another work of the same year, he discovered 
similar changes in the gemmules in animals which have been subjected 
to the vapors of ether, chloroform and alcohol. In other animals treated 
with injections of trional the pronounced modifications in the gem- 
mules, as well as other changes in the central system, were attributed 
to the derangement of general nutrition and not to the specific action 
of the drug. 

In further pathological studies with the Gonci method, SoukHAN 


182 Journal of Comparative Neurology and Psychology. 


OFF (’98) observes that the gemmules are lost in varying degrees in the 
nerve cells of animals subjected to poisoning by arsenic, rabies, tuber- 
culin and also of animals suffering from thyroidectomy. These studies 
were checked by preparations of nerve cells from a normal guinea 
pig killed by decapitation. The nervous tissue was quickly placed in 
the fixing reagents and received like treatments with the abnormal 
tissues. The preparations showed gemmules present almost univer- 
sally upon the dendrites. 

In collaboration with CZARNIECKI, SOUKHANOFF (02) has studied 
the dendrites of the ventral horn cells of the rabbit with the Goucr 
method. By killing the animals quickly with chloroform the authors 
considered that the tissue was found in the normal condition. 

Upon the dendrites of certain cells very few gemmules were 
found; in others they were numerous, beginning to appear on the 
dendrites nearer the cell body and becoming more numerous as the 
distance from the perikaryon increased till in the distal region they al- 
most covered the process. In another type of cell, which lay with the 
protoplasmic processes partly within the white substance, that part of 
the dendrite which lay within the white substance bore no gemmules, 
while the part lying within the grey substance was abundantly supplied 
with them. And even when the dendrite lay in the border line between 
the grey and the white substance the side of the dendrite which faced 
the grey bore more gemmules than did the side facing the white. The 
authors conclude that the gemmules are much less numerous upon the 
ventral horn cells than upon the cells of the cerebral cortex, but that 
they are much more variable in size and shape. They may be pyri- 
form, filamentous, club-shaped, tubercular, or finely branched. Cer- 
tain of these forms which the authors call ‘‘rejitons,” which are very 
irregularly fibrillar and club-shaped, are not found in the cells of the 
cerebral cortex. 

GEIER ('o1) has studied with the Gouci method the cerebral cortex 
of mammals and birds which have been subjected to the vapors of 
ether and chloroform for from five to ten minutes. In some of the 
experiments the gemmules showed a tendency to disappear, while in 
others the cells appeared perfectly normal. The disappearance of the 
gemmules was found to be concomitant with the moniliform condition 
of the dendrites. As GEIER considers the moniliform condition of the 
dendrites as morbid, due probably to exhaustion or want of nutrition, 
he would also interpret the disappearance of the gemmules as indi- 
cative of morbid processes in the cell. 

In a later work GEIER (02) described the development of the pro- 


Cocuit1, Structure of the Nerve Cell. 183 


toplasmic processes of the cells of the spinal cord of the rabbit and cat. 
Besides the ordinary club-shaped gemmules there are others, in the 
animal just born, in the form of fine filaments or spines which often 
arise from a small conical projection of the dendrite. In the middle of 
this filament may sometimes occur a small thickening. The processes 
of the posterior horn cells have the same type of gemmules but have 
them in much larger numbers. 

In a rabbit two weeks old the processes have become more regu- 
lar in outline. This change appears only in the basal part of the den- 
drites and advances with age towards the periphery. The filamentous 
gemmules do not appear at this stage all along the dendrites as they 
did in the rabbit one day old, but occur only in the more distal, irregu- 
lar part of the process. In a rabbit one month old they are found 
only on the extreme terminal branches of the dendrite. In cats from 
birth to one month old the same mode of development is followed. 
But in kittens two months old Geter found no typical filamentous 
gemmules upon the anterior horn cells. In place of them were similar 
processes of much larger size. This, together with the fact that in an 
animal three days old the filamentous gemmules are two or three times 
larger than they are at birth, indicates that some at least of these gem- 
mules grow into dendritic branches. GErER believes that all such gem- 
mules of the young cells are dendrites in the process of development. 

This peculiar type of gemmule is not found upon the posterior 
horn cells, but the more complex forms are very abundant on the 
dendrites and occur also on the cell body. GerER concludes that the 
gemmules are relatively rare upon the anterior horn cells and of a con- 
stant form while they are exceedingly numerous and variable in form 
upon the cells of the posterior horn. Their absence in any case is as- 
sociated with the moniliform condition of the dendrites. 

PaTON (oo) interprets the gemmules as artifacts which mark the 
points at which the fibrillae of the pericellular net enter the cell or come 
in contact with it. He asserts that the appearance of the gemmules 
upon the cortical cells of the embryo is synchronous with the appear- 
ance of neurofibrils. 

That the gemmules mark the point of continuity between the in- 
tracellular and the pericellular fibrils is denied by Harar. He de- 
monstrates the neurosomic net within the gemmule and the neurosomic 
nature of the axone terminals which compose this pericellular net. 
But, while the two fibril systems come into intimate touch with each 
other, especially at the gemmules, they differ sufficiently in structure 


184 Journal of Comparative Neurology and Psychology. 


and reaction to enable one to determine a boundary line between 
them. 

As to the physiological significance of the gemmules, their finer 
structure and their reaction to anesthesia as wellas the features of their 
distribution as noted above, would seem to justify us in according to 
them an important part in the maintenance of the conduction paths 
within the central system. 

Golet’s Pericellilar Net. 

The network of fine fibers which Go.ar first described as sur- 
rounding the nerve cells of the central and peripheral system has been 
treated by subsequent writers as both nervous and non-nervous. The 
more recent work, however, by HELD, BETHE and others demonstrates 
that this net is continuous with the terminals of medullated axones. 
Haral (’o3) confirms this position and shows further that the fibrillae 
of the net are of the same nature as those of the axone. That is to 
say, they are a modified neurosomic reticulum. We have treated the 
relation of the net to the nerve cell in the foregoing section upon the 
gemmules. 

Harat’s observations would seem to be in harmony with Houm- 
GREN’S (99) views regarding the pericellular net of the spinal ganglion 
cell of Zophius. This net lies between the capsule and the cell and 
between the lamellae of the capsule. It is continuous with fibers 
which come from other regions of the spinal ganglion and with fibrils 
which penetrate deeply into the cell. But these fibrils do not become 
continuous with the protoplasm of the cell into which they penetrate. 
A light.area always separates them from the surrounding protoplasm. 


Intracellular Canatliculs, 


In 1886 FrRirscu first discovered an intracellular system of ves- 
sels in the nerve cell. His-observations were made upon certain 
large cells in the medulla of Zofhiws. He interpreted the structures 
as genuinely vascular. HOLMGREN (’99) discovers similar structures 
in the spinal ganglion cell of Zoffzus and claims that he is first to con- 
firm the observations of FrirscH. But during the same year of 
HoiMGREN’s publication NELts (99) introduces ‘‘un nouveau detail” 
in the protoplasmic structure of the nerve cell, which has many fea- 
tures in common with the intracellular vessels of FrrrscH and HoLMm- 
GREN. These structures, the ‘‘Gefasse” of FrirscH. the ‘‘KanAl- 
chen” of HOLMGREN and ‘‘l’état spiremateux’’ of NELIs, we shall for 
convenience designate as intracellular canaliculi. 


CoGHILL, Structure of the Nerve Cell. 185 


HOLMGREN (’99, ’oo) asserts that the canaliculus is continuous 
with the pericellular lymph space and that it is accompanied by trabe- 
culae of the connective tissue capsule of the cell. Along with it occur 
also the nuclei of its membranous walls and connective tissue nuclei 
which have migrated in from the capsule of the cell, while corpuscles 
of the lymph circulate through the canaliculus. 

KOLSTER (00) observes canaliculi also in the nerve cell of the 
spinal cord and spinal ganglia of Petromvzon. He has demonstrated 
them successfully in unstained sections of cells fixed in osmic acid. 
He traces them from the periphery of the cell into the deepest part 
where they seem to be continuous with a perinuclear space of the same 
nature. <A slight invagination of the endothelial capsule may occur 
where the canaliculus enters the cell and free nuclei are found in the 
protoplasm which are interpreted as nuclei of the capsule; but Kor- 
STER,. even with the technique employed by HoLMGREN, fails to find a 
nucleated membranous wall surrounding the lumen of the canaliculus. 
It is bordered simply by the granular protoplasm of the cell. Still, in 
a later work, HOLMGREN (oo) confirms his first observations by dem- 
onstrations of the canaliculus in the nerve cells of mammals and birds 
with all the features originally described for Zopfiws. He further 
shows that electrical stimulation of the nerve cell causes an expansion 
of the canaliculi. 

HoLMGREN’s interpretation of the canaliculi receives positive sup- 
port from the observations of PUGNAT (or) upon the embryological 
development of the canaliculus in the nerve cell of the chick. PuGNatT 
finds that the canaliculi appear first in the outer zone of the spinal 
ganglion cell on the eleventh day. By the fifteenth day they have 
reached the central zone. These canaliculi, according to PuGNAr also, 
have membranous walls and are continuous with extracellular vessels 
of the same nature. 

Canaliculi have been recognized also by BocHENEK in the largest 
nerve cells of Hedzx. As to the structural and topographical features 
of the system, BocHENEK agrees in the main with HoLMGREN. He 
finds the connective tissue fibrillae and cells very conspicuous in the 
protoplasm of the nerve cell and even invading the basal portion of the 
axone. He explains the structure as a simple invagination of the cap- 
sule into the body of the nerve cell or as clefts in the cell. His fig- 
ures and descriptions would not give one the idea of a clearly defined 
membranous wall about these clefts, yet he says ‘‘Si, dans cet exposé 
des faits, nous sommes en complet accord avee le travail de Hoim- 


186 Journal of Comparative Neurology and Psychology. 


GREN, nous ne pouvons pourtout pas souscrire a ses déductions 
théoretiques.” 

The theoretical deduction of HotmGreN to which BocHENEK 
cannot subscribe is regarding the significance of the canaliculus in 
flelix, HOLMGREN holds that the nerve cells are poorly or richly sup- 
plied with canaliculi according to the functional condition. BOCHENEK 
has observed, however, that the canaliculi of Avex are equally de- 
veloped in winter and in summer; that is, during the periods of 
activity and inactivity. He believes, therefore, that they are constant 
features and are to be explained as an adaptation of a large cell for in- 
creased absorbing surface. 

The ‘‘nouveau détail” which NELIs (99) calls ‘‘l’état spiremateux” is 
in the form of a spireme-shaped or much coiled, continuous band. In 
material hardened in GILson’s fluid or 5% formalin and stained in 
HEIDENHAIN’s iron haematoxylin and eosin or erythrosin these bands 
appear uncolored and amorphous, and marked off from the colored 
ground substance by regular, parallel lines. The position of the 
spireme varies in position and extent in different cells. It may le near 
the periphery of the cell, near the center or in close relation to the 
nucleus. In some cases one of its borders is indistinguishable from 
the nuclear membrane; although the author considers that the two 
elements do not in reality coincide. 

Netis finds the spireme in the plexiform ganglion of the dog, and, 
less conspicuously, in the superior cervical ganglion. It is present in 
the pyramidal cells of the cerebral cortex and in the spinal ganglion 
cells also. He considers that this is a normal structure, but that under 
certain pathological conditions it may become much more extensively 
developed and more easily demonstrated. As to its significance, 
Ne.Is is undecided, but he is inclined to interpret it as a protoplasmic 
element of the cell. 

De Buck and bE Moor (’99), in a work upon the lesion of the 
nerve cells accompanying experimental tetanus in the guinea pig, find 
a system of vacuoles which they identify with the spireme of NELIs. 
These vacuoles may approach very near the border of the cell, but are 
always separated from it by a thin layer of protoplasm. VAN GEHUCH- 
TEN and NELIs (‘0o) have observed the structure also under pathological 
conditions and conclude that it is accentuated by arsenic poisoning, 
tetanus, etc. 

Among these various descriptions of intracellular vessels it is quite 
easy to identify the type described by Ko.tsrer with the canaliculus of 
Ho_MmGREN, by assuming that Ko.srer has failed to demonstrate the 


CoGuHILL, Structure of the Nerve Cell. 187 


membranous walls of the vessel. Furthermore, the general form and posi- 
tion of the spireme of NELISs harmonizes well with the canaliculus of 
HoLtmMGREN. Though Nexis does not find nucleated membranous 
walls, he does find parallel walls with a sharp contour. It only re- 
mains to demonstrate the continuity of the structure with extracellular 
lymph vessels in order to identify it with the canaliculus of HOLMGREN. 
But as to the interpretation of BoCHENEKk’s clefts we find greater diffi- 
culty. He has compared his preparations with the original prepara- 
tions of the spireme made by Ne tis and has decided that the two struc- 
tures are totally different. He expresses himself as surprised, also, 
that HotmGreEN should homologize the canaliculi of Ae/ix with the 
spireme. This suggests that HOLMGREN and BOCHENEK may be deal- 
ing with altogether different structures. It may be that BocHENEK has 
not seen the genuine canaliculus with membranous walls, but that he 
has demonstrated only deep clefts in the cell which are filled with the 
capsular tissue. 


The Nucleus. 


HoLMGREN (99) finds that the size of the nucleus in the spinal 
ganglia of ZopAius varies with the size of the cell. The linin net and 
chromatic granules, which stain red with toluidin blue and erythrosin, 
are massed thickly around the nucleolus and radial branches stream 
out from this to the nuclear membrane which is acidophile also. On 
the side of the nucleus which lies nearest the center of the cell the 
contour may become flattened or even indented by a mass of tigroid 
substance which accumulates at this point. The nuclear membrane 
of this region thickens and changes its reaction to the stain, for it now 
stains dark blue in toluidin-erythrosin, deep black in iron haematoxylin 
and green with the triple Bronpi stain. Simultaneously with this 
change in the nuclear membrane there come changes in the tigroid 
mass, which is heaped upon the nucleus in this region. The large 
tigroid bodies, which, earlier in the process, were packed closely to- 
gether here, have become resolved into small granular heaps or scat- 
tered granules suspended in a homogeneous or purely granular ground 
substance. The latter stains blue with toluidin-erythrosin, gray or per- 
haps black with iron haematoxylin and red with the triple acid stain. 
Following this condition the thickened part of the nuclear membrane 
disappears either throughout the entire extent or at intervals. Through 
this cleft the cytoplasm becomes continuous with the karyoplasm. The 
union takes place through protoplasmic bands (Ziige) which radiate 
from the centrosome into the nuclear substance and become continuous 


188 Journal of Comparative Neurology and Psychology. 


with the linin net. The part of the hnin net which enters into the 
radiating bands contains granules which stain a darker red than the 
other acidophile elements and black with iron haematoxylin. In the 
radiating bands beyond the limits of the nucleus there occur granules 
which stain black also in iron haematoxylin but dark blue in toluidin- 
erythrosin. They are sharply differentiated from the tigroid elements 
by their reaction to DELAFIELD’s haematoxylin and the triacid stain. 
In the former they stain blue-black, while the tigroid elements stain 
faint blue; in the latter, they appear green while the tigroid elements 
appear red. ‘This reaction places them in the category of basichro- 
matin and they must be considered as such elements which have mi- 
grated out from the nucleus. ‘They become basophile during their 
migration from the nucleus and represent the nuclear chromatin. 

While these changes are going on the nucleus enlarges and mi- 
grates towards the periphery of the cell, till, in some cases, a mere 
film of protoplasm separates it from the cell membrane. In the mean- 
time, also, the acidophile granules of the nucleus have increased 
greatly in number and during the process also the nucleolus sends off 
fragments into the cytoplasm. 

KOLSTER (00) also contributes interesting facts upon the general 
morphology of the nucleus. In a large series of preparations he finds 
that only a part of the nuclear border has a regular outline and limit- 
ing membrane. As studied in serial sections the nuclei, practically 
without exception, lose their membrane in a particular region and the 
karyoplasm pushes out in pseudopodia-like processes into the cytoplasm. 
This appears to the author to be a constant feature and not due to any 
peculiar physiological condition. He interprets it as concerned in the 
nutrition of the nucleus. But, compared with HoLMGREN’s work, 
KOLsTeER’s results are noteworthy from the fact that the side of the nu- 
cleus which is marked by this irregular contour may lie opposite the 
centrosome while HOLMGREN finds it directed toward the centrosome. 

Irregularities in the border of the nucleus have been observed 
also by BOCHENEK (or) in certain large nerve cells of //e/ex. 

The idea that the nuclear membrane breaks down and that there 
is an interchange of formed substance between the nucleus and the 
cytoplasm, especially as described by HOoLMGREN, is opposed by 
Scott (99). He believes this appearance is due to the action of the 
knife in cutting. However, it hardly seems probable that both Houm- 
GREN and KotstTer should be utterly deceived in this manner. More- 
over, it does not seem that Scorr’s fundamental thesis or his results 


CoGHILL, Structure of the Nerve Cell. 189 


exclude the possibility of such ruptures in the nuclear membrane as 
HOLMGREN and KOLsTER describe. 


The Nucleolus. 


The behavior of the nucleolus in the spinal ganglion cells of Zo- 
phius as described by HOLMGREN (99) has already been mentioned in 
the section relating to the nucleus. Regarding the finer structure and 
chemical nature of the nucleolus the works of KouisrEr, Harai and 
SCOTT are noteworthy. 

In the spinal ganglion cell and the FReup’ schen cells of Petvo- 
myzon, according to KOLSTER, the nucleolus appears homogeneous only 
in preparations fixed in sublimate and stained in iron haematoxylin. 
In all other methods which the author used he found two rather sharp- 
ly differentiated zones, a dark, relatively large central portion sur- 
rounded by a shell of substance which stains more faintly than the 
central body. In some preparations there appeared a granular, inter- 
mediate zone between the central core and outer shell. KoOLsTER is 
inclined to interpret the nucleolus, not as a solid mass, but as a vacuole 
with peculiar liquid contents. The reaction of the contents to reagents 
accounts for the structural features which appear by different methods. 
PuGNAT, on the other hand, considers that the central, granular ap- 
pearance of the nucleolus is due to the presence of formed bodies. 

Scotr (99) and Harat (03) both demonstrate an oxyphile center 
with basophile peripheral zone in the nucleolus. Only the basophile 
part represents the chromatin, while the oxyphile center is the true 
nucleolar substance. 

The behaviour of the nucleolus of the nerve cell during mitosis 
has been carefully worked out by Harar. While in the adult nerve 
cell the larger part of the nucleolus stains blue with toluidin-erythro- 
sin, in the germinal cells the entire nucleolus stains a deep red. In 
the later telophase stage of mitosis the nuclear substance, which has 
become closely massed around the chromosomes, dissolves and ac- 
cumulates again in small spherical masses which collect near the cen- 
ter of the nucleus. Each granule of this group sends out a process 
from either pole. ‘These processes from the various granules anasto- 
mose to form a net with granules at the angles of the meshes. The 
linin and the basophile nuclear substance now collect around this 
group of acidophile granules to form the nucleolus of the adult nerve 
cell. But if the cell is to divide again, the linin which has accumu- 
lated around the nucleolus breaks up in the early prophase and the 
nucleolar granules separate. As the spireme forms they collect upon 


190 Journal of Comparative Neurology and Psychology. 


it and ensheathe it, and form groups in the nuclear net. ‘That which 
clings to the chromosomes become modified to form the ‘‘Halbspindel 
fasern.”” As the spireme splits, nucleolar substance still persists 
around the daughter spiremes. ‘This tends to collect at the middle of 
the curved chromosomes which are turned with the convexity towards 
the centrosphere. As the daughter spiremes separate, nucleolar sub- 
stance unites with the linin to form the rays of the central spindle. 
The linin in this phase stains slightly deeper than the cytoplasmic 
reticulum but not so deeply as does the nucleolar substance. It is only 
in the telophase stage that the nucleolar substance, which has been 
associated with the linin, becomes indistinguishable from it. 

There seems to be conclusive evidence, therefore, that the nu- 
cleolus of the adult nerve cell is a heterogeneous structure with an 
oxyphile center which is structurally and chemically allied to the linin, 
and with a peripheral zone of basophile chromatin. 


The Centrosome. 


HoLMGREN finds that the centrosome in the spinal ganglion cell of 
Lophius is located in the center of the cell. It forms the center of the 
concentric circles and radial ‘‘Ziige” of the cytoplasm. HoOLMGREN 
suggests that, since its reproductive function must have ceased, and 
since it holds this constant relation to the trigroid substance, it is prob- 
ably concerned in the nutritive functions of the metabolism of the cell. 
The object which LENHOsSsEK first interpreted as the centrosome in 
the spinal ganglion cell of Raza is, according to HOLMGREN, nothing 
other than a section through an invaginated trabecula of the capsule. 

KoLsTeER identifies the centrosome in the nerve cells of Petromy- 
zon even in unstained preparations, but it is not located in the center 
of the cell. The centrosphere is surrounded by an irregularly shaped 
mass of granules which are arranged in the form of a dense reticulum, 
which we have already discussed in connection with the ground sub- 
stance of the cytoplasm. ‘The interior of the body in unstained prep- 
arations appears as dark, circular lines separated by bright points. In 
other methods, it appears as a circular space in which the centrosome 
lies. 

The centrosome in the nerve cell of the dog and rabbit infected 
with rabies has been studied by Netis. He holds that the organ is 
not visible in the normal nerve cells of mammals, but that it is brought 
into plain view during chromatolysis which accompanies rabies. He 
suggests that this reappearance of the centrosome immediately before 
the nucleus atrophies indicates a tendency toward cell division at that 


CoGHILL, Structure of the Nerve Cell. IgI 


time. Such a hypothesis is supported also by the fact, observed by 
several investigators, that karyokinetic figures occur in the nerve cells 
of animals infected with rabies. 

Haral, however, finds the centrosome present in the nerve cell 
of the adult rat, though it is not so generally found in the adult as in 
the young. ‘The centrosphere is here densely surrounded with neuro- 
somes which go out in radial lines from it, somewhat as KoutsTrer finds 
in Petromyzon. Within the clear centrosphere Harat finds, also, radil 
of extremely fine granules centering in the centrosome and staining 
like it. In some cases the place of the single centrosome may be 
taken by a number of smaller granules, but in such cases the radial 
arrangement in the centrosphere is lost. Harar (02) describes also 
the behavior of the centrosome in the mitosis in the embryonic nerve 
cell. One of the two centrosomes seems to migrate to the opposite 
pole of the nucleus and then each divides, giving two centrosomes in 
each centrosphere during the mitotic process. 


The Tigroid Substance and Chromatolysts. 


LT. Structural and Chemical Features.—The studies of Scorr (99) 
upon the chemistry of the tigroid substance of the nerve cell are espe- 
cially noteworthy since they are based upon both embryological and 
comparative methods, and since he has employed both cytological and 
micro-chemical technique. He has not confined himself to the use of 
the Nissi method, but has used toluidin blue and eosin to differentiate 
the oxyphile and the basophile substances. 

By the haematoxylin method for the Prussian blue reaction after 
treatment of the tissue with acid ferrocyanide, and by the ferrous 
sulphide reaction after treatment with ammonium sulphide and glycer- 
ine, the basophile and oxyphile nuclear substance and the tigroid 
bodies show the presence of iron. By the oxide of molybdenum re- 
action after treatment with a nitric acid solution of ammonium molyb- 
date followed by phenylhydrazin hydrochloride the same elements of 
the cell show the presence of phosphorus. In digestive tests Scorr 
finds that immersion for several days in 0.2 per cent hydrochloric 
acid, at 37°C., does not affect the oxyphile nuclear substance, but 
after digestion in pepsin and hydrochloric acid the oxyphile substance 
cannot be demonstrated by the most vigorous stains. In the pepsin 
experiments the nucleolus sometimes disappears, but Scorr considers 
that it is only loosened from the slide by the digestion of its oxyphile 
center by which it may have been attached. 

While treatment of the nerve cell with acid alcohol aids in dem- 


192 Journal of Comparative Neurology and Psychology. 


onstrating the presence of iron, prolonged treatment will extract all 
the iron and render the tissue colorless under the toluidin blue stain. 
Yet after all the iron has been extracted phosphorus is still demon- 
strable in the tigroid substance and in the oxyphile and basophile nu- 
clear substance. Treatment with alkalies removes the iron from the 
tigroid substance but not from the nucleolus and the oxyphile nuclear 
substance, excepting when the treatment is prolonged, while the nu- 
clei of neuroglia cells in the same preparations stain normally in eosin 
and toluidin blue. Prolonged treatment in the alkalies, however, 
does not affect the phosphorus of the cell. ‘The author finds that 
fresh defibrinated ox-blood, owing to its alkalinity, has the same effect 
as potash of soda upon the nerve cells fixed in alcohol. 

By these differential methods Scorr. concludes that the tigroid 
substance is one of at least three nuclein compounds found in the 
nerve cell, the other two being the ‘‘basophile covering of the nucleo- 
lus and the oxyphile nuclear substance.” The descent of the three 
compounds was traced by Scorr from the chromatin of the germinal 
cell. ‘‘The chromatin,” he says, ‘‘divides into two parts, each con- 
taining iron and phosphorus, but the one is oxyphile and remains in 
the nucleus, while the other is basophile and diffuses into the cell body 
and becomes the Nissi granules.” This position would seem to be 
supported, also, by vAN GEHUCHTEN (97) who is inclined to think 
that the nuclein (chromatin) of the karyochrome cell is equivalent to 
the chromatin substance of the somatochrome cell. 

If the nuclear chromatin is the source of the first chromatic ele- 
ments in the cytoplasm of the embryonic nerve cell, does it continue 
this role in the adult cell? If it does, in what manner is the dis- 
tribution of the chromatic elements from the nucleus to the cytoplasm 
brought about ? 

Ho_MGREN (’99) has described an elaborate process, which we 
have discussed in the section relating to the nucleus, by which the nu- 
clear wall breaks down and the oxyphile nuclear substance migrates 
into the cytoplasm and becomes at the same time metamorphosed into 
basophile tigroid substance. By the same process also the basophile 
covering of the nucleolus breaks off in large masses which are carried 
out into the cytoplasm. Scorr, however, since he considers that the 
breaking down of the nuclear membrane and the displacement of the 
nucleolus is an artifact, is convinced that, if the transference of chro- 
matic substance from the nucleus to the cytoplasm continues during 
adult life, the process is diffusion and in no sense a transposition of 
formed chromatic bodies. However, the nuclear origin of the tigroid 


CoGHILL, Structure of the Nerve Cell. 193 


substance, at least in the adult, is opposed by vAN Durer, who 
believes that the tigroid substance is derived from the nucleo-albumins 
of the lymphocytes. 

Van GEHUCHTEN (’97), accepting the reticular structure of the 
ground substance, believes that the tigroid substance accumulates at 
the nodal points of the net. These accumulations enlarge in certain 
regions and form masses which appear homogeneous when they be- 
come sufficiently dense to obscure the reticular framework. A mesh 
of the reticulum which remains unfilled produces a vacuole. VAN 
GEHUCHTEN attributes the formation of these bodies to the affinity of 
the protoplasmic net for a special chemical substance. It is, there- 
fore, the form and disposition of the cytoplasmic net that determines 
the size and distribution of the tigroid bodies; and this, in turn, is 
governed by the function of the neurone. 

Scotr (99), on the contrary, argues that the shape and distribu- 
tion of the tigroid bodies are determined by the modification in the 
shape of the cell during growth. The tigroid substance diffusely per- 
meates the whole cytoplasm in the early history of the cell. But the 
growth of the cell and especially the development of the protoplasmic 
processes break the substance up, by a purely mechanical process, into 
separate bodies. ‘The distribution of these bodies would seem, there- 
fore, to be governed by the proportions and shape assumed by the 
cell. 

Scotr takes the position, furthermore, that the tigroid substance 
cannot be considered as a part of the cytoplasmic net since it diffuses 
into the cytoplasm after the net is formed. Though the two substances 
may be intimately associated, they are structurally distinct. He con- 
siders that the granules are homogeneous and _ that appearances to the 
contrary, including vacuoles, are to be explained by irregularities in 
their surfaces. 

In Lophius HOLMGREN (99) finds that the tigroid body may be 
resolved into two constituents: a homogeneous ground substance, 
which stains bluish gray in iron haematoxylin and which tends to stain 
in both colors with toluidin-erythrosin ; and granules which are sus- 
pended in the ground substance and which stain black in iron haema- 
toxylin and deep blue in toluidin-erythrosin. The ground substance 
forms in areas of varying shape and size and the granules may be dif- 
fusely distributed through it or massed into solid bodies of different 
proportions. HOLMGREN does not discover any definite relation of 
these bodies to a formed ground substance of the cytoplasm. 

Although the substance occurs in comparatively small amounts in 


194 Journal of Comparative Neurology and Psychology. 


the nerve cells of ZLopfius, HOLMGREN describes an interesting feature 
of its distribution in the cell. Its ground substance has a two-fold 
arrangement relative to the centrosome ; in radii which widen as they 
approach the periphery of the cell, and in concentric circles around 
the centrosome. Both the radial and circular bands are more or less 
irregular in outline. This typical arrangement, however, is often 
found modified or obscured. ‘The circular bands may overlap each 
other and those which come nearest the nucleus are more or less di- 
verted from their symmetrical course so as to encircle the nucleus. 
And onthe side of the nucleus nearest the centrosome the tigroid 
substance collects into a mass of unusual size and becomes involved 
in the process of transfusion of nuclear substance into the cytoplasm 
as we have described in the section relating to the nucleus. 

HOLMGREN (’oo) believes that the distribution of the tigroid bodies 
is determined by the arrangement of the canaliculi. He has noticed 
that the tigroid substance of a given cell is most abundant in the 
region of the most conspicuous canaliculi; also, that it is very abun- 
dant in the nerve cells of animals which are characterized by numer- 
ous canaliculi. Furthermore, electrical stimulation of the nerve cell 
is accompanied by an increase in the tigroid substance and also by an 
expansion of the canaliculi. 

Although HoLMGREN’s interpretation regarding the increase in 
tigroid substance under electrical stimulation of the nerve is open to 
serious objection, his observation would nevertheless support his thesis 
that the condition of the tigroid substance is correlated with that of 
the canaliculi. ‘This idea received further support from the observa- 
tions of PuGNaT (or) who finds that the canaliculi appear synchro- 
nously with the tigroid bodies in the embryonic nerve cell of the chick. 

Regarding the function of the tigroid substance, its relation to 
the ground substance and its embryogenesis point to the same conclu- 
sion: that it is a nucleoproteid whose kinetic energy is transformed 
into potential energy by the metabolism of the cell. The distribution 
of the substance through the cytoplasm may, as ScorrT points out, 
contribute to a more prompt and rapid metabolism than if the activ- 
ities were restricted to the nucleoproteids within the nucleus. This 
interpretation seems to be born out further by the facts of chroma- 
tolysis. 

IT. Chromatolysis.—In the strict sense ‘‘chromatolysis” applies 
only toa progressive diminution of the chromatic substance of the 
cell, but other phenomena which seem to be concomitant with this 
change will be, for convenience, included in this discussion. 


CoGHILL, Structure of the Nerve Cell. 195 


Van DurRME (or) has studied with the Nissi method the Pur- 
KINJE cells and the cells of the cerebral cortex of the rabbit under 
conditions of rest, fatigue and exhaustion. In the cerebellum of the 
normal specimen at rest he finds cells of two types: ‘‘chromophiles,” 
with 


” 


with relatively large amount of chromatin; and ‘‘chromophobes, 
relatively small amount of chromatin Both types vary greatly in size. 
In the chromophiles the protoplasm is uniformly blue with sharply 
colored chromatic bodies of various form and size. ‘The larger ones 
lie near the nucleus and a crescent of chromatic substance rests upon 
the side of the nucleus. ‘The nucleus is of oval form and the karyo- 
plasm stains uniformly blue. Nissi bodies occur also in the proximal 
portion of the axone. ‘The reticular structure of the cytoplasm cannot 
be seen. In the chromophobes, however, the cytoplasmic reticulum 
is apparent, while the cell body is on the average larger than the chro- 
mophiles. The peripheral zone is in many cases comparatively free 
from chromatic substance and the axone is entirely free from it. 

Whether these two types are actual or due to functional conditions 
VAN DuRME is not positive, for, as he points out, it is impossible to 
find all the cells of the nervous system in a condition of absolute rest. 
He finds, accordingly, that in rabbits which have been killed in the 
early morning there is great variation in the proportion of the two 
types of cells. 

For studying the condition of the cerebral and cerebellar cells 
during activity and fatigue vAN DURME stimulated these regions indi- 
rectly through the spinal cord with electricity. He examined the 
cerebrum and cerebellum after continuous stimulation of the cord for 
periods of five minutes, thirty minutes, two and one-half and seven 
hours. He concludes from his experiments that abundance of chro- 
matic substance and an oval nucleus are characteristic of the condition 
of rest. Activity is accompanied by a reduction of chromatic sub- 
stance in both the cell body and the nucleus, and an increase in vol- 
ume of the cell body and nucleus. Fatigue, in like manner, is char- 
acterized by the presence of cells extremely impoverished of chromatic 
substance and rich in vacuoles. The author’s explanation of this proc- 
ess is noticed in a following paragraph. 

Regarding functional changes in the nerve cell of the cerebral 
cortex, GEERAERD has experimented upon the guinea pig. To produce 
fatigue he employs natural methods in preference to artificial stimuli 
such as electricity, which, he believes, is highly objectionable. His 
argument against it, indeed, seems rational. He recognizes that under 
natural conditions there is a physiological barrier to over-stimulation 


196 Journal of Comparative Neurology and Psychology. 


of the central nervous system, but electrical stimulation may drive the 
central cells beyond the limits of natural activity into morbid processes. 
From a series of experiments he concludes that activity causes a reduc- 
tion in size and number of Nissi bodies in the cortical cells, and a 
diffusion of the chromatic substance into the cytoplasm. There is no 
noticeable change in the nucleolus. This condition is initial to fatigue 
and becomes more and more accentuated. Finally the cell, making a 
last effort, comes into a state of fatigue which is accompanied by in- 
crease in volume of the cell body and disappearance of nearly all the 
chromatic substance of both the cytoplasm and the nucleus. 

GEERAERD followed these studies with experiments upon recupera- 
tion. By similar methods he examined the cortex of animals which, 
after complete exhaustion, had been allowed to rest for periods vary- 
ing from five minutes to an hour. The first indication of repair was 
discovered after thirty minutes of rest, when the contour of the cell 
body is found to have regained its normal condition. After three- 
quarters of an hour a blue zone appears around the nucleolus, which 
is finely granular with conical projections reaching out to the nuclear 
membrane. But while the process of repair seems to appear first in 
the nucleus, the process in the cytoplasm advances from the periphery 
towards the nucleus. The first tigroid bodies appear next to the cell 
membrane and gradually invade the deeper regions of the cell. He 
finds further that while the large pyramidal cells are last to be affected 
by fatigue they are first to recover. 

GEERAERD Calls attention to the fact that in the earlier stages of 
activity the cytoplasm stains a deeper blue than normal but that this 
is due, not to an increase in the tigroid substance, but to the breaking 
up into small granules. He believes that this fact accounts for the 
erroneous position taken by certain authors that activity causes an in- 
crease in the tigroid substance. 

In comparing the retina of a bird which had been subjected to a 
bright light for a prolonged period with the retina of another which 
had been confined for a like period in a dark room, CARLSON (03) 
finds there is a ‘‘constant difference in the amount and appearance of the 
Wissl substance tn the cells of the ganglionic and bipolar cell layer. The 
ganglion cells of the stimulated retinae are poorer in Nissv’s substance, 
the Nissi’s granules present are less distinct than in the resting retinae, 
and the protoplasm of the cell bodies takes a diffuse blue stain.” This 
difference is not equally marked in all preparations nor in all regions 
of the same preparation. 

The lesions of the nerve cell accompanying anemia have been 


CoGuHILL, Structure of the Nerve Cell. 197 


studied by DE Buck and DE Moor (oo). Their experiments con- 
sisted in an examination of the lumbar cord after temporary and re- 
peated compressions of the abdominal aorta in the rabbit for from five 
minutes to one hour, and after permanent ligature. They find that 
following a ligature of one hour no lesion can be discovered if the ani- 
mal is killed immediately ; but if it survive for one hour and a half after 
the ligature is removed, lesions are apparent. One-half hour is sufficient 
period of ligature to cause a marked lesion. The chromatic elements 
break up and ultimately disappear, leaving the cytoplasmic reticulum 
in view. The nucleus is more resistive than the cytoplasm but finally 
undergoes homogeneous atrophy. Lesions of this character are more 
marked in prolonged, continuous ligature than in repeated, tempo- 
rary ligature. In twenty-four hours after a ligature of an hour many 
cells were found to be completely destroyed. To all these processes 
the spinal ganglion cells are more resistant than the cells of the cord. 
The authors conclude that these changes relating to the cytoplasm 
cannot be considered as characteristic of anemia, for similar modifica- 
tions arise from other causes, such as infectious diseases and toxins. 
The nuclear changes, however, they think, may be characteristic. 

VAN GEHUCHTEN’S earlier position regarding the lesion of the 
nerve cell resulting from section of the axone was that all such cases 
were followed by chromatolysis in the cells of origin. His more re- 
cent work (’98), however, leads him to the conclusion that section, or 
ligature, or a nerve will not always produce chromatolysis in the cells 
of origin. He observes such a case in the section of the sciatic nerve 
of the rabbit, in which case the cells of origin are found in the pykno- 
morphic condition but not in a state of chromatolysis. This condition 
he attributes to the traumatism. Later researches, in collaboration 
with VAN BIeERVLIET (00), convince VAN GEHUCHTEN that the lesion 
of the cell of origin following injury to the nerve varies both according 
to the intensity of the injury and according to the nerve involved. 
The cranial nerves appear to be much less resistant than the spinal 
nerves. The authors conclude also that the cell of origin which is 
affected by section of the axone may recuperate without regeneration 
of the axone. 

Regarding the comparative cellular lesion which follows mere sec- 
tion of the nerve and extraction of it, pe BEULE has experimented 
upon the rabbit by extracting and sectioning the hypoglossal nerve. 
The cells of origin were examined at from one to thirty-five days after 
the operation. He found that on the fourth day the cells were still 
increasing in size, but on the sixth day they had begun to grow smaller, 


198 Journal of Comparative Neurology and Psychology. 


though they had not yet returned to the normal size by the tenth day. 
By the fifteenth day more than half the cells had disappeared, while 
at the end of thirty-five days there was nota trace of a cell to be 
found in the position of the nucleus of origin of the affected nerve. 
The author believes that while, in case of section of a nerve, the cells 
of origin enter upon a phase of reaction, this is followed by recupera- 
tion; but in ‘‘arrachment” the phase of reaction is followed by pro- 
gressive atrophy of the cell. 

Following poisoning by arsenic SOUKHANOFF finds that changes 
of varying intensity appear quickly in the spinal cord and spinal gang- 
lia, and that in many preparations scarcely a normal cell would be 
found. ‘The lesions of the cell body were marked by diffuse colora- 
tion, by loss of regular contour of the chromatic bodies and by turges- 
cence of the cell. More accentuated lesions were characterized by 
clear spots around the periphery of the cell, owing to the loss of chro- 
matic substance. This was followed by a still more marked lesion ex- 
pressed by vacuolization of the cytoplasm. The degree of vacuoliza- 
tion varies with the duration of the poisoning. SOUKHANOFF finds no 
evidence of peripheral chromatolysis which has been described by 
other authors as characteristic of arsenic poisoning. In the nucleus 
there appears a diffuse coloration, obscurity of the nuclear membrane 
and shrinkage. 

In his paper upon the finer structure of the nerve cell, VAN 
GEHUCHTEN (’97) took the position that chromatolysis is essentially a 
dissolving of the tigroid substance. This results in turgescence of the 
cell which, beginning at the center, mechanically forces the nucleus 
towards the periphery of the cell, and causes expansion of the cell. A 
reconstruction of the chromatic bodies reverses the process. VAN 
DurMe (or) explains the turgescence of the cell during chromatolysis 
upon the hypothesis that the katabolic products in the cell, notably 
sarcolactic acid, increase the osmotic power of the cell and that this 
produces turgescence. 

Chromatolysis itself, vAN GEHUCHTEN (97) holds, need not be 
considered as a lesion in the cell. He suggests also, through vAN Brerv- 
LIET (99), that chromatolysis is, ina sense, a return of the cell to 
the embryonic condition: that is to say, a condition in which the 
chromatic substance exists in solution. VAN BreRVLIETr also concludes 
that chromatolysis is perfectly compatible with the normal activities of 
the cell. Dr BEULE (or) believes that all nerve cells which undergo 
a non-physiological excitation, which may be traumatic, physical or 


CoGHILL, Structure of the Nerve Cell. 199 


chemical, undergo chromatolysis. This is a useful reaction, a utiliza- 
tion of the material to support a special strain upon the cell. 

It seems probable, therefore, from the conclusions of these authors, 
and also from the numerous experiments especially upon poisoning, 
anemia, and high body temperature, that the nerves may perform 
their normal function while the cells of origin are undergoing rather 
marked chromatolysis, and that the cellular lesions resulting from any 
acute condition may be due in a large measure to general disturbances 
in the system rather than to the specific disease itself. 


LITERATURE CITED: 


Bochenek, Adam. 
702. Contribution a l’étude du Systéme Nerveux der Gastéropodes 
(Helix pomatia Lin.). Anatomie fine des cellules nerveuses. 
Le Névraxe, Vol. III, Fasc. 1, pp. 83-108. 
Carlson, A. J. 
703. Changes in the Nissl’s Substance of the Ganglion and the Bipolar 
Cells of the Retina of the Brandt Cormorant, Phalacrocorax 
pentcillatus, during Prolonged Normal Stimulation. Am. Jour. 
Anatomy, Vol. II, No. 3, pp. 341-348. 
Geeraerd, N. 
701. Les variations fonctionnelles des cellules nerveuses corticales chez 
le cobaye étudiées par la méthode de Nissl. Jmstituts Solvay, 
Travaux du Laboratoire du Phystologte, T. IV, Fasc. 2, pp. 209- 
248. 
Geier, T. , 
700. Contribution 4 l’étude de l’état moniliforme des dentrites corticales. 
Le Névraxe, Vol. Il, Fasc. 2, pp. 217-226. ; 
De Beule. 
701. Contribution a l’étude des lésions des cellules de l’hypoglosse aprés 
Varrachement du nerf. Le Mévraxe, Vol. III, Fasc. 2, pp. 143- 
156. 


200 Journal of Comparative Neurology and Psychology. 


De Buck and De Moor. 
799. Lesions des cellules nerveuses dans le tetanus experimental de 
cobye. Van Gehuchten’s Travaux, ’99, I. 


Ewing, James. 
798. Studies on Ganglion Cells. Archives of Neur. and Psycho-Path ology, 
Vol. I, No. 3, pp. 263-432. 
Hatai, Shinkishi. 
701. Observations on the Efferent Neurones in the Electric Lobes of 
Torpedo occidentalis. Jour. Cin. Soc. Nat. Hist., Vol. XX, No. 1. 


7Ola. The Finer Structure of the Spinal Ganglion Cells in the White 
Rat. Jour. Comp. Neurol., XI, 1, pp. 1-24. 


’7O1b. On the Presence of the Centrosome in Certain Nerve Cells of the 
White Rat. Jour. Comp. Neurol., XI, 1, pp. 25-39. 

7O1c. On the Mitosis in the Nerve Cells of the Cerebellar Cortex of 
Foetal Cats. Jour. Comp. Neurol., XI, 4, pp. 277-296. 

703. The Finer Structure of the Neurones in the Nervous System of the 
White Rat. Zhe Decennial Publications, Univ. of Chicago. 


703a. On the Nature of the Pericellular Network of Nerve Cells. 
Jour. Comp. Neurol,, XIII, 2, pp. 139-148. 
Holmgren, Emil. 
799. Zur Kenntnis der Spinalganglienzellen von Lophius Piscatordus 
Lin. MERKEL werd BONNET Anatomische Heft, 38, pp. 75-154. 


700. Noch weitere Mitteilungen itiber den Bau der Nervenzellen ver- 
schiedener Tiere. <Amatom. Anz., XVII, Nr. 6 u. 7, pp. 113-129. 
Kolster, Rud. 
700. Studien iiber das Centrale Nervensystem. II. Zur Kenntnis Ner- 
venzellen von Petromyzon fluviatilis. . 
Nelis, C. 
799. Un Nouveau détail de structure du protoplasme des cellules ner- 
veuses. (Etat spirémateux du protoplasme.) TZvavaux, 1899, 
Fasc: 1. 
700. L’apparition du centrosome pendant le cours de l’infection rabique. 
Le Nevraxe, Vol. I, Fasc. 1, pp. 13-30. 
Paton, Stewart. 
700. A Study of Neurofibrillae in the Ganglion Cells of the Cerebral 
Cortex. Jour. Ex. Med., Vol. V, 1, pp. 21-25. 
Pugnat, Amédée. 
701. Le biologie de la cellule nerveuse et la théorie des neurones. 
Bibliographie Anatomigue, T. IX, Fasc. 5 et 6, pp. 276-334. 
Scott, F. H. 
99, The Structure,,Micro-Chemistry and Development of Nerve Cells, 
with special Reference to the Nuclein Compounds. TZyvams. 
Canadian Institute, Vol. VI, pp. 405-438. 


CoGHILL, Structure of the Nerve Cell. 201 


Soukhanoff, Serge. 

798. Contribution a l’étude des modification des cellules nerveuses de 
Pécorce cerebrale dans l’anémie expérimentale. VAN GEHUCH- 
TEN’S Travaux, 1898, Fasc. 1, pp. 73-82. 

"98a. De Vinfluence de l’intoxication arsénicale sur les cellules ner- 
veuses. WAN GEHUGHTEN’S J7ravaux, I, Fasc. 1, pp. 97-116. 

’98b. Contribution a l’étude des modifications que subissent les pro- 
longements dendritiques des cellules nerveuses sous l’influence 
des narcotiques. VAN GEHUCHTEN’s Jravaux, 1898, Fasc. 2, pp. 
191-202. 

’98c. L’anatomie pathologique de la cellule nerveuse en rapport avec 
Patrophie variqueuse dendrites de Vécorce cérébrale. VAN 
GEHUCHTEN’S 7ravaux, 1898, Fasc. 2, pp. 203-224. 

702. Sur le réseau endocellulaire de Golgi dans les eléments nerveux de 
Pécorce cérébrale. Le. Nevraxe, Vol. IV, Fasc. 1, pp. 45-54. 


Soukhanoff, S. and Czarniecki, F. 
702. Sur l’état des prolongements protoplasmatiques des cellules ner- 
veuses de la moelle épiniére chez les vertébrés supérieurs. 
Le Névraxe, Vol. IV, Fasc. 1, pp. 77-90. 
Van Blervliet, J. 
700. Lasubstance chromophile pendant le cours du developpement de 
la cellule nerveuse (chromolyse physiologique et chromolyse ex- 
perimentale). Le Mevraxe, Vol. I, Fasc. 1, pp. 31-56. 
Van Durme, Paul. 
701. Etude des différents états functionnels de la cellule nerveuse corti- 
cale au moyen de la méthode de Nissl. Le Mévraxe, Vol. II, 
Fasc. 2, pp. 116-174. 
Van Gehuchten, A. 
797. L’anatomie fine de la cellule nerveuse. Travaux, 1897. 
’97a. Chromatolyse centrale et chromatolyse peripherique. Travaux, 
1897, Fasc. 2. 
798. A propos du phénoméne.de chromatolyse. Zvravaux, 1898, Fasc. 
I, pp- 25-34- 
799. Les phénomenes de réparation dans les cellules nerveux aprés la 
section des nerfs pérphériques. Zvavaux, 1899, Fasc. I. 
700. A propos de l’état moniliforme des neurones. Le Névraxe, Vol. I, 
Fasc. 2, pp. 137-150. 
Van Gehuchten, A. and de Buck, D. 
798. La Chromatolyse dans les cornes antérieures de la moelle aprés 


désarticulation de la jambe et ses rapports avec les localizations 
motrices. Zvravaux, 1898, Fasc. I. 


202 Journal of Comparative Neurology and Psychology. 


Van Gehuchten, A. and Nelis, Ch. | 
798. Quelques points concernant la structure des cellules des ganglions 
spinaux. TZvavaux, 1898, Fasc. 1, pp. 53-66. 
700. Les lésions histologiques de la rage chez les animaux et chez 
Phomme. Le Mévraxe, Vol. 1, Fasc. 1, pp. 77-114. 
Van Gehuchten, A. and van Biervliet, J. 
701. Le noyau I’ occulomoteur commun 16, 19 et 21 mois apres resection 
du nerf. Le Névraxe, Vol. II, Fasc. 2, pp. 207-216. 


PIGERAKY NOTICES. 


Van Gehuchten, A. La dégénérescence dite rétrograde ou dégénérescence 
Wallérienne indirecte. Le Névraxe, Vol. V, Fasc. 1, pp. 1-106, April, 


1903. 

An extensive review of the literature on Wallerian degeneration, 
followed by experimental studies on degeneration of peripheral and 
central neurones. The degeneration which occurs between the point 
of section and the perikaryon is cellulifugal and therefore typically 
Wallerian. For this phenomenon the author proposes the same ‘‘dé- 
-générescence wallériene indirecte.” It occurs in both the central and 
peripheral systems. In the former, certain fiber tracts undergo only 
direct degeneration while others undergo both direct and indirect de- 
generation. he author insists that it must be known exactly which 
tracts undergo indirect degeneration before the degeneration phenom- 
ena can be accepted as trustworthy evidence on certain physiological 
questions. Gab aC. 


Rossi, Gilberto. Sopra una via efferente encefalo-spinale nell ’ Emys euro- 
paea. Archivio di Fistologia, I, 3, 1904, pp. 332-336. 

The forebrain was removed from fifteen turtles and the forebrain 
and thalamus from fifteen. After about three months degenerated 
fibers can be demonstrated by VASSALEF’s modification of MARcHI’s 
method, these being confined to the brain if the forebrain only has 
been removed, but extending through the whole length of the spinal 
cord if the thalamus also is removed. This fasciculus thalamo-spinalis 
is diffusely scattered through the fasc. longitudinalis medialis. 

CJ. H. 


Langley, J. N. On the Effects of Joining the Cervical Sympathetic Nerve 
with the Chorda Tympani. Proc. Roy. Soc., LXXIII, No. 4890, Feb. 24, 


1904. 

In this very brief preliminary communication it is mentioned that 

the cervical sympathetic and the chorda tympani have opposite effects on 
the blood vessels of the submaxillary gland, the former causing contrac- 
tion of the vessels and the latter dilation. ‘Two experiments were made 


204 Journal of Comparative Neurology and Psychology. 


on cats to determine whether the cervical sympathetic, if allowed an op- 
portunity to become connected with the peripheral nerve cells in the 
course of the chorda tympani, will in part change their function from 
vaso-constrictor to vaso-dilator. The superior cervical ganglion was 
excised and the central end of the cervical nerve was joined to the 
peripheral end of the lingual, which contains the chorda tympani 
fibers. After allowing time for union and regeneration of the nerves, 
the cervical sympathetic was stimulated ; it caused prompt flushing of 
the submaxillary glands, and the effect was repeatedly obtained. 

The experiment is interpreted as showing (1) that vaso-constrictor 
nerve fibers are capable of making connection with peripheral vaso- 
dilator nerve cells and becoming yaso-dilator fibers, and (2) that 
whether contraction or inhibition of the unstriated muscle of the arter- 
ies occurs on nerve stimulation depends upon the mode of nerve end- 
ing of the post-ganglionic nerve fiber. The cervical sympathetic gave 
a less scanty and more prolonged secretion than normal, so that some 
of its nerve fibers had become connected with the peripheral secretory 
nerve cells of the chorda tympani. Co. 7H. 


Carlson, A. J. The Rate of the Nervous Impulse in the Spinal Cord and in 
the Vagus and the Hypolossal Nerves of the California Hagfish (Bdedlos- 
toma dombeyt). Amer. Jour. Physiol., Vol. 10, pp. 401-418, 1904. 


By the use of a graphic method the rate of nerve transmission 
was determined. Electrical stimulation served to initiate the impulse. 
In the spinal cord the impulse moves antero-posteriorly, with but 
slight individual variations, at the rate of 4.50 m. per second. The 
rate in the opposite direction is 2.50 m. per second, and it is more 
variable as well as slower than the rate for transmission in the antero- 
posterior direction. The vagus shows a rate of about 2.50 m., and the 
mandibular of 4.50 m. 

The fibers of the cord as well as those of the peripheral nerves in 
the hagfish are non-medullated. As the author remarks, this low form 
of fish has slower transmission in the spinal cord than have certain of 
the annelid worms in the ventral nerve cord. Furthermore, ‘‘the rate 
in the peripheral motor nerves is the lowest recorded for any verte- 
brates and even lower than that in the motor nerves of some of the 
molluscs.” 

This paper is of value because of its suggestions of possible ap- 
plications of the reaction-time method in the study of the physiology 
of the nervous system, as well as for the interesting facts which it pre- 
sents. Attention is called to evidence in the results of the experi- 
ments described ‘‘that the rapidity of the processes of conduction in 


Literary Notices. 205 


the nerve stands in direct relation to the rapidity of the process of con- 
traction in the muscle.” In the light of this possible relation between 
the rapidity of muscle contraction and that of nerve transmission the 
author is led to suggest that ‘‘a similar relation may exist between the 
processes of conduction in the secretory nerves and the processes of 
secretion in the glands. The rate of the nervous impulse would thus 
constitute a measure of the relative rapidity of the metabolic process 
in muscle and gland.” As evidence of this relationship the following 
table seems worthy of reproduction : 


Comparison between the contraction-time of the muscle and the rate of 
propagation of the impulse in the nerve. 


Muscle. Nerve. 
Species Contraction- Rate of the 
Muscle. time Nerve. impulse 
in seconds. in m. 
Frog bale ecaleg gastrocnemius 0.10 sciatic 27.00 
(medullated) 
Snakeman: |) lyoglossus 0.15 hypoglossus 14.00! 
(medullated) 

IEabpSter intial =) it flexor of chelae 0.50 first ambulacral 6.00? 
(Homarus) (non-medullated) 

SMM! 4G 6) 5 mantle (fin) 0.20 | mantle nerve 4.508 
(Zoligo) (non-medullated) 

Jeleyeaisioy © 5G — retractor of jaw 0.18 mandibular 4.50 
(non-medullated) 

Iplevermicly | ayo ae gill sac 0.45 vagus 2.50 
(non-medullated) 

Octopus . . . | mantle 0.50 pallial 2.003 
(non-medullated) 

Slug Rhee, pee foot 4.00 pedal Te25S 
(Limax) (non-medullated) 

mea Mare i. = | foot 10.00 pedal 0.75° 
(Pleurobranchaea) (non-medullated) 

Slucmeper tia. 1.0: foot 20.00 pedal 0.403 
(Ariolimax) (non-medullated) 


‘Carlson. Archiv fiir die gesammte Physiologie, ci, p. 23, 1904. 

? Fredericq and Vandevelde. Suziletins del’ Académie Royale du Belgique. 

3 Jenkins and Carlson. American Journal of Physiology, viii, p. 251, 1903. 
Jo Mls We 


Carlson, A. J. Beitrage zur Physiologie der Nervensystems der Schlangen. 
Phliiger’s Archiv, Bd. 101, pp. 23-51, 1904. 


This paper is a report of an experimental study of the physiology 
of the snake. Its results include (1) certain functional indications of 
the nature and courses of the nerve tracts in the cord, (2) the deter- 
mination of the rate of nerve impulse, it being in the cord 16 m. pet 


206 Journal of Comparative Neurology and Psychology. 


second (for the centrifugal), and in the hypoglossus nerve 10.5 m. per 
second, (3) observation that the brain is able to execute apparently 
conscious functions at least two and a half hours after separation from 
the spinal cord. Re Me ay. 


Kiesow, F. Contribution a l’étude dela vélocité de propagation du stimulus 
dans le nerf sensitif del’ homme. Archives Staliennes de Biologie, t. 40, 
Pp- 273-280, 1903. 

By carefully measuring the reaction-time of thoroughly trained 
subjects to tactual stimuli applied at different regions of the arm or leg 
Kresow has succeeded in showing to his satisfaction that the rate of 
transmission in the sensory nerves of man is practically the same as 
for the motor nerves, 30 to 33 m. per second. 

The work is very clean cut, and the results are so uniform that 
one cannot doubt the truth of the author’s conclusions. R. M. Y. 


Motora, Yujiro. A Study on the Conductivity of the Nervous System. Amer. 
Jour. Psy., Vol. 14, pp. 329-350, 1903. 

This is a brief discussion of theories of nerve conduction, and a de- 
scription of certain experiments upon which the author bases his so-called 
hydraulic theory. 

For the facts of nerve transmission, he writes: ‘‘I propose an 
hydraulic explanation. It supposes that nervous conduction is a trans- 
mission of a water wave in a protoplasmic tube and that the protoplas- 
mic tube not only helps the transmission by its own elasticity but is 
excitable at any point by means of a stimulus directly applied to it.” 

Morora experimented with water-filled tubes under various con- 
ditions to determine whether the phenomena characteristic of nerve 
conduction are exhibited also by them. The experiments deal with 
the following topics: Experiment 1—Rate of transmission of water 
wave in rubber tubes. It was found to be about too feet per second, 
or approximately the same as the nerve rate. Experiment 2—Evi- 
dence of an action current. Under certain conditions, we are told, 
the wave in a tube filled with slightly acidulated water is accompanied 
by what appears to be a thermo-electric current. The author writes 
concerning the action current in the nerve, ‘‘I believe that the action 
current is explicable as a thermo-electrie current produced between 
two points of the nerve where the electrodes touch it.” Experiment 3 
—Inhibition phenomena. This study of the interference of water 
waves leads the author to the conclusion, that the phenomena of atten- 
tion and inhibition ‘‘are very conveniently explained under the sup- 
position of a protoplasmic tube” (filled with fluid). 


Literary Notices. 207 


Although the paper yields no definite results so far as our knowl- 
edge of the nature of the nerve impulse is concerned, it contributes 
several curiously interesting facts, and a few analogies of problematic 
value. Rs Me... 


Lillie, Ralph S. The Relation of Ions to Ciliary Movement. Amer. Jour. 
Phystol., Vol. 10, pp. 419-443, 1904. 

Gowers, William R. Subjective Sensations of Sight and Sound, Abiotrophy, 
and other Lectures. Philadelphia, P. Blakiston’s Sons & Co., 1904. 

This is a collection of lectures mostly published before, but well 
worth having united in book-form, and carefully revised. 

The lecture on subjective visual sensations limits itself largely to 
the conditions in migraine, epilepsy; the one on subjective sensations 
of sound to the various forms of tinnitus. As such they form an in- 
teresting supplement to any chapter of hallucinations. A note (p. go- 
95) is a plea to change the accepted form of designating musical notes 
as C, C,G,C C' C’ C’ C* C’ C’, which gives the ‘‘neutral C” to the mid- 
dle C between the bass and treble staves, and has some mnemotechni- 
cal advantages concerning the number of vibrations (C;=33; C.=66; 
further C’ the first number with four figures, i.e. 1065, and C’=4224). 

The lecture on Abiotrophy; (diseases from defect of life) intro- 
duces a new term for deficiency of vitality of special tissues and parts 
of tissues: skin, baldness, muscles, nervous system, ete., and the sup- 
plementary interstitial overgrowth, either as deficent constitutional 
endowment, or as such defect brought on through toxic and toxinic 
factors with selective degenerations. Leture IV, on Myopathy and a 
Distal Form, deals with an important type of this group. 

The remaining lectures, on Metallic Poisoning, Syphilitic Dis- 
eases of the Nervous System, Inevitable Failure (a study of syphilitic 
arterial disease), Syringal Haemorrhage into the Spinal Cord, Myas- 
thenia and Ophthalmoplegia, and the use of drugs, are probably of 
more exclusively medical interest. 

It is to be regretted that the ‘‘Dynamics of Life” are not included 
in this collection. A. M. 


Bourneville. Recherches et Therapeutiques sur L’Epilepsie, L’Hysterie et 
L’'Idiotie. Vol. 23, Parts, Félix Alcan, 1903. 


This Annual Report of the Institution at Paris is followed as usual 
by the study of a number of cases: The Mongolian type (with histo- 
logical examination of two brains); the role of alcoholism in the pro- 
duction of idiocy, etc. This is the 23d Volume of a very creditable 
series. A. M. 


208 Journal of Comparative Neurology and Psychology. 


Raymond, F. and Janet, Pierre. Les Obsessions et la Psychasthénie, Vol. 
Il. Parts, Felix Alcan, 1903. 

This second volume of the very interesting work of Professor 
JANET brings the clinical material underlying and further illustrating 
the discussions of the first volume. It is a treasure of clinical informa- 
tion, full of masterly descriptions and analyses. The whole work is a 
remarkable continuation of the similar set of two volumes—‘‘Névroses 
et idées fixes.” A. M. 


Mills, Wesley. The Neurones and the Neurone Concept Considered from the 
Anatomical, Physiological, Pathological and Psychological Point of View. 
Montreal Medical Journal, Dec., 1903. 


An illustrated summary of the leading facts on which the neurone 
doctrine is based, occupying 22 pages. Caras 


Dogiel, A. S. Ueber die Nervenendapparate in der Haut des Menschen. 
Zeus. f- Ws L001, Bd.7 5 velit, pp. 4O-LiT gel kV ML Vey TOO3. 


Methylene blue method. An important histological paper. 
tebe 
Hiibschmann, Paul. Untersuchungen iiber die Medulla oblongata von Dasy- 
pus villosus. Zezts. f. w. Zool., Bd. 75, H. 2, pp. 258-280, 1903. 
is MBS Hh. 


Marenghi, Giovanni. Alcune particolarita di struttura e di innervazione della 
cute dell’ Ammocoetes branchialis. Zeéts. f. w. Zool., Bd. 75, H. 3, pp. 


221-429, 1903. 


The author finds by the GoLe1 method, in addition to the free 
nerve endings already known, sense cells in the epidermis which give 
rise to centripetal fibers. The reviewer has studied the same struc- 
tures, which are frequently impregnated in his preparations of Zam- 
petra, and has come to the conclusion that they are ordinary epider- 
mal cells, the precipitate upon which is continuous with that upon 
neighboring free nerve fibers. J. Boe 


The Journal of 


Comparative Neurology and Psychology 


Volume XIV 1904 Number 3 


AN ENUMERATION OF THE MEDULLATED NERVE 


i. 
Le 


UME 


LV. 


WAL, 


Vill. 


FIBERS IN| TRE. VENTRAS ROOTS OF THE 
SPINAL NERVES OF MAN. 


By CHARLES E. INGBERT. 


(From the Neurological Laboratory of the University of Chicago). 


With 38 Figures in the Text. 


Introduction. 
fTtstorical Statement. 


, Determination of the areas of the cross-sections of the ventral roots of 


the spinal nerves of man. 

I. KOLLIKER’s determination. 

2. STILLING’s determination. 

3. Author’s determination. 

4. Comparison of areas. 

5. Discussion of Figures 1 and 2. 

Determination of the number of nerve fibers in the ventral roots of the 

spinal nerves of man. 

I. STILLING’s estimate. 

2. Author’s enumeration. 

3. Comparison of STILLING’s estimate with the author’s enumeration. 

4. Determination of fine nerve fibers. 

The number of nerve fibers per square millimeter of the cross-section of 

the ventral roots of the spinal nerves of man. 

1. Determinations and comparisons. 

2. Discussion of Figure 3. 

Relation between thz Saebal and dorsal roots. 

I. Relation of areas of cross-sections. 

2. Relation of the sizes of the nerve-fibers. 

3. Relation of numbers of nerve fibers. 

4. Comparison of the ratio of the number of nerve fibers in the ventral 
and the dorsal roots of the frog, of the rat, and of man. 

5. Relation of small and large fibers. 

On the relative area of the cross-section of the roots forming the brachial 

and lumbo-sacral plexuses in the male and the female. 

Summary. 

Tables and figures. 

Bibliography. 


210 Journal of Comparative Neurology and Psychology. 
Ll. Introduction. 


Having completed ‘‘The Enumeration of the Medullated 
Nerve Fibers in Dorsal Roots of the Spinal Nerves of Man” 
(June, 1903), the author attempted to determine how many of 
these dorsal root fibers innervated the muscles and other deep 
tissues, and how many, the skin. For this purpose it was nec- 
essary first to determine the number of nerve fibers in the ven- 
tral roots. This was done. Using the number obtained in 
this enumeration, an estimate was made ‘‘On the Density of the 
Cutaneous Innervation in Man” (October, 1903). 

The purpose of this present paper is to give in detail the 
results obtained from the study of the number of fibers in the 
ventral roots. 


LTT. Htstorical Statement. 


Although estimations of the number of medullated nerve 
fibers in different spinal and cerebral nerves of man and de- 
terminations of the areas of their cross-sections have been made 
by D. RosenrHaL (1845), STILLING (1859), TERGAST (1872), 
Kuunt (1879), W. Krause (1876 and 1880), SALzER (1880), 
and VoISCHVILLO (1883), no complete count of the spinal nerves 
had been made prior to the author’s observations cited above 
(June, 1903). We are now able to add a similar enumeration 
of the medullated nerve fibers in the ventral roots of the spinal 
nerves of the same man. For a description of the material, the 
reader is referred to the paper first mentioned above. 


Ill. Determination of the Areas of the Cross-Sections of the 
Ventral Roots of the Spinal Nerves of Man. 


ZI. Kéolliker’s Determination.—Under conditions which 
have been described elsewhere in detail (INGBERT, June, 1903, 
p. 55), KOLLIKER (1850, p. 434) determined the area of all the 
cross-sections of all’ the ventral roots of the left spinal nerves 


1 KOLLIKER does not give the areas of the ventral roots of the sacral nerve 
IV and V. We estimate their combined area as about 0.2 mm? and have cor- 
rected his results by adding this amount. 


INGBERT, Ventral Roots of Spinal Nerves. 211 


of a man to be (when corrected by adding .2 mm.’) 34.51 mm’. 

2. Stilling’s Determination.—In the paper just referred to 
(INGBERT, June, 1903, p. 55) the details of the conditions un- 
der which STILLinG (1859, p. 346) made his measurements are 
also given. His determination for the total area of all the ven- 
tral roots of the left spinal nerves in a woman was 35.23 mm’. 

3. Author's Determination.—Using a method similar to 
that employed in the measuring of the areas of the dorsal roots 
(INGBERT, June, 1903, p. 56), it was found that the total area of 
the ventral roots of the left spinal nerves of the same individual 
amounted to 26.50 mm’, 

4. Comparison of Areas.—The total areas of the cross- 
sections of the ventral roots of the left spinal nerves obtained 
by the preceding investigations are as follows : 

K6GLLIKER (male) 34.51 mm? 
STILLING (female) 35-23 mm? 
Author’s Case (male) 26.50 mm? 

As the case here presented shows a smaller area than that 
found by either KOLLIKER or STILLING some comment is called 
for. It may be stated at the outset that the areas for the ven- 
tral roots in the author’s case were measured in 365 distinct 
fascicles; that, further, from the total area first determined in 
this way there was ultimately subtracted 1.54 mm’, represent- 
ing the excess of area caused by fascicles cut obliquely. In 
the case of KOLLIKER’S measurements it is readily seen why 
they should be large, since he included all the connective tissue 
within the roots in his determination. For example, when the 
roots in the author’s case were measured by the method of 
KOLLIKER they gave an area of 40.81 mm’. This not only 
shows why KOLLIKErR’S area is large but also indicates that in 
the particular spinal cord the roots of which he measured, the 
roots themselves were rather small. This conclusion is sup- 
ported by the fact that STILLING, in the case of a woman, found 
the area of the left ventral roots to be 35.23 mm*. Yet STILLING 
measured the roots in fascicles, by means of a planimeter, and 
thus included much less connective tissue than KOLLIKER. That 
STILLING’S result is larger than that of the author might be ex- 


212 Journal of Comparative Neurology and Psychology. 


plained in part by the fact that he divided the roots into a 
smaller number of fascicles (211 against 365) and that he did 
not correct for the fascicles cut obliquely. At the same time 
it seems necessary to assume that the ventral nerves in STILL- 
TABLES 
Areas in sq. mm. of Cross-Sections of the Ventral Roots of the Left 
Spinal Nerves of Man. 


Average length 
of Segments in 


No. of mm. according to KKGOLLIKER INGBERT STILLING 
Spinal DONALDSON and 

Nerve. DAVIS, 1903. Male Male Female 
I He? 1.00 25 3 

- Il OF 1.21 69 1.32 
5 Ill 12.4 SI BI ET 
2 IV 14.3 255 .84 1.02 
a) Vv 12.4 Te 74. 2.81 2.78 
a VI 13.9 1.79 2.69 2450 
VIl 12.9 2.82 1322 2.10 
VIII lige 1.79 eS 2 1.81 

I 12.8 1.00 .76 1.15 

Il 14.2 255 45 51 

Ill Wes 55 53 48 

IV 20.9 ‘ -64 -44 557. 

— V 21.9 .49 33 .66 
= VI 23.6 .92 .52 53 
o. . Vil 24.2 .g2 .46 58 
es. Wait 25.1 .92 .49 202 
IX 23 3 88 .49 -74 

xX 22.5 77 58 .68 

XI 21.4 1.00 57 -49 

XII 19.6 .Q2 60 56 

I 18.3 2 66 63 

m II 12:9 1.04 81 70 
= Ill 11.8 2.43 1.87 TASS 
e IV 10.6 1.96 Ley 2.69 
4 V 8.2 1.96 2M, 2.06 
= I Ta 2.82 1.98 2.68 
mB II 8.4 1.59 61 2.75 
a “* Up 25 any Tals 
4 f 1 10 33 

Vv 4.8 it oa 09 -10 

8 I 2.5 04 02 02 

Y 
Totals 31 441.9 mm. 34.51 mim?. 26.50 mm? 35.23 mm? 


1 Interpolated. 


InGBERT, Ventral Roots of Spinal Nerves. 213 


ING’S case were relatively large in their cross-sections. 

Corresponding with Table I* in the earlier paper (INGBERT, 
June, 1903, p. 58), there is here given a table showing the 
areas of the ventral roots as determined by the investigators 
above named..\(Table I, p: 212.) 


100 Fié.I. Absolute areas of ventral roots 
: A. Kolliker. 
80 yrs Inébert. 
60 C= iil ling. 
40 
ZAG) ROS IES SS IN reer eS 
100 Fig.I. Areas of ventral roots 
iS Area of largest root — 100% 
80 x A. Kolliker. 
Ba NU, goo Ree 
40 
ZOP eee eee 
100 ° id. III. Se eS Areas of ventral roots 
UNG as in Fig I(Ingbert) 
80 Pak B.— — —Number of fibers. 


Greatest number in ony root = 100% 


itm VYUWWInm WwW Vv WW vm i X WM 1 wmvInMM 
CERVICAL THORACIC LUMBAR SACRAL 


Fig. 7. Curves showing the area in sq. mm. of the cross-section of the ven- 
tral roots of the left spinal nerves. Each sq. mm. is represented by twenty 
divisions on the axis of the ordinates. 

Fig. 2. Curves based on the measurements in Table I, the values in each 
curve being entered in percentages of the greatest area which is taken as 100 per 
cent. One mm. on the axis of ordinates equals I per cent. 

Fig. 3. Curves showing in per cent the area of the cross-sections of the 
ventral roots of the left spinal nerves and the percentage distribution of the num- 
ber of medullated nerve fibers in each ventral root. 

For publication these figures, originally drawn on the base line of 441.9 mm., 
have been reduced so as to make base line 96 mm., which is a reduction to about 
0.22 of the original linear dimensions. 


In order to better compare the areas of the cross-sections 


entered in Table I, they are exhibited in the form of curves 
(Figs. 1 and 2), which are constructed in the same way as were 


214 Journal of Comparative Neurology and Psychology. 


the curves for the areas of the dorsal roots (INGBERT, June, 
1903.) p: (OL). 

5. Discussion of Figs. 1 and 2.—The three curves in Fig. 
1 are based on the absolute areas of the cross-sections of the 
ventral roots of the left spinal nerves, and show a general sim- 
ilarity. Thus, they all show C. III smaller than C. Il. A 
marked elevation for the roots innervating the muscles of the 
limbs and a depression for the thoracic roots is evident: Yet 
individual roots may vary considerably in area. In KOLLIKER’s 
curve the largest cervical root is C. VII, a root considerably 
diminished in the author’s curve and in STILLine’s. Again, C. V 
is large in STILtING’s and author’s curves, but not so in KOuti- 
KER'S.) Lneall, there seems’ to bea tendency to a depression at 
C. VI. The interesting fact in connection with these points is 
that C. V-VI correspond roughly to the roots innervating the 
muscles of the shoulder and upper arm, and C. VII to the in- 
trinsic muscles of the hand. In the lumbar region attention is 
called to the position of the curve between L. III and S. II, 
which exhibits two elevations bounding an intervening depres- 
sion represented by one or two roots. . In the curve from the 
author’s data the first elevation is at L. III, and the second at 
LV, with L. 1V depressed. ~ Here e- Ill represents theszoen 
partly innervating the main flexors of the leg and foot. It is also 
evident that the largest root in the cervical or lumbar regions 
may be shifted one or more segments cephalad or caudad from 
an intermediate position. The three curves in Fig. 2 are based 
on the areas represented as percentages of the largest root in 
each series. The discussion of Fig. 1 applies to this figure 
also. 


LIV. Determination of the Number of Nerve Fibers in the Ven- 
tral Roots of the Left Spinal Nerves of Man. 


As the study of the number of nerve fibers in the ventral 
roots was carried on in a manner similar to that used for the 
dorsal roots, the reader is referred to the preceding paper (ING- 
BERT, June, 1903, pp. 62-67) for a general statement of the 
technique and sources of error. Certain specific statements, 


INGBERT, Ventral Roots of Spinal Nerves. 215 


however, require to be made concerning the ventral roots, and 
these will be given as briefly as possible. 

r. Stilling's Estimate.—STiLuinG (1859, p. 600) counted 
in a series of squares 1-156 of a squre line in area, the number 
of cross-sectioned nerve fibers seen within them, and from this 
estimated the the number for an entire square line.’ This he 
found to be from 120 to 156, average 138, for the ventral roots. 
He does not state what roots he examined, nor how many 
counts were made. If 1-156 of a square line of the section 
contains 138 fibers, one square line will contain 156 < 138, or 
21,528 fibers, which is equal to 4231 fibers for each square 
millimeter. Since in his case there were 35.23 mm’. in the 
area of the ventral roots of the 31 left spinal nerves, there will be 
35.23 X 4231, or 149,058 nerve fibers in all of them. And 
since the right ventral roots were found to have an area of 37.17 
mm’, they will have 37.13 X 4,231 or 157,266 nerve fibers, 
and the ventral roots of both sides, 306, 324. 

STILLING’s estimate for the number of nerve fibers in the 
ventral roots of both sides is, however, not 306,324 but 303,- 
265. This difference is due to the fact that he based his final 
estimate on the area of ventral roots as obtained by his method 
of weighing, which gave 71.697 mm? for both sides, and the 
calculations I have made are based on his areas as obtained by 
the planimeter, which give 72.40 mm’. The latter areas were 
selected because they may be more properly compared with my 
own, which were also obtained by planimetric measurements. 

2. Author's Enumeration.—By the methods and under the 
conditions referred to in the earlier paper there were found in 
all ventral roots of the spinal nerves of the left side 203,700 
nerve fibers. The details of this enumeration are given in the 
accompanying Table II. 

In Tables VIII-XXXVIII are to be found the numbers of 
nerve fibers for each fascicle, and in Table II are found the 
totals for each root. 


1 STILLING used the Paris line, the value of which is 2.2558 mm. 


216 ournal O Com arative Neurolog and Ps cholog = 
ey, Wy LY, 
PA'BiES TL, 


Showing the Number of Nerve-Fibers Counted in the Ventral Roots 


of the Left Spinal Nerves of Man. 
No. of nerve 


No. of Area of No. of nerve fibers, in 
spinal roots in fibers in thousands, 
NErve. “Sq. mm. each root. per Sq. mm. 
I 2 3,406 13.4 
= II .69 4,259 6.2 
§ Ill 31 3,850 12.3 
‘3 IV 84 5,955 qt 
2 V 2.81 13,548 4.8 
VI 2.69 11,794 4.4 
VII 1.22 8,913 733 
Vill 1.52 8,435 5.5 
I .76 7,276 9.5 
II 45 55,025 12.6 
ie eee 53 7,235 13.5 
a} IV 44 7,625 17.2 
S V 53 6,736 12.7 
= VI 52 6,298 12.2 
Be ov TL .46 5,055 1272 
Vitti .49 6,074 1255 
IX -49 5,789 11.9 
x 58 7 step 12:3 
XI 57 7,761 13.7 
XII .60 7,596 12.9 
i I 66 7,944 Li. 
3 lil 81 6,014 7.4 
‘g III 1.87 11,138 5-9 
5 IV 52 7,349 5.8 
A V PN | 10, 366 4.8 
I 1.98 8,598 4.3 
ra II 61 4,406 72 
3 III 17 2,340 13.5 
Sf IV s1O 2,323 23.9 
V .09 1,702 19.0 
8 I 02 519 30.0 
7 
31 26.50 mm? 203,700 Hel 


In Table II attention is called to the following points : 
1. The total number of fibers in the ventral roots of the 
left side is 203,700. 
2. The small root C. III has 3,850 fibers. 
3. The large roots C. V-VI—innervating in part the mus- 
cles of the shoulder and flexors of the upper arm. 


InGBERT, Ventral Roots of Spinal Nerves. 27, 


4. The uniformity of the number of fibers in the thoracic 
roots. 

5. The number of fibers in the largest cervical root, which 
is twice the average number in the thoracic roots. 

6. The large roots in the lumbo-sacral region—L. Iil— 
innervating in part the adductors and flexors of the 
thigh ; and L. V—innervating in part the flexors of leg 
and foot. 

7. The depression at L.IV—corresponding to the demar- 
cation between the lumbar and the sacral plexuses. 

8. In this case—a male—the four largest cervical roots 
(C.V, VI, VII, VIII) contain more fibers than the 
four largest successive lumbo-sacral roots (L. III, IV, 
V andS. I.) 

g. That the number of nerve-fibers per sq. mm. of the 
cross-section of the ventral roots shows that the fibers 
in the roots passing to the brachial and the lumbo- 
sacral plexuses have an average diameter which is 
large, and that the fibers in the thoracic roots have an 
average diameter which is small. 

3. Comparison of Stilling’s Estimate with the Author's Enu- 
meration.—The determinations of the number of medullated 
nerve fibers in the ventral roots of the left spinal nerves of man 
in the case which we have just discussed, give the following 
result : 
Author’s Enumeration 203,700 nerve fibers. 

This result shows that STILLING’s estimate, 149,057, Is 
73.17% of the author’s enumeration, or, in other words, the 
author’s result is 26.83% greater than STILLING’s. On search- 
ing for the cause of this difference, we find two significant state- 
ments made by STILLING. First, he says that he did not ob- 
serve in either the ventral or the dorsal spinal roots (at least 
not in the material fixed in chromic acid), nerve fibers of such 
diameters as KOLLIKER reports (2.7 to 4.5 4); and secondly, that 
the diameters of the medullated nerve fibers in the ventral roots 
range from 7.5 to 22.5 # (STILLING, 1859, p. 678). It is thus 
evident that one source of difference between STILLING’s esti- 


218 Journal of Comparative Neurology and Psychology. 


mate and my own is the fact that STILLING’s estimate does not 
include the nerve fibers, the diameter of which is less than 
7-5 2: 

As we have already noticed, my results are 26.83 % greater 
than SriLiine’s. The question, therefore, is to what extent 
this difference can be accounted for by the nerve fibers in the 
ventral roots, the diameter of which is less than 7.5 yu. 

KOLLIKER (1850) makes the statement that in the ventral 
roots three-fourths of the fibers range from 13.5 to 24.9 p, and the 
small fibers are for the most part from 5.6 4 to 6.84. 

To determine the relation between the fine and the large 
fibers in the ventral roots of man, SIEMERLING (1886-'87) count- 
ed in each root, mostly on the left side, the nerve fibers seen in 
g sq. mm. of the ocular micrometer (oculus 3, system 7, Hart- 
NACK). He thus counted in the ventral rocts 559 fibers, the 
diameter of which was less than 7.5 w and 552, the diameter of 
which was more than 7.5 y. 

In other words, the fine and large fibers were found by 
him to be about equal in number. 

Such a small count as this must be considered, however, 
very inadequate in the determination of a relation, subject to 
such considerable local variations. 

4. Determination of the Fine Fibers in the Ventral Roots.— 
To determine this point, the author has made counts from a 
few fascicles of each of the ventral roots of the spinal nerves. 
In making these counts, such fascicles were selected as had the 
same number of nerve fibers per square mm. of the cross-section 
as the average found for the entire root. The fibers, the diam- 
eter of which was 7.5 4 or more were considered large fibers, 
and those the diameter of which was less than 7.5 “ were con- 
sidered small fibers. After finding what per cent of the select- 
ed fascicles was represented by small fibers, the number of 
small fibers in the entire root was calculated in accordance with 
this relation. 

The results are presented in Table III. 

According to the calculations in this Table there are in the 
ventral roots 80,747 nerve fibers the diameter of which is less 


INGBERT, Ventral Roots of Spinal Nerves. 


219 


than 7.5 4. Since there are in all 203,700 nerve fibers in the 
ventral roots of the left spinal nerves and of these 80,747 are 
small fibers, it appears that the small fibers constitute 39.64% 


TABICE una: 


Showing counts made in the different ventral roots in order to de- 
termine the relation between the number of large fibers (7.5 # or more 
in diameter), and the number of small fibers (less than 7.5 w in 


diameter). 
No. of Fasc. 
I<OO Can |e OEey LISS. 
7s 8-28. 
I 15, 17 
II 235 12 
5 OU Oval 
ey 9 
iy AW 19, 26 
oO VI 4, 16, 19 
Vil 19 
VIII 4 
i 7 
II 2 
Ill All 
IV All 
2 Wi 105, 12 
eae |) 3,5 
g VII All 
& VII 3 
IX 4 
xX II 
XI Py 
XII Dp (ik 
I I 
a It a 8 
coe Ld 9, 10, 16 
Be Vi eit, Fite? 
a oo vist 
I aces 
i HL 8 
£ It Iz 
3s IV All 
eae All 
8 I I 
Y 


No. of 


| fibers 


310 
1522 
736 
412 
731 
1057 
gi2 
407 
857 
803 
7235 
7025 
1565 
1785 
5655 
2182 


° 


Mu 


WAnAO WMO COU) NN Go Go Go Ga G2 
OOD UaUnNrwenNN OsNTOMN 


| 
— 


oO 


Small 
fibers 


in % 


Calculated 
small fibers in 
entire root. 


715 
468 


486 


Total 80747 


Note—The numbers marked by a star * do not represent the fibers counted, 
but were obtained by subtracting the small fibers which were counted in these 


fascicles from the entire number of fibers in the fascicle. 


220 Journal of Comparative Neurology and Psychology. 


of the entire number. We have already stated that the author’s 
enumeration of the nerve fibers in the ventral roots of the left 
spinal nerve is 26.83% greater than the estimate made by 
StTitytinc. And we have also shown that STILLING failed to in- 
include in his estimate the nerve fibers the diameter of which 
is less than 7.5 w. It therefore seems probable that these small 
fibers would account for the difference (26.83%) between the 
author’s enumeration and STILLING’s estimate. Were this ex- 
actly the case, the small fibers should amount to about 26.83 % 
of the entire number in the ventral roots. But we have found 
that the calculation made above places the small fibers at 39.64%. 
It therefore becomes necessary to search for the cause of this 
discrepancy. The above reasoning, (i. e., that the percentage 
of small fibers should exactly account for the difference) is valid 
only on the assumption that the number of large fibers was 
similar in the two cases compared. We must therefore deter- 
mine whether or not the ventral roots used by STILLING proba- 
bly contained the same number of large fibers as the ventral 
roots used by the author. To simplify this matter we shall 
again compare the areas of the ventral and dorsal roots of the 
left spinal nerves, as determined by STILLinG and by the author. 


Total area of ventral Total area of dorsal Ratio 
roots roots 
STILLING 
(female) 25-23. a0m-2 57-95 mm.” 1:1.64 
Author 
(male) 2055 Ommes 54.03) = <6 1:2.07 


We have already suggested that the ventral roots in STILL- 
ING’S case were larger than we should expect and the table 
above illustrates this point. Taking the areas of the dorsal 
roots as standards and assuming our own area for the ventral 
roots to be correct, then the following proportion (54.93: 
57.05.: : 20.50 : x) gives 27.906 mm.7 as the area to: beanticr 
pated for the ventral roots in STILLING’s case. From this it is 
evident that if we could assume the same ratio to exist between 
the ventral and dorsal roots in males and females, the area of 
the ventral roots in Srittine’s case should be 27.96 mm.” in- 
stead of 35.23 mm.*. We have here, probably, the reason for 
the discrepancy between the number of fibers by which the 


INGBERT, Ventral Roots of Spinal Nerves. 22K 


of 


author’s enumeration differs from STILLING’s estimate (26.83 %) 
and the number of small fibers actually found (39.64%). 

To test this, another calculation becomes necessary. The 
ventral roots of the left spinal nerves, according to STILLING, 
have an area of 35.23 mm.* and contain 149,058 nerve fibers. 
If these ventral roots had an area of only 27.96 mm.’, their 
area would be in the same ratio to the area of the dorsal roots 
as are the areas in the author’s case, and would contain (accord- 
ing to STILLING’s method of estimation) only 118,299 nerve 
fibers. This is 58.07% of the author’s estimation ; or, in other 
words, it is 41.93% less. But from our calculation above the 
small fibers in the author’s case constitute 39.64%, hence we 
conclude that the difference between STILLING's estimate of the 
number of nerve fibers in the ventral roots and the author’s 
enumeration is accounted for within 2% by the small fibers 
which STILLING omitted. It does not seem probable that this 
increased area in the ventral roots in STILLING’s case was due to 
large masses of connective tissue for he was on his guard against 
this source of error; but a diffused increase might have been 
present. 

Finally, the difference may be due to individual variation, 
or may be due to difference in sex. This later possibility will 
be considered further on. 


V. The Number of Nerve Fibers per Square Millimeter in the 
Cross-Sections of the Ventral Roots of the Left Spinal 
Nerves of Man. 


. 

1. Determinations and Comparisons.—According to STILL- 
ING, the ventral roots of the left spinal nerves have an area in 
cross-section of 35.23 mm.* and contain 149,058 medullated 
nerve fibers, or, in other words, they contain 4,231 nerve fibers 
per sq. mm. of the cross-section. 

According to the author’s results, the ventral roots of the 
left spinal nerves have an area in cross-section of 26.50 mm.’, 
and contain 203,700 medullated nerve fibers, or, 7,687 nerve 
fibers per sq. mm. of their cross-section. 

The difference between the number of nerve fibers sq. mm. 


222 = Journal of Comparative Neurology and Psychology. 


obtained by STILLING and that obtained by the author, has the 
same explanation as the difference in the total number of fibers 
—STILLING did not include the fibers, the diameter of which 
was less than 7.5 4, and at the same time, for some reason not 
yet apparent, his areas are large. 

In Tables VITI-XXXVIII and Figures 8-38, are given the 
number of fibers per sq. mm. in each fascicle expressed in 
thousands. A study of these shows that great variations may 
occur in the neighboring roots, and even in fascicles of the same 
root. The small number per sq. mm. in the roots forming the 
brachial and lumbo-sacral plexuses is due to the large fibers in 
these roots, there being relatively few small fibers in them. 
The large number per sq. mm. in the thoracic region is due to 
the very great number of small fibers, many of which, no doubt, 
pass to the white rami communicantes. The large number per 
sq. mm. for the root C. III, correlated with the small size of 
this root, indicates a small diameter for the fibers in this root. 

In order to show better the relation between the number 
of fibers in the roots and the area of the cross-sections of roots, 
I have constructed, on the basis of the data in Table IV, Fig. 
3 (see p. 213). These curves has been drawn in the same 
manner as the corresponding chart in the author’s earlier paper 
(INGBERT, June, 1903, p. 72). 

2. Discussion of Figure 3.—In this figure the relative 
areas of the ventral roots are contrasted with the relative abund- 
ance of the fibers in them. 

For each series the largest value is taken as 100%, and the 
other values are calculated on this as a standard. As the root 
with the largest area (C. V.) is also the root with the largest 
number of fibers, the two maxima coincide. It is sufficient in 
this place to call attention to the fact that in the intumescentiae 
the number of fibers and the area of the roots change in the 
same manner, so that the two curves are parallel, and that in 
the thoracic region the number of fibers remains relatively 
large while the area of the roots is much diminished, thus show- 
ing that in these roots the diameter of the fibers is on the average 

much decreased. 


INGBERT, Ventral Roots of Spinal Nerves. 223 


TABLE DV. 


Giving the percentage values of the cross-section of the ventral 
roots of the spinal nerves as compared with the percentage distribution 
of the number of medullated nerve fibers in each ventral root. The 
greatest value in each series is taken as 100%. 


No. of spinal Percentage Value. (INGBERT) Male. 
nerves Areas No. of Fibers 
I 8.9 25 al 
II 24.5 Bins 
Ht II.O 28.4 
IV 29.9 43-9 
a ENG 100.0 100.0 
SB Wal 95-7 87.0 
oP wu 43-4 65.8 
VIII 54.1 62.2 
I 27.0 53-6 
II 16.0 41.5 
III 18.9 53-4 
IV 15.7 56.3 
ot V. 18.9 48.2 
SS Walt 18.5 46.5 
a WADI 16.4 41.7 
LUT 17.4 44.8 
IX 17.4 42.7 
x 20.6 52.9 
XI 20.3 eS 
XII 21.3 56.0 
gl 23"5 58.7 
cS, ol 28.9 44.4 
@ Ill 66.5 82.2 
Bp 45.2 54-2 
V Tinee 76.5 
I 70.5 63.4 
we Jul Zier 32.5 
g Ill 6.0 0723 
Jey MIN Bak 16.4 
Vv Bee Wa 7/ 
I 0.7 3.8 


Coc. 


VI. The Relation Between the Ventral and Dorsal Roots. 


Z. Relation of Areas of Cross-sections.—For comparison 
we have arranged the areas of the ventral and dorsal roots in 
tabular form, adding the measurements by K6LLIKER (1850, p. 
433) on the spinal nerves of a female. 


224 Journal of Comparative Neurology and Psychology. 
; Total area of Total area of eee 
Observer : eae ; ai aa pews Ratio 
ventral roots dorsal roots 
KOGLLIKER (male) 34.51 mm.’ 79.74 mm.? 132591 
ee (female) 33-48 mm.? 6840 mm.? 1:2.04 
STILLING , (female) 25.23 mm. 57-95 mm.? 1:1.64 
INGBERT (male) 26.50 mm.? 54-93 mm.? 1:22:07; 


The lowest ratio appears in STILLING’s case, and the rea- 
son for this diminished value is the large area of the ventral 
roots in his case. The ratio for the author’s case (male), 
1:2.07, is almost the same as. that for KOrLIKEr’s (female) 
1:2.04. 

In order better to compare the relation between the areas 
of the two series of roots in the case under investigation, Figs. 4 
and 6 have been constructed on the basis of data given in Ta- 
bles V (ps. 226). 


Area of largest toot =100% 


Fi¢.IV.Comparison of areas of spinal roots (Inébert) 
100 eon Agee Ventral roots 
80 ee H Area of largest root =100% 
: i é 4 B-—— —Doreal roots Dd 
60 E eel 


ees ae =~ s ae 
nes a ee 


Fig. V.Comparison of numbers of fibers in spinal roots(Ingbert) 


100 By A> — — Number in ventral roots 
80 Ve \ largest number ~!00% i a 

; he Ny B= —— Number in dorsal roots ix \\ 
60 / = largest number ~100% \ 


IMM WY Vivivt tm Ww YY vs V0 Wm KX X M XT W MWVI TWH 
CERVICAL THORACIC LUMBAR SACRAL - 


Fig. g. Curves comparing the area of the ventral and dorsal roots of the 
left spinal nerves, the values in each curve being entered in percentages of the 
greatest area, which is taken as 100%. One unit on the axis of the ordinates 
equals 19%. 

fig. 5. Curves for comparison of the numbers of medullated nerve fibers 
in the ventral and the dorsal roots of the left spinal nerves. These curves were 


constructed as those in Fig. 4. 


INGBERT, Ventral Roots of Spinal Nerves. 225 
5 


In Fig. 4 is found a comparison between the relative 
areas of the ventral and dorsal roots of each nerve. In general 
the two curves are similar—showing that there is the same pro- 
portional difference between the large and small ventral roots 
that occurs between the large and small dorsal roots. The 
largest ventral roots are located further cephalad in the cord 
than the largest dorsal roots and this is true for both the cervi- 
cal and lumbar enlargements. 

Moreover, as compared with the curve for the dorsal roots, 
that for the ventral is distinctly irregular—especially in the in- 
tumescentiae. 


Bes ue ee areas | of ventral and dorsal rools(Ingbert) 
AvesVentral roots. 
oe —-—-—Dorsal roots. 


we a oe ~——$--—— 


Fig ULM Nuniber of fibers in ventral and dorsal rools(Ingbert) 
A> —-—Ventral roots. 
B--—- —Dorsal roots. 


=== 


ITM VY VWI im wv v WoW WW wm X M XE TL 0 MVVIOH 
CERVICAL THORACIC LUMBAR SACRAL 


Fig. 6, Curves showing the absolute areas of the cross-sections of the ven- 
tral and the dorsal roots of the left spinal nerves. Each sq. mm. is represented 
by 20 divisions on the axis of ordinates. 

Fig. 7. Curves showing the number of medullated nerve fibers in the ven- 
tral and the dorsal roots of the left spinal nerves. Each thousand nerve fibers 
is represented by two units on the axis of ordinates. 


The accompanying figure 6 represents the absolute areas of 
the cross-section of the ventral and dorsal roots. Despite the 
considerable absolute difference, it has just been shown (Fig. 4) 
that the relative differences are only slight. 


226 Journal of Comparative Neurology and Psychology. 


TABLE V:; 


showing in square millimeters the relation between the absolute areas 
of the cross-sections of the ventral and dorsal yoots. 


No. of spinal Ventral Roots Dorsal Roots Ratio 
nerve 
I a2 13 T2065 
I] 65 228 ery 
III Sahl 2.14 1:6.9 
IV 84 2.01 e233 
V 2.81 2.82 [10 
VI (2.69 4.65 Tse 
Vil 1322 4.72 1:3.8 
VIII 1.52 Spiel 133.3 
I .76 Life) Tee 
ia 45 97 1221 
EET 53 .98 1:1.9 
IV “44 -gO 17250 
bY 53 .68 ve Be 
vel 52 59 ee ee 
VE 46 98 1:2.1 
VIII “49 71 Teil 
IX -49 67 Tte4! 
xX 58 86 1:1.5 
XI 57, gI 30 
JUL .60 1.25 132.1 
I .66 1.75 E207, 
Il SI B22 1:2.8 
III 1.87 2.52 131.3 
IV 12 2.93 Tis28 
V Dey, 3.20 1:2:4 
I 1.98 3-44 iets) 
II OI 1.92 Tegial 
III 17, 1.18 1:6.9 
IV Si) 40 1:4.0 
Vv .O9 13 1:1.4 
I 02 03 Tes 
Totals 31 26.50 mm.’ 54-93 mm.? 1:2.07 


2. Relation of the Size of the Nerve Fibers.—Ilf the reader 
will imagine the curve for the area of the dorsal roots (Fig. 6) 
overlaid by the curve showing the absolute number of fibers in 
the dorsal roots (Fig. 7) it will be readily seen that the two 
curves coincide remarkably; the greatest difference occurring 
in the lumbo-sacral nerves. In an earlier paper (INGBERT, 
June, 1903, Chart III), these two curves are drawn superposed. 


The fact that the two nerves run nearly parallel shows that in 


INGBERT, Ventral Roots of Spinal Nerves. 22 
7 


general when the area of a dorsal root changes, it is due toa 
change in the number of nerve fibers composing it, while the 
average diameter of the fibers remains about the same from 
root to root. This is also expressed by the fact that the num- 
ber of thousands of fibers per square millimeter (see INGBERT, 
June, 1903. p. 67) undergoes but slight variation. 

If the corresponding curves for the ventral roots are now 
examined, some interesting differences between the ventral and 
dorsal roots at once appear. In the ventral roots (see curves 
in Figs. 6 and 7) the enlargement of the areas of the cross-sec- 
tions is not due so much to an increase in the number of fibers 
in the roots as to the increased diameter of the nerve fibers ; 
hence at the intumescentiae the curve for the areas rises far 
above the curve for the number of the fibers. In the same 
way this fact is expressed by the number of thousands of fibers 
per square millimeter of the cross-section of the different ventral 
roots of the cord, which ranges from 5 in the intumescentiae to 
about 12 in the thoracic region (see Table II). 

3. Relation of the Number of Nerve Fibers in the Ventral 
and Dorsal Roots. The relation between the number of nerve 
fibers in the ventral and dorsal roots, as estimated by STILLING 
and enumerated by the author, is as follows: 


Ventral roots Dorsal roots Ratio 
STILLING (female) 149,058 262,919 1:1.8 
Author (male) 203,700 653,627 Tege2 


A large part of this difference in ratio is no doubt due to 
the fact that STILLING failed to include about 39.64% of the 
nerve fibers in the ventral roots, and about 60% of those in the 
dorsal roots, or in other words STILLING’s numbers as given 
above are only about 61% of the ventral and 40% of the dorsal 
fibers, which were probably present. Another factor is the 
relatively large size of the ventral roots in STILLING’s case, as 
already mentioned. 

In order better to compare the number of fibers in the dif- 
ferent ventral and dorsal roots, the curves of Fig. 5 have been 
constructed from data recorded in Table VI. The ordinates 
have been obtained by taking the largest number of each series 


228 Journal of Comparative Neurology and Psychology 


as 100% and expressing the other areas as percentages of 
this standard. Each percent in the values thus obtained, is rep- 
resented by 1 mm. on the axis of the ordinates. 

In the curves in Fig 5 one sees the relative number of 
fibers in each of the dorsal and ventral roots, and it is at once 
evident that this number undergoes a much greater variation in 
the dorsal than in the ventral roots. 


TCAD Vial 


Showing the Number of Nerve Fibers in the Ventral and Dorsal 
Roots, and Relation Between ‘Them. 


No. of No. of nerve No. of-nerve 
spinal fibers in ven- fibers in dor- Ratio 
segments tral roots sal roots 
I 3,406 1,808 1:0.5 
ape UL 4,259 28,375 1:6.6 
§ Il 3,850 27,119 1:7.0 
ee 53955 27,102 1:4.5 
Sak 13,548 28,204 Te2a0 
VI 11,794 46,549 13350 
Vil §,913 50,278 1:5.6 
VIII 8,435 50,173 13529 
I 7,276 17,891 1:2.4 
II 5,025 14,432 W2e4 
Il] 752215 11,701 1:1.6 
ev IV 7,025 Pls 75 Tslns 
= NY 6,736 8,352 16) 673 
6 6«(VI 6,298 Fats I:t.1 
& VII 5,655 12,32 Ie22 
ar Vat 6,074 8,983 I:1.4 
IX 5,789 8,163 Tele 
x Telopl 10,612 ited 
XI Hewson’ 11,403 Lts5 
XII 7,596 14,12 16) G6) 
ol 
a I 7,944 18,861 le2ed. 
Bye sl 6,014 23,640 3349 
4 Ill 11,138 31,328 17258 
IV 7349 39,053 1:5.4 
\ 19,365 43,128 1:4.1 
ze! 8,595 47,461 1:5.5 
see 4,406 25,545 1:5.8 
ay ull 2,340 W722 1A 
I\ 2328 8,580 1237, 
Fs \ 1,702 2222 Totes 
oe 519 761 1:1.4 


INGBERT, Ventral Roots of Spinal Nerves. 229 


In Table VI attention is called to the following points: 


Ite 


10. 


The total number of nerve fibers in the ventral roots of 
the left spinal nerves is 203,700. 

The total number of nerve fibers in the dorsal roots of 
the left spinal nerves is 653,627. 

The ratio of the number of nerve fibers in the ventral 
and dorsal roots is 1:3.2. 

The number of fibers in the dorsal root C. IV and the 
ventral root C. III is small. ; 

The ratio between the number of nerve fibers in the 
ventral and dorsal thoracic roots (I-XII) is, on the 
average, about 1:2. 

The number of nerve fibers in the largest ventral cervi- 
cal roots (C. V, VI) is twice the average number of 
nerve fibers in the ventral thoracic roots. 

The number of nerve fibers in the largest dorsal cervi- 
cal roots (C. VII, VIII) is nearly five times the aver- 
age number of nerve fibers in the dorsal thoracic 
roots. Hence in the nerves supplying the arm, the 
great gain has been in the number of fibers in the 
dorsal or sensory roots. 

The number of nerve fibers in the largest cervical roots, 
both ventral and dorsal, is greater than that in the 
largest lumbo sacral roots, ventral and dorsal. 

The arm, relatively to its weight of muscle, is better 
supplied with motor nerve fibers than is the leg. 

The arm, relatively to its dermal area, is better supplied 
with sensory nerve fibers than is the leg. 


In Figure 7 are given curves based on the absolute num- 
ber of fibers in the ventral and the dorsal roots. They show in 
a very striking manner the great numerical increase in the sen- 
sory fibers innervating the limbs, while the number of motor 
fibers at the corresponding levels is but slightly increased. 

That the difference between the number of fibers in the 
ventral and dorsal thoracic roots (trunk) is so small, is what 
might be expected. That the neck should show an increase in 
the nerve fibers in the dorsal roots, does not require much com- 


230 Journal of Comparative Neurology and Psychology. 


ment if we bear in mind the relatively high sensibility of the 

skin of the neck, and the small motor supply to the muscles. 

But that the roots going to the arm should show a relatively 

smaller number of sensory fibers than does the leg, needs some 
TABLE Vil: 

Showing the ratio between the number of nerve fibers in the ventral 

and the dorsal roots of man at different levels in the cord. 


Ventral Roots. Dorsal Roots Ratio. 

Neck (C. I—IV) 17,470 $4,404 1:4.8 
Arm (C. V—Th. J) 49,966 . 193,095 1:3.9 
Trunk (Th. I—L.1) 81,509 136,487 Neila 
Leg (L. I1—Coce. I) | 54,755 239,641 1:4.4 
203,700 653,627 133.2 


explanation, as the arm has a greater number of sensory fibers 
per square unit of surface than the leg. The reason for this 
smaller ratio for the arm is due to the fact that the arm has a 
much larger number of motor fibers in proportion to its weight 
than has the leg, and this fact accounts for the ratio found. 

4. Comparison of the Ratio of the Number of the Ventral 
and Dorsal Roots of the Frog, the Rat and Man.—Having now 
the ratio between the number of fibers in the ventral and the 
dorsal roots of man, it may be of interest to compare this ratio 
with similar ratios for some lower animals. We have found the 
ratio between the number of fibers in the ventral and dorsal 
roots of man to be 1:3.2. This ratio can also be obtained by 


taking three typical roots only. 


Ventral Dorsal Ratio 
Cel 11,794 46,549 
Thy Vi 7,625 115375 
Ie apaett 6,014 23,640 

25,433 80,564 B3.2 


This being so, we have some ground for believing that the 
ratio between these three pairs of roots in other animals may 
also give very closely the ratio between all the fibers in the ven- 
tral and dorsal roots. 

Hatal (1903) counted in the white rat the nerve fibers in 
the ventral and the dorsal roots of three pairs of the left spinal 
ferves (Ge Wily. "Th. IV and L. II), and obtained the ratio 


POM, 


InGBERT, Ventral Roots of Spinal Nerves. 231 


BrrGE (1882) counted the number of fibers in all the dor- 
sal and ventral roots of three frogs (Rana esculenta) having 
body-weights of 23, 60 and 63 grams respectively. The ratios 
individually were : 


Frog-Weight Ratio 
23 grms. 1:1.07 
60 grms. Tse: 
63 grms. 1:1.24 


Average for all three frogs = 1:1.15, or rounding the num- 
ber tor the. decimali—. 121.2. 

STANNIUS (1849) states that in fish, as a rule, the ventral 
roots are larger than the dorsal. There are, however, a num- 
ber of exceptions to this relation. In estimating the value of 
this statement in the present instance, it must be remembered 
that the ratios already given are between the zambers of fibers, 
and that in a comparison like this, the number of fibers and 
area of roots do not necessarily vary together. In the case of 
fish, the number of fibers in the roots has not yet been de- 
termined in any instance. 

Tabulating these results, we have the following: 


Ventral Dorsal 
Frog I ; ita 
White Rat I : 228 
Man I : By 


In this series increasing rank in the zoological scale is ac- 
companied by a relative increase of the number of fibers in the 
dorsal roots. 

5. Relation Between the Small and the Large Fibers in the 
Ventral and Dorsal Roots.—According to the author’s estimate, 
the ventral roots contain 39.64% of nerve fibers the diameter 
of which is less than 7.5 » and the dorsai roots60%. The com- 
parison may therefore be made as follows : 


Diameter of fibers. Ventral roots. Dorsal roots. Ratio. 
7.5 # and greater 122,953 272,451 D322 
Less than 7.5 4 80,747 381,176 TA, 


It thus appears that, compared with the ventral roots, the 
dorsal roots are more than twice as rich in fibers, the diameter 
of which is 7.5 # or more and nearly five times as rich in fibers 
less than 7.5 in diameter. 


232 Journal of Comparative Neurology and Psychology. 


VIT. On the Relative Areas of the Cross-sections of the Roots 
Forming the Brachial and the Lumbo-sacral Plexuses in 
the Male and the Femaie. 


To determine whether or not the roots of the brachial 
and the lumbo-sacral plexuses show any difference in size in the 
two males, (KOLLIKER and the author) and the two females 
(KOLLIKER and SriLLinG) the spinal roots of which have been 
measured, I have added the areas of the cross-sections of the 
four largest ventral and dorsal roots in the cervical and the lum- 


bar regions respectively, as given by the several authors. These 
results may be arranged as follows: 


(a) Relation of the Area of the Cross-sections of Four Roots 
of the Brachial Plexuses. 


2 males 2 females 
Ventral (C. V—VIII) 16.38 mm.” 16,02 mm.? 
Dorsal (C. V—VIITI) 40.04 mm.? 21920) mim? 

56.42 mm.” 47.32 mm.? 


From this it is evident that the roots here compared are 
better developed in the male, and would indicate that the males 
have a little better motor and much better sensory inner- 
vation for the arm. 


(b) Relation of the Area of the Cross-sections of Four Roots of 
the Lumbo-sacral Plexus. 


2 males 2 females 
Ventral (L. IV, V and S. I, II) 14.36 mm.? 17.46 mm.? 
Dorsal ( s Eo y buss =) 31.04 mm.” 33.24 mm.? 

45.40 mm.” 50.70 mm.? 


From these results it is evident that the roots here com- 
pared are better developed in the female, and would indicate 
that the females have a better motor and sensory innervation 
of the hips and legs. 

These results may also be arranged so as to bring out the 
relative development of these roots in the brachial as against 
the lumbo-sacral roots in males and females. 


INGBERT, Ventral Roots of Spinal Nerves. 233 


(c) Relation of the Area of the Cross-sections of Four Roots in 
the Brachial and in the Lumbo-sacral Plexuses. 


Brachial (C. V—VIII) Lumbo-sacral (L. IV, V & SI, II) 
2 males 56.42 mm.? 45.40 mm.? 
2 females 47.32 mm.? 50.70 mm.? 

Hence we can conclude in that in the two males the area 
of the cross-sections of these four roots of the branchial plexus 
is better developed than that of the four roots of the lumbo- 
sacral plexus, while in the two females the reverse relation holds 
true. Although these results are based on too small a number 
of cases to establish fully a relation of such importance, they 
are very suggestive, and may serve as a basis for further investi- 
gation. 


Summary. 
(A) AREAS OF ROOTS. 


1. The total area of the cross-sections of the ventral roots 
of the left spinal nerves of a large man was found to be 
26/50 mm" ‘(Table I). 

2. Since the total area of the cross-section of the ventral 
roots of the left spinal nerves is 26.50 mm.*, and that 
of the dorsal roots 54.93 mm.”, the ratio of their areas 
iss:2:07 (Table Vp. 212), 

3. In the cervical region, the third ventral root and the 
fourth dorsal are interesting because of the diminution 
in their areas, as well as in the number and diameter of 
their fibers (Page 225). 

4. In the dorsal roots the area of the cross-sections is pre- 
dominantly a function of the number of fibers, while in 
the ventral roots the area of the cross-section of the 
roots is chiefly a function of the size of the fibers 
(page 225 ). 

5. The largest ventral roots arise one to two segments 
cephalad to the largest dorsal roots, and the ventral 
cervical depression (C. III) is one segment cephalad to 
the dorsal cervical depression (C. IV) (page 224). 

6. In two male cords the sum of the areas of the four 


34 


N 


LO: 


1 


12. 


ournal of Comparative Neurology and Psychology. 
Ss Oy 


largest dorsal and ventral cervical roots (C. V-VIII) is 
greater than that of the corresponding roots of two 
females, and also greater than that of the four largest 
lumbo-sacral roots (L. IV-V and S. I-II) of the same 
males (pp. 232-233). 
In two female cords the sum of the areas of the four 
largest ventral and dorsal cervical roots (C. V-VIII) is 
less than that of the corresponding roots of the two 
male spinal cords, and also less than that of the four 
largest lumbo-sacral roots (L. IV-V and S. I-II) of the 
same females. This shows that in the male, the roots 
contributing to the cervical plexuses, and in the female, 
the roots contributing to the lumbo-sacral plexuses, are 
the better developed (pp. 232-233). 

(B) NUMBER OF FIBERS. 
The total number of medullated nerve fibers in the ven- 
tral roots of the left spinal nerves of the same man is 
203,700; and the total number on both sides would 
therefore be about 407,400 (Table IJ). 
Since, according to the author’s enumeration, there are 
203,700 medullated nerve fibers in the ventral roots of 
the left spinal nerves, and 653,627 in the dorsal, the 
ratio of the number of fibers is 1:3.2 (Table VI). 
In the increase of the nerve supply to the limbs, the 
gain has been far more in the sensory than in the motor 
fibers (page 230). 
The ratio between the number of fibers in the ventral 
and dorsal roots of man is 1:3.2 (INGBERT), of the white 
rat 1:2.3° (HaTaAr); and the frog 1:1:2 (BIRGE)s_ From 
this we may conclude that probably the relative sensory 
supply increases as we ascend in the zoological series. 


(C) SIZE OF FIBERS. 
According to the author’s estimates, there are about 
80,747 (39.1%) fine fibers (less than 7.5 y4) in the ven- 
tral roots, and 381,176 (60%) fine fibers (less than 
7.1 #) in the dorsal roots—in other words, the ratio of 


13. 


14. 


te 


a7; 


18. 


No. 


No. 


InGBERT, Ventral Roots of Spinal Nerves. 235 


fine fibers in the ventral to those in the dorsal roots is 
Iao7 (page 231): 

There are about 122,953 (60.90%) large fibers (7.5 
or more in diameter) in the ventral roots, and 372,451 
(40%), in the dorsal roots—a ratio of 1:2.2 (page 231). 
In the ventral roots the fibers, the diameter of which is 
less than 7.5 4, are most abundant in the thoracic re- 


gions. 
Fibers less evi = 12% 
than 7.5 4 Tihs Vilv—=1709, 
in diameter( S. I. = 14% 


(D) NUMBER OF FIBERS PER SQ. MM. OF THE CROSS-SECTION. 

There are on the average 7,687 medullated nerve fibers 
to every sq. mm. of the cross-sections of the ventral 
roots of man against 11,900 for the dorsal roots (page 
Za) 

In C. VII-VIII the dorsal roots have nearly twice as 
many (9,800) nerve fibers per sq. mm. of the cross-sec- 
tion as the ventral (5,500), and in S. I. the dorsal root 
has more than three times as many (13,800) as the ven- 
tral (4,300) (page 216). 

In the thoracic region the number of nerve fibers per 
sq. mm. of the cross-section of the roots is nearly the 
same for both ventral and dorsal] roots—namely, about 
12,000 (page 216). 

SEELINGS estimate for the fibers_per sq. mm. in the 
ventral and dorsal roots is close to the estimation here 
made, for fibers the diameter of which is 7.5 # or more. 
Fibers below 7.5  STILLING did not recognize and did 
not include. 


of fibers 7.5 “ or more in diameter, per sq. mm. in the ventral roots: 


STILLING 4,231 
Author 4,556 


of fibers above 7.5 yor more in diameter, per sq. mm. in the dorsal roots: 


STILLING 4,537 
Author 4,960 


bo 


36 = Journal of Comparative Neurology and Psychology. 


In the following figures (8-38), are given the projections of the 
ventral roots of the left spinal-nerves of man. Their magnification is 
33 diameters. Within the outlines of each fascicle are found two 
numbers: the first designating the number of the fascicle, and the 
second the number, in thousands, of the nerve fibers per sq. mm. of 
its cross-section. Thus, in C.I the first fascicle has 12.3 thousands, or 

2,300 nerve fibers per sq. mm. of its cross-section. In a few of the 
outlines of the fascicles is founda letter ‘‘c.” This is to signify that 
the fascicle was found to be cut obliquely, and that the number indi- 
cating the nerves per sq. mm. is that of some neighboring fascicle sim- 
ilar in constitution, and that the corrected area of this fascicle was ob- 
tained by dividing the number of fibers in the fascicle by this number 
per sq. mm. The outlines are always those of the wncorrected projec- 
tions. In the Tables VIII-XXXVIII accompanying the projections 
are found the data for each root. These tables have four columns of 
figures. In the first is found the number given to each fascicle; in 
the second the area in sq. mm. of the cross-section of each fascicle ; in 
the third the number of nerve fibers counted in the cross-section of 
each fascicle; and in the fourth the number, in thousands, of nerve 
fibers per sq. mm. of the cross-section of each fascicle. In cases where 
a fascicle was found to have been cut obliquely and its area has been 
corrected, the number indicating the corrected area is placed in the 
column itself and the number indicating the uncorrected area after it 
in parenthesis. At the bottom of the table are found the totals. 
These totals have been brought together in Table II. 


INGBERT, Ventral Roots of Spinal Nerves. 237 


TABLES AND FIGURES. 


Journal of Comparative Neurology and Psychology. 


i) 
Ww 
(oe) 


INGBERT, Ventral Roots of Spinal Nerves. 


IDANBIE IS; WAMOL (Cp Ie 


Number of 
nerve fibers in 
each fascicle 


Number of 
nerve fibers in 
thousands, 
per sq. mm. 


WwW 


96 1253 
149 Len2 
146 Mies 
296 Tile 
202 19.2 
245 13.9 
251 16.4 
493 10.5 

94 14.0 
231 16.2 
271 14.4 
161 Teter 

49 Il.I 
133 17.9 
199 13.8 
313 16.1 
11I 1352 

66 2162 

3406 13.4 


ANSE; USCC. IO 


Number Area of fasci- 
of cle in 
Fascicle sq. mm. 
I .0078 
2 .O113 
3 .O127 
4 =: 202 
5 .O105 
6 .0176 
7 -O153 
8 .0467 
9 .0067 
10 .O142 
1! 0188 
12 .0145 
13 -0044 
14 O74 
15 .O144 
16 0132 
17 0084 
18 0031 
Totals 18 2532 
Number Area of fasci- 
of cle in 
fascicle sq. mm. 
I .0049 
2 SLONy, 
3 .0662 
4 -0547 
5 .0283 
6 .0 36 
7 -0374 
8 9080 
9 0235 
10 .0319 
Tt .0704 
I? -O715 
13 .O10I 
14 .0469 
10 .0518 
16 .0469 
Totals 16 .6868 


Number of 
nerve fibers 
in each 
fascicle 


46 


Number of 
nerve fibers, 
in thousands, 
per sq. mm. 


AN DHADOININ Hn UN DO 
FPHNO DO NNN HUN Db OM 


lon) 
tv 


Journal of Comparative Neurology and Psychology. 


Figs. 10, 11 


INGBERT, Ventral Roots of Spinal Nerves. 241 


TABOR, Xe: Wr. 


Number of Number of 
Number Area of fasci- nerve fibers nerve fibers, 
of cle in in each in thousands, 
fascicle sq. mm. fascicle per sq. mm. 
I .0058 78 13-4 
2 .O131 159 120 
3 .0099 134 ret 
4 0081 109 13.6 
5 .0129 124 9.6 
6 .O1S9 250 13.2 
7 .O1SQ 1QI 10.1 
8 .0183 228 12.5 
9 .0255 314 12a 
10 .0251 286 11.3 
II .O102 116 11.3 
12 0217 272 2c 
13 .0062 87 14.0 
14 .0234 261 Tet 
15 .0095 127 13.3 
16 .O122 162 13.3 
17 .0097 117 12.0 
18 .0329 422 12.8 
19 .0299 413 . 13.8 
Totals 19 S322 3850 es 
TAB GE Sc C. Ve 
Number of Number of 
Number Area of fasci- nerve fibers nerve fibers, 
of cle in in each in thousands, 
fascicle sq. mm. fascicle per sq. mm. 
I .0349 (.0481) 212 OSI 
2 -1201 (.1545) 733 6.1 
: -11 6 (.1725) 681 6.1 
4 .1360 (.1866) 830 6.1 
5 .0880 54! 6.1 
6 .0077 47 6.1 
7 .OO17 744 12.0 
8 LOZ 123 Te 
9 .0525 4i2 7.8 
10 -O412 491 11.9 
II .O158 189 11.9 
12 .1494 952 6.4 


Totals 12 8361 5955 


NI 
= 


N 


Journal of Comparative Neurology and P. sychology. 


Fig. 12 


IncBert, Ventral Roots of Spinal Nerves. 243 


PABLE Xi Cav. 


Number of Number of 
Number Area of fasci- nerve fibers nerve fibers, 
of cle in in each in thousands, 
fascicle sq. mm. fascicle per sq. mm. 
I .0502 B27 6.5 
2 1293 565 4-3 
3 .0514 210 4.1 
4 .0239 157 6.5 
5 .0693 347 5.0 
6 -2139 952 4-4 
7 .1076 704 6.5 
8 .0235 10; 4-4 
9 .0225 109 4.8 
fe) .1370 603 4.4 
iB .1206 562 4.6 
12 .1339 664 4.9 
13 .1392 647 4.6 
14 0547 299 5-5 
15 3005 1346 4.4 
16 035" 236 6.7 
17 1774 845 4.9 
18 .0509 343 6.7 
19 .0621 318 Soil 
20 .0309 206 6.6 
21 £1923 $93 4.6 
o 22 .1462 Wae 4.9 
23 Sin 451 4.3 
2 31328 612 4.6 
25 .20605 881 4.2 
26 -0909 413 4.5 


Totals 26 2.8147 13,548 


5 
ora 


244 Journal of Comparative Neurology and Psychology. 


INGBERT, Ventral Roots of Spinal Nerves. 245 


INOS, S000 WAL 


Number of Number of 
Number Area of fasci- nerve fibers nerve fibers, 
of cle in in each in thousands, 
fascicle sq. mm. fascicle per sq. mm. 

I .1230 462 BES 
2 .0867 7 4.2 
3 .0256 147 5-7 
4 0554 341 6.1 
5 .2277 836 3-7 
6 .0254 142 Gols 
7 .0218 147 6.7 
8 .1839 761 4.1 
9 eel 558 4.1 
10 .0058 24 4.1 
II .2212 839 3.8 
12 .0 34 202 6.0 
13 .0809 454 5.6 
14 .06 34 329 Gee 
Is .1622 728 4.3 
16 ° .OQ6I 426 4.4 
17 .0612 306 5.0 
18 .1848 744 4.0 
19 .0685 302 4.4 
20 .0849 418 4.4 
21 .1291 576 4.4 
22 .2250 990 4.4 
23 .0809 341 4.2 
24 1444 578 4.0 
25 .0851 451 5e3 
26 .0658 321 4.8 
Totals 26 2.6893 11,794 4.4 


246 Journal of Comparative Neurology and Psychology. 


INGBERT, Ventral Roots of Spinal Nerves. 247 


CA BIE XLV C2 Vale 


Number of Number of 
Number Area of fasci- nerve fibers nerve fibers, 
of cle in in each in thousands, 
fascicle sq. mm. fascicle per sq. mm. 
I .0506 202 3.9 
2 .0336 124 Bey 
3 .0262 196 7.4 
4 .0250 101 4.0 
5 .O150 92 6.1 
6 0704 475 6.7 
7 .0474 312 6.5 
3 .04f2 398 8.6 
9 .0490 332 6.8 
10 .0629 439 6.9 
II .0689 575 8.3 
12 .O165 126 7.6 
13 .0194 175 9.0 
14 .0126 81 6.4 
15 .0329 291 8.9 
16 .0502 469 9-3 
17 0339 353 10.4 
18 .0502 4.9 8.1 
19 1238 QI? Wee 
20 .0762 612 8.0 
21 .0918 749 8.1 
22 .0631 489 rey 
23 .0608 501 8.4 
24 .0899 500 5-5 
Totals 24 1.2165 8913 a3 
IUNIBIUIS ROY Co WAIL 
Number of Number of 
Number Area of fasci- nerve fibers nerve fibers, 
of cle in in each in thousands, 
fascicle ; sq. mm. fascicle per sq. mm. 
I .1650 (.2341) 892 5-4 
2 0842 (.1354) 455 5-4 
3 -2111 (.3031) 1086 5-4 
4 -0745 407 5-4 
5 .0359 241 6.6 
6 .1003 (.1276) 662 6.6 
7 .1103 628 o7/ 
8 .0888 (.1162) 506 Sor 
9 .1290 (.2032) 697 5-4 
10 .O179 (.0273) 97 5-6 
II .0792 449 5-6 
12 0882 595 6.7 
13 .2079 1043 5:0 
14 .0630 306 5-8 
15 .0622 311 5.0 
Motalsy 1s 1.5175 8435 5:5 


oe) 


Journal of Comparative Neurology and Psychology. 


Figs. 16, 17 


InGBERT, Ventral Roots of Spinal Nerves. 


AUANIBICIE, ROVE Isls Ie. 


Number of 


Number of 


Number Area of fasci- nerve fibers nerve fibers, 
of cle in in each in thousands, 
fascicle sq. mm. fascicle per sq. mm. 
I .0650 508 7.8 
2 .0569 596 10.5 
3 .0822 641 7.8 
4 -O711 go08 8.3 
5 .0829 591 10.9 
6 .0571 638 se) (i 
7 .0940 857 g.1 
8 .0400 643 13.9 
9 .0266 445 16.7 
10 .1807 1449 8.1 
Totals 10 .7625 7,276 9-5 
TDANBIEI SS OVAOE AN Sl Tle 
Number of Number of 
Number Area of fasci- nerve fibers nerve fibers, 
of cle in in each in thousands, 
fascicle sq. mm. fascicle per sq. mm. 
I .0236 418 fay) 
2 .0688 803 11.6 
3 .0904 1016 TE 2 
. 4 .0640 543 8.5 
5 .0466 527 eS 
6 -0549 637 11.6 
7 .0436 811 18.6 
8 .0537 870 16.4 
Totals § -4456 5,625 12.6 


NO 


Journal of Comparative Neurology and Psychology. 


Figs. 18, 19 


ws 


Totals 


Totals 


INGBERT, Ventral Roots of Spinal Nerves. 


fascicle 


COn~a AnBWN | 


oO 


Number 
of 
fascicle 


aRABICE) XOVLE EEL. hl. 


Area of fasci- 
cle in 
sq. mm. 


-0394 
.0659 
-1142 (.1873) 
.0566 
.0789 
.0398 
0945 
0415 


5395 


Number of 
nerve fibers 
in each 
fascicle 


574 
826 
1505 
739 
9590 
563 
1473 
605 


7235 


TABU, XX: WE LV: 


Area of fasci- 
cle in 
sq. mm. 


0354 
.0358 
.0166 
.0520 
.0209 
.O152 
-O104 
.0188 
.0219 
.0510 
.0283 
.( 246 
Ol 85 
.0463 
.0458 


4415 


Number of 
nerve fibers 
in each 
fascicle 


605 
663 
379 
689g 
35! 
236 
204 
326 
427 
733 
535 
399 
428 
1014 
645 


7625 


Number of 
nerve fibers, 
in thousands, 
per sq. mm. 


14.5 
12.6 
12.3 
Ign 
12.0 
14.1 
15.5 
14.8 


13-5 


Number of 
nerve fibers, 
in thousands, 
per sq. mm. 


17.0 
18.5 
22.8 
rae2 


No 


Journal of Comparative Neurology and Psychology. 


Th.VI 


Figs. 20, 21 


INGBERT, Ventral Roots of Spinal Nerves. 253 


SPAIBIEE, SXGXe vey Wi 


Number of Number of 
Number Area of fasci- nerve fibers nerve fibers, 
of cle in in each in thousands, 
fascicle sq. mm. fascicle per sq. mm. 
I .0361 367 10.1 
2 .0 309 509 16.4 
3 0510 73! 14.3 
4 .O119 145 1252 
5 .6462 616 ea 
6 £0216 194 8.9 
Fh .0490 (97 14.2 
8 0434 456 10.5 
9 .0288 47 16.7 
fe) .0466 (.0717) 569 W252 
II .0809 (.1147) 987 W252 
12 -O815 (.1390) 994 12.2 
Totals 12 5279 6736 Ta 
AMANO Thsl, WME 
Number of Number of 
Number Area of fasci- nerve fibers nerve fibers, 
of cle in in each in thousands, 
fascicle sq. mm. fascicle per sq. mm. 
I .0805 (.2175) 982 r252 
2 -0733 (.2428) 896 12-2 
3 -1118 (21393) 1364 r2:2 
4 -0393 (.0685) 479 NOY 
5 -0345 (.:.506) 421 12.2 
6 0275 (.0422) 336 Lee 
7 .09 24 1130 12.2 
8 .0286 (.0381) 349 222 
9 20279 (.0518) 34 12.2 
Totals 9 5158 6298 12.2 


Journal of Comparative Neurology and Psychology. 


NN) 
Loat 
TS 


Figs. 22, 23 


INGBERT, Ventral Roots of Spinal Nerves. 


TU Nsbie; LOGU) Waieg WAU. 


Number of 


Number of 


Number Area of fasci- nerve fibers nerve fibers, 
of cle in in each in thousands, 
fascicle sq. mm. fascicle per sq. mm. 
.0600 749 10.8 
2 .023 4 356 15.2 
3 .0520 578 11.1 
4 .0485 <8 11.9 
5 -0639 (.0935) 8.8 12.8 
6 -0798 (.1239) 1022 12.8 
7 .0582 743 12.8 
8 .0784 808 10.3 
Totals 8 .4642 5655 12.2 


Totals 


Number 
of 
fascicle 


mP WN ww 


wn 


ANGIE, POSVO inst WAVE, 


Area of fasci- 


cle in 
sq. mm. 
1065 (.1540) 
-1005 (.137 ) 
-1788 (.2221) 
.0630 
.0309 


4957 


Number of 
nerve fibers 


Number of 
nerve fibers, 


in each in thousands, 
fascicle per sq. mm. 
1301 1473 
1301 1282 
2182 1252 
828 Ti 
462 14.9 
6074 n2e5 


256 Journal of Comparative Neurology and Psychology. 


Figs. 24, 25 


IncBert, Ventral Roots of Spinal Nerves. 257 


IVIL, OO Isle ID. 


Number of Number of 
Number Area of fasci- nerve fibers nerve fibers, 
of cle in in each in thousands, 
fascicle sq. mm. fascicle per sq. mm. 
I .0382 492 12.9 
2 .0474 671 14.1 
3 -0355 464 13.0 
4 .0535 598 ile2 
5 .0383 543 14.2 
6 -0275 392 14.2 
7 .1148 1205 10.5 
8 .1342 1424 10.5 
Totals 8 .4894 5789 11.9 
RA BIE) SOCVes AE Xs 
Number of Number of 
Number Area of fasci- nerve fibers nerve fibers, 
of cle in in each in thousands, 
fascicle sq. mm. fascicle per sq. mm. 
I 0435 (0551) 534 P23 
2 .0482 (.0600) 593 1233 
3 -0645 (.1290) 793 12.3 
4 0479  (.0702) 390 12.3 
5 .0278 417 15-0 
6 .0697 773 11.1 
7 0477 (.0599) 587 12.3 
8 -0469 (.0672) 577 W228 
9 -0600 (.0966) 739 1253 
fo) .0423 (.0783) 521 12.3 
II -0859 (.1275) 1047, 1233 
Totals 11 5844 7171 1253 


bo 


58 Journal of Comparative Neurology and Psychology. 


Ca te Xi 
GE DR’ 


Figs. 26, 27 


INGBERT, Ventral Roots of Spinal Nerves. 259 


TABLE XXVI TH. XI. 


Number of Number of 
Number Area of fasci- nerve fibers nerve fibers, 
of cle in in each in thousands, 
fascicle sq. mm. fascicle per sq. mm. 
I .0236 (.0371) 281 7.6 
2 .0586 691 11.9 
3 20150 222 14.8 
4 .0356 6S2 19.1 
5 .0813 1216 Ii. 
6 . 286 587 20.5 
7 .0239 474 16.0 
8 0925 904 9-7 
9 .0236 258 10.9 
10 .065 5 1131 72 
II .1094 1207 10.3 
12 s .0084 108 12.9 
Totals 12 .5660 7761 1e7, 
ADANIBIE Sy NOOO WSIs. 10 
: Number of Number of 
Number Area of fasci- nerve fibers nerve fibers, 
of cle in in each in thousands, 
fascicle sq. mm. fascicle per sq. mm. 
I .1026 1077 10.5 
2 .0682 898 13.1 
3 .0426 398 14.0 
4 .0235 278 11.8 
5 .0462 586 12.6 
6 .0408 4601 Tee 
7 .0199 281 14.1 
8 .0617 737, 11.9 
9 .O119 207 17.4 
10 .0076 124 20.2 
11 -0631 761 12.0 
12 . 1099 1358 1252 


Totals 12 .5980 7596 12.9 


260 = Journal of Comparative Neurology and Psychology. 


Figs. 28, 29 


INGBERT, Ventral Roots of Spinal Nerves. 


DA BIGE XOXO TT es 


Number of Number of 
Number Area of fasci- nerve fibers nerve fibers, 
of cle in in each in thousands, 
fascicle sq. mm. fascicle per sq. mm. 
I .0212 264 12.5 
2 0354 314 8.8 
3 .0082 659 9.6 
4 .O814 971 11.9 
5 -0877 834 g.1 
6 .1264 10S 8.3 
7 -0924 1530 16.5 
8 .0862 1181 137 
9 .0360 507 14.0 
10 .0299 633 2162 
Totals 10 .6648 7944 II.9 
TABS, XOOUXeIls lile 
Number of Number of 
Number Area of fasci- nerve fibers nerve fibers, 
of cle in in each in thousands, 
fascicles sq. mm. fascicle per sq. mm. 
I 0801 463 5-7 
2 -0397 244 6.1 
2 .0580 414 71 
4 .0998 896 8.9 
5 .0839 636 7.6 
6 .0084 76 g.1 
ii .0454 455 10.0 
8 .O514 462 8.9 
9 .0313 228 fe? 
Io -O59I 461 7.8 
11 .1871 1109 5-9 
12 .0549 471 8.6 
13 -o108 99 g.1 


Totals 13 .8099 6014 


NI 
a 


Journal of Comparative Neurology and Psychology. 


N 
OV’ 
to 


ee 


(:) Qs 
\9.2 


a 


Fig. 30 


Totals 


INGBERT, Ventral Roots of Spinal Nerves. 


Number 
of 
fascicle 


ee | 
PWNHH OD CON AMF WN HS 


15 


TABLE XXXL. IT: 


Area of fasci- 
cle in 
sq. mm. 


Number of 
nerve fibers 
in each 
fascicle 


1169 
1145 
652 
1015 
540 
357 


Number of 
nerve fibers, 
in thousands, 
per sq. mm. 


MPN DH OMIT AO DA RUN 
MNIWMWOW OhUHMN Onn O NE NAT 


wn 
‘Oo 


263 


264 Journal of Comparative Neurology and Psychology. 


Figs. 31, 32 


INGBERT, Ventral Roots of Spinal Nerves. 265 


TABLE WOT IL. LV: 


Number of Number of 
Number Area of fasci- nerve fibers nerve fibers, 
of cle in in each in thousands, 
fascicle sq. mm. fascicle per sq. mm. 
I -1455 792 Bq) 
2 -0312 251 8.0 
3 .0851 465 5-5 
4 .0S62 518 6.0 
5 -0654 447 6.5 
6 -2064 1144 4.7 
7 .0986 571 5.8 
8 .0408 279 6.8 
9 .0216 179 8.3 
10 .1062 666 6.3 
II 1562 854 5-4 
12 1548 784 5.0 
13 .0680 399 5.8 
Total 13 1.2660 7349 5.8 
TABICE, SOX Ly Vie 
Number of Number of 
Number Area of fasci- nerve fibers nerve fiber, 
of cle in in each in thousands, 
fascicle sq. mm. fascicle per sq. mm. 
I 3122 1490 4.8 
2 -O175 121 6.9 
3 0392 283 HER 
4 -0503 300 5-9 
5 .2940 1270 4-3 
6 -1436 i 5-4 
7 2165 1039 4.8 
8 5491 2392 4.3 
9 2334 1106 4.8 
+f) -0529 335 6.3 
Il 2569 1260 455 


Totals 11 2.1656 10366 


oS 
ao 


iS) 


Journal of Comparative Neurology and Psychology. 


Figs. 33, 34 


INGBERT, Ventral Roots of Spinal Nerves. 26 


TABOR XX XUN S: 1: 


Number of Number of 
Number Area of fasci- nerve fibers nerve fibers, 
of — cle in in each in thousands, 
fascicle sq. mm. fascicle per sq. mm. 
I .1568 836 5-9 
2 -1607 753 4:7 
3 3596 1626 4.2 
4 -2823 1043 3-7 
5 -2073 993 4-4 
6 .2969 1281 4.3 
Hi .OOS8I 74 Sif 
8 -0975 424 4.4 
9 -4106 1658 4.0 
Totals 9 1.9795 85958 4.3 
TABU XOXSsIN: Sani: 
Number of Number of 
Number Area of fasci- nerve fibers nerve fibers, 
of cle in in each in thousands, 
fascicle sq. mm. fascicle per sq. mm. 
I .1695 g60 5-6 
2 .0580 346 5-9 
3 -0377 313 8.3 
4 .1489 82 5-6 
5 .OL2I 113 9-3 
6 .0660 679 10.3 
7 -0577 598 10.4 
8 .0582 568 9.7 
Totals 8 608 | 4406 7.2 


Journal of Comparative Neurology and Psychology. 


Gy Coe-l 


Figs. 35, 36, 37, 38 


INGBERT, Ventral Roots of Spinal Nevves. 


Number 
of 
fascicle 


Totals 2 


Number 
of 
fascicle 


OW NH 


Totals 3 


Number 
of 
fascicle 


Number 
of 
fascicle 


A BICR XXGXGV (Ss ULE: 


Area of fasci- 
cle in 
sq. mm. 


£105 
.0627 


21732 


Number of 
nerve fibers 
in each 
fascicle 


1647 
693 


2340 


TABLE: XXXVI S.1V. 


Area of fasci- 


Number of 
nerve fibers 


cle in in each 
sq. mm. fascicle 
.009I 256 
.0309 783 
.0568 1284 
.0968 2323 


TABLE, XXXVI Ss. V- 


Area of fasci- 
cle in 
sq. mm. 


.OQOI 


ADMIN, OO. VUE (COX s Ale 


Area of fasci- 
cle in 
sq. nm. 


O71 


Number of 
nerve fibers 
in each 
fascicle 


Number of 
nerve fibers 


in each 
fascicle 


519 


Number of 
nerve fibers, 
in thousands, 
per sq. mm. 


14.9 
II.0 


Number of 
nerve fibers, 
in thousands, 
per sq. mm. 


tN 
1os) 
Ne) 


Number of 
nerve fibers, 
in thousands, 
per sq. mm. 


19.0 


Number of 
nerve fibers, 
in thousands, 
per sq. mm. 


30.0 


269 


270 Journal of Comparative Neurology and Psychology. 


BIBLIOGRAPHY. 
Birge, E. A. 
1882. Arch. f. Anat. u. Physiol., Heft 5und 6. Lerpzreg. 
Donaldson, H. H. 
1894. J. Morph., Boston. Vol. 1X, No. I, p. 154. 
Donaldson, H. H. and Davis, D. J. 
1903. jour, Comp. Neur., Granville, Vol. XIII, No. 5. 
Hatai, S. 
1903. Jour. Comp. Neur., Granville, Vol. XIU, p. 179. 
Ingbert, C. E. 
1903. /Jour. Comp. Neur., Granvilie, Vol. XIII, p. 53. 
Ingbert, C. E. 
1903. Jour. Comp. Neur., Granville, Vol. XIII, p. 209. 
Kolliker, A. 
1850. Mikroscopische Anatomie, Lep27g, p. 434. 
Krause, W. 
1876. Anatomie, Hannover, p- 165. 
1880. Arch. f. Ophth., Bd. XXVI, Abth. II, p. 102. 
Kuhnt, H. 
1879. Arch. f. Ophth., Bd. XXV, Abth. ITI, p. 179. 
Rosenthal, D. 
1845. De numero atque mensura microscopica fibrillarum elementarium 
systematis cerebro-spinalis symbolae. Dissertatio. Vratislaviae. 
Salzer, F. 
1880. Sitzungsb. ad. K. Akad. d. Wrossensch. 2u Wien, Math. Naturw. 
Classe, Wien, Bd. LXXXI, Abth. IIIT, pp. 7-23. 
Siemerling, E. 
1886. Bull. Acad. de med., Paris, XXIX, 1008-1012. 
1887. Anat. Unters. it. d. Menschl. Ruckenmarkswurzeln. Berlin, 
Stannius, H. 
1849. Das peripherische Nervensystem der Fische, Rostock. 
Stilling, B. 
1859. Neue Untersuchungen iiber den Bau der Riickenmarks.  Casse/. 
Pp. 346. 
1859. Atlas. Taf. XVIII. 
Tergast, P. 
1872. Arch. f. mikr Anat., Bonn, Bd. IX, Heft I, pp. 26-46. 
Voischvillo, |. (or Woischwillo). 
1883. Relation of Calibre of Nerves to the Skin and Muscles of Man. 
Inaug. Diss. (Russian). St. Petersburg. 


EDITORIAL: 


The comparative method is one of the distinguishing char- 
acteristics of modern science. Nowhere has it been more fruit- 
ful in its application than in the natural sciences, which assume 
the unity of nature. Comparison here means that in the midst 
of the detailed analysis to which science subjects natural phe- 
nomena there is an accompanying synthesis. Things, to be 
compared, must be at once different and yet related. The aim 
of the comparison is to state more comprehensively the relations 
as well as to define more accurately the differences. But it is in 
the biological sciences that the comparative method becomes 
conspicuously serviceable, since here the doctrine of evolution 
has come in to reinforce the idea of nature as a unity or system. 
Here unity means continuity, function becomes significant only 
through genesis, physiology through morphology, and homol- 
ogy gives to comparison a meaning it never could have had so 
long as it expressed simply superficial resemblance. But a still 
further step is implied in the comparative method, a step which 
is best represented in what have been called the hyphen 
sciences such as astro-physics, physical-chemistry, psycho-phys- 
ics, physiological-psychology. Without prejudging a movement 
which is still in its infancy, it may be said that the significance 
of this tendency is likewise toward an organic interaction be- 
tween the various sciences, an interaction which promises to be 
most fruitful and, in the present period of scientific specializa- 
tion, is greatly needed. It is one aim of this Journal to con- 
tribute to this development of the comparative method by bring- 
ing together researches which, both from the structural and the 
functional sides, will show what is meant by the evolution of 


action. 
* 
* 


272 Journal of Comparative Neurology and Psychology. 


Action is a category common to all science, whether we 
are dealing with the motion or energy of physical science, with 
the ‘‘reactions’” so-called of living organisms in the case of 
tropisms, reflexes, and instincts, or with the ‘‘mental processes”’ 
or ‘‘mental activity’ so vaguely conceived at the present time 
under the figure of a ‘‘stream of consciousness.’’ OsTWALD’s 
recent attempt to subordinate the psychical to the idea of energy 
is indicative of the demand for a category of action which may 
serve as a platform upon which the various sciences may get to- 
gether to discuss those important problems where their respective 
fields overlap. BALpwiIn’s conception of ‘‘psychophysical evo- 
lution” and of ‘‘bionomic”’ and ‘‘psychonomic”’ forces is a simi- 
lar attempt to find a basis upon which we can discuss the prob- 
lems of mutual interest to biology and psychology, without rais- 
ing metaphysical issues. The evolution of action, then, in the 
application of the comparative method to neurology and 
psychology, means the evolution of the organism, especially of 
the nervous system, as a machine for converting stimulus into 
response, as a mechanism susceptible to, and in turn mediating, 
measurable changes in the phenomenal world. Whether men- 
tal process is simply a phase of action and, if so, in what sense 
this is true, are questions which here are not raised, the posi- 
tion taken by this Journal being simply that for the comparison 
of the mental and the neural, the two sets of phenomena must 
be facts of the same order. The facts of comparative psychol- 
ogy, as truly as the facts of comparative neurology, are acts or 
reactions, whether or not, in the last analysis, we distinguish 
the ‘‘psychic’’ as distinct from the ‘‘psychological”’ and ‘‘phys- 
ical’ facts, which latter are here brought into comparison. 


Feces’ 


*k 
* 


The Carnegie Institution has established a Department of 
Experimental Biology under the charge of Professor C. B. 
Davenport, now of the University of Chicago. In this De- 
partment two Stations have already been arranged for. One at 
the Dry Tortugas, Florida, under charge of Dr. A. G. Mayer, 
will undertake the investigation of tropical marine faunas. The 


Editorial. 273 


other at Cold Spring Harbor, Long Island, will be devoted to 
an experimental study of evolution. This Station will be on 
the grounds lying between the New York State Fish Hatchery 
and the Biological Laboratory. About twelve acres of ground 
have been leased for a period of 50 years and through the co- 
operation of generous neighbors the use of much additional land, 
both forest and pasture, will beavailable. A building of brick, 
about 35 by 60 feet, will be erected on the ground to serve as 
administrative quarters and for the breeding of some of the 
smaller animals and plants. An experimental garden of about 
an acre, completely covered from access of birds by wire netting 
will be started at once, and there will be two acres of supple- 
mentary gardens. 

The staff of the Station will consist of Professor DAVEN- 
PORT as Director (who will retain for the present also the direc- 
tion of the Biological Laboratory); Mr. Frank E. Lutz, who 
will have charge chiefly of biometrical variation investigations ; 
Dr. GrorGE H. SHULL, who will work chiefly on plants, and of 
Miss Anna M. Lutz, who besides serving as secretary will 
make certain cytological investigations. The output of the 
Station will be increased by others residing there for a greater 
Oiless part of the year. Professor R. S. Licrie’ will thus be 
in residence during 1904-05. There will also bea class of As- 
sociates which will include biologists who receive special aid for 
work in Experimental Evolution from the Carnegie Institution 
or whose work is aided by the Station. The Station and its 
Associates will cooperate in the work and the results of the in- 
vestigations of the Associates will, in so far as aided by the Sta- 
tion, be published as results of the Station. 

The lines of investigation to be taken up by the Station in- 
clude not only the evolution of morphological characters but 
also of physiological ones. Especial attention will be paid to 
the question of the limit of inheritableness of acquired charac- 
ters, both static and dynamic. It hoped that results of import- 
ance for Psychology and Neurology will be gained of which 
the readers of the Journal may expect duly to be advised. 


COLOR VISION. 


The frequent appearance of new theories of color vision is suffi- 
cient proof that there is still a feeling of dissatisfaction with the theo- 
ries chiefly in vogue. The most recent candidate! for public favor has 
been somewhat caustically reviewed by Mrs. LApD-FRANKLIN in the 
Psychological Review (X, 5, Sept., 1903) and, as the monograph is still 
incomplete, notice is withheld. But the occasion is opportune for call- 
ing attention to the very excellent and useful summary of this subject 
published by Professor Mary Wurron CALKINs in A7ch. f. Anat. u. 
Phys., Physiol, Abt., Suppl. 1902, entitled ‘‘Theorien iiber die Emp- 
findung farbiger und farbloser Lichter.” 

We desire, however, first to call attention to what we deem a 
fundamental error (often in language only, it may be admitted) which 
serves to introduce more or less confusion into all of the current dis- 
cussions. 

Considered from the purely psychic point of view, such a thing 
as composition or ‘‘mixing” of sensations is impossible, and this will ap- 
ply with special force to color sensations. As a matter of fact—of im- 
mediate experience—any color, shade or tint is a separate discrete fact 
of apprehension. From a score of shades of red we may select any 
one as an objective unit and no one of the twenty will be experienced 
asa mixture. If it be a fact that there are four primary colors in the 
spectrum by the mingling of which all secondary colors can be pro- 
duced, this mixing is not a psychological mixing (though it is a psycho- 
logical mixing so to describe it) and the fact in no way disproves the 
statement of the discrete and separate character of every color sensa- 
tion. Black has just as real an experimental independence as though 
it had a definite wave length as its external occasion. 

That this should be so is readily seen on the basis of the writer’s 
equilibrium theory of consciousness. If every conscious state is but 
the result of an equilibrium of the cortical activities involved, it makes 


1 EGON RITTER VON OppolL“zeR. Grundziige einer Farbentheorie. Zests. 
f. Psychol. u. Phystol. d. Sinnesorgane, X XIX, 3, 183-203. 


HERRICK, Color Viszon. 275 


no difference whether one color impression was acting or a dozen were 
coéperating to impress their mode as the dominant in the equilibrium. 
The result in either case would be a unitary impression or feeling. 

But is it not true that all shades of green, for instance, are recog- 
nized as phases of one color? To a certain extent this is true. Differ- 
ent kinds of green are all called green, though when placed side by 
side they seem to differ greatly. But it is impossible for me to say 
that one out of the many is a pure green and the others are mixtures. 
It does not appear that there is a composition of simple sensations of 
which one element (say in this series of greens) remains constant and 
serves to label all of these nuances ‘‘green,” while a variable element 
affords a means of identifying one as emerald green and another as 
grass green, etc. In fact, it is possible to arrange a series of shades 
which pass imperceptibly from green into blue, as would not be the 
case if green and blue were fundamentally different sensations in any 
other sense than are various sensations of green. Such fusion as there 
is must be infra-conscious—a nervous process or, at least, a process be- 
low the threshold of consciousness. 

Professor CALKINS, in criticising the HELMHOLTZ theory of color, 
says ‘Yellow looks to us simply yellow and does not in the least ap- 
pear like a mixture of red and green nor like any other color mixture.”’ 
We would go farther and add that any color or shade whatever looks 
like itself and by no means like a mixture of other colors. If various 
shades of green, e. g., resemble each other more than they do some 
other primary color this is a subjective fact by itself as is the very fact 
that certain nervous processes give rise to the mode ‘‘green” rather 
than some other mode of sensation (a fact wholly inexplicable like any 
‘genetic mode’’). But, as a matter of experience, some shades classed 
as green resemble some shades classed as blue more than they do the 
extreme shades of green. The fact of such resemblance is not to be ex- 
plained as the result of mixture but as the result of the power of a cer- 
tain range of color-stimuli to awaken, concomitantly with their color 
sensations, accessory activities and to call them into sympathetic vibra- 
tion in the equilibrium. 

The basis of resemblance and difference perception is undoubtedly 
cortical and is a function of the equilibrium resembling those elements 
upon which we base judgments of position, etc., even though they are 
not separately perceived. 

Now if we attempt a discussion of the nature of the analysis of 
light into what are called primary colors we are at once struck by the 
fact that light itself affords us no such analysis. A light wave is not a 


276 Journal of Comparative Neurology and Psychology. 


composite of three or four wave lengths any more than water is a mix- 
ture of two discrete energy-complexes known as oxygen and hydrogen, 
each with its peculiar properties different from those of water. 

It is true that white light can be broken up by a prism into an in- 
definite series of wave-lengths of which those between certain rates 
produce a sensation ‘‘red’” and those lying between certain other 
limits produce sensations of yellow, green, blue, etc., and that between 
certain of these colors definite lines of demarkation appear while be- 
tween green and blue, for example, the boundary is vague. But it is 
incorrect to say that light is broken up into four primary ingredients 
by the spectrum. The true spectrum, pysically speaking, is a con- 
tinuous series. Where then is the analysis affected which gives us 
color ? 

The answer seems to be plain: It is in the retina. The retina is 
anatomically a part of the brain wall with the addition of ectodermal 
structures. 

Upon the prevailing theory of the non-specific nature of nerve 
conduction great difficulties arise as to the subsequent fate of the pro- 
ducts of analysis. Indeed it is often claimed that vision offers an ex- 
ception and that ‘‘it is only in the sense for color that occasion arises 
for making a different assumption, and hence analogy from other cases 
is entirely without force” (BALDW1N’s Dict. Philos., Vision, p. 3 of re- 
print). Here, moreover, we must remember that the optic nerve 
fibers are not homologous with the peripheral nerves but with the as- 
sociational fibers of the cortex and on the equilibrium (or any other) 
theory of consciousness the specific quality of the stimulus must ulti- 
mately be communicated za fibers to the reticulum of equilibrium or 
other conceived center for unification. 

But, admitting that certain segments of the spectrum—i. e. light 
waves the rates or lengths of which fall between the upper and lower 
assigned limits—are capable of producing (let us say in the pigments 
of the retina) a definite chemical reaction, and no other, then the 
way is open for the application of some one of the numerous chemico- 
vital theories of the color vision. 

Certain possibilities are then to be considered : 

1) Aneye might be so formed that its color-receiving pigment 
would be chemically affected by any and all rates of vibration 
between certain extremes and the resultant sensation would be the 
same in any such event. The chemical product of decomposition or 
the process of decomposition might be the adequate stimulus to disen- 
gage a sensation of light simply. This might be white light or any other 


HERRICK, Color V7szon. 2a, 


color. The world would seem either light or dark or would be lighter 
or darker. Such condition is conceivable as actually occurring in case 
of the pineal eye of some vertebrates or the pigment fleck of lower 
forms. 

ta) Instead of the visual material being competent to react to all 
rates of vibration, it might be specifically affected by only one 
kind of light and so in white light and in the colored light correspond- 
ing to its reaction capacity there would be sensation, while in all other 
kinds of light there would be none. This possibility might be consid- 
ered in some forms of color blindness. 

2) The color conditions might be as above but separate stations 
be developed for producing the local indices or the elements to be 
used in the formation of space perception. The fusion of several or- 
gans of the elementary type resulting in the development of elemen- 
mentary rod cells imbedded in a single pigment would produce this 
result. 

3) We might assume the existence of three or four different pig- 
ments or reaction-substances and that each of these is sensitive to 
only a limited range of vibrations, while all are sensitive to white light 
in so far as the latter contains potentially their own specific range. 

4) It might be assumed that but two kinds of pigment exist, but 
that during a regeneration phase each of these produces a different 
color effect from that produced during a degenerative phase, i. e., dur- 
ing the actual decomposition while acted on by light. In this way 
there would be produced in the nervous apparatus the foundation for 
four color sensations. This would perhaps require that a third sub- 
stance should be present for the production of white and black impres- 
sions or it might be supposed that simultaneous action of the two sub- 
stances postulated would be adequate for white production. 

5) Still again, it might be supposed that in transition from the 
simple condition in (2) some of the cellular elements retained the prim- 
itive material sensitive to light only, while others had undergone 
higher differentiation and so were more complex and contained a 
visual compound of greater molecular complexity capable of several 
stages of decomposition before losing the bio-photic power. In this 
case white sensation may be produced either (a) by the effect of homo- 
geneous light acting on those elements (rods) containing the more 
primitive pigment or (b) as a result of extreme alteration in the com- 
plex pigment as an after effect of long or intense stimulation. 

Other postulates might be formulated but these may serve to in- 
troduce the table which we translate from Dr. Calkins’ paper above 
referred to. 


278 Journal of Comparative Neurology and Psychology. 


I. The YoUNG-HELMHOLTZ Theory of Color-Mixture. 


Statement, 


There are three fundamental col- 
ors: red, green, violet. 

Colored light is not a simple but a 
complex sensation, it results from a 
mixture of colored lights. 


Response, 


Contrary to psychological color 
analysis and to observation. 
No explanation is given for: 
I. peripheral color-blindness. 
2. color-blindness in case of feeble 
illumination. 
3. total color-blindness. 


II. Theories of Contrast Colors of HERING, M@LLER and ERBBINGHAUS, 


There are four fundamental colors : 
red, green, yellow, blue. 


There are two pairs of contrasting 
colors: red-green and yellow-blue. 

Colorless light sensations result from 
the function of a retinal black-white 
visual pigment (HERING) or through 
cortical processes (MULLER) if two 
contrast colors have mutually neu- 
tralized each other. 


The facts of the color systems, par- 
ticularly that the two types of red- 
green blindness are deficiency phe- 
nomena, are not taken into considera- 
tion. 


Mixtures of red and green do not 
produce colorless light. 


See below. 


III. Theories that Colorless-Light Sensations are Produced by the Func- 


tions of the Rod-Pigment. 

There are three color-sensations 
which are produced by the activities 
of the cones (Vv. KRIEs) or the de- 
composition of the visual purple and 
the retinal pigment (KONIG). Color- 
less light sensations arise in two 
ways: by irritation of the rods or by 
combination of more than one color 
process. 


Psychological analysis demands the 
existence of four different fundamen- 
tal sensations. 

It is not probable that two sensa- 
tions subjectively completely similar 
would be produced by two totally 
diverse retinal processes. 


IV. C. L. FRANKLIN’s Theory of Molecular Dissociation. 


There are four fundamental color 
sensations, which are produced by 
partial decomposition of differentiated 
molecules of the photo-chemical reti- 
nal substance of the cones. 

Colorless light sensations are pro- 
duced by 1) complete decomposition 
of the undifferentiated rod molecule, 
2) of the differentiated cone molecule. 
The dichromasy of the normal retinal 
periphery and the majority of cases 
of partial color-blindness form an in- 
termediate stage in the development. 


See below. 


Herrick, Color Vision. 279 


To the above Miss CaLkKins remarks: It may be assumed from 
psychological analysis that there are four and not three fundamental 
colors and that white is not a mixed but a fundamental sensation. 
This disposes of the YouNG-HELMHOLTz theory. 

The fact above noted, that a mixture of red and green light does 
not produce white light is not reconcilable with HERING’s theory. 

The anatomical structure and distribution of the rods indicates 
that these structures can produce only colorless light and this confirms 
the view shared by v. Krres, K6niG and Lapp-FRANKLIN. 

The fact that rods and cones originally were similar and that the 
cones differentiated in the course of evolution, makes it probable that 
a chemical process which goes on in the same way in the rods and 
cones produces white light and, furthermore, that various phases or 
stages of this chemical process in the cones are the causes of colored 
light. These considerations recommend the LApp-FRANKLIN theory 
of molecular dissociation. 


According to the LADD-FRANKLIN theory, the basis for color dis- 
crimination is a four-fold chemical process in the cones but white light 
is simply produced by the decomposition of the elementary form of the 
pigment, which decomposition may be supposed to produce a stimulus 
communicable along the fibers of the optic nerve. Certain other 
rates of vibration are capable of producing a change in the more 
complicated cone-pigment corresponding to the sensation of ‘‘red,’’ 
“‘oreen” ‘‘yellow” or ‘‘blue” respectively. It may be ventured as a 
suggestion in line with this theory that, if the complicated pigment of 
the cones is genetically related to that in the rods, it is also probable that 
in its process of formation it will pass through a stage like that in the 
rods. In this event, there will always be material in the cone capable 
of reacting to white light independently of a decomposition of the 
proper complicated pigment in its mature state. 

Up to this point no psychological question has been raised except 
in so far as in the use of language there has been an incautious impli- 
cation that there has been a mixing of sensations. But suppose wave 
lengths corresponding to red and blue impinge at the same time on the 
cones, then either the double stimulant causes a new kind or degree of 
chemical decomposition, or both the red and blue phases of decompo- 
sition are going on concurrently in different ingredients—at any rate 
the chemical resultant of this mixing zs @ nerve stimulus different from 
that for red or blue alone and must be conveyed along the fibers or 
fibrils of the optic nerve as such, or else the retinal ganglia, as a portion 


280 Journal of Comparative Neurology and Psychology. 


of the walls of the brain, may be supposed to convert the complex 
stimuli into an element of cortical reaction capable of taking a place 
in the equilibrium directly. There is certainly much in the structure 
of the retina to suggest codrdination of a high order, rather than the 
view that the sole tunction is to transmit the stimuli direct to the brain, 
and it is not improbable that the ganglia serve to impress upon stimuli 
their specifically offic character. The existence of centripetal fibers 
suggests accommodation processes in the retina itself. 

But none of these suggestions removes the mystery as to what 
actually passes over the optic nerve when we see. If a simple kind of 
chemical reaction formed by the vibration of w/o/e light produces a 
white sensation, there seems to be no reason to suppose that the other 
chemical process resulting from the mingling of various fractional light 
vibrations should go to the brain or receiving center as discrete stimuli 
each to produce a sensation, which separate sensations now unite to 
form a composite sensation, say of purple. We know no such psycho- 
logical process as this. Each color sensation is complete and discrete 
in itself. C. L. HERRICK. 


LITERARY “NOTICES. 


Mark Anniversary Volume. Mew York, Henry Holt and Company, pp. X1v, 
513, 36 plates, 1903. 


This volume, which contains in addition to twenty-five papers an 
excellent photogravure of Professor MARK, bears the inscription, ‘‘To 
Edward Laurens Mark Hersey Professor of Anatomy and Director of 
the Zodlogical Laboratory at Harvard University in Celebration of 
Twenty-five Years of Successful Work for the Advancement of Zodlogy 
from his former Students 1877-1902.” 

The following papers of the volume are within the scope of this 
Journal: 


Locy, William A. A New Cranial Nerve in Selachians. Art. III, pp. 39-55: 


This research is a careful description of a new cranial nerve, 
homologous with Pinkus’ nerve, in Sgualus acanthias, Mustelus cants, 
Raja, Carcharias littoralis, Syphrna tiburo and Scoliodon terrae novae. 
Its existence has also been determined in embryos of Zorfedo and in 
other selachians making in all 19 genera and 24 species of adults. 

In all the forms described the nerve enters the brain in the median 
furrow, usually on the ventral surface of the (secondary) forebrain. In 
Squalus, however, it enters midway between the dorsal and ventral 
surfaces and in the skate on the anterior dorsal surface. The fibers 
are traced in the brain to a mesial eminence of the infolded pallium. 

Peripherally the nerve is distributed to the nasal epithelium, the 
greater part going to the antero-lateral part of the olfactory cup. The 
exact termination was not ascertained. In some forms the nerve 
exhibits a ganglionic enlargement along its course. 

Embryologically the nerve has its own independent connection 
with the epithelium which precedes that of the olfactory nerve. 

Locy is inclined to homologize the nerve with the new nerve de- 
scribed by Prykus in Profopterus and by ALuIis in Amia—certainly the 
differences in point of connection with the brain would hardly justify 
one in seriously doubting the homology. Locy also thinks that ‘‘its 
separateness in origin and differences from all other olfactory radices” 
would justify its being called a ‘‘new nerve” even if it should prove to 
be an aberrant olfactory bundle. Apropos of this, the fact may be 


282 Journal of Comparative Neurology and Psychology. 


mentioned that in the adult skate the writer of this criticism has ob- 
served a number of medullated nerve fibers in the nerve in question. 

It is to be hoped that more information will be gained respecting 
the precise origin and termination of this nerve, also the precise nature 
of its ganglionic enlargements. On S.6Se 


Reighard, J. The Natural History of Amia calva Linnaeus. Art. IV, pp. 
57-109, pl. 7. 

The very commendable general standpoint of this work was to 
study the natural history and especially the behavior of a fish in its 
natural habitat. Practically all the observations and experiments re- 
corded were made in the field. That this method of working is neces- 
sarily a tedious and laborious one and produces results slowly will be 
apparent to everyone. The present paper stands as a model to show 
further that the method is capable of producing just as exact and de- 
tailed results as any laboratory work can, and of solving problems 
which never could be solved in the laboratory. The paper is not alone 
valuable as a considerable contribution to knowledge in a field where 
very little has been known, but also as an indication of the possibili- 
ties in work on the behavior of aquatic organisms in their natural en- 
vironment. 

Amia calva, the form chosen for study, is a fish which spawns in 
“nests.” It was this habit which first aroused the author’s interest in 
the subject, and the bulk of his work on the natural history of the fish 
has to do with its habits during the breeding season. A very careful, 
detailed description and analysis of its behavior during this period 
takes up the larger part of the paper. The nests are shallow circular 
areas on the bottom cleared of vegetation, and are built by the males, 
usually at night. Each nest is the property of a single male and is 
guarded by that male. If a female does not appear the male will 
finally abandon the nest. The spawning usually occurs at night and 
is intermittent. The females are not seen on the spawning grounds 
except when spawning. The behavior during the actual process of 
spawning is described. After the eggs are laid the male fish guards 
the nest until the larvae are about 12 mm. long. This stage is reached 
in about eighteen days, and at about this time the larvae leave the nest. 
While in the nest the larvae develop peculiar progressive swarm movye- 
ments. The individual larvae aggregate in a closely packed group, 
which from a distance looks like a solid black mass. Within this 
swarm group individuals behave much as do Paramecta caught in a 
drop of weak acid. When an individual comes by chance to the 
boundary of the swarm it reacts and turns back into the swarm again. 


Literary Notices. 283 


“*The larvae, though not progressing continuously as individuals, form 
a swarm which nevertheless progresses, one way and another, with 
many internal irregularities. The movement reminds one of the in- 
definite flowing movements of an Amoeba, in which pseudopods are 
put out this way and that and often withdrawn, but the animal as a 
whole progresses definitely.” This swarm formation and movement is 
a most interesting phenomenon and presents a number of problems 
deserving of further study. Particularly interesting would be an ex- 
perimental analysis of the reflexes and reactions of the individual larvae 
which result in the composite swarm effect when large numbers of in- 
dividuals are massed together. 

When the swarm of larvae leaves the nest it follows the male, ap- 
parently by scent. When separated from the male the schools of 
larvae do not make progressive movements as a whole, but circle 
about in the same spot until the male comes back. The larvae at this 
stage do not respond to a mechanical shock in the water, but at a later 
stage, when they have taken on bright colors and are from 30 to 40 
mm. long, the schools respond very quickly to mechanical shock by 
scattering and hiding in the plant material at the bottom. ‘The light 
reaction (negative to strong intensities) is more pronounced in the 
older, bright colored larvae. As the larvae grow larger the schools are 
less closely guarded by the males, and finally when they are about 100 
mm. in length the schools probably disperse. 

The paper is illustrated by a finely executed plate showing the 
coloration of Ama at three different stages in its life history. 

Raee: 


Eigenmann, C. H. The Eyes of the Blind Vertebrates of North America. V. 
The History of the Eye of the Blind Fish Amblyopsis from its Appearance to 
its Disintegration in Old Age. Article IX, pp. 167-204, pls. 12-15. 

In this, the fifth of his interesting contributions to the subject, 
Professor EIGENMANN gives a detailed account of the development of 
the eye of the cave fish Ammblyopsis. The eggs of this species are of 
large size and carried in the gill chamber until the embryos are 10 mm. 
in length. Egg bearing females were taken in March and April. The 
object of the research was to compare the development of degenerate 
and of normal eyes, and to determine (1) whether the development of 
the degenerate organs is direct or palingenetic, (2) whether there is a 
constant ratio between the extent and degree of phylogenetic and onto- 
genetic degeneration, (3) the causes leading to these degenerative 
changes, and (4) whether there is evidence that rudimentary organs are 
retained by the embryo because they are of use to it, although useless 


284 Journal of Comparative Neurology and Psychology. 


to the adult. The stages of development of the eye are divided into 
four periods. 

During the first period (from appearance of first protovertebrae to 
embryos 4.5 mm. long) the optic vesicle and lens are formed as in 
normal embryos, but there is retardation in cell-division and growth. 

In the second period (embryos 5 to ro mm. long) the optic nerve 
forms; its diameter is only 12 micra and it does not increase in size. 
The lens separates from the ectoderm but its cells do not differentiate 
into lens fibers and degenerate before the end of the period. A rudi- 
mentary iris forms from the margins of the optic vesicle ; the cavity of 
the vesicle is practically obliterated, and the choroid fissure becomes a 
groove which may remain open. In the retina the pigment layers and 
inner reticular layer are developed; outer and inner nuclear layers 
are not differentiated, nor are the cones or dividing cells present as 
would be the case in the normal eye. 

The third period (length from 1o to roo mm.) is characterized by 
the degeneration of the nerve cells of the retina, the sinking of the 
eye to a position 5 mm. beneath the surface of the skin, the closure of 
the pupil and the complete disappearance of the vitreous body. Scle- 
ral cartilages show progressive development. 

During the fourth period (fish more than too mm. long) the 
scleral cartilages become well developed and the eye muscles show no 
signs of degeneration. The pigment layer of the retina forms a thin- 
walled vesicle of considerable size while the nervous layer is less than 
o.2 mm. in diameter and is markedly degenerate. In one individual 
observed the eye was completely disintegrated. 

The author concludes ‘‘that there is no constant ratio between the 
extent and degree of ontogenic and phylogenic degeneration.” From 
the rapid degenerative changes observed in ontogeny it is evident that 
the ultimate fate of the eye of Amdlyopsis is total distinction. 

The incomplete development of the eye is due (r) to retardation 
and final cessation of cell division; (2) to retardation of morphogenic 
processes; (3) to the extinction of histogenic activity. All three 
phenomena weaken as development proceeds. This may be caused 
by external or internal influences. As, however, the eye remains de- 
generate in individuals reared in the light, and is well developed in 
other cave-inhabiting species, the factor of light may be eliminated. 
There is moreover, no evidence to show that atrophy is due to pressure 
from other organs or to lack of nutrition. It only remains to conclude 
that the causes of the degeneration are inherent in the ovum and are 
inherited by the embryo. 


Literary Nottces. 285 


In discussing the law of biogenesis and the significance of rudi- 
mentary organs EIGENMANN points out that the eye is not retained by 
the embryo Amblyopsis because it is a functional organ at this stage, 
since during cave life the eyes are as useless to the young as to the 
adult. Go We (Pi 
Linville, Henry R. The Natural History of Some Tube-forming Annelids 

(Amphitrite ornata, Diopatra cuprea). Art. XI, pp. 227-235. 

This paper gives a description of the tube-forming activities of 
the two annelids named in the title. Amphitrite constructs a U-shaped 
tube of mud and sand collected by the tentacles and held in place by 
mucus. The tube begins as a ring immediately behind the bases of 
the tentacles and the gills, and as the process of building is continued 
this ring is pushed backward by muscular action to make room for the 
materials which are brought by the tentacles. The author calls atten- 
tion to the curious fact that this annelid is unable to reconstruct a new 
tube after the whole of its original tube has been removed. This he 
thinks, is due possibly to the absence of a stimulus from the tube which 
ordinarily initiates tube-repairing activities. The worm when young 
possesses an instinct which determines the construction of a tube, but 
this instinct after the formation of the first tube becomes valueless 
and disappears, hence when the animal is stripped of its tube it is un- 
able to begin a new one. The presence of even a small portion of the 
old tube, however, is sufficient to initiate the appropriate tube-building 
actions. 

Diopatra constructs a tube of sand, pebbles, bits of glass or any 
other material within reach. According to the observations of Dr. 
LINVILLE, it gives no evidence of selection of materials. The particles 
gathered are glued together with mucus secreted by the ventral glands. 
The animal first places a few pebbles in position then rubs the glands 
over them until they are firmly cemented. If, during the gluing 
process, the tentacles be touched with a piece of stone the process at 
once ceases, and the animal begins to gather material again. Thus 
the tactile stimulus determines the activity. The author mentions 
several interesting observations in connection with food taking and 
respiration. Ria M0, We 


Neal, H. V. The Development of the Ventral Nerves in Selachii. I, Spinal 
Ventral Nerves, Art. XV, pp. 291-313. 


While this research by no means clears up definitely the much 
discussed question of the histogenesis of the peripheral nerves, it nev- 
ertheless is a useful contribution and will serve to deter many from ac. 


286 Journal of Comparative Neurology and Psychology. 


cepting uncritically the results of such recent researches as those of 
BaLLAnce and Srewarv and of BETHE. 

The method relied upon chiefly was fixation and staining by vom 
Ratn’s fluid, followed by pyroligneous or pyrogallic acid. The research 
contains a number of careful drawings. It is rather to be regretted, 
perhaps, that black and white drawings and line reproductions were 
used. Outlines of cells and fibers are of great importance in such a 
research and the effect of such a method of illustration must inevitably 
be to exaggerate their definiteness as compared with the actual prep- 
arations. 

The first neuroblasts are found to be developed not from rounded 
‘‘cerminative” cells, but from the ordinary epithelial cells of the neural 
tube. The neuraxone is formed before any migration takes place. 
NEAL agrees with DoHRN, BeTHE and others in asserting a migration 
of the cells from the neural tube along the ventral root. This view 
certainly seems to be now best supported and makes it easier to under- 
stand the processes of histogenesis and regeneration if such views as 
those of BALLANCE and Stewart and BErHE be correct. NEAL, how- 
ever, denies that these migrated cells take part in the formation of the 
ventral root fibers and believes they form the neurilemma, possibly 
also contributing to the connective tissue sheaths and the sympathetic. 
The migration of the cells is shown by the presence of cells half in 
and half out of the medullary wall, also by their presence in the part 
of the nerve next the neural tube. NEAL is also inclined to believe 
that mesenchyme cells contribute extensively toward the formation of 
the neurilemma. 

These migrated cells of the ventral nerve are believed to have noth- 
ing to do with the formation of neuraxones because they are peripheral 
to and with their long axes perpendicular to the fibrous portion of the 
nerve when the neuraxones are forming most rapidly, because they do not 
exhibit the staining reactions of the cells of the dorsal ganglia, because 
they do not undergo the characteristic changes of shape of the latter 
and because nothing resembling a neuraxone was to be found in their 
cytoplasm, On the other hand, the spinal ventral nerves in their 
earliest stages of development certainly ave processes of medullary cells 
and devoid of nuclei and the same continuity can be made out later. 
The number of neuroblasts whose axones can be traced into the nerve 
also corresponds with the estimated number of neuraxones in the nerve. 

These reasons bring Neat to the conclusion that the process the- 
ory of the development of the ventral nerve fibers is the correct one. 
NEAL thus agrees with the prevailing view of His, though differing 


Literary Notices. 287 


from him regarding the earlier differentiation of neuroblasts and regard- 
ing the migration of cells into the ventral root from the neural tube. 
There would seem to be important differences between the histogenesis 
of the ventral nerves in the shark and the chick when we compare this 
account with BETHE’s. OuSe.S. 


Jennings, H. S. Asymmetry in Certain Lower Organisms, and its Biological 
Significance. Art. XVI, pp. 315-337. 

In addition to the commonly recognized radially symmetrical and 
bilaterally symmetrical types of organism, there is, as JENNINGS points 
out, another type of structure which may be called the spiral type, since 
the organisms necessarily move in a spiral course, or the one-sided un- 
symmetrical type. An unsymmetrical organism, were it not for rota- 
tion about its long axis, would move in a circular instead of a spiral 
course. 

Organisms which move in a spiral course maintain a definite posi- 
tion with reference to the axis of the spiral ; the same surface always 
faces outward, the same inward. In most of the unsymmetrical or- 
ganisms it is noticable that reactions do not differ in form according to 
the location of the stimulus, as in more highly organized animals, but 
that no matter which side is stimulated the animal always turns in the 
same direction. 

The relation of structure to behavior is considered in detail in 
ease of the Infusoria and Rotifera, and the author concludes that there 
is always striking adaptation of structure to the ‘‘mode of life and 
movement.” 

In criticism of the author’s conclusions one might say, certainly 
there can be no doubt of the close correlation of structure with mode 
of life, but is it so clear that structure is an adaptation to behavior 
rather than behavior to structure? Rather, it would seem impossible 
that either could in all cases be an adaptation to the other. Possibly 
our safest position would be to consider both adaptations to something 
which is not to be described as either structure or mode of life. 

The paper emphasizes the importance of studying structure and 
behavior side by sile, and of attempting to arrive at definite knowl- 
edge of their correlation. tay 0s aXe: 


Floyd, R. A Contribution to the Nervous Cytology of Periplaneta orientalis, 
the common Cockroach. Art. XVII, pp. 341-357, pls. 25-27. 


By a careful series of experiments the author has determined the 
effect of various fixing reagents on the structure of nerve cells from 
the thoracic ganglia of the cockroach. Tissues fixed in vom RAtTH’s 


288 Journal of Comparative Neurology and Psychology. 


fluid, picro-formalin, VAN GEHUCHTEN’Ss fluid, corrosive sublimate and 
chrom-oxalie acid showed more or less shrinkage of the cytoplasm and 
injury to its finer structure. In all the cells of these preparations a 
central, darkly staining, granular region was demonstrated, and a peri- 
pheral zone formed by a network of fibrillae. In the nerve fibers the 
fibrillae also exhibited anastomoses. Fresh, living ganglia, stained 
with Nissu’s methylene blue and studied in normal salt solution, 
showed little or no skrinkage of the cytoplasm. They were entirely 
devoid of a cell membrane, and though the fibrillar networks were 
clear and distinct, there was no evidence of the darkly staining gran- 
ules characteristic of fixed tissues. This normal structure was also 
observed when ganglia were fixed by the vapor of formalin, and when 
stained with methylene blue and fixed with ammonium molybdate ; 
graded formalin and diffused alcohol are recommended for larger 
masses of tissue. In agreement with Hep, the author finds that the 
chromophile granules (Nissi substance) are not normal structures but 
are formed in the cytoplasm both during post-mortem changes and 
during the action of most fixing reagents. The substance is not de- 
monstrated by staining after treatment with sodic hydrate nor after pro- 
longed faradization ; probably not after strychnine poisoning. Arsenic 
poisoning causes an increase in the amount of the substance present 
in the cells. 

These observations are at variance with the results of BerHE and 
von LENHOSSEK, who saw the NIssi’s plates in living nerve cells of 
vertebrates. From various other points of evidence BETHE maintains 
that the Nissi substance is a normal product of the cells. It is un- 
fortunate that the author did not have opportunity to study the fibrillar 
structures which he describes by more specific staining methods. The 
evidence of preparations obtained by Berue’s toluidin blue method 
would not support Dr. FLoyn’s statement that a general anastomosis 
exists between the neuro-fibrillae of nerve fibers. 

The conclusions of this paper are of great value. They show 
that most of the common fixing reagents cannot be depended upon 
for the preservation of delicate nerve cell structures, and em- 
phasize the necessity, too often overlooked, of studying fresh tissues 
to control results obtained from fixed material. Ch Wraps 


Literary Notices. 289 


Yerkes, Robert Mearns. Reactions of Daphnia pulex to Light and Heat. 
Arts << Vill pps 359-3717. 


The author defines as phototactic ‘‘all those reactions in which the 
direction of movement is determined by an orientation of the organism 
which is brought about by the light,” and as photopathic, those ‘‘in 
which the movement, although due to the stimulation of light, is not 
definitely directed through the orientation of the organism.” ‘‘In both 
intensity of the light, not the direction of the rays, is the determining 
factor. 

Daphnias were introduced into a flat dish of water illuminated 
only by a band of light focussed on the bottom and measuring 1 x 16 
cm., one end of which was brighter than the other. The animals 
swim into an intensity of roo candle-power and remain there, and they 
do this even when the adiathermal screen is not used, so that they die 
of heat within a few seconds after reaching the brightest spot. ‘There 
is no evidence of an ‘optimal’ intensity between o and too candle- 
power.” The directive influence of light grows no less as the animals 
progress toward their goal, i. e. there seems to be no ‘‘adaptation,” 
nor is there any evidence of fatigue. A sudden change in the inten- 
sity of the light is a stronger stimulus than a gradual change. The 
brighter the light the faster the progress of the animals, and this is due 
not only to the greater precision of orientation but also (contra DAVEN- 
porT and CANNON) to swifter swimming movements. 

Daphnias are negatively thermotactic at a temperature of 28° C. 
The thermotactic reaction is elicited by the actual temperature of the 
water about them, whereas the radiant heat accompanying light has no 
appreciable influence. The thermotactic ‘movement is not direct, 
but irregularly wandering. It is, however, in all probability due to 
differences in the intensity of stimulation for different regions of the 
animal’s body and is therefore in principle the same as the photopathie 
reaction,” or the phototactic. Fag Bs vil: 


Sargent, Porter Edward. The Torus Longitudinalis of the Teleost Brain ; 
its Ontogeny, Morphology, Phylogeny and Function. Art. XX, pp. 399- 
416. 


The interesting longitudinal thickenings of the roof of the mid- 
brain known as the torus longitudinalis has been the subject of several 
researches by the above author, whose previous results are here in part 
summarized and also extended over more forms. A description is 
given of its variations in certain members of the Siluridae, Cyprinidae, 
‘Salmonidae, Amblyopsidae, Gasterosteidae, Atherinidae, Sciaenidae, 


290 Journal of Comparative Neurology and Psychology. 


Labridae and Pleuronectidae. In general its development is found to 
vary pari passu with the development of the optic lobes and visual ap- 
paratus, especially shown by its small size and simple structure in the 
cave-inhabiting fishes. It is found, in a rudimentary state, in Amphi- 
oxus, is present also in Cyclostomes, is more developed in ganoids, 
but reaches its climax in teleosts. In the latter the large cells of its 
homologues in other forms (Dachkern and nucleus magnocellularis) are 
replaced by a greater number of smaller cells. 

The torus cells ‘‘are usually bipolar, but may be unipolar or multi- 
polar. In every case, however, three neurites ultimately arise from 
the cell, either directly or indirectlf by the division of a chief pro- 
cess.” The dorsally directed neurites are non-medullated and form 
two tracts. One of these, the tractus toro-tectalis, breaks up in the 
superficial fiber zone of the tectum, there coming in contact with optic 
nerve terminals. ‘The other tract, the tractus toro-cerebellaris, passes 
laterad to the dorsal decussation and thence ventrad parallel with the 
posterior commissure. It is difficult to trace, but SARGENT believes 
it to be identical with JOHNSTON’s tractus toro-cerebellaris in Aczpenser. 
‘The chief centrifugal neurite, or axone,” of the torus cells is some- 
what coarser. These neurites form several fasciculi which ultimately 
‘unite to form the fiber of ReIssNeR which runs posterior into the 
canalis centralis and through the posterior portion of its course gives 
off branches which enter the ventral part of-the cord and probably run 
to the musculature.” 

These important relations of the processes of the torus cells are 
only illustrated diagramatically by figures. Such schemata should al- 
ways be supported by drawings of the elements in question as shown 
in the preparations that we may be sure how far and how precisely the 
cell processes have been actually traced. It is often surprising upon 
how few direct observations many an extensive neurological schema 
rests. Such drawings are especially demanded where the relations are 
so unusual. This defect in the present instance has been partially 
supplied by the author’s figures in previous articles and will undoubt- 
edly be completely remedied in the more extended publication an- 
nounced as in press. 

The physiological significance, according to SARGENT, of the fiber 
of REISSNER and of the toro-tectal tracts is that they constitute a short 
circuit for quick optic reflexes. Such a view rests in part upon the 
assumption that there are no other ‘fone neurone” paths from tectum 
to motor nuclei in the cord, which is probably not the case ; and that 
the fiber of RrISSNER passes out directly to the muscles. he latter 


Taterary Notices. 291 


is asserted above but not demonstrated, though the course of the mes- 
encephalic root of the trigeminus would support such a view. This 
view hardly furnishes an explanation of the peculiar position of ReEtss- 
NER’s fiber. On S28. 

Parker, G. H. The Phototropism of the Mourning-Cloak Butterfly Vanessa 

antiopa Linn. Art. XXIII, pp. 453-569, pl. 33. 

V. antiopa orients itself in sunlight with its head away from the 
sun and so that a straight stick held vertically at an appropriate point 
casts a shadow that falls exactly on the length of the butterfly’s body. 
So invariably is the head directed away from the sun that when rest- 
ing on tree trunks the butterflies face toward the foot of the tree. If 
the surface on which it rests ‘‘is perpendicular to the sun’s rays the in- 
sect settles without reference to the direction of the rays.” Neverthe- 
less, ‘‘V. antiopa creeps and flies toward a source of light, that is, it is 
positively phototropic in its locomotor responses.” This positive pho- 
totropism of flight or other locomotion and negative phototropism in 
rest are otherwise not unknown. 

Now the author finds that the resting animal keeps its wings spread 
in sunlight and that the position of negative orientation most fully ex- 
poses the wings to light and makes the insect conspicuous. The habit 
is therefore probably a means of bringing males and females together, 
Furthermore, it is the eyes which govern the reaction, since any part 
of the body except the head may be shaded without disturbing the 
animal, which, however, flies away if the head is shaded. This ob- 
servation is confirmed by various experiments on animals of which the 
eyes have been painted over. If one eye is blackened, that side of 
the insect keeps in motion and the body moves ‘‘in a circle, with the 
unaffected eye toward the center.” If both eyes are blackened, the 
insect does not come to rest, but flies upward, showing a negative geo- 
tropism which is readily verified on normal individuals in a perfectly 
dark room. 

V. antiopa discriminates little, if at all, between different intensi- 
ties, much more between lights of different area. It ‘‘remains in flight 
near the ground” and, although in locomotion positively photropic, does 
not fly upward toward the sun, ‘‘because it reacts positively to large 
patches of bright sunlight rather than to small ones, even though the 
latter, as in the case of the sun, may be much more intense.” These 
reactions are probably based on retinal images which the insect gets. 
If the sun is clouded over the animals fold their wings. 

The ‘‘heat-rays” of sunlight seem not to influence the reactions, but 
an actual change of temperature of the air is effective. A marked de- 


292 Journal of Comparative Neurology and Psychology. 


crease in temperature, as at night-fall, independent of any decrease in 
light, causes the insets to settle down; and it is probably the daily 
changes of temperature which make JV. antiopa retreat into hiding- 
places at night and emerge in the morning. 

It is not true, as has been paradoxically alleged, ‘‘that moths, 
which avoid daylight, fly into a flame at night, while butterflies, which 
fly by day, do not possess this fatal instinct.” Butterflies also fly into 
aflame. The author does not confirm the hypotheses put forward by 
Loer and by DAvENPoRT in order to explain this supposed paradox. 

E, Baek 


Hyde, Ida H. The Nerve Distribution in the Eye of Pecten Ivradians. Art. 
XXIV, pp. 473-482, pl. 34. 


The application of improved methods in histological research to 
the eye of Pecten indicates, according to the findings of Dr. Hype, 
that the descriptions of this organ given by Parren, HENSEN and oth- 
ers are not entirely reliable. 

A brief but clear description of the histology of the organ is given, 
and the author then turns to amore detailed consideration of the nerve 
supply and of the retinalelements. The main conclusions of the paper 
are thus stated: 1. The rods are not, as was formerly supposed, 
innervated by fibers from at least three series of nerves. ‘‘2. The so- 
called retinophorae are not the visual sensory cells whose peripheral 
fibers form the basal optic nerve, but they are the supporting cells of 
the median layer of the retina. 3. The inner ganglionic cells do not 
connect with the side branch of the optic nerve, but are the nerve- 
cells of the bipolar nerve elements. 4. The outer ganglionic cells form 
a single layer whose inner fibers are disposed in a special reticular 
structure in the retina and whose outer fibers make direct connection 
with the side branch of the optic nerve.” 

The author believes that the visual apparatus of the retina is com- 
posed of afferent and efferent neurones, and that the rods are true 
peripheral visual neurones. 

The text is accompanied by an excellent plate which gives the 
general histology of the eye in one figure, and in others the details of 
structure of the retinal’ elements, together-with their ganglionic con- 
nections. R..iMa We 


GME ASSOCIATIVE PROCESSES OF, THE-GUINEA 


By Jesste ALLEN. 


CONTENTS. , 


INTRODUCTION. Review of literature. Problem of the work. 


PAR Te 


THE ASSOCIATIVE PROCESSES OF THE GUINEA PIG. 


l. Habits of Guinea Pigs. 


HL. 


Jtitite 


lV. 


V. 


Characteristics of the Developing Chea Piz; 


A. Description of the young guinea pig at birth. 
Test I. Is the mother a specific stimulus for her young ? 
B. Experimental work. 
Introduction. < 
Test II. Recalling a simple Ger 
Test III. Alteration in habit. : c 
Test IV. Does the odor of the previous neth furnish the 
stimulus ? ; : 
Test V. Complexity of associations. 
C. Summary of work with young. 


‘Lexperiments with the Adult. 


Test VI. Preliminary. . 

Test VII. Distinction of stimuli. 

Test VIII. Learning a labyrinth. 
Conclusions from the labyrinth experiment. 
Test IX. Learning without the aid of vision. 
Conclusions from the four tests. 

Test X. Preference for the dark. 

Test XI. Means of orientation. 

Test XII. Efficiency of contact stimuli ioe fallow a ancl 
Conclusions from Tests X, XI and XII. 
Summary of work with adult. 


The Development of the Guinea Pig Compared with that of Ve 


White Rat. 


The Psychic Life of the ae Pig Goan with that of the 


White Rat. 


[ 1] 


Pia oes LUDY-OF Tir BSYCHICAL DEVEL 
OPMENT OF AN ANIMAL WITH A NERVOUS 
SY ole WELL MEDUELATED AT BIRTH. 


QO Go 
b&w BK HN KH w= 
bh ONNWQ =O 


BK WwW WD Fo KH W Ww W Lo 
ios) 


Ko W W G GW Lo 
Qa 5 


is) 
Go 
oo 


294 Journal of Comparative Neurology and Psychology. 


Part II. THE CENTRAL NERVOUS SYSTEM OF THE GUINEA Pic. 
Introduction. : : : 2 : : ; : : 
Z. Description of Transverse Sections Through the Meduila Spinalis 
of the Guinea Pig at Birth. 


Cervical. 


Co ww 
+ + 
_ -_ 


abe 
ve 


Thoracic. 


as 
nn 


to W & Lo 
f 
ios) 


Lumbar. : : : : : : : : 
11, Development of the Medulla Spinalts from Birth to Maturity. 347 
Cervical. : ; : : F : ‘ : : 347 
Thoracic. : : : , : : : : 349 
Lumbar. : : 5 : : : : ° 3 
Summary of changes in medullation of the medulla spinalis. 350 
Increase in area of cross-sections of the medulla spinalis 


from birth to maturity. 25 
TIT. The Encephaton of the Guinea Pig. 353 
Cerebrum. : : . ; : ; . yO 852 
Development of the cerebral hemispheres. ' : BIG 
Cerebellum. : : : 2 : : 356 
Increase in the area of cross-sections of the encephalon. 357 

ZV. Comparison Between the Nervous System of the Guinea Pig 
and that of the White Rat. . ; : : ; 358 


INTRODUCTION. 


In the study of animal psychology the attem pt is made to 
understand in their simplest manifestations the psychical fac- 
tors entering into reactions to stimuli. 

With this in view reactions of all grades of intelligence 
have been investigated. Two different points of view have 
given opposing interpretations of the phenomena manifested by 
the lower animals. 

M. Binet! has observed the reactions of Paramecia to 
acids and alkalis, and has concluded * that an action of adapta- 
tion involves spatial perception of the external object, choice 
between objects and movements of approach or avoidance. 

On the other hand, JENNINGS” gives a physio-chemical ex- 
planation of these same reactions. All the movements of ap- 
proach and retreat are automatically performed without regard 
to the ‘‘pleasure”’ or ‘‘pain’’ involved. The mechanism of the 

' Binet. Psychic Life of Micro-organisms. Transl., Checago, Open Court 
Pub. Co., 1889. 
2 P60: 


3H. S. JENNINGS and E. M. Moore. Studies on Reactions to Stimulj 
in Unicellular Organisms, VIII. Amer. Jour. Physiol., Vol. V1, 1902. 


[ 2] 


ALLEN, Association in the Guinea Pig. 295 


movements is put into play by the physical or chemical proper- 
ties of the medium. 

The insects exhibit a comparatively complex organization. 
Lussock and Romangs attribute a high degree of psychical devel- 
opment to bees, wasps, spiders and ants. Dr. and Mrs. PEcK- 
HAM are more conservative, but conclude that there are pres- 
ent memory, spatial perception, and occasional adaptations of 
means to end. 

ALBRECHT BETHE! represents the extreme mechanical in- 
terpretation of insect activities, believing them to be expressi- 
ble in terms of immediate sensory stimuli followed by the motor 
response. 

BETHE'S principal opponent is AuGcust ForEL,” whose re- 
cent work on the ants leads him to conclude ‘‘that sensation, 
perception and association, inference, memory and habit follow 
in the social insects on the whole the same fundamental laws as 
in the vertebrates and ourselves. Furthermore, attention is 
surprisingly developed in insects." These faculties are, how- 
ever, manifested in a feeble form. 

Loss * is inclined to attribute a small amount of intelligence 
to ants. The question here is whether these animals do or do 
not have any psychical life. The criterion of intelligence now 
generally used in experimental work with lower animals is that 
of educability. LoEs* discusses the distribution of the associa- 
tive processes among the lower animals. When his book was 
published only tree frogs, among frogs, were known to possess 
memory. 

YERKES,’ in an extended series of careful experiments, 
finds that the green frog has associative processes, but that as- 


' BETHE. Diirfen wir den Ameisen und Bienen psychische Qualitéten 
zuschreiben ? Arch. f. d. ges. Phystologte (PFLUGER’S), LXX, p. 15, 1898. 

» FOREL. Ants and Some Other Insects. (Translated by W. M. WHEELER.) 
Monist, Vol. XIV, pp. 33-66, 177-193, 1903-1904. 

3 LoEsB. Comparative Physiology of the Brain, 1902, p. 224. 

peloe city, Pps 210) sh: 

° YERKES. The Instincts, Habits and Reactions of the Frog. Harvard Psy- 
chological Studies, Vol. I, 1902. 


296 Journal of Comparative Neurology and Psychology. 


sociations are very slowly acquired. The sensory elements 
which enter into them are visuai, tactual and kinesthetic. 
YERKES used a simple labyrinth, testing the frog’s memory ofa 
path to water; he kept records of time as well as of movements 
made. A straight path was learned by a process of selection 
from random movements of those which led to the desired 
object. 

YERKES work on the crustaceans stands almost alone. 
The green crab and the crawfish both profit a little by experi- 
ence and learn simple labyrinth paths.’ BetTHE had shown that 
Carcinus maenas could not readily learn to inhibit deep-seated 
instincts.” SPAULDING® finds that hermit crabs profit by experi- 
ence with considerable rapidity when visual and taste sensations 
may be associated. 

Upon comparing the fish, the frog and the turtle * 
YeRKES found that the turtle’s associations were formed most 
rapidly, a somewhat complex path being learned in five trials. 

Very little other experimental work has been attempted 
with animals of this grade. TrripLterr’ found that perches can 
remember a glass partition which has been removed from the 
aquarium. He verified the possibility of teaching pikes to in- 
hibit their habit of devouring minnows (MogEsius’ experiment). 

DeveoevrF ° has observed lizards in captivity and finds that 
they differ in disposition and intelligence. They can remember 
people and places, and they seem to possess the higher emo- 
tions as fear, love, jealousy. 

| R. M. Yerkes and Gurry E. Hucorys. Habit Formation in the Craw- 
fish. Harvard Psychological Studies, Vol. 1, 1902. 
VERKES. Habit Formation in the Green Crab, Carcinus granulatus.  Buo- 
logical Bulletin, Vol. Ill, 1902. 
2 BeTHE. Das Centralnervensystem von Carcinus maenas. II Theil, Arch. 
f. mkr. Anat., Bd. LI, p. 447. 
3 E.G. SPAULDING. Association in Hermit Crabs. /our. Comp. Neurol. 


and Psychol., Vol. XIV, p. 49, 1904. 
+ VERKES. Formation of Habits in the Turtle. Pog. Sc?. Mo., LVIII, p. 519, 


1901. 

6 TRIPLETT. The Educability of the Perch. Amer. Jour. Psychol., Vol. 
XII, p. 354, 1901. 

6 Dre_porur. The Affections and Jealousies of Lizards. Pop. Sci. Mo.. 


Vol. L, 1897 and Revue Scientiigue, Vol. IV, pp. 363-307, 690 and 805. 
/ g PP- 393-397, 09 


[ 4] 


ALLEN, Association in the Guinea Pig. 297 


Animals with complex psychical processes have been 
studied more extensively than the lowest forms, and the work 
done here comprises the principal literature in animal psychol- 
ogy. The classical treatises of Principal Ltoyp MorGan are 
the model and the stimulus for all subsequent investigation. A 
recent book of his, ‘‘Animal Behavior,” contains summaries 
and critical notes of all new literature on animal psychology, 
and a timely discussion of the current conceptions and hypo- 
theses. 

MorGan, who has worked with chicks especially, finds 
memory, intelligent. adaptations and a considerable discrimina- 
tion of objects among birds. Besides the numerous researches 
upon the chick, few other birds have been observed with re- 
spect to their psychical processes. 

Wes.ey Mitts’ is among the pioneers in the field of ex- 
perimental psychology. His observations upon a large number 
of animals, and suggestions concerning the correlation between 
physical and psychical development, are of especial value as 
recognizing the problems and methods of most recent investi- 
gations. 

The employment of the laboratory method of observation 
and experimentation has led to fruitful results in that, as condi- 
tions are known and controllable, explanations of given reac- 
tions may be made with a greater degree of assurance. 

THORNDIKE has given explicit and clear-cut formulation to 
the method of experimentation with animals. His free-and-easy 
psychological terminology, with his desire for a severely scien- 
tific interpretation of results, as well as unusual confidence in 
the meaning of facts observed, stimulate competition, not to say 
contradiction. My work on the guinea pig has been under- 
taken from a point of view somewhat similar to that assumed 
by THORNDIKE; viz., the point of view that the law of parsi- 
mony must govern interpretation, and a sufficient number of 
control experiments must condition every statement made. 
Reference will be made to specific points of THoRNDIKE’s work 
as occasion arises. 


'Mitis. The Nature and Development of Animal Intelligence, 1898. 


Lee 


298 Journal of Comparative Neurology and Psychology. 


Hosuouse, the latest author in the field of animal psychol- 
ogy, has brought keen psychological analysis to bear upon the 
results of a close experimental study. A dog, a cat and a mon- 
key furnished the best material, while other animals gave cor- 
roborative data which, if not taken by HosuouseE himself, were 
controlled and edited by him. 

HosuousE is more generous in his estimationiof his ani- 
mals than is THORNDIKE, perhaps because the psychical mani- 
festations for which he looks are clearly defined and character- 
ized in his own mind. An advanced grade of intelligence is not 
vaguely suggested by the term ‘‘free ideas,’’ but is discussed in 
concrete and comprehensive statements about ‘‘the practical 
judgment,’’ and the ‘‘practical idea.’’ By a practical idea is 
meant ‘‘the function which directs action, not necessarily in ac- 
cord with habit or instinct, to the production of a certain per- 
ceptible result. It is further a necessary part of such an idea 
that it rests on a perceptual basis, and is capable of being 
brought into relation with another such idea, for example, as 
means to end.” . . . ‘‘The correlation of’ such an idea with a 
remoter end, I call a practical judgment.” ! 

The possession of practical ideas and the ability to make 
practical judgments Hosuouse attributes to dogs, elephants, 
cats, otter, monkeys and chimpanzees, those being the animals 
which he examined. 

The work of Kine,” followed by that of SmaLt,’ has direct 
bearing upon the problem of the present investigation. The 
life habits of the white rat as described by SMALL, present many 
points of contrast with the habits of the guinea pig. SMALL 
furnishes a diary of the young white rat, in which its immaturity 
at birth and subsequent development are described, and later 
its intellectual development as shown in ability to learn a laby- 
rinth and to solve other simple problems. 

In the study of the psychical processes of the guinea pig I 
have tried to determine: 


1 Hopuouse. Mind in Evolution, p. 207, 1901. 
2 Amer. Jour. Psvchol., Vol. X, p. 276, 1898. 
% Amer. Jour. FPsychol., Vol. XI, p. 80, 1899. 


eal 


ALLEN, Association in the Guinea Pig. 299 


(1) What processes are characteristic of the adult guinea 
pig. 

(2) How these processes develop from birth to maturity. 

More specifically, it was undertaken to show what prob- 
lems could be learned, at what age the most complex problems 
were first learned (thus affording an indication of psychical ma- 
turity), and what elements contributed to the learning of the 
problem. As far as possible, the purpose was to gain an in- 
sight into the psychical processes of the guinea pig. 

The problem and method of work were suggested to me by 
Professor ANGELL and Professor Donatpson. They have con- 
stantly defined the inquiry, and indicated the general bearing of 
particular observations. 

The investigation is a complement to that made by Dr. 
Watson in this laboratory, and to his work’ there will be con- 
stant reference; before the close there will be a comparison of 
our results with deductions from them. Iam under obligation 
to Dr. Watson for constant suggestions and help, as well as for 
the method of work.’ 

However, it is quite essential, both from a psychological 
and a neurological point of view, that this work should be un- 
dertaken. The white rat is born very immature, its eyes are 
not yet open, it is naked, its nervous system is entirely unme- 
dullated. The guinea pig, a rodent closely related to the white 
rat is, on the other hand, born very mature. It is quite able 
to take care of itself at birth, has full possession of all its senses, 
is well covered with hair, and, as will be seen, its nervous sys- 
tem is almost completely medullated. The psychical imma- 
turity of the white rat is such as would be expected from its 
physical immaturity; whereas the guinea pig has a compara- 
tively complete mental equipment at birth. 


1 Joun B. Watson. Animal Education, Chicago, 1903. 
2yeocs cits, Pp. 5-0: 


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Part I. THE ASSOCIATIVE PROCESSES OF THE GUINEA Pic. 


From the literature we can glean very little concerning 
guinea pigs in the feral state. Originally from South America, 
they were brought to Europe for pets soon after the discovery 
of the new world. They were first named, pictured and de- 
scribed by GEsNER in his Natural History Folio.' GEsNER 
knew it as ‘‘indische Kaninchen,”’ or ‘‘indisthe Schweinchen,”’ 
indicating the current belief that its home was a part of Asia. 
Many other names were applied to it in the first descriptions. 
ALFRED BReEuHM calls it ‘‘Huf-pfotler” (hoof- or claw-footed). 

The pets brought to England were smooth, short-haired 
and slender, and are now known as English cavies, or common 
guinea pigs. When they were interbred with different varieties 
in the London Zoological Garden, and with the French cavy, 
other breeds were produced, and there are now four varieties 
recognized by fanciers—the English, Abyssinian, Angora and 
Peruvian cavies.” 

The variety used in this investigation was the English 
cavy, though individuals of all varieties have been under obser- 
vation without giving evidence of any characteristic differences 
in habits or intelligence. In one case a series of experiments 
was made with a solid red Peruvian (probably not of pure 
stock, however), and numerous minor experiments were made 
with other varieties. No difference was found between them 
and the common guinea pig. 


I. Ffabits of Guinea Pigs. 


So far as we have been able to observe, all or nearly all the 
activities of guinea pigs may be termed instinctive, since they 
are present from birth and hence are carried out without pre- 
vious training or experience.’ Certain characteristic modes of 


1 GESNER. Appendix historiae quadrupedum viviparorum Conradi Gesneri 
Tigurini, Zurech, 1554. 

* Mrs. STANLEY WALKER MIRICK, ‘“‘All About Cavies,”’ published by Amer- 
zcan Stockkeeper, Boston, 1901. 

3 LLoypD MorGAN. Animal Behavior, pp. 63-71, 1902. 


[ 8] 


ALLEN, Association in the Guinea Pig. 301 


behavior which develop shortly after birth with the perfection 
of the muscular coordination, may be termed ‘‘deferred char- 
acteristics.” . 

Individual differences in habitual behavior of the guinea 
pig may be considered either as intelligent adaptations, or as 
accidental variations; probably when these slight modifications 
are analysed, the more tenable view will be that the majority of 
the individual characteristics are variations. Individual charac- 
teristics show themselves in rapidity of movement, habitual ac- 
tivity, tameness, adaptability to changing situations, and in such 
habits as climbing, gritting the teeth, squealing, etc. 

Certain characteristics become modified and altered as time 
goes on. One group of guinea pigs at first chuckled a great 
deal, the cause of which i am unable to state. Appar- 
ently the noise was made by the rapid gritting of the 
teeth. One individual would begin it and immediately every 
guinea pig in the room would take it up and continue for half a 
minute or more. Within three months this habit was discon- 
tinued almost entirely. 

In its diet the guinea pig resembles the rabbit. It is vora- 
cious and will gnaw almost anything in the vegetable kingdom. 
Its foods in the laboratory are carrots, oats, hay, grass, lettuce 
and parsnips. It gnaws constantly, the wire, the floor, the par- 
tion, anything within reach. In this, too, it resembles the rab- 
bit. Its manner of eating and of searching for food would lead 
one to the conclusion that it is a grazing animal in its natural 
habitat. 

The guinea pig bears constantly, and is quite prolific in 
confinement. The average number in a litter is two, though 
litters of one or three occur frequently. The period of gesta- 
tion is from 65 to 69 days, and the young are weaned about 
the end of the second week. Growth is retarded by birth for 2 to 
5 days. From 5 days to 12 months there is a steady increase in 
weight. The age of sexual maturity is extremely variable, but 
seems to be about four months. 


1 MInNoT. Senescence and Rejuvenation First Paper: On the Weight of 
Guinea Pigs. Jour. of Phystol., Vol. XII, p. 97, 1891. 


fo 


302 Journal of Comparative Neurology and Psychology. 


A description of the development of the habits in the 
young, ona subsequent page, will, I think, show that most of 
the habitual reactions of the guinea pig are of the instinctive 
type. Fear of specific objects is probably not instinctive; re- 
action to warning cries seems to be acquired from the mother 
after birth ; and domestication leads to the modification of some 
sounds, and probably, to a certain extent, to a partial inhibition 
of running and jumping activities. 

The guinea pig isa social animal. When several are put 
into a cage they huddle together in one corner, and when they 
are alone in contiguous cages with wire partitions between them, 
they are generally to be seen as close together as the wire will 
permit. 

As arule there seemed to be greater activity in the dark 
than in the light, more freedom of movement being present. 
Several times I noticed when the light was turned out the 
animal would immediately begin to eat. This observation 
is confirmed by a remark of ERNsT voN FRIEDL, who, in speak- 
ing of the guinea pigs’ natural habits, says ‘‘They lie down in 
the long, dry grass where they live, and keep concealed most 
of the day. They are more night than day animals.”’ The 
possible differences in activity in the dark as compared with 
light has been borne in mind during experimentation. 

The note of warning is a sharp cry. Usually it is uttered 
when any dark object passes the window. Once or twice I 
have known it to.be given when a shrill whistle sounded near 
by. Many visual stimuli will call it forth. At first my reach- 
ing my hand to turn on the electric light overhead caused the 
note of alarm—not of fear. The cry produced instant quiet 
throughout the room. I have not heard it responded to except 
by a mother with young who utters a very low ‘‘burr-r-r’’ to 
them and thus quiets them. The cry of fear is loud and shrill, 
seeming to indicate nothing of caution or concealment, while the 
alarm call is softer and more deliberately uttered. Guinea pigs 


1 FRIEDL. Zur Familiens- und Lebens-Geschichte des Meerschweinchens, 
Cavia cobaya, Marcgrave. Zoologische Garten, April, 1889. 


[ 10 ] 


ALLEN, Association in the Guinea Pig. 303 


do not seem to understand the significance of the warning note 
until they are three or four days old. Now that the guinea pigs 
are quite thoroughly tamed, both the note of warning and ex- 
pressions of fear are rarely observed. 

Other sounds uttered are series of shrill squeals and cries 
indicative of hunger. When I enter the room, if it is near 
feeding time, the little fellows remind me of their presence. 
When I approach the basket of carrots, and particularly when 
the sound of cutting reaches their ears, their squeals are urgent 
and vociferous. Each individual can be recognized by its voice, 
as there is great individual variation. 

If general conversation is ever maintained amongst the 
guinea pigs at their social gatherings, it consists only in an oc- 
casional ‘‘ghrr-r-hr,’’ a sort of gutteral aspirate sound like a note 
of perfect content with life. There is a characteristic tone 
uttered by the male to attract the attention of the female. This 
is the ‘‘coycobaya,”’ which is said to have furnished the South 
American natives with their name for the animal (Cobaya, Span- 
ish, Cuy or Coy). The female responds with a low, musical 
“r-rerp-rerp. 

If the guinea pig is surprised, or if anything of doubtful 
character attracts the attention of the whole group, a ‘‘burr-r’’ 
is uttered, and there is instant quiet throughout the room. If 
the experimenter keeps perfectly still the guinea pigs remain 
noiseless for several minutes. If, on the other hand, the cus- 
tomary laboratory occupations go on, confidence is restored 
and they return to their gnawing or eating. 

Observations of the young would lead to the conclusion 
that fear is not present at birth. No motor expression of fear 
could be produced by moving objects, or by any noise, or by 
touching, pushing or striking. The only reactions to sound 
that seem to be indicative of fear are those produced by a shrill 
whistle as described later. It must be remembered that labora- 
tory conditions are unfavorable for the awakening of fear in 
those animals whose only enemies are creatures of the grass 
and copse. 

The hiding instincts of the guinea pigs remind us distinctly 


[11] 


304 Journal of Comparative Neurology and Psychology. 


of a time when a quick retreat would bring them under the 
friendly cover of a tuft of grass or a little hillock. If the ex- 
perimenter attempts to catch them they dodge under hay or any 
cover at hand. No cover being forthcoming, the spot next 
chosen for safety is a corner of the cage where they huddle up 
and watch proceedings. Unfortunately laboratory cages were 
not made to harmonize with their particular color effects, so 
that the desired result of being invisible is not accomplished. 
In order to study this point a cage was fitted up simulating the 
scenery of their grassy South American home. To obtain the 
best conditions the light was rendered dim by a high board 
fence, while sticks, stones and mounds of earth completed the 
realism. It is thought, from observations of both young and 
old under these conditions, that they rely for escape, not so 
much on protective coloration, as upon hiding under grass in 
little inequalities of the ground. However, the English variety, 
which is presumably nearer the original than any other in the 
laboratory, is particularly harmonious in color with surrounding 
grassy mounds. 

When undisturbed, the guinea pigs wander contentedly 
around and nibble grass, but let them suspect that an enemy 
may spring upon them and they approach their food only by 
making a bold dash out of their retreat, and drag the food back 
into a dark corner. In the experimental work this was almost 
invariably the way food was seized from the boxes, even when 
the environment was uniformly lighted, so that there could have 
been no immediate advantage in snatching the food backward a 
few inches. At first my own movements attracted much atten- 
tion from certain individuals. This has to be taken into ac- 
count in the first series of experiments, as will be noted. How- 
ever, when the strangeness has worn off and the work becomes 
habitual this factor is greatly reduced, if not entirely eliminated.’ 

At first perfect quietness in the room is apt to delay reac- 
tion with all the individuals upon which I have worked. After 


1 THORNDIKE has discussed the fact that dogs pay more attention to the ex- 
perimenter and less to the experiment than do cats. Animal Intelligence, p. 38. 


[12] 


ALLEN, Assoctation in the Guinea Prg. 305 


the food is reached only one or two bites may be taken, and 
then even if hungry, the guinea pig remains quiet. But if I 
rattle paper or my keys during that time, or talk to it, it begins 
to chew and continues to eat. 

The movements of the guinea pig are not well adapted to 
climbing or jumping. Asa rule it has a strong dislike to jump- 
ing off a board to the floor of the cage. It will look around 
and try every means of climbing down, and when compelled to 
jump does so very awkwardly. On the other hand, it will run 
off the edge of the table if left alone, and fall to the floor. If it 
happens to have approached the edge very slowly it will not 
fall; but generally it seems to have not the least idea that the 
plane surface upon which it runs does not extend over the 
rest of the universe. In this too, however, there is indi- 
vidal variation. It may be due to the inadequacy of vision. 
The suggestion has been made by Dr. Watson that the differ- 
ence between the rat and the guinea pig in this respect may be 
due to a difference in the clinging power of the claws, and in 
the sensitiveness of the feet to touch. At least it may be safely 
concluded that the guinea pig has no sixth sense! which warns 
it when there is danger of falling. 

Observations leads me to believe that vision in the guinea 
pig serves primarily for orientation, and for detecting the pres- 
ence of moving objects. I have not been able to formulate ex- 
periments to determine this point definitely. All experiments 
with colored cards, colored light, and distinctively visual stimuli 
have given ambiguous, not to say negative results. 

The monocular vision which the guinea pig necessarily 
possesses on account of the position of the eyes and the con- 
figuration of the nose, undoubtedly prevents the clear differen- 
tiation of objects at close range. There is no demonstrable 


' SMALL discusses the phenomenon as a ‘“‘sense of support.’”? He says that 
all young land animals show hesitation when they approach a void (Amer. Jvuur. 
Psychol.. Vol. XI, p. 80). YERKES finds that there is a difference in the space 
perceptions of tortoises, land species showing more hesitation when they 
approach a void than water species. (Space Perception of Tortoises. /our. 
Comp. Neurol. and Psychol,, Vol. X1V, 1904). 


[13] 


306 Journal of Comparative Neurology and Psychology. 


fovea! or other modified area of the retina. It seems the most 
probable hypothesis that vision serves, as said before, for gen- 
eral orientation, and for the organization of a situation in which 
a stimulating odor forms one of the important elements. That 
the one reinforces the other, and that both are utilized in ordi- 
nary life processes is indicated by the comparison between re- 
actions to a probiem in ordinary daylight, and reactions to the 
same problem in the dark where vision is practically useless. 
The complete elimination of the food odor, and the employ- 
ment of only a visual stimulus of food have thus far given nega- 
tive results. 


IT. Characteristics of the Developing Guinea Pig. 
A. Description of the Young Guinea Pig at Birth. 


As stated above, the guinea pig at birth is well covered 
with hair, its eyes are open, it can hear, smell, touch and taste. 
Movement is not coordinated, and slight muscular weakness is 
apparent. Frequently when the little creature stops running 
one hind leg is left sprawling behind the body. The head is 
proportionally much larger than that of the adult. There is no 
fear of an approaching object, such as the hand in front of the 
eyes, nor of persons. But a shrill squeal like that of a rat causes 
first an instantaneous jump, and then a twitching of the muscles. 
This is a momentary reaction; it may be followed by hiding 
under the mother, but there seems to be no ‘‘panic,’”’ nor rapid- 
ity of movement as if to escape. While this may be an initial 
stage of fear, still the attitude of the little fellow is quite differ- 
ent from that of the frightened adult. 

A carrot or other vegetable food produces no motor reac- 
tion toward it, though before the first day is over the small 
guinea pig will eat grass, bread and milk, and nibble ata carrot. 


Test |. Is the mother a specific stimulus for her young ? 
Observation had indicated that carrot or other vegetable 
food furnished no stimulus toward which the very young guinea 


1 Preparations of the guinea pig’s eye were kindly made and examined by 
Dr. J. R. SLONAKER, in this laboratory, and the above statement is made upon 


his authority. 


[ 14 ] 


ALLEN, Association in the Guinea Pig. 307 


pig would react. Therefore I desired to find whether the 
mother herself could furnish a motive for a solution of a prob- 
lem. In order to do that the following preliminary experiment 
was made: 

I put guinea pigs two hours old in the experimental cage 
while the mother was placed in a wire box in plain sight. They 
could reach her by going to the small opening in the wire. She 
seemed not to be a stimulus, and there was no attempt to reach 
her. The little ones’ independence of their mother is empha- 
sized by the fact that they ran about quite freely and content- 
edly for an hour or more away from her. On her part she paid 
no attention to them, and only in rare cases did any mother 
gnaw and attempt to reach her young family, even though the 
little ones had been away from her for an hour or more. In 
one case I removed a guinea pig five hours old from the mother 
and left it three hours. At that time the mother was put in an 
experimental cage within a simple wire labyrinth (Text-fig. 1). 


A 


B 


Text-icure 7. Labyrinth I. 


A Bis the experimental cage used throughout all the experiments. The 
floor is of wood, and the sides of small wire. It is 3% ft. long by 3 ft. wide, 
and usually rests upon two stools or a table at such a level that the light from the 
windows, VW, gives uniform illumination over the cage. 

The labyrinth, Z Z, is of light weight wire, 4% in. mesh. The wire box, 4, 


is 10 by Io by Ito in., thus being perfectly comfortable for a large guinea pig. It 
is entered by a small entrance, y, just large enough for a little guinea pig. 


fens: 


308 Journal of Comparative Neurology and Psychology. 


The little ones were placed at x, 24 inches from the open- 
ing y. The mother was plainly visible through the wire, and 
could probably have been smelt by a sensitive nose. But she 
seemed to provide no stimulus leading to definite purposive ac- 
tivity. The young guinea pig gnawed a little at the wire ; 
probably an instinctive reaction, for there seemed to be no rec- 
ognition of the proximity of the mother, i. e., no association 
was yet set up between the sight of the mother in this en- 
vironment and the satisfaction of hunger, if hunger were pres- 
ent. Another female was put in the place of the mother, and 
the attitude of the young remained unchanged. When the 
young one was replaced in its home cage, it immediately found 
its mother and began to suck. The other female was substituted 
for the mother and the little one attempted to suck her. 

At 38 hours the guinea pig squeal in its infantile form is 
fully developed. Movements are almost as well coordinated as 
in the adult and there is great activity. The movements about 
the cage are similar to those of the adult while hunting food. 
The fore feet creep forward, the bright eyes are on the alert 
the belly is flattened to the ground, and the hind part of the 
body is dragged forward. 

The peculiar movement of the guinea pig, so characteristic 
of the first three weeks of existence, begins to appear on the 
second day. I can attempt only a description of the move- 
ment; what its significance may be, why it arises and disap- 
pears as it does, and what form it assumes in the adult I do not 
know definitely. The guinea pig will run for a few steps, then 
give a sudden jump forward or in some other direction, then 
run and jump again. The jump may not be preceded bya run- 
ning movement; it may be forward close to the ground, or 
shorter and somewhat more in the air. The jump is so sudden 
and violent as to be quite startling. It reminds one of the play- 
fulness of a little calf kicking its heels. For some days this is 
almost the only method of locomotion. It is probably a sign 
of superfluous activity conspicuous in young animals; and the 
sudden zig-zags of the course may have facilitated escape at a 
time when movement could not be inhibited. 


[ 16 ] 


ALLEN, Association in the Guinea Pig. 309 


At the age of 62 hours evidence of the mother’s acting as 
a specific stimulus is given by the act of the guinea pig in mak- 
ing a real attempt to get to her through the wires of the box. 
With many individuals such definite recognition of the mother 
occurs even later. 

Development varies greatly in individuals. It seems true 
without doubt that the larger the guinea pig at birth the more © 
active it is, and the sooner it reaches full coordination and the 
ability to solve problems presented to it (problems which de- 
pend upon activity). 

From Mrnot’s observations’ it was concluded that the 
length of gestation is shorter the larger the litter, and the shorter 
the gestation the smaller the litter. Therefore it is probable 
that variation in activity and development is a question of ma- 
turity, since the small animals are in the large litters. In a lit- 
ter of two, one pig is apt to be somewhat smaller than the other, 
and to be a few hours behind it in the appearance of character- 
istics indicative of progressive stages of maturity, e. g., the 
jerky running movement which seems to be a good objective 
criterion of development. 

In spite of their social instincts I have never seen the little 
guinea pigs play together. There is never anything like mock 
combats among the young such as form a striking feature of 
rats’ play.’ 


B. Experimental Work. 
Introduction. 


In the experimental work the kinds of problem to be given 
the guinea pigs were determined by careful preliminary obser- 
vation of their natural habits and tendencies. No problem 
should be given to an animal which involves the inhibition of 


ESWoes cits. sp. Lg. 

2 This small amount of play activity offers a suggestion in favor of the theory 
of play described in MorGAN’s Animal Behavior, p. 315. If play is a preparation 
for the serious defensive and offensive work of adult life, the animal which never 
makes an attack and has no defence except to run away, could not be expected 
to spend its youth in sham battles. 


[17] 


310 Journal of Comparative Neurology and Psychology. 


a deep-seated instinct.’ Those experiments in which the time 
element (the interval between stimulus and response) is of im- 
portance should not be foreign to the natural tendencies; all 
innate proclivities should be seized upon and, so far as possiple, 
should be utilized. The stimuli depended upon with the guinea 
pig were hunger and desire for company. The former, since it 
could be carefully controlled and kept a constant factor, was 
used almost entirely. 

It was found that problems whose solution involved activ- 
ity were solved most readily, while those which involved inge- 
nuity were not solved at all. By ingenuity is meant a very 
simple process, the putting of two and two together. <A paw 
or a nose may be used to attain an object when other methods 
have failed. Within narrow limits the guinea pig is very active, 
many of his movements being made at random. It can select 
a few movements which have been successful and omit those 
which have not, so that a path is learned merely by a proper 
direction of activity. But there is no adaptation of movement 
to a complication in the problem offered which would involve 
even a simple new coordination. The absence of all power of 
adaptation is the absence of all ingenuity. 

The guinea pig is a grazing animal, as has been mentioned ; 
it neither digs nor climbs for its food, but runs about. It 
scarcely ever pulls or pushes obstacles violently, and its gnaw- 
ing is not adapted to getting intoa box. A guinea pig will 
gnaw for five minutes at a freely swinging door without happening 
to give it a hard enough push to open it. The gentle swinging 
of the door back and forth seemed to suggest nothing. All at- 
tempts made thus far to give problems similar to those solved 
by cats and dogs (by THORNDIKE, HosuHouse and others) were 
unsuccessful, in the case of the adult as well as the young. 

Even though extremely hungry the little fellow will get dis-. 
couraged after finding that all the methods he knows fail to reach 
the food, and he will sit down in a corner of the cage and re- 
main there. At,one time I left my brightest guinea pig six 


1 VERKES and HuGGIns. Habit Formation in the Crawhsh. Harvard 
Psychological Studies, Vol. 1, 1902. 


[ 18] 


ALLEN, Assocration in the Guinea Prg. 311 


hours on a simple problem of ingenuity,’ and returned to find 
it in the same position. Another guinea-pig was left all night 
to solve a problem’ but failed. 

The problems which could be most successfully solved 
were simple boxes with doors swinging from the top so that 
they could be easily pushed open; and various forms of laby- 
rinth. It will be seen that the prerequisite for solution of such 
problems is activity and not ingenuity. The mentality required 
was only recollection of the path leading to the food sufficiently 
distinct to modify successive reactions. The associations which 
might be formed were controlled as carefully as could be, and 
will be mentioned under the various experiments. 


Test Il. Recalling a simple path. 


Simple problems of finding the way were given to the 


A 


Text-figure 2. 


! The door of a wire box was to be pulled open by a string running over a 
pulley and hanging free outside about the level of the guinea pig’s nose. 

2 The problem was to walk up an inclined plane, push open a wooden door 
hung at the side, pass through a short wooden passage to a wire door also hung 
at the side, and pushing that open, to walk down another inclined plane to food 
in the next cage. The food was visible and could be smelt through the wire 
partition between the two cages. 


[ 19 ] 


312 Journal of Comparative Neurology and Psychology. 


young guinea pig. The apparatus used was a wire box (6 by 
6 in.). The apparatus was placed in the experimental cage (de- 
scribed under Text-fig. 1), so that there was never any crowding 
or cramped quarters for the animals. In many of the experi- 
ments where the path chosen was of importance, and direction 
of turning and number of random movements were to be ob- 
served, the floor of the experimental cage was covered with 
glazed paper which had been smoked some days before. Pre- 
liminary experiments showed that the guinea pig was in no way 
disturbed by any contact, noise or odor of the paper, and never 
observed it any more than the usual floor of the cage. 

A guinea pig, age I day, was placed at 4A within the wire 
box which had a swinging door, +. The larger box had two 
simple openings at y and zs. The mother was placed outside in 
the experimental cage. The wires and experimental cage had 
been carefully freed from all odors by scalding. It will be re- 
membered that at the age of one day spontaneous movement is 
very slight, and though the smoked paper shows some move- 
ment within 4, the guinea pig did not find its way out. It 
saw its mother for it usually faced her as she wandered about 
the cage. 

Age, 2 days. Conditions and apparatus the same. KRan- 
dom movements were directed toward finding a way out, and 
the first solution of the problem was made in 12 minutes. 

It was replaced. For .25 min. it-sat perfectly still with 
back to the opening and to the mother. Then it turned, and 
in .083 min. had found her. This is the first proof of the for- 
mation of an association. 

Upon being replaced for the third time, it found the first 
opening, but the mother had moved and it went directly toward 
her. Finding the wire in the way, it went to the second open- 
ing, y, as usual. Time, .75 min. Few random movements 
here occurred: 


Test Il}. Alteration in habit. 


The experiment was then modified, and the swinging door 
turned from the opening. 


[ 20 | 


ALLEN, Association in the Guinea Pig. 312 


When put inside, the guinea pig immediately pushed the 
wire at the point where the swinging door had been before, and 
so pushed the wire box against the other wire (as in the dotted 
lines, Text-fig. 3), thus cutting offone path to the second opening. 


Text-figure 3. 


It still scratched and gnawed at the old place, but failing to get 


out, set out on an exploring tour. In 1.33 min. it had found 
the door. It then ran around the box in the direction of the 
arrows to get out at y, but found itself shut off there. It began 
to look again, and in .58 min. had found the opening at z. To- 
tal time, 2.083 min. 

Replaced in A (Text-fig. 4). 

The guinea pig sat perfectly still for 1.91 min. Then it 
turned around and pushed gently at the point where the door 
had been in the first problem. Not finding the wire to swing 
easily, it turned directly back and pushed the door open with- 
out any random movements. Time, 2.16 min. Then it again 
went in the direction of the arrows, and found its way closed ; 
then turned and immediately found the opening at z. Total 
time, 2.5 min. The smoked paper showed a minimum of ran- 
dom movements. 

Results: At the age of two days there is unquestionable 
evidence of recollection. It will be noticed that the random 
movements made in the last trial are almost identical with those 


[20] 


wt 


314 Journal of Comparative Neurology and Psychology. 


of the other trials, except that minor random movements have 
been eliminated, and only the principal movements chosen for 
emphasis. The guinea pig had not succeeded in getting out by 


Text-figure 7. 


going in the direction of the arrows, yet this same path was 
chosen the second time, it having been one of the major move- 
ments which, as a group, were previously successful. 

Test 1V. Does the odor of the previous path furnish the stimulus ? 

Age, 3 days. There is a possibility that the odor of the 
path just taken might serve as immediate indication of the path 
to be chosen again. Therefore the reaction would be mechan- 
ical, i. e., in terms of immediate stimulus and response, not of 
recollection. 

In order to test this the odor of previous trips was elimi- 
nated by thorough scalding of the wire cages and boxes to be 
used. The wire cages were then set upon glass instead of 
smoked paper. The apparatus was set up as in Text-fig. 2. 

Time for guinea pig to find his way out, .33 min. No 
random movements. The apparatus was then set up as in Text- 
fig. 4. 

Time. .83 min., the path being the one chosen on the pre- 
vious day, i. e., including the major random movements. 

Upon a second trial of the problem at this time (the wires, 


[ 22] 


ALLEN, Association in the Guinea Pig. 315 


etc., being washed) the time was cut down to .33 min. All 
random movements were eliminated except a little push at x; 
the route chosen was direct. 

One important conclusion, I think, is that the path was 
not learned by tracking, i. e., that smell did not enter into the 
formation of the association. 

The slow disappearance of random movements suggests 
that kinesthetic sensations are an important factor in learning a 
path, though that they are not the only factor is shown by the 
elimination of unessential movements, indicating that something 
beside mere sequence of sensations enters into the association. 

Test V. Complexity of associations. 

The most difficult labyrinth experiment which was to be 

presented to the adult was now presented to the three days old, 


in order to determine how complex a path could be learned. 
A 


Textfigure 5. 


As usual the labyrinth was made entirely of wire. A, B, Care alleys from 
which there is no exit. The entrance to the wire box, X, is very small and is 
open. 

Care was taken to have the whole cage free from any odor. 
The mother was placed at X and the little one at Y. 

Time for finding the mother in the first trial was 5.166 
min. 


[ 23 | 


316 Journal of Comparative Neurology and Psychology. 


In the second trial the time was reduced 2 min. There 
were few random movements, and no blind alleys were entered. 

The question arose, How far did the previous experi- 
ments with the guinea pig aid it in learning the more complex 
path ? 

A guinea pig from the same litter that had never been 
used for experiment was now tested. It was smaller and not 
quite so mature as the first one used. When placed in the 
labyrinth, conditions as for I, it wandered about 45 minutes 
without finding its way in. This seemed merely chance, as its 
activity was sufficient to make it wander all over the cage. It 
paid no attention to the mother, nor had the first one, so far as 
I could judge, since finding her seemed a matter of accident the 
first time.’ I simplified the labyrinth by removing the part di- 
rectly in front of the entrance (A); the mother was found in 

33 min., probably by chance. 

The apparatus was washed and replaced as in the first 
instance (Text-fig. 5). Time, 3.166 min. 

Repeated. Time, .416 min. All random movements 
were eliminated. The recollection of the pathway chosen per- 
sisted, since experiments on the next day (age, 4 days) with the 
different individuals showed few random movements and short 
time reactions. 

Close observation of all individuals, as to manner of turn- 
ing and of moving about, indicates that kinesthetic sensations ' 
are a controlling factor in the learning and retention of a path 
to food. A movement once made and ‘‘stamped in” by the 
pleasure incident to the obtaining of food quickly becomes au- 
tomatic. 


1 Tt is hard to know when the young are actually trying to reach the mother 
(i. e., when she is a specific stimulus). I found definite indication that she fur- 
nished a stimulus for the young at the age of 62 hours (p. 309); but even later 
many of them at times would apparently pay no attention to her, and would not 
go to her when in the same box. 

1 YERKEs has rightly insisted upon the importance of the kinesthetic sensa- 
tions with animals of a simple psychical organization. (Instincts, Habits and 
Reactions of the Frog. Harvard Psychological Studies, Vol. I). 


[ 24 ] 


ALLEN, Assoctation in the Guinea Prg. 217; 


The experiments were repeated on four different groups of 
young during an interval of five months. The smaller ones 
were always a little later in their solution of the problems than 
their larger brothers, because their movements were neither so 
rapid nor so numerous. When the way was once found they 
remembered as accurately as the others. 


C. Summary of Work With Young. 

1. The guinea pig at birth is physically mature with the ex- 
ception of slight muscular weakness and inaccurate coordi - 
nation. 

2. That no experimental indications of associative processes 
were obtained at the age of one day seems to be due to the 
small amount of activity at that time. 

3. All individuals examined learned a simple path to their 
mother at the age of two days. 

4. The most complex problem solved at all was solved at 
the age of three days, and the recognition of it persisted. 
There was no indication of increase in complexity of psychical 
processes after the third day. The problems learned between 
one and three days depended upon increasing activity, and not 
upon increasing intelligence. 

5. For the reasons previously given, it is probable that 
kinesthetic sensations are of paramount importance in deter- 
mining the recollection of a path. 


Ill. Experiments With the Adult. 


It was found that if the guinea pig had been without food 
for twenty-four hours, the odor and sight of food were sufficient 
to induce continuous movement for a considerable length of 
time, and if mere activity could solve the problem it was most 
quickly solved under these conditious. 

Objections have been made by Mitrs' and by MorcGan” 
that experiments upon animals which have been starved before- 
hand were rendered invalid by the abnormal conditions. In 
my experimental work on the guinea pig I have not been igno- 


1 Psychological Review, Vol. V1, p. 265. 
2 Animal Behavior, p. 151. 


[ 25 | 


318 Journal of Comparative Neurology and Psychology. 


rant of these objections, and so far as they are legitimate, they 
will hold against my work. But I do not think the presence of 
hunger can be considered as vitiating the experiments. The 
desire for food is a natural condition, and can scarcely be regard- 
ed as an abnormal stimulus in any case. The guinea pig isa 
phlegmatic animal, insusceptible to considerable variations of 
temperature and food, as one would naturally suppose from its 
thick covering of fur, and its ready accumulation of fat upon 
which it may live. When beginning my experiments even with 
animals perfectly tame, the problem was to get them to attend 
to the food in the problem box. The incentive to obtain the 
food had to be rendered quite strong. My custom was to feed 
the guinea pigs once a day, about five o’clock in the afternoon ; 
enough hay and oats were left in the cage to last all night and 
well into the next morning. Those animals with which I in- 
tended to experiment were left unfed one day and experiment- 
ed with at about 2:30 p. m. the next day, when they were fed as 
usual. This was found to produce the requisite degree of hun- 
ger to gain attention to the problem, though there was nothing 
like the ‘‘utter hunger’ of THORNDIKE’s cats and dogs. In no 


) 


case was there ‘‘frantic activity” indicative of an abnormal state. 
Previous observations had demonstrated that hunger any less 
intense did’ not succeed in eliminating mere curious exploration, 
or even quiescence in one corner of the cage. 

Upon first introducing the guinea pigs into the laboratory 
they were wild and easily frightened, and disturbed by my pres- 
ence, or by any unusual sound or movement. An attempt was 
made to carry on the experiments in their customary room, but 
the sight of the other guinea pigs, and when that was shut off, 
their sound proved a disturbing factor. For that reason the 
animals to be experimented upon were removed to another 
room. 

A few weeks of persistent and continuous petting, hand- 
ling and training finally accustomed them to the presence of the 
experimenter, and gradually the problem came to absorb atten- 
tion to the neglect of any outside element. Animals born in 
the laboratory did not have to pass through this preliminary 


[ 26 | 


ALLEN, Assoctation in the Guinea Pig. 319 


training. It was found that less disturbance was produced with 
them by working in the animal room, as all the guinea pigs 
were now accustomed to the presence of the experimenter, and 
did not alter their daily routine. Later all experiments were 
carried on in the animal room without any complications arising. 


Test VI. Preliminary. 


January 24. I took adult guinea pigs from their cages to 
another room where conditions of noise, etc., could be gov- 
erned. Owing to their extreme timidity and fear of handling 
they did not recover from the removal sufficiently to give any 
reactions. It then became necessary to tame them, to accus- 
tom them to their new surroundings, and to acquaint them with 
the first apparatus to be used. For this purpose each animal 
was brought to the experimental room and left in the wire cage 
several hours daily. Each guinea pig was also handled and pet- 
ted as much as possible. 

January 29. They had become used to the petting and 
apparatus, and had practically learned the simple problem to be 
taught them first. They had not solved the problem, but had 
been taught. 

The method of teaching was as follows: When first placed 
in the cage they remained quiescent in one corner. I placed 
food very near them, and soon they made a dash for it. Grad- 
ually I removed the food farther away, but they were afraid to 
enter the box. When they became accustomed to my hand I 
held the food toward them and tolled them to the box. After 
a few trials they learned to get into the box for the food. 

This record of the manner of teaching an animal has inter- 
est because of THORNDIKE’S observations upon the same sub- 
ject. He concludes! from a questionnaire to animal trainers, 
that ‘‘None of these [the trainers] would naturally start to teach 
a trick by putting the animal through the motions. . . I 
see no reason for modifying our dogma that animals cannot 
learn without the impulse.” 


' Psychological Review, Mon. Suppl., Vol. Il, p. 72. 


[ 27] f, 


320 Journal of Comparative Neurology and Psychology. 


In his experimental work THORNDIKE emphasizes the 
method of learning as that of a selection from a large number 
of random movements of certain movements which are stamped 
in by the pleasure of success. I believe, however, that a guinea 
pig may be taught a trick without waiting for selection from 
among random movements. What was done was to ‘‘control the 
impulse,” and by impulse we mean the amount and direction of 
muscular innervation. 

On the previous Saturday the guinea pigs had remained 
almost motionless for two hours after being put into the experi- 
mental cage. On Thursday the problem had been learned. 

A typical series of reactions is given, after the problem has 
been learned. Until that time the difficulties of fright, strange- 
ness, etc., already mentioned, rendered any time record or 
other measure wholely meaningless. 

The apparatus used was a wire box, 10 by Io by 10 in., 
with a wire door hung from the top so as to swing freely in and 
out Care was taken that nothing should distinguish the door 
from the rest of the box. In every case the guinea pig has had 
no food for 24 hours. The food stimulus used is always carrots 
freshly cut, which has a strong odor; also it is in plain sight in 
the wire box. The animal is adult, and in this example is of 
the solid red Peruvian variety, though mixed with the solid red 
English. 


Jan. 29.! Time. 
Door to food box open -5 min. 
Door to food box open .o83 min. 
Door to food box open .066 min. 
Door closed .066 min. 
Door closed .66 min. 

Jan. 30. 
Door open .5 min. 
Door open .25 min. 
Door open .25 min. 
Door closed 25 min. 
Door closed .I5§ min. 
Door closed 133 min. 

Jian ge 
Door open .415 min. 
Door closed .183 min. 


1 Tt will be observed that throughout the work more than one trial was given 
during an experiment. At any one time only a little food was given. 


[ 28] 


ALLEN, Association in the Guinea Prg. 321 


The reactions took place almost mechanically. The box 
seemed to be the thing-to-be-run-into. It was always in the 
same position. In this way, whether the door was open or 
closed seemed to make no difference; it was pushed open 
rapidy when the position of the entrance became an habitual 
one, and the reaction was not perceptibly lengthened. 

From the preliminary test it was concluded that the guinea 
pig would react to a stimulus under laboratory conditions. The 
elements entering into the situation were (a) the sight and odor 
of food; (b) the sight of the box, and association of the gen- 
eral environment with food; (c) the association of a certain 
series of kinesthetic sensations with the satisfaction of hunger. 


Test VII. Distinction of stimuli. 


An attempt was made to determine what the stimulus was 
which induced the reaction to the problem. 

The food was covered with a glass dish, and care was taken 
to eliminate all possible odor from the box. There seemed to 
be no shyness of the glass dish as it was treated with indiffer- 
ence when left in the cage. Nevertheless, the possibility that 
fear might not have been observed though present, must be 
borne in mind. 


Jan 30. Time. 
De .5 min. 
2s -75 min. 
3 .083 min. 
4. .083 min. 


The first time I did not give any food when the guinea pig 
got into the box. The effect of this disappointment is seen in 
the second reaction; at that time I gave food, then removed it 
quickly. The same was done in the third reaction. 

At this point in the experiment it seems certain that a 
smeil stimulus is not necessary to produce the reaction after the 
situation has been learned. 

In order to determine if possible what stimulus is the 
strongest a choice experiment was introduced. 

A dish was arranged in a wire box with the carrot in plain 
sight but covered with glass. Into another and similar wire 


[ 29 ] 


22 Journal of Comparative Neurology and Psychology. 


box carrots were placed, lightly covered with sawdust. A third 
wire box was empty. 


Visual Blank Olfactory 


min. 1.25 min. 


Two wire cages made on the same plan as that first learned 
but smaller were used. One was empty, the other had a visual 
stimulus as before. The new boxes were first learned in the 
ordinary way, by placing the food in one in an open dish. It 
was first entered in 1.083 min., and the next time in .483 min. 
The food was then covered with a glass dish and placed in the 
other cage. The cages were about 1% ft. apart, and exactly 
alike. The guinea pig was placed 3 ft. away, facing them. Every 
time the box with food was entered the guinea pig was given 
a bite of food, and the food was then transferred to the second 
cage. During the time of rearranging the apparatus the guinea 
pig was always removed from the experimental cage. 

Visual stimulus. 
Box with food. Box without food. 


.25 min. 
.066 min. 


.55 min. 
.399 min. 
25 min 
2 min 
Feb. 5s. 
: .166 min. 
-15, min. 
pit soohlors 
33 min- 
.187 min. 
.cC66 min. 
.313 min 
313 min 
264 min 
Feb. 6. 
.5 min. 
.66 min. 
.I min. 
.264 min. 
.0$3 min. 
.083 min. 


.066 min. ° 


[ 30 ] 


ALLEN, Association in the Guinea Pig. 323 


From this experiment we conclude that no choice is pres- 
ent. That is, no immediate discrimination is made between 
the two boxes. This leads to the inference that the food in 
itself furnishes no stimulus. But when placed in a given situa- 
tion the guinea pig reacts to the environment as a whole. 


Test VIIi. Learning a labyrinth. 
The next step in the experiment was to complicate the 
path to the food, thus to find how quickly a more complex path 
would be learned. 


For this purpose a wire labyrinth was constructed (Text- 
fig. 6). 


A |BIC) x 


Text-fieure 6. 


The apparatus is described on page 315. Theicage was 
floored with smoked paper. The guinea pig was placed at Y. 
A typical series of reactions will be given. 


[31] 


324 Journal of Comparative Neurology and Psychology. 


Feb. 12. The animal explores the cage, but is perfectly passive most of the 
time. Found the food in I hr. 55 min. 


Rebs 13 Time 31 min. 
Feb. 14 1.462 min. 
Peb. m5 9.75 min. 
Feb. 16 5.5 min. 
Feb. 20 15 min. 
Repeated 1.33 min. 
Feb. 25 .5 min. 
Repeated .25 min. 
Feb: 26 2.616 min. 
Repeated -83 min. 
Repeated .483 min. 
Pebs27 4.516 min. 
Repeated .55 min. 
Feb. 28. For some reason did not goin. Left 22.5 min. 
Mar. I .366 min. 
Repeated .2 min. 
Mar. 3 2.316 min. 
Repeated .513 min 
Repeated 1.75 min. 
Mar. 5 6 min 


In this problem there was choice of two directions to be 
taken to the entrance. The guinea pig was always put down 
in a fixed spot, namely at Y. It could go to the right or left. As 
a matter of fact, some individuals learned one way and some the 
other, and the direction taken was not always the same with the 
same individual. As a rule, when the problem had been learned 
the blind alleys were omitted. Attempts to gnaw through the 
wires at various points were abandoned after the first few times, 
when another method had proved more successful. 

The six guinea pigs which learned this problem, three of 
which were used at the same time as the example given, were 
remarkably uniform in their results. There was no sufficiently 
important variation to deserve remark. The variations which 
did occur were to be accounted for by difference in tameness, 
or by some chance noise producing fear and thus requiring 
time for recovery. Two curves of the time required are here 
given. (Text-fig. 7.) The time in minutes is indicated on the 
ordinate, while the divisions of the abscissa represents the num- 
bers of the trials. 


oo 


XVI XVII 
50 


45 


40 


35 


30 


NAN 


| 
a ie | e 
IX x 
Curve showing the time of learning the labyrinth, two individuals, A&B 
Curve of persistence of the habit. 63 days later. 


Xl 


XIV 
Text-figure 7. 


XVIII 


XIX 


XX 


326 Journal of Comparative Neurology and Psychology. 


The paths taken by each individual were preserved by the 
smoked paper. The most interesting points which the smoked 
paper shows aretwo: (1) The number of motions on the part 
of the adult as compared with the young is much smaller, and 
are less free: (2) There is ca tendency on+the part of the 
adult to keep as close as possible to the wire. 

The early movements are different from the adult in kind 
as well as in number and freedom; the jumping movements 
mentioned previously are soon lost. 

The adult guinea pigs have, a peculiar and characteristic 
method of sneaking across an open space, or of stealing up on 
food and snatching it back into an imagined retreat. Domesti- 
cation partially removes this fear of being seen, and the move- 
ment does not develop early or strongly in the laboratory young. 
I think it probable that the ‘‘agora-phobia’”’ is an acquired 
characteristic, or an instinct which, in accordance with JaMEs’ 
“law of transitoriness,’’ has lacked fixation by habit, and so 
has faded away.’ 

The typical series of reactions to the labyrinth was com- 
pleted March 5. On April 20 the same guinea pig was given 
the same problem, having been free from experiment during 
the interval. Conditions of hunger were the same as those 
previously obtaining. 

Time required for the solution, I min. Some time was 
lost in exploring the cage, but after once entering the labyrinth 
only .3 min. elapsed before the food was found. Each turn 
was made accurately, showing perfect familiarity with the path- 
way. Two blind passages were barely entered. 

April 22, a day having been omitted to preserve the food 
conditions constant, the times were (1) .33 min. (2) .33 min. 

April 24, tine, .166 min. 

Therefore we conclude from the elimination of random 
movements and from the short time required, that the recollec- 
tion of the problem persists at least 48 days, undiminished in 
its efficiency. 


1 Principles of Psychology, Vol. I], pp. 398-402 


[ 34 ] 


ALLEN, Association in the Guinea Pig. 327 


On July 27, 63 days later, the same test was repeated with 
the same animal. Time required, .33 min. Conditions were 
the same as before. The apparatus was freshly washed, and 
smoked paper used to show the movements. The only differ- 
ence was that the guinea pig was taken at the usual feeding 
time, and it had not been handled for two months. 


July 27 Time; <33, mint 
July 28 1.33 mln. 
July 30 2 min. 
July 31 .415 min. 
Anis. 3 .166 min. 


At this time this and several other of the experiments were 
repeated on other individuals, and the memory in every case 
was almost perfect. 


Conclusions from the labyrinth experiment. 


I. The guinea pig can learn.a complex path to food. 

I]. The time curve for learning is very abrupt for the 
adult, and for any one individual is also irregular. It tends, 
however, to reach a minimum at which point it is, after a few 
trials, nearly constant. In the labyrinth used this minimum 
will be observed to be .166 min. 

III. Tle curve for elimination of random movements fol- 
lows very closely the time curve, as random movements neces- 
sarily increase the time required. 

IV. There are two kinds of random movements: (1) 
Those made in attempt to reach the food, as biting the wire, 
running into blind alleys; (2) those of superfluous activity or 
Curiosity, as exploring the cage, running about, and jumping. 
When the guinea pig seemed in too playful a mood to attend 
to business, it was a sign that it was not hungry, and therefore 
conditions were not uniform. 


Test IX. Learning without the aid of vision. 


Granted that the guinea pig can learn a complex path, the 
problem arose, What sense elements contribute to this result ? 
What does the guinea pig remember ? 

The guinea pig may orient itself by means of vision, by 


] 


[3 


on 


328 Journal of Comparative Neurology and Psychology. 


means of smell, or by kinesthetic impressions. It will be re- 
membered that when the simple wire box was placed before 
the guinea pig, it ran in exactly as it was accustomed to do, 
although no food was inside. The box itself was then the 
stimulus, as being associated with food 

To determine how quickly the odor of food alone could 
set up the association, a series of experiments was designed, 
in which the visual factor was eliminated. 


Text-figure 8. 


The apparatus used in this test was a simple wooden box, 
6% by 6% by 6% inches, with numerous small holes bored in it 
(Text-fig. 8). A door was swung by hinges at the top A cop- 
per spring inside the door made contact witha plate in the top of 
the box when the door was pushed open. Connection was made 
with an electric light in a dark box entirely outside the experi- 
mental cage. The experimental cage was covered with a black 
cloth frame, and all experiments were performed at night, so 
that no light should be present. Noises and other accidental 
disturbances were thus diminished. 

In the first series of experiments it was possible, after the 
reaction had been made and the light turned on, for a faint 
glow to penetrate the cloth covering of the experimental cage. 
At a later time these results were verified in the dark room 
where no light could enter, and the arc connected with the ap- 
paratus was so arranged that no illumination of the room was 
possible. 

The typical series given was taken from an adult guinea 
pig about nine months old, of the smooth English variety. It 
had not been used before for any experimental work, and there- 
fore the first thing that had to be done was to tame it, and ac- 


[ 36 ] 


ALLEN, Association wn the Guinea Pig. 329 


custom it to being brought upstairs. As usual, the quickest 
way seemed to be to associate the experience with food. On 
Feb. 12 it was taken to the dark room at the usual feeding time 
and put in the experimental cage. After having been left there 
about half an hour it was returned to the guinea pig room and 
fed lightly. 
He bamais: 
been placed there. 
the cage to be eaten. 


Hebe) 


pig was now becoming tame, and behaved naturally when removed to the ex- 


It was taken to the experimental cage, food having ‘previously 
In 5 min. the food was found and was pulled to one side of 


The food was put in a wire box, but was not found. The guinea 


perimental room. 
EDs. LO: The food 
was not visible in the dark, and the door was left open in order that the slight 


Fright had disappeared. 
The electric food-box was used with the door open. 


grating of the hinges, the noise of the contact of the spring with the plate, and 
the touch of the door itself might not frighten the timid animal. The time was 
recorded from the moment of placing the guinea pig in the experimental cage 
until the sound of pulling out the food was heard. (When the door to the box 
was closed the appearance of thie electric light gave a more accurate time limit.) 


The food was found, seemingly accidentally, in 2.264 min. 


Feb. 17. Animal very active. Food not found. 

Feb. 18. Door to electric box open. Time  .05 min 
Door to electric box open. Time 25 min 
Door to electric box open. Time 1.083 min. 
Door to electric box open, Time 5.581 min.! 

Feb. 22. Door open. Time 1.85 min. 

, Heb. 24. Door open. Time 11,838 min. 

Repeated. Mimies y= tag emits 
Door closed. Time .43 min. 
Door closed. Time .35 min. 

Feb. 25. Door closed. Time 2.913 min. 
Door closed. Time .528 min. 
Door closed. Emme °43)min. 

Feb. 26. Door closed. Time 4.726 min. 
Door closed. Time .783 min. 

Feb. 27. Rattling of windows in the wind frightened the guinea pig, and 


therefore no reactions. 


Feb. 28. Door closed. Time .83 min. 
Mar. 1. Door closed. Time  .89 min. 
Mar. 2. Door closed. dime) 9-25) mun: 
Mar. 3. Door closed. Time 1.363 min. 

Door closed. Time 1.783 min. 

Door closed. Time 1.783 min. 
Mar. 5. Door closed. Time .183 min. 


1 This increase in time was probably due to two things; (a) not so hungry 


‘Door closed. 


Lan] 


imey 282 


min. 


330 Journal of Comparative Neurology end Psychology. 


The results of this series of experiments when compared 
with a similar series taken in the light are these: (1) The 
range of variation in reaction-time is greater in the dark than 
in the light; (2) A longer time is required to form a definite 
habit of entering the cage for food; (3) The average time 
required, even omitting the excessively long periods, is longer 
than that required for the analogous experiment in the light. 
This is true in spite of the greater activity of the animal in the 
dark and the greater freedom with which exploration is made; (4) 
It follows, therefore, that the number of random movements 1s 
much greater in the dark than in the light. This the smoked 
paper shows to be almost invariably the case. 


Conclusions from the four tests. 


In those tests in which only a visual stimulus of food 
was permitted in a situation not previously associated with food, 
there was no attempt to obtain the food; it apparently did not 
attract attention. Other experiments, particularly the choice 
experiment of test VII, gave negative results as to the eff- 
ciency of a visual stimulus when not reinforced by other 
stimull. 

From the sixth and seventh tests it was concluded that, 
after a situation is once connected with food, it is reacted to as 
a whole with the appropriate movements. An odor stimulus 
of food is then not a part of the situation essential to the reac- 
tion. 

From the eighth test we found that the situation might be 
considerably complicated without diminishing the appropriate- 
ness of the reaction. A situation which presents difficulties of 
the kind which the animal would meet in its natural environ- 
ment, is rapidly learned and reacted to almost automatically. 

The ninth test has shown that vision is an important ele- 
ment in learning the problem, but cannot be the only element, 
since the problem was learned without it, though more slowly. 
after eating the bite or two allowed at each entrance, (b) a little fright and dis- 
couragement from being repeatedly removed from food. The lengthened time 


of reaction was often noticed if the experiments were repeated several times in 
succession, and therefore too frequent repetition was hereafter avoided. 


[ 38 ] 


>) ie) ie) [@) 
ic w st oO 


100 


Xt 


Xl 


Vl Vill IX 


VI 


Wh lV 


45 
Ben 
Oo 
oo 
ag 
repre) 
aa 

{ 

' 

H 


Curve of learning simple food box, 


Text-figure Q. 


332 Journal of Comparative Neurology and Psychology. 


The paths taken throughout all the experiments by the 
guinea pigs, their customary accuracy in turning corners, and 
the general precision of their movements after the problem is 
learned give unmistakable evidence of the great importance of 
kinesthetic sensations in the recollection of the path. 


Test X. Preference for the dark. 


A series of experiments was now tried which did not lead 
to anything definite, and hence will be only mentioned. 

Observation had not indicated any preference of the guinea 
pigs for the dark side of the cages, or for remaining under cover 
except when frightened, but the fact that always in the evening 
they are most active suggested that there might be a preference 
for dark passages. 

A large galvanized iron box was divided into a light and a 
dark compartment, and an opening was so arranged that the 
partition in the box divided it also into halves. Food was 
placed in equal amounts at the distant ends of both compart- 
ments, and the guinea pigs were placed outside in the experi- 
mental cage. That tracking or any odor other than the food 
might not complicate the situation, the box and cage were al- 
ways carefully washed after each trial. 

The first few records with two of the four animals tried in- 
dicated a slight preference for the dark side; but all the rest of 
the trials, forty or more, showed the choices of the light side 
to be equal to those of the dark side.’ 

The conclusion, therefore, was that for this particular kind 
of test there was no preference for the dark. 

Green, blue and red glass covers were substituted first for 
the white glass, and then for the black glass covering the re- 
spective compartments, but in a large number of trials no pref- 
erence was indicated. 


1 Dr. Watson found with the white rat no preference for dark passages. 
Animal Education, p. 56. 


[ 40 ] 


ALLEN, Association in the Guinea Pig. 33 


oy) 


Test XI. Means of Orientation. 


It was hoped to determine more accurately the signs which 
the guinea pig uses to learn its way. 


Text-jigure 10. 


At cc cards of different colors could be slipped into a frame. A 4 are blind 
alleys, and # # removable partitions of glass. X is the food. 


Preliminary experiments were made to see whether the 
guinea pig tends to form a habit of going in a certain direction 
for food. If any preference were shown it was for the rignt hand 
path (Text-fig. 10.) <A glass partition was then put at fon the 
left path. The right path was soon learned. The cards (white and 
red) at c c were interchanged. Nota particle of difference was 
noticeable in the action of the guinea pig. When the partition 
was put to the right side the guinea pig learned the left path in 
three trials, with numerous random movements. 

Two guinea pigs were tested a large number of times in 
this way. For one a green card always indicated the side of 
the partition, and when the partition was changed the card was 
changed. With the other guinea pig several colors were tried. 
They almost invariably chose the path which had led to the 
food at the previous trial, regardless of the cards. Two guinea 
pigs, tried without any cards, did the same thing. 

The apparatus was made of wire and glass, so that I could 
wash it after each trial and thus do away with any possible path 
~ odor. 


[ 41 ] 


334 Journal of Comparative Neurology and Psychology. 


I believe my series of experiments too limited to draw any 
conclusions as to the effect of any particular sign in the field of 
vision. My experiments lasted two months and were performed 
every other day, two trials being given each day. 

It will be noticed that the experiment is borrowed from 
YERKES.' Ina long series of experiments on frogs he came to 
the conclusion that the frog observes colored cards and modi- 
files its actions accordingly. 


Test XII. Efficiency of contact stimuli for following a path. 


It was suggested by Mr. G. H. Meap that the reactions of 
the guinea pig might be direct responses to immediate con- 
tact stimuli, and that a distant stimulus, e. g., a recollection of 
the path, was not responsible for the reaction. While it is 
difficult for me to conceive how random movements could be 
eliminated and a path followed accurately after two months, if 
the performance were merely in terms of direct response to im- 
mediate stimulus, nevertheless I welcomed the suggestion of: 
testing the part played by contact sensations in the learning and 
recollection of the labyrinth. 

The labyrinth of text-figure 6 was taken into the dark room. 
I used three animals which had never before been in the la- 
byrinth but which were perfectly tame. As the conditions for 
all were the same, and this number was used only to obviate | 
any error arising from individual variation (which proved to be 
unimportant). I shall give a typical series from one animal. 

The labyrinth was first learned in the light (electric). Car- 
rot, as usual, was the food stimulus. Smoked paper was not 
put.on the floor. The tameness of the animals prevented long 
delays as in the first experiments, and their activity was like that 
in their home cages. 


1 Harvard Psychological Studies, Vol. 1, pp. 589-594. 


ALLEN, Association in the Guinea Pig. 335 


Aug. 10. Time 1 min. Was evidently accidental. 
Aug. 12. Time 3.166 min. 
Aug. 13. Time 33) min. 
Aug. 14. Time  .2I min. 
Aug. 15. Time .783 min. 
Aug. 16. Time 1.166 min. 
Aug. 17. Time 2:33 aint 
Repeated. Time .264 min. 
Repeated. dimes si233 "min: 
Aug. 18. Time®* .913 min. 
Repeated. Time .264 min. 


I then substituted the wooden box used in test IV (text-fig. 
8) for the wire food box, and turned out the light, but a loud 
noise in the next room frightened the guinea pig, so that the 
experiment was discontinued © 

Aug. 19. The room is again made perfectly dark, the wooden electric box 
in the labyrinth. Time 3 min. 

The guinea pig knocked against the wire at A (text-fig. 6) which seems to 
suggest inaccuracy of contact sensations. 

Repeated. Time 2 min. 

The times are rather longer than in the light. I replaced the 
wire box in the labyrinth and arranged the lighting wire so that 
when the swinging door was pushed open it would make the 
current. The contact conditions were then exactly the same as 
those obtaining in the light. 

Repeated. Time 2 min. 


The wire A was pushed down, which had never happened in the light, and 
the guinea pig walked over it to get in. 


Aug. 20. Time I min. 
Repeated. Time 1.25 min. 
Aug. 21. Time 1.25 min. 
Repeated. ime 2.5. mim. 
Repeated. Time 1.83 min. 


The wire labyrinth was now learned since there were few 
random moverents, and though the time was longer than in the 
light, there was the accuracy of movement showing familiarity 
with the turns to be made. 

To test whether the successive steps of the path were 
recollected through immediate contact stimuli, it was necessary 
to change the character of the contact and leave all the other 
conditions the same. Only the first reaction after such a change 


[ 43 ] 


336 Journal of Comparative Neurology and Psychology. 


would have significance. Should the recollection of the path 
be due to successive tactual sensations we would anticipate con- 
fusion and a lengthening of the reaction time when the contact 
stimuli have been changed. 

A labyrinth similar to the wire labyrinth in its proportions 
was constructed of cardboard. (The advantage of the darkness 
is now apparent, since the visual conditions were not modified. 
The cardboard used had been purposely left in the experimental 
cage when the latter was not in use, but even then the odor 
conditions may have been slightly different.) Holes were made 
in the cardboard food-box, and the door was swung from the 
top as usual. <A black cloth was spread over the floor of the 
experimental cage to change still more the tactual conditions. 
The electric wire was attached to the door to make contact 
when the door should be pushed open. The guinea pig was 
then brought to the dark room. 


Aug. 22. Time 1.75 min. 


In order to test whether this time was accidental another 
trial was given. 

Repeated. Time 75; min: 

One would hesitate to lay much stress on the guinea pig’s 
sense of touch in comparison, e. g., with that of the white rat, 
because of the difference in the vibrissae. While the white rat’s 
vibrissae are long, motile, and extremely sensitive, those of the 
guinea pig are shorter, coarse, and are not continually in use. 
The hair of the guinea pig serves fora covering rather than for a 
sense organ. I made a number of experiments by touching 
various parts of guinea pigs which were quite wild. If great 
precaution be taken that the guinea pig shall see no move- 
ment, its hair can be touched lightly at any accessible spot on 
the body behind the head without causing a reaction. I never 
succeeded in touching any part of the face without being seen. 

We have seen that there was no lengthening in the reac- 
tion time when the contact conditions are changed, therefore 
we infer that the path through a labyrinth is not learned solely, 
or even largely, in terms of tactual sensations 


[ 44 ] 


ALLEN, Association in the Guinea Pig. 237 
Conclusions from tests X, XI and XT1I. 


I. There are no indications that the guinea pig prefers a 
dark passage, or any particular color of light. 

II. A colored object in the visual field, if it be station- 
ary, apparently has no significance in the recollection of the 
path to food. 

III. Alterations in the tactual conditions of the environ- 
ment, other conditions being as far as possible unchanged, cause 
neither increase in reaction time nor confusion of movement. 

IV. Since neither odor, vision nor touch is alone of para- 
mount importance, and since, when light is shut out, the odor ofa 
previous path being at the same time impossible and tactual con- 
ditions being new, the recollection of a path remains accurate and 
unconfused, we conclude that the factors of greatest importance 
in recalling a path are the sensations of running and-turning, 
and of other movements gone through during a previous trial. 
The innervations of these movements are no doubt especially 
significant. 

V. Hearing, seeing, touching and smelling are all of them 
important in the reactions of the guinea pig. 


Summary of Work with the Adult. 


1. The guinea pig can learn problems the solution of which 
depends upon activity, but not those requiring ingenuity. 

2. The path to food is found first by accident, but when 
it is once found, random movements are rapidly dropped out 
and the reaction becomes almost automatic, providing no out- 
side disturbing factors enter. 

3. Odor of food is a stimulus which induces reaction, but 
the time required to learn the path from an odor stimulus alone 
is longer than from stimuli affecting all the sense organs. 

4. Experiments to determine the efficiency of a visual 
stimulus alone were negative. 

5. Kinesthetic sensations are of great importance in the 
recollection of a path. 


[ 45 ] Igy 2 * te @ 


338 Journal of Comparative Neurology and Psychology. 


LIV. Development of the 
the 


GUINEA PIG. 


Weight: Varies greatly atbirth. Av., 
female, 70. 8 gr.; male, 70.1; Adult, 
fe, S00.5); 4. ,.7.70-0.or2 

Senses: Eye functions fully at birth. 
Ear functions at birth. 


Touch never very sensitive. 


Smell perfect at birth. 
Taste perfect at birth. 

Body: Thoroughly covered with fur; 
complete muscular development ex- 
cept the hind legs. 

Nervous system: practically completely 
medullated. 

Spontaneous movements not numerous 
but strong at birth. On second day 
movements very numerous. 

Coérdination: imperfect for first three 


days but perfect thereafter. 


Random movements: increase in num- 
ber from 2 to 8 days. 


throughout maturity. 


About constant 


Guinea Pig Compared with that of 
White Rat. 


WHITE Rat. 


AW5 355 at birth. Adult, female 


200; male, 250 gr. 


er. 


Opens 16 to 17 days. 
Functions fully after 13th day. 
Sensitive around the mouth, other- 
wise dull. . 
Sensitive at birth. 
Present, but no differentiation be- 
tween pleasant and unpleasant. 
Naked, ill-developed, immature in form 


and musculature. 
No medullation at birth. 


Movement very slight and weak at 
birth, and does not attain vigor un- 
til fifth day. 

The few movements attempted are co- 
ordinated, and after learning to crawl 
(from 4th day) codrdination rapidly 
increased. 

Increase in number and vigor from 4th 


to 60th or 7oth day. 


Psychical Development. 


Instincts: 
birth. 
Memory : 


almost fully functioning at 


proved to be present at sec- 
Perfect at 3 days. 
3rd day. 


ond day. 
Psychical maturity : 


Instinctive reactions are characteristic 

of life up to 12th day. 
Develops soon after 10th day. Perfect 
at 19 days. 


23 to 27 days. 


The data for the white rat are derived from the records of SMALL? and 


WATSON.? 


U MINOT: 


2 Amer. Jour. Psychol , Vol. XI, pp. 


3 Animal Education, Chzécago, 1903. 


Senescence and Rejuvenation, /owrn. PAyszo’., Vol. XII, p. 131. 
J 3 


80-100. 


[ 46 ] 


ALLEN, Association in the Guinea Pig. 339 


V. The Psychic Life of the Guinea Pig Compared with that 
of the White Rat. 


The Use of the Senses. —With the white rat, in the search 
for food, the sense of smell is paramount.’ Smell is by far the 
most necessary sense in the life economy. This sense does not 
play nearly so important a part with the guinea pig. It is an 
efficient sensation, but is apparently neither a definite nor a 
strong incitement to reaction. 

As with the guinea pig, so with the rat, vision seems to 
function mainly for orientation. But the rapidity with which mov- 
ing objects, especially those which cast a shadow, are seen in- 
dicates that the guinea pig uses his sense of sight to detect the 
approach of dangerous objects. 

The noises most quickly reacted to are those indications of 
danger and other signals made by the guthea pigs themselves ; 
and sounds associated with feeding time. 

The most important senses with the guinea pig are the 
kinesthetic. We can almost say that the guinea pig does the 
greater part of its remembering in kinesthetic terms. WATSON 
suggests that the memory of a path by young rats is motor.” 
How prominent a feature of rat life motor reactions are has not 
been discovered by any experiments yet carried out. 

Memory Processes —\W aTson found that memory processes 
of the white rat are not present before the twelfth day (p. 63), 
but beiore the twenty-second day they have reached a develop- 
ment sufficient to enable the solution of problems conditioned 
chiefly upon activity (p. 73). Psychical maturity is reached at 
from twenty-three to twenty-seven days of age (p. 83). 

The experiments upon which these conclusions are based 
are: (a) A simple labyrinth used to test the earliest appear- 
ance of memory of a path to the mother; (b) other more com 
plex labyrinths, in the solution of which activity was mainly 
involved, with memory of the path chosen; (c) boxes with dif- 
ferent methods of opening, involving a memory of more com- 


dD) 


plex movements than merely those of following a path to food. 


1 Animal Education, p. 84. 2 oa cit., pos, toot-noter 


1 47 J 


340 Journal of Comparative Neurology and Psychology. 


The obtaining of the food may have first occurred acci- 
dentally and the successful movements have been rapidly select- 
ed for retention by being ‘‘stamped in,” or by the elimination 
of random movements not pleasurably emphasized ; or an in- 
telligent factor may have entered into the selection of move- 
ments once found to produce the desired result of obtaining 
food. At any rate, it was found that ‘‘No form of problem 
which the adult rat is capable of solving presents insurmount- 
able difficulties to the rat of twenty-three days of age’’ (p. 84). 

The guinea pig stands in complete contrast to the white 
rat. Though no experimental records of memory were ob- 
tained from the guinea pig during its first day, a simple path 
was learned upon the second day, and upon the third day the 
most complex problem was solved, being a complicated laby- 
rinth. 

No experiments were made with the rat to determine how 
early a complicated labyrinth could be learned, but Watson's 
rats solved a simpleJabyrinth at nineteen days. 

When the guinea pig has found his way through a labyrinth 
he has reached the end of his psychical powers. He cannot 
pull a latch nor push a bolt, he will not depress an inclined 
plane, he will not chew a string nor stamp his foot. All the 
ingenuity which the white rat acquires after he has solved the 
labyrinth is a terra incognita to the guinea pig who thus pays 
the penalty of his early maturity. 

The experience of the white rat extends to strange com- 
binations of wires and springs, and all the delightful surprises 
revealed by secret doors. But when the guinea pig has turned 
the proper number of corners his dinner must be waiting for 
him or he does not get it. 

The rat at three days is just learning to crawl, has never 
seen an object and remembers nothing. The guinea pig at that 
age has triumphantly recalled a complex path, at the end of 
which he sits eating his well-deserved carrot. 

At twenty-three days the rat is lifting latches neatly, and 
forming what Hosuouse calls ‘‘practical judgments” as to the 
value of an inclined plane in a situation at the center of which 


[ 48 ] 


ALLEN, Association in the Guinea Pig. 341 


is his food—a desired thing, an end. The guinea pig is still 
wearing out the floor of the same labyrinth. 

Were we to anticipate our later work we would suggest 
that the significant contrasting features in the two animals are 
their nervous systems. In the one a mature nervous system is 
accompanied by psychical maturity; in the other, neural imma- 
turity permits great psychical development. 


Part II]. THe Centrat NERVOUS SYSTEM OF THE GUINEA P1G. 
Introduction. 


The investigation of the central .nervous system of the 
guinea pig has for its purpose the description of the conditions 
present at birth, and the changes in the medullation of fibers 
between birth and maturity. 

When an adequate notion of the nervous system and its 
growth changes has been obtained, it will be desirable to cor- 
relate these facts with the physical and psychical responses de- 
scribed in a previous part of this work. In view of the corre- 
sponding investigation of the white rat, a comparison will be 
made between the nervous system of the guinea pig and that of 
the white rat. 

The progressive medullation of the central nervous system 
has been correlated by many authors with the progressive ac- 
quisition of function." Nevertheless, Watson has shown in the 
case of the white rat * that both the peripheral and the central 
nervous systems are entirely without medullated fibers at birth, 
while many impulses are at that time transmitted to the central 
system and there coordinated; and that complex associative 
processes are present before the medullation of those areas 
which may mediate associations in the cortex. Furthermore, 


1 A summary of the previous work on medullation will be found on pages 
108 to. 111 of Animal Education. The discussion of FLECHSIG’s work is on 
pages 6 and 7, and a criticism of his wholesale correlations between function and 
medullation on pages 121-122. 


? Animal Education, p. 117. 


[49] 


342 Journal of Comparative Neurology and Psychology. 
the complexity in the psychical life of the white rat is wholly 
out of proportion to the very few tangential fibers to be found 


in the cortex. 


Technique. 
The guinea pigs used for histological study were of the 
common English variety. From a large number of nervous 
systems hardened and stained the following ages were selected 


for examination: 


Birth, male, 108 grams, used for illustration. 
3 hrs, sc 101.5 
I day, “6 84.5 ee 
2 days, female 83 
3 days, aS 106 : 
3.5 days, aC 87 a 
6 days, oe 70 
II days, ce 176.4 
30 days, 250.41 ‘¢ used for illustration. 
Adult, male, 617.9 ‘« used for illustration. 


Each guinea pig chosen for study was in good physical 
condition, the wide range of weight indicated in the table being 
within the bounds of normal individual variation. Most of 
those animals used in the psychological experiments were after- 
ward killed for examination. 

The central nervous system was exposed and hardened zz 
situ in MULLEr’s fluid. The tissue was kept in the dark during 
the hardening process, which required about fifty days for the 
small animals, and from sixty to seventy days for the adults. 
The sections were embedded in celloidin, ten grades being 
used,' and were cut 21y thick. They were stained according 
to the PAL-WEIGERT haematoxylin method, modified slightly to 
obtain the best results from this particular tissue. In detail the 
modified method is as follows: After cutting sections in 70% 
alcohol they were run to distilled water, then mordanted in 
MULuLer’s fluid 24 hours, at a temperature of 36 to 40° C. 
Washed thoroughly in distilled water, 2 to 4 hrs. Fresh WEI- 
GERT’s haematoxylin (cold) was poured over them, and they 


1} HARDESTY: Neurological Technique, p. 69. 


[5° ] 


ALLEN, Association in the Guinea Prg. 343 


were placed in a temperature of 40° C, 24 hrs. Washed well in 
numerous changes of tap water about 12 hrs. In differentiat- 
ing no attempt was made to complete the permanganate decol- 
orization at once, but the sections were allowed to remain in 
the permanganate from 15-25 secs., washed in distilled water, 
then placed in the oxalic-acid-sulphite mixture for several min- 
utes, or until differentiation ceased to be apparent. Then they 
were washed in distilled water, replaced in permanganate. 
a short time and the former process repeated. The best results 
were obtained when the tissues were carried back and forth 
three or four times. Subsequent washing in tap water was 
very thorough. 

The sections of the spinal cord were made at the level of 
(1) the sixth cervical nerve roots and ganglia; (2) the eighth 
thoracic nerve roots; and (3) the third lumbar nerve roots. 
The levels were chosen thus in order that the sections might 
pass through the largest parts of the cervical and lumbar intu- 
mescentiae, and through the smallest region of the thoracic 


cord. 
Sections of the encephalon were made (1) transversely, 


perpendicular to the base of the brain in front,of the infundi- 
bulum and behind the optic chiasm, being located accurately by 
means of the tracts of the thalami; and (2) in the case of the 
cerebellum, sagittally, through the vermis. 

Three ages have been chosen for reproduction, and draw- 
ings made with the help of a camera lucida. The magnifica- 
tion of the half tones of the cord is 2134 diameters; of the en- 
cephalon, 9% diameters. 


1. Description of Transverse Sections Through the Medulla 
Spinalis of the Guinea Pig at Birth. 
Cervical Level. 

A section through the cervical level at birch is reproduced 
in fig. 1, plate V. Reference to this figure will show that at birth 
a large number of fibers are medullated, and that the whole 
area of the white substance is almost uniform in its coloration. 
The gray substance is traversed by a large number of medull- 
ated fibers running in all directions. 


[51] 


344 Journal of Comparative Neurology and Psychology. 


The dorsal funiculus is subdivided into the fasciculus cu- 
neatus and fasciculus gracilis, and the latter is again subdivided 
into two fasciculi by a clearly marked septum. A similar sub- 
division was found in the medulla spinalis of the white rat.’ As 
in the white rat so in the guinea pig the fasciculus is very late 
in medullating. In the guinea pig this fasciculus presents an 
area considerably lighter than the substance immediately sur- 
rounding it, the medullated fibers in it being both small and 
comparatively few. In the fasciculus cuneatus a tongue of 
heavily medullated fibers passes from the level of the tip of the 
fasciculus gracilis down the septum posterior medianus to the 
commissura posterior (alba). On either side of the ventral por- 
tion of this tongue is a light oval area bounded laterally by the 
cervix columnae dorsalis, and extending from the commissura 
posterior to the substantia gelatinosa (fig. 1, plate V). This 
is the locality of the pyramidal tract. 

A third area slightly lighter than the rest of the white sub- 
stance is to be found in the lateral funiculus just ventro-lateral 
to the lateral apex of the substantia gelatinosa. Possibly there 
are in this locality some pyramidal fibers also. 

In the cervical cord of the guinea pig at birth there are, 
then, three light areas: (1) the fasciculus gracilis; (2) the pyra- 
midal area in the fasciculus cuneatus along the boundary of the 
cervix; and (3) an area containing a few fibers, around the lat- 
eral border of the apex of the dorsal column. 

In the cervical cord the portion of the white substance im- 
mediately surrounding the gray substance is much darker than 
the white substance at the periphery of the cord, as is indicated 
in the figures. This appearance is due to two factors, (a) the 
great number of fibers passing between the ventral columns and 
the white substance, these fibers seeming to radiate from the 
ventral columns like spokes froma hub; (b) numerous. fibers 
following the border of the gray substance; e. g., the fibers of 
the anterior commissure do not all pass directly to the cells of 
the gray substance, but have to wind in and out about the edge 


1 Animal Education, p. 94. 


[ 52] 


ALLEN, Assocation in the Guinea Pig. 345 


before they can effect an entrance. A further cause of darken- 
ing in the ground bundles around the margin of the gray sub- 
stance may be. that the longitudinal bundles are there more 
dense. In other words, in the section there may be more trans- 
versely cut fibers in the ground bundles than in the peripheral 
white substance. An enumeration of the fibers shows that in 
a given area there are in the lateral funiculus 16.7% more cross 
sections of fibers close to the ventral column than at the peri- 
phery. In the ventral funiculus the difference is 20.2% in 
favor of the given area close to the ventral column as opposed 
to a peripheral area in the same funiculus. 


Thoracic Level. 


At the thoracic level the lightly medullated area in the 
fasciculus cuneatus at the postero-lateral margin of the cervix 
columnae dorsalis (the pyramidal tract) is less well medullated 
than in the cervical region. It extends further toward the me- 
dian line, so that in its ventral half it approaches nearer the 
median septum and extends ventrally as far as the commissura 
posterior. 

The light area ventral to the lateral tip of the substantia 
gelatinosa appears in the thoracic segments. The fasciculus 
gracilis shows the two subdivisions commented upon in the de- 
scription of the cervical level, the dorso-medial being the less 
well medullated. 

In the thoracic as in the cervical cord the number of me- 
dullated fibers in the gray substance is worthy of attention. 


Lumbar Level. 


The light area in the funiculus cuneatus of the lumbar 
level occupies a position corresponding to that noticed in the 
section of the cervical, i. e., an oval area following the border 
of the cervix of the dorsal column, from the edge of the sub- 
stantia gelatinosa to the commissura posterior, but separated 
from the latter by a well marked area of medullated fibers. 
This area is somewhat smaller than the corresponding area in 
the cervical, and contains a larger number of scattered medul- 
lated fibers than appear at the levels above it. 


seicl 


346 Journal of Comparative Neurology and Psychology. 


The light area ventral to the lateral tip of the substantia 
gelatinosa is present in the lumbar region, and corresponds to 
the similar area of the higher levels. 

At the lumbar level the fasciculus gracilis does not appear 
in the section, and the funiculi dorsales are depressed below the 
level of the dorsal column on either side. 

In all levels of the spinal cord there is a large amount 
of medullation, numerous well medullated fibers of all classes 
being present. Throughout the gray substance everywhere 
there are fibers passing in every direction, both large and small, 
separate and grouped into heavy bundles. Commissural fibers 
cross the median line on both sides of the canalis centralis, the most 
conspicuous commissure being the anterior. Here fibers running 
in the plane of the section are extremely abundant. They pass 
among many cross sections of fibers. Two bundles are enclosed 
by these commissural fibers (fig. 3, plate V, v), and are to be 
found in this position at all levels and in all individuals exam- 
ined. 

Small bundles of fine fibers are seen passing longitudin- 
ally at the junction of the cervix and caput of the dorsal col- 
umn (fig. 1, Plate V, 7). They constitute a part of a very .ex- 
tensive reticular formation which in this region passes through 
one-half or two-thirds of the cervix. The processus reticularis 
is well marked in the lateral region of the gray substance at 
every level. 

1. In summarizing the appearances in the medulla spinalis 
of the guinea pig at birth emphasis is to be laid upon (1) the 
three partially medullated areas in the cervical and thoracic lev- 
els, to be found (a) in the fasciculus gracilis, (b) at the ventral 
border of the fasciculus cuneatus (the pyramidal tract), and (c) 
at the ventral margin of the apex of the dorsal column; (2) 
the two partially medullated areas in the lumbar cord, (a) the. 
pyramidal tract which is less well marked than at higher levels, | 
and (b) the area ventro-lateral to the substantia gelatinosa. 
The fasciculus gracilis is not present in the lumbar cord. 

2. In transverse sections the peripheral third of the white 
substance does not appear to contain so many medullated fibers 


{ 54 ] 


ALLEN, Association in the Guinea Pig. 347 


as are to be found near the margins of the ventral columns. 
3. At all levels there are many medullated fibers passing 
in every direction throughout the gray substance. 


ll. Development of the Medulla Spinals from Birth to Maturity. 
Cervical Level. 


Between birth and the third or fourth days the formation of 
medullary substance in the medulla spinalis is apparently at a 
standstill. After the third day the light areas which have just 
been described, show a rapid darkening, so that before the 
eleventh day the medullation of the whole section has become 
practically uniform, the light areas being closely packed with 
medullated fibers. These fibers appear to have a smaller aver- 
age diameter than the fibers of the neighboring funiculi, but 
their number is sufficient to render these areas as dark as those 
about them. Between eleven and thirty days the only notice- 
able change, besides increase in the area of the whole transverse 
section, is the still further darkening of the areas a, b and c. 

In order to compare the white rat of thirty-five days with 
a guinea pig at approximately the same stage of development 
(thirty days), the transverse sections from the three levels of a 
thirty-day guinea pig are reproduced (figs. 5, 6, 7, plate V). 

Upon reference to the figure of the cervical level it will 
be seen that the whole field has become darker than at birth by 
the great increase in number and in size of medullated fibers. 
The gray substance is traversed by a relatively larger number 
of fibers than is present at birth. The drawing of the thirty-day 
cervical section shows particularly well the cork-screw arrange- 
ment of the intra-medullary portion of the fibers passing into 
the gray substance from the zone of entering roots. 

A small light area is to be found in the thirty-day cord 
also, at the ventro-lateral tip of the substantia gelatinosa. About 
the tip of the substantia gelatinosa are many fibers running in 
the plane of the section. 

In the cervical cord of the adult (fig. 8, Plate V) the num- 
ber of medullated fibers is largely increased, the white substance 
appearing nearly black. Throughout the entire section 


or 


348 Journal of Comparative Neurology and Psychology. 


the white matter adjacent to the gray appears darker than at 
the periphery of the section. That this darkening is not due 
wholly to mere enlargement of fibers already medullated at 
thirty days is inferred from the presence of small fibers in all 
parts of the cord. 

In order to determine in how far new medullated fibers 
were responsible for these appearances a tentative enumeration 
of the fibers in several areas of the cervical cord was made. 
The areas chosen are represented diagrammatically in text-figure 
11 below. 


Text-figure II. 


Diagram of the cervical cord indicating the areas in which an enumeration 
of fibers was made. 

In comparing the enumeration of these fibers in the adult 
with an enumeration in similar regions of the young at birth 
we find that in the adult there has been both a slight increase 
in the number of fibers and a considerable increase in their aver- 
age diameter. The following table presents evidence of increase 
in number of fibers in the given areas between birth and ma- 
turity. The standard area within which the fibers were counted 
contained .00366 sq. mm., i. e., it was .06048 mm. on a side. 


TABLE SHOWING NUMBER OF FIBERS IN GIVEN AREAS OF THE CERVI- 
CAL CorD AT BIRTH AND AT MarTuriry. 


Dorsal funiculus. Lateral fun. Ventral fun. 
At birth, 301 PLS BI 218 ? 
Adult, 408 2037 246 ? 


+ Average of enumeration at periphery and at margin of ventral column. 


[ 56 ] 


ALLEN, Association in the Guinea Pig. 349 


It will be seen that the total increase in number of fibers, 
all the funiculi being considered together, is 16.81%. The in- 
crease in number of fibers, then, can only partially account for 
the enlargement of the cord during this period. 

In the adult the fasciculus gracilis is notably darker than 
the adjacent areas, whereas it was previously somewhat lighter. 
Similarly there is a corresponding darkening in the pyramidal 
area. The areas have been darkening by a great increase in 
number of medullated fibers. A count of the fibers in a given 
area of the fasciculus gracilis of both the adult and newborn 
shows that there has been an increase of 35.5% of medullated 
fibers in the older animal. In the newborn many fibers were 
too small to contribute to the darkening of the light areas. 

Casual inspection shows that the fibers in the ventral funi- 
culi are much larger than those of the dorsal fasciculi; this 
leads us to the conclusion that the number of fibers per unit of 
area is greater in the dorsal funiculus than in the ventral funi- 
culus, and a count proves this to be the case. That is, those 
regions which show the smallest number of medullated fibers 
in early life ultimately possess a greater number of fibers than 
tracts which at that time are practically complete. 

In the lateral funiculus there are somewhat fewer cross sec- 
tions of fibers at the periphery than in the ground bundle near 
the ventral column, the ratio being 1:1.22. In the ventral 
funiculus it is found, likewise, that at the periphery there are 
fewer fibers than near the ventral column, the ratio being here 
1:1.69. In both the lateral and the ventral funiculi the fibers 
at the periphery are larger than those near the gray substance. 


Thoracic Level. 


Little if any change occurs in the thoracic cord before the 
fourth day, as was found to be true also in the case of the cer- 
vical. The section at the sixth day shows much greater uni- 
formity of medullation, and at eleven days the pyramidal tract 
can not be distinguished from the neighboring white substance. 
At eleven days also the fasciculus gracilis is becoming darker 
than the surrounding regions. In the fasciculus gracilis at 


Lond 


350 Journal of Comparative Neurology and Psychology. 


thirty days the medullation is much heavier, and in the adult it 
appears as dark as the corresponding area at the cervical level. 

As at the cervical level, the white matter is darker at the 
border of the gray substance than at the periphery. 


Lumbar Level. 


The light area noted in the fasciculus cuneatus of the lum- 
bar level does not disappear quite so completely as the corre- 
sponding areas of the more cephalic levels of the cord. By 
the sixth day the medio-ventral part has become evenly medul- 
lated, but at the eleventh day there is still an area in which 
there has been little or no increase in medullation. Notwith- 
standing the fact that in the lumbar level this light area was at 
birth very faintly marked, a suggestion of it persists here longer 
than in the levels above. Even at thirty days it is not quite 
lost in the general increase of medullary substance. 

The fasciculus gracilis does not appear in the lumbar cord 
of thirty days, the dorsal funiculi being depressed in such a way 
as to form a groove at this region. Numerous fibers in the en- 
tering root zone and in the fasciculus cuneatus have made this 
groove relatively less deep than at birth. At maturity this de- 
pression can still be detected ; and the fasciculus gracilis, though 
comparatively very small, appears at this level. 

In the lumbar cord the crowding of the fibers in the ground 
bundle of the lateral and the ventral funiculi is not so conspicu- 
ous as it has been higher up. Fibers radiating from the ventral 
columns appear to be quite as numerous, but the longitudinally 
coursing fibers are probably not so numerous. 


Summary of Changes in Medullation of the Medulla Spinalis Be- 
tween Birth and Maturity. 

t., Inthe cervical and thoracic levels three areasaunitne 
white substance are at birth noticeably lacking in medullated 
fibers: 

a) the fasciculus gracilis, 

b) the pyramidal area in the fasciculus cuneatus, 

c) in the lateral funiculus an ill-defined area ventro-lateral 

to the substantia gelatinosa. 


[ 58 ] 


ALLEN, Association in the Guinea Pig. 351 


2. Before eleven days the first two areas are medullated 
uniformly with the surrounding regions. The area in the lateral 
funiculus has received many new fibers and can be distinguished 
only as a narrow light zone bordering upon the lateral apex of 
the substantia gelatinosa. 

3. By thirty days the two areas in the dorsal funiculus 
just distinguished as medullating late have become darker than 
the surrounding region. In the adult these areas are relatively 
still darker than at thirty days. 

4. Inthe adult the light area in the lateral funiculus still 
has small fibers, many of which pass longitudinally within the 
limits of the substantia gelatinosa itself. 

5. Since the lumbar level at birth does not possess a fas- 
“ulus gracilis it lacks one light area mentioned for the levels 
above. The other two light areas are present, though less 
well marked than at the higher levels. 

6. The ventral half of the pyramidal area soon becomes 
well medullated, but its dorsal half remains poorly medullated 
for a longer time than at the higher levels, since even at thirty 
days it is still a little lighter than the adjacent white substance. 

7. On the whole the cord of the guinea pig at birth is 
very well medullated in all its regions. 


Increase in Area of Cross Sections of the Medulla Spinalis from 
Birth to Maturity. 

The changes in the spinal cord which have been described 
above are such as are apparent by inspection of the various fun- 
iculi represented in the drawings. Contemporaneous with the 
darkening of the section by the increase in the size and the 
number of medullated fibers there has been an enlargement of 
the total area of the cord. 

A selection of typical sections was made, and their transverse 
areas ascertained with the planimeter. The results are indi- 
cated in the following table : 


IBRARY } 33 


[59] 
AYO By 


352 Journal of Comparative Neurology and Psychology. 


IAB EE ae 


Table showing the increase in area of cross sections of the spinal cord of 
the guinea pig from birth to maturity. 


Weight, Age, Level, Substance. 

grms. White, Gray, Total. 

108 birth Cerv. 2.88sq.mm. 2.34sq.mm. 5.22 sq. mm. 
Mow e575 84 2.59 
Lumb. 1.42 1.38 2.80 

106 3idays ~CGerv..) (2.90 2.47 ee 
Mhor, e324 85 2.19 
Lumb. 2.01 2.02 4.03 

250.41 goidays iCery.. ~ 3.67 2.16 5-83 
dior: § 2221 .93 3-14 
Lumb. ene m93 6.05 

617.9 adult Cerv. 6.90 2.69 9.68 
Thor. 74576 94 5-70 
Lumb. 5.80 3.07 8.87 


The percentage increase in the white and gray substances. 
and in the total area of the cross sections in the entire cord is 
graphically shown in the following table: 


TABLE II. 


The percentage increase in cross sectioas of the white substance from 
birth to maturity. 


Age env: Thor. Lumb. 
Birth 100 100 100 
Adult 138.81 172 308.4 


The percentage increase in cross sections of the gray substance from 
birth to maturity. 


Age Cerv. Thor. Lumb. 
Birth 100 100 100 
Adult 14.9 11.0 122.9 


The percentage increase in total area of cross sections of the cord. 
from birth to maturity. 


Age Cerny. Thor. Lumb. 
Birth 100 ‘100 100 

3 days 2.8 15 43-9 
30 days 11.6 212 116.0 
Adult 85.4 120.08 216.78 


ALLEN, Assoctation in the Guinea Pig. 353 


It will be seen that the percentage increase in both the 
gray and white substance is much greater at the lumbar level 
than at the levels above, the lumbar cord, therefore, showing 
the greatest amount of developmental change from birth to 
maturity. 

The progress of medullation in the thirty day guinea pig 
has attained about the stage reached by a thirty-five day white 
rat. The table below compares the areas of the spinal cords 
of the two animals. 

ADAVEVLIS. AWE: 


Table showing the areas of the cross sections of the spinal cords of a 
guinea pig thirty days old, and of a white rat thirty-five days old. 


Animal, Age, Level, White, Gray, Total. 
Guinea 30 days Cerv. 3.67 2.16 5-83 
pig Thor. 2.21 .93 3-14 
Lumb. Ba2 2.93 6.05 
White 35 days Cerv. 3.83 3.67 7.50 
rat Thor. 2.08 1.18 3.26 
Lumb. DRAM 4.07 6.48 


It will be seen that the absolute areas are closely compara- 
ble, the cervical cord of the white rat being, however, larger 
than that of the guinea pig; so that in volume of the spinal 
cord as well as in the stage of medullation the guinea pig of 
thirty days may be compared with the white rat of thirty-five 
days. 

To repeat what has been said before, by way of summary, 
the spinal cord of the guinea pig increases in area by the devel- 
opment of new fibers, and by the growth of fibers already 
formed at birth. When we see how heavily medullated the 
adult cord is, and know how much it has increased in'‘area we 
conclude that there has been a very great addition of substance 
by both of these methods. 


Ill. The Encephaton of the Guinea Pig. 


Cerebrum. 


In the encephalon at different ages the relation of the parts 
is not the same, so that it is impossible to get exactly compar- 
able sections, and structures in the optic thalami were chosen 


[ 61] 


354 Journal of Comparative Neurology and Psychology. 


as being the most reliable marks for the determination of simi- 
lar levels. 

At birth the cerebral hemispheres show many well-medul- 
lated tracts. The section reproduced in figure 14, plate VI, 
is through the cornu Ammonis, ventral to which lie the thala- 
mic structures. An outline drawing has been introduced (Text- 


Text-figure [2. 


fig. 12) asa key to the representations of the sections of the 
cerebral hemisphere. The letters in parenthesis refer to corre- 
sponding figures in the diagram. 

In the diencephalon the thalamus opticus (7%. 0) with 
fibers (Radiatio lateralis thalami, A) radiating into the internal 
capsule (Capsula interna, (Cz); the fasciculus of Vicq d’Azyr 
(fasciculus thalamo-mammillaris, 77); the Columna fornicis (C/); 


[ 62] 


ALLEN, Association in the Guinea Prg. 355 


and the lateral geniculate body (Corpus geniculatum laterale, 
Cg) appear as prominent features. The principal fiber tracts 
are already medullated. 

As in other rodents in which the olfactory apparatus is well 
developed, the Ammon’'s horn (Cornu Ammonis, CA ) isa con- 
spicuous structure. In the guinea pig at birth the fibers of the 
Ammon’s horn have only begun to be medullated in delicate 
layers separated by large areas of cells and unmedullated fibers. 
At the tip of the Ammon’s horn the fimbria is already darkly 
medullated. Dorsal to the Psalterium (Ps) and immediately 
ventral to the Corpus callosum (Cc) is seen a group of fibers 
belonging to the Fornix longus (/ 7). 

Extending from near the median line dorsal to the fornix 
around the cortex and ventro-lateral to the lenticular nuclei is a 
dark mass of fibers, the white substance of the hemispheres, 
from which already numerous radial bundles emerge, passing 
in the direction of the cortical cells. 

Not only are fibers to be seen radiating toward the surface, 
but also there are many fibers in the deeper portions of the 
cortex running parallel to the cortical surface. By using a high 
power very fine fibers are visible in the zonal layer (Z). But 
with this magnification no fibers are to be seen at the margin 
of the cortex. In the white rat this system of fibers does not 
begin to medullate until after the forty-second day. 


Development of the Cerebral Hemispheres. 


The drawings of the encephalon at thirty days and at ma- 
turity show a gradual increase in number and complexity of 
pathways formed by medullated fibers. The most remarkable 
changes have been in the Ammon’s horn (CA), in the Psal- 
terium (/s), in the internal capsule (Cz), and in the white sub- 
stance of the hemispheres. The optic tract appears well me- 
dullated. The bundles of fibers radiating toward the cortical 
surface from the white substance of the hemisphere become 
more abundant between birth and maturity, and extend further 
toward the surface. The fibers of the stratum zonale become 
more evident and the layer becomes thicker. In general, there- 


[ 63 ] 


356 Journal of Comparative Neurology and Psychology. 


fore, the tracts of medullated fibers become more densely me- 
dullated in the older animals. 

The area of the cross section of the encephalon has in- 
creased in size, and incipient sulci are distinctly more marked 
in the adult than in the newborn brain. At the temporal mar- 
gin of the cortex a sulcus, scarcely indicated at birth, has be- 
come well marked in the course of development. The increase 
in size of the temporal lobe seems, as indicated in the draw- 
ings, not to have been a progressively symmetrical growth; up 
to thirty days the ventral portion has developed most, after 
that the ventro-lateral portion undergoes the greatest change. 


Cerebellum. 


The sections from which the drawings were made were 
taken in the median sagittal plane, passing therefore through 
the vermis. The changes in this part of the encephalon are 
readily appreciated from comparison of the drawings. 

As to general contour, it will be seen that the folia are 
numerous at birth, and in the course of development become 
larger and more pronounced. The PurKINJE cell layer is marked 
in the drawings by a white line (the cells not staining by this 
method) separating the molecular and granular layers. 

At birth the molecular layer is free from medullated fibers. 
The granular layer contains fibers radiating from the white lam- 
inae; these fibers are especially numerous at the apex of the 
laminae. In the granular layer very many fibers are seen run- 
ning more or less parallel to the white laminae. Further out 
in the granular layer such fibers are shorter and finer. Almost 
all the fibers seem to be medullated in the white laminae even 
at birth, and are densely packed together. 

There is a great increase in the number of fibers found in 
the granular layer from birth to maturity. Such an increase is 
particularly marked in the fibers at the junction of the laminae 
and granular layer. It can be seen that the folia, present at 
birth and reaching the surface of the vermis, tend to divide as 
the animal becomes older, and that the folia deep-seated at birth 
push their way towards the surface. 


[ 64 ] 


ALLEN, Association in the Guinea Pig. a7 


The changes in the encephalon between birth and maturity 
as exhibited in the figures may be recapitulated as follows : 

I. At birth no important cerebral pathways are unmedul- 
lated. 

II]. The number of fibers increases very greatly up to 
maturity. 

III. The Ammon’s horn corresponds in its development 
to the cortex, and at birth has very few medullated fibers. 

IV. Few tangential fibers of the zonal layer are present 
at birth, and at no time are such fibers numerous in the stratum 
zonale of the guinea pig. 


Increase in Area of Cross Sections of the Encephalon. 
Q 


There are no observations showing the increase in weight 
of the encephalon of guinea pigs between birth and maturity. 
Linear measurements, however, show clearly that during this 
period the encephalon increases in size as well as in number of 
fibers. 

The, area of the cross sections used for illustration, of 
both cerebrum and cerebellum was measured, and is presented 
in the following table: 

TABLE IV. 
Table showing the increase in area of cross sections of the encepha- 
lon between birth and maturity. 


Age, One cerebral Cerebellum (mesial sec- 
hemisphere, tion of vermis). 
Birth 60.73 30.89 
30 days 73-52 45-29 
Adult 83.05 58.70 
TABLE V. 


Table showing percentage increase in area of cross sections of enceph- 
alon between birth and maturity. 


Age, Cerebral hemisphere, Cerebellum. 
Birth 100 . 100 

30 days 21.06 45-15 
Adult 36.77 90.03 


[ 65 ] 


358 Journal of Comparative Neurology and Psychology. 


IV. Comparison Between the Nervous System of the Guinea 
Pig and that of the White Rat. 


At the end of the study upon the psychical processes of 
the guinea pig a comparison is made between the psychical and 
physical development of the guinea pig and the white rat. It 
was found that the white rat is born extremely helpless and un- 
developed, whereas the guinea pig is independent and well de- 
veloped. On the psychical side the guinea pig has reached the 
limit of his possibilities by the third day, while the white rat 
reaches psychical maturity from twenty-three to twenty-seven 
days. It was suggested that the contrast between the nervous 
systems of the guinea pig and of the white rat might be analo- 
gous to the contrast in their physical and psychical develop- 
ment. 

We have seen in detail what is the condition of the guinea 
pig’s nervous system at birth, and what changes occur during 
progress to maturity. 

A description of the same cycle for the white rat will be 
found in Animal Education, pp. 87-111. Summarizing these 
results we find that in the white rat there are no medullated 
fibers present at birth; that in the spinal cord certain tracts 
(pyramidal tracts, fasciculus gracilis, etc.) medullate slowly, and 
that even in the adult the pyramidal tracts do not stain com- 
pletely ; that development in the cerebellum is more rapid than 
in the cerebrum; that medullation in many regions of the cere- 
brum is very slow up to the twenty-fourth day, after which the 
fibers rapidly mature. 

Now, if we compare the sections of the guinea pig’s spinal 
cord with sections of the white rat’s spinal cord we see that the 
guinea pig at birth has reached the same stage of development 
attained by the white rat at twenty-four days. Similarity be- 
tween the new-born guinea pig’s psychical processes and those 
of the twenty-four day white rat is correlated with surprising 
accuracy with the similarity in their nervous systems. The 
similarity is present in a less marked degree between the cerebral 


| 66 | 


ALLEN, Association in the Guinea Pre. 359 


cortices owing to the fact that medullation in the guinea pig ap- 
pears to be more advanced. 

Very little change occurs in the central nervous system 
during the first three days of the guinea pig’s life. Medullation 
then increases quite steadily but slowly as compared with the 
white rat. When the white rat is thirty-five days old it has a 
neural development at the same stage as the thirty day guinea 
pig. 

Our conclusion then is that the guinea pig is psychically 
mature soon after birth, and at that tirae has a well medullated 
nervous system; furthermore, the degree of development of the 
nervous system corresponds to that of the white rat at 23-27 
days, or its period of psychical maturity. 


[ 67 ] 


5 


Journal of Comparative Neurology and Psychology, Vol. XIV. Plate V. 


Fic. 1. Cervioal Cord. At birth 
Fic. 5. Cervical Cord. Thirty Days. 


Fic. 8. CervicalCord. Adult. 


Fic. g. Thoracic 
Cord. Adult. 


Fic.2, Thoracic Cord. At birth. Fic. 3. Wumbar Cord. At birth, 


Fic. 6. Thoracic Cord. Thirty Days. 


Fic. 4. Dorsal 
Column of 
‘Thoracic Cord. 
Thirty days. 


Fic. 7. Lumbar Cord. Thirty Days. 


Fic. 10, Lumbar Cord. Adult. 


* 
“ 


Journal of Comparative Neurology and Psychology, Vol. XIV. Plate VI. 


Fig. 15. 
Cerebral 
Hemisphere. 
Thirty 

days. 


Fic. 13  Vermis of Cerebellum. Adult. 


Fic. 11. Vermis of Cerebellum, At birth, 


Fic, 16, 
Cerebral 
Hemisphere. 
Adult. 


Fic. 12. Vermis of Cerebellum. Thirty days. 


<i __ 


Fic. 14. Cerebral Hemisphere. At birth. 


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EDITORIAL. 


SOME UNEMPHASIZED ASPECTS OF COMPARATIVE PSYCHOLOGY. 


We desire to enter a plea for a more detailed and extend- 
ed study of what, for lack of a better term, we may call imita- 
tion in the mental processes of animals. : 

The word imitation is not used in any exact sense by 
writers on comparative psychology. Kinxaman' and Lioyp 
MorGan’ have summarized the main facts covered by the word 
probably better than any of the other contemporary writers 
who deal exclusively with the mental processes of animals. 
They agree in the following classification of imitative behavior : 

1. Mimicry which lies below the level of imitation. 

2. Instinctive imitation, or automatic behavior. 

3. Intelligent imitation : 

a) of actions. 
b) of results. 

BaLpWIN’ uses the terms ‘simple’ and ‘‘persistent.”’  Ex- 
amples of these various types of imitation cannot be given here. 
We shall assume that every one is more or less familiar with 
them. In this paper the word imitation designates what Mor- 
GAN Calls zutelligent wnitation. 

THORNDIKE states emphatically that imitation in the above 
sense does not exist in animals lower than the primates. In the 
Mental Life of Monkeys (p. 42) he concludes: ‘‘Nothing in 
my experience with these. animals then favors the hypothesis 


1A. J. Kinnamay. Mental Life of Two Macacus Rhesus Monkeys in Cap- 
tivity, I]. American Journal of Psychology, Vol. XIII, No. 2, p. 196. 

2 Lroyp MorGan. Habit and Instinct, pp. 169-174. 

3 Mental Development, p. 132. 


Editorial. 361 


that they have any general ability to learn to do things from 
seeing others do them.”” KINNAMAN in his Studies of the Men- 
tal Life of Rhesus Monkeys in Captivity, comes to a different 
conclusion: ‘‘Again, of the simple form as discussed by Batp- 
win, I observed one very clear case. . . . This appears 
to me to come ciearly under MorGan’s class of intelligent imi- 
tation Jofanjact' ...\": There were many other cases of 
this type, as it seems to me, though they are more difficult to 
demonstrate. . . . But again I have observed two cases 
of imitation of the persestent and zntelligent types. ' 

SMALL' writes as follows: ‘‘My conclusions from all this 
experimental work, and from much other observation of rats is 
that they do imitate but that imitation with them is relatively 
simple. They imitate simple actions; but I have seen no case 
of what may, in lack of a better term, be called inferential imi- 
tation.” 

As far as our’ observations have gone, we thoroughly agree 
with this conclusion of SMALL. 

Hosuovuse’, who is by far the most liberal interpreter of 
animal behavior, takes up no experiments which are especially 
designed to show this form of mental activity. He criticizes 
THORNDIKE very severely for denying outright that animals can 
learn by being put through an action. In fact he citesan experi- 
ment, conducted by himself, which is designed to prove the con- 
trary (p. 148). In discussing imitation in animals lower than the 
primates (pp. 149-151), he says it remains uncertain whether they 
have the power of ‘‘reflective imitation’’—imitation based on 
the perception of another's act and its result to that other. 
Hosuouse rightly insists that the possibility of a still simpler 
mental act must first be settled—‘‘learning by the perception 
of an event and its consequence—when that consequence di- 
rectly affects the learner.’’ His ‘‘Experimental Results” (pp. 


1 WHLLARD S. SMALL. Experimental Studies of the Mental Processes of the 
Rat. American Journal of Psychology, Vol. X1, No. 2, p. 162. 


2 Joon B. Warson. Animal Education. 


8 HopHuouse. Mind in Evolution. 


362 Journal of Comparative Neurology and Psychology. 


152-207) go to show that animals do learn by this perception of 
what the experimenter does, and its results. In the same sec- 
tion (pp. 207-5), he finally concludes that there is no natural 
tendency to learn by perception; still less by ‘reflective,’ as dis- 
tinct from ‘‘simple’”’ imitation. From this I gather that, while 
HosHovuseE assumes that there is no xaturva/ tendency to imitate, 
still this mental act may be acquired in much the same way 
that habits of attention may be acquired by animals (p. 204). 
When on p. 259 he discusses ‘‘Articulate Ideas,’’ he mentions a 
case of reflective imitation in the Rhesus monkey. He even 
puts it more strongly: ‘‘To transfer the act and apply it to 
himself and his own needs, was, at lowest. a strong case of re- 
flective ‘imitation.’ But the use of the term imitation in this con- 
nection is really misleading. At most my act served as a hint.” 

Coming finally to PorTEr’s' excellent piece of work on the 
Psychology of the English Sparrow, we find this problem still 
untouched: ‘There is some proof of ability to profit by the 
experience of others, or of imitation. However, before any 
description of the real nature of this imitation can be given, ad- 
ditional and varied experiments are needed.” 

This short and incomplete survey of the field serves to show 
what inadequate experimental treatment this most important 
subject has had. That the subject is important, is evidenced 
by the fact that every investigator, at the end of the discussion 
of his results, mentions imitation. Yet few experiments have 
been especially designed to bring out the positive facts—if such 
there be. And no sane reader would deny utterly, on the basis 
of the few records we have, that animals can learn by imitation. 

Most of us have been too busy, either in ascribing habit 
formations to lower and lower orders of animals, or in describ- 
ing the mental processes i general in the higher animals, to give 
enough time and thought to a complete study of any one of the 
more typical mental acts. We are not criticizing any of the 


1 James P. Porter. A Preliminary Study of the Psychology of the English 
Sparrow. American Journal of Psychology, Vol. XV, p. 345. 


Editorial. 363 


experimental work here. Such work as has been done is 
abundantly necessary—the ground must be broken—but we do 
plead for long and careful studies in more restricted lines than 
that represented by simply taking an animal and watching its 
general behavior. It is time to put the animal in such situa- 
tions that some one mental act may be exhibited to the exclu- 
sion of others. JOHN B. WATSON. 


LITERARY NOTICES. 


Bethe, A. Allgemeine Anatomie und Physiologie des Nervensystems. Lesg- 
stg, G. Thieme, 1903, pp. vil-485, 95 figs., 2 plates. 

This volume is a series of monographs on different phases of the 
same subject rather than a textbook of comparative neurology, as the 
substance of many of the chapters represents the author’s own research. 
The first three chapters are devoted to a historical account of the. 
structures of the nervous elements; and in the comparative descrip- 
tion of the nervous system (chapters 4 and 5), the structure and rela- 
tion of these elements is given a more prominent place than would be 
possible in a textbook. 

In all forms possessing a nervous system the neurofibrillae are the 
essential nervous elements. The motor and sensory fibrillae of inverte- 
brates are connected by networks in the ganglion cells, and are also 
continuous with each other in the neuropil. The nerve fibers of ver- 
tebrates are composed of strands of fibrillae imbedded in perifibrillar 
substance; at RANVIER’s nodes the latter substance is interrupted, but 
the fibrillae are always continuous. Fibrillar networks are formed 
chiefly in the sensory ganglion cells; in most other cells the fibrillae 
pass directly through; they may enter by one dendrite and pass out 
by another without entering the neurite of the cell. Brerae maintains 
that motor and sensory fibrillae are put into direct connection by the 
‘*GOLGI nets” which envelop most of the central ganglion cells. 

The peripheral networks of cells and non-medullated fibers are 
dealt with in chapters 6 and 7. The entire nervous system of the 
medusae is composed of these structures. They are also found in the 
integument, vascular system and digestive tract of mollusks, arthro- 
pods, worms and vertebrates. That these networks and not the muscles 
are the true conducting elements of the medusae is shown by the fact 
that two distinct bands of muscle may be made to contract by stimu- 
lating one of them. If the entire central nervous system of’ a gastro- 
pod mollusk is removed, stimulation of the body wall at one point will 
produce a general muscular response. Ina similar manner the applica- 


Literary Notices. 365 


tion of a stimulus to the intestinal wall of the frog will produce con- 
traction of the muscles of the stomach and oesophagus. 

Chapter 8 gives a detailed account of the staining reactions of the 
nervous elements. Nussi’s plates and the neurofibrillae owe their pe- 
culiar staining powers to two specific substances. The ‘‘Nrssi sub- 
stance” is soluble in aqueous solutions of HC] and ammonia; the 
‘fibrillar substance” is soluble in acid aleohol and many of the ordi- 
nary fixing reagents. It may be fixed by corrosive sublimate and is 
insoluble in water, chloroform and ether. Good preparations of the 
fibrillae may therefore be obtained by fixing in ether and substituting 
ether for alcohol as a dehydrating reagent. Two methods of this kind 
are described. Centrosomes, intracellular canals, pigmentation, and 
changes in structure produced by poisons, or due to other abnormal 
conditions, are briefly discussed in chapter 9. 

Nerve degeneration and regeneration form the subject matter of 
chapters 10-12. The first evidence of degeneration is the disappear- 
ance of the fibrillar substance and consequent loss of staining power. 
Degeneration is not necessarily due to the lack of continuity between 
fiber and cell but a wound which does not affect the conductibility of 
the fibrillae may produce degenerative changes. The conductibility 
of fibers may be interrupted by application of pressure or of injurious 
gases but degeneration will not ensue. The cutting of a peripheral 
nerve, however, may lead to the degeneration of both the central por- 
tion of the fiber and its ganglion cell. 

After the lapse of two months or more the normal structure and 
functional activity of an isolated and degenerate peripheral nerve may 
be completely restored (auto-regeneration); if severed a second time 
the distal portion only will degenerate; but if the two ends of such an 
auto-degenerated nerve are grafted together, a union, both structurally 
and functionally perfect, will be established. 

The peripheral nerves of the chick (chapter 13) are formed as 
chains of cells which may be observed before the processes of the neu- 
roblasts within the spinal cord have become prominent. These chains of 
nerve cells differentiate from their substance the axis cylinders, and 
later become the sheath cells of the fibers. The dendrites of ganglion 
cells are also developed from a syncytium of nerve cells, and not as 
outgrowths of single neuroblasts. 

The nature of nervous transmission is the subject of chapter 14. 
If by compression, the perifibrillar substance is practically eliminated 
from a certain portion of a fiber without injury to the neurofibrillae, the 
conductibility of the fiber is not affected. The neurofibrillae must, 


366 Journal of Comparative Neurology and Psychology. 


then. be the conducting elements. When through degeneration, pro- 
longed pressure. or the application ot distilled water. a nerve fiber is 
rendered non-conductile. staining shows that the fibrillar substance 
has disappeared. Upon the removal of the abnormal conditions or 
upon the regeneration of a fiber, it is found that the return of func- 
tional activity is accompanied by the reappearance of the fibrillar sub- 
stance. This substance is therefore connected with nervous transmis- 
sion. A constant current of 0.05-0.2 milliamperes acting for 10 minutes 
upon a nerve will produce a polarization of the fibrillar substance 
and render the nerve non-conductile. If at once fixed and_ stained. 
that portion of the nerve near the anode will be much lighter, that 
portion near the kathode much darker than normal. If after polariza- 
tion the fixation is delayed until the conductibility of the nerve returns, 
it will be stained with equal intensity throughout its course as in the 
case of normal fibers. The change which takes place during polariza- 
tion is a chemical one. The fibrillar substance is set free at the anode 
and accumulates at the kathode. Darkly stained granules represent- 
ing free fibrillar substance were observed at the anode among the 
fibrillae of the nerve. This chemical change takes place only in living 
and functional nerves and is theretore evidently a vital process essen- 
tial to nervous transmission. According to BeTHE the nervous im- 
pulse is produced by a chemico-physical process. A condition of in- 
creased affinity for the fibrillar substance passes wavelike along the 
fibrillae and the molecules of fibrillar substance are drawn toward the 
point of stimulation. Coincident with this chemical change, a nega- 
tive electric current is produéed. Either this current or the progress- 
ive movement of the fibrillar substance may be instrumental in trans- 
mitting the stimulus. BerHe believes that the chemical changes are 
of most importance in producing nervous impulses ; the changes which 
take place are not oxidation processes, but merely fluctuations in the 
chemical affinity of the neurofibrillae. 

Chapter 15 discusses the peculiar properties of the central nerv- 
ous system, such as tonus. and inhibition of reflexes; on the ground of 
his well known experiment upon the brain of Cavc/nus, the author re- 
assérts that both tonus and the transmission of reflexes are not depend- 
ent on the ganglion cells. In chapters 16-18 a review is given of the 
various phenomena characteristic of nervous reflexes. An interesting 
account of the effects of various poisons on the nerve elements follows 
(chapter 19). Most poisons affect first the elements of the central 
nervous system, because the fibers there are not protected by the thick 
sheaths which surround most peripheral fibers. Narcotics inhibit the 


Literary Notices. 367 


changes in affinity between the fibrillae and fibrillar substance ; they 
therefore interfere seriously with nervous transmission. ‘The state of 
increased sensitiveness to stimuli, which is one of the first symptoms 
of narcotic action, is due to the destruction of a substance peculiar to 
the elements of the central nervous system, which normally inhibits 
reflexes to a certain degree. 

In chapter 20 it is shown that there are two types of muscle tonus. 
The tonus of striated muscle is due to the action of the central nervous 
system; in the case of certain non-striated muscles tonus is independ- 
ent of the nervous system, and represents a state of rest. Such muscle 
passes into a state of tetanus when the central nervous system is re- 
moved (gastropod mollusks); the nervous system normally inhibits such 
a condition, 

A brief review of the factors concerned in the inhibition of reflex 
action (chapter 21) is followed by a description in chapter 22 of the 
author’s important work on the rhythmical contractions of muscle. It is 
shown that the number of respiratory movements in fishes is not regu- 
lated by the amount of O or CO, present in the water, but that if the 
sense organs of the mouth cavity are paralyzed by cocain the move- 
ments will soon cease completely. The rhythmical muscular contractions 
during respiration are due to peripheral stimuli, not to a special power 
with which the muscle is endowed, nor to the influence of the cells of 
the central nervous system. 

From the physiological standpoint the vertebrate heart and the 
bell of the medusa are very similar. If the sinus venosus of the heart, 
or the sense organs of the medusa are removed, rhythmical contrac- 
tions cease, but in each case may be maintained by prolonged artificial 
Stimulation; the contractions are true reflexes produced by definite 
stimuli. The transmission of the stimuli from the sinus yvenosus to the 
ventricle has been assumed to be a purely muscular function because 
the heart of the embryo chick begins to contract before the nervous 
structures have developed. BETHE points out that muscle fibers are 
not yet differentiated at this stage. The weightiest argument against 
the assumption of nervous transmission in the heart, is the slow rate 
of conduction (only 30 mm. per second in the frog). But BETHE 
shows that the rate of transmission in the dog’s heart is about 300 mm. 
per second; also that if the muscle fibers of the atrium are rendered 
functionless by exposure to low temperature, or by the action of mus- 
karin, stimulation of the atrium will cause contraction of the ventricle, 
although the muscle fibers of the atrium exhibit not the slightest reaction. 
It has been observed, too, that the apex of the ventricle often con- 


368 Journal of Comparative Neurology and Psychology. 


tracts sooner than its base, and that a strip of heart muscle stimulated 
at one end may begin to respond first at the other extremity. All of 
the above facts point toward nervous transmission of definite stimuli. 
In the case of the medusae the stimuli originate in the sense organs of 
the bell; the source of the stimuli regulating the heart’s action is 
practically unknown. 

Following the text of the book is a valuable list of the recent lit- 
erature on the nervous system. Much of the original work described 
by Berue is necessarily incomplete, and as he himself states, the theories 
advanced are but preliminary, and will undoubtedly be subjected to 
future correction. They have already proved of value, however, in 
stimulating research along similar lines ; and the many valuable results 
of the author serve to emphasize the importance of combining histolog- 
ical and physiological methods in attacking the abstruse problems of ’ 
neurology. Co. Wi, Be: 
Goldschmidt, R. Ueber die sogenannten radiargestreiften Ganglienzellen von 

Ascaris. Stolog. Centrél,, Band NNIV, No. 5, pp. 173-182, 1904. 

Discusses the radially striped ganglion cells of -dscavvs. He finds 
them in all parts of the nervous system. The striped appearance is 
due to radial projections from the glia capsule extending into the cell 
for some distance, finally disappearing in the cytoplasm. He believes 
these to be characteristic of all ganglion cells and supposes the GoLGI 
nets of mammalians to be of the same nature. They are probably not 
trophic. Their elastic nature may serve to suspend the cells in such 
a manner as to respond easily to vibrations. According to this sup- 
position, a tearing of these projections is suggested as an explanation 
of the serious disturbance of the nervous system caused by severe me- 
chanical shock. G. WAGNER. 
Kolmer, W. Eine Beobachtung iiber vitale Farbung bei Corethra plumicornis 

(Vorlaufige Mittheilung). Bzo/og. Centrb/., Band XXIV, No. 6, pp. 221- 
23, 1904. 

Larvae kept for weeks in methylene blue solutions showed no 
staining. After feeding on Stentor killed with methylene blue, they 
showed staining of nervous elements. This staining appeared and dis- 
appeared at intervals. As the animal remained alive for many hours 
afterward, the staining was probable truly ¢vtva vifam. 

G. WAGNER. 
Coggi, A. Sviluppo dei organi di senso laterale, delle ampolle di Lorenzini, e 
loro nervi rispettivi in Torpedo. Archivio Zoologtco, Vol. 1, Fasc. 1, pp. 
59-107, 1yo2. 


A detailed discussion of the development of the lateral line and 


Literary Notices. 369 


Lorenzinian ampullae and their nerve supply in Zo7fedo. The Loren- 
zinian ampullae are homologous with the ‘*terminal buds” of other au- 
thors. There are no ‘‘pit organs” in Zorpfedo. There is no genetic re. 
lation between the ampullae and the lateral line organs. There is no 
morphologic distinction between the lateral line and the organs of 
Savi. The latter are mere modifications of the former. 
G. WAGNER. 

Spitzka, Edward Anthony. Contributions to the Encephalic Anatomy of 

the Races. First Paper:—Three Eskimo Brains, from Smith’s Sound. 

The Amertcan Journal of Anatomy, II, 1, pp. 25-71. 

Well illustrated with figures of the different surfaces of the brains, 
with very full descriptions and measurements. G. Esc: 
Dexter, Franklin. The Development of the Paraphysis in the Common Fowl. 

The American Journal of Anatomy, II, 1, pp. 13-24. 

The paraphysis first appears in the 6.7 mm. embryo, and persists 
in the adult. By Es-C, 
Hardesty, Irving. The Neuroglia of the Spinal Cord of the Elephant with 

some Preliminary Observations upon the Development of Neuroglia 
Fibers. The American Journal of Anatomy, II, 1, pp. 81-103. 

The so-called ‘‘neuroglia cell” is a reduced syncytium, and the 
origin of the fibril is intrasyncytial rather than intracellular or inter- 
cellular. GEL: 
Bardeen, Charles Russell. The Growth and Histogenesis of the Cerebro- 

Spinal Nervesot Mammals. 7he American Journal of Anatomy, II, 2, pp. 
231-258. 

The author has employed the method of isolating the nerves in 
early embryonic stages and studying them in teased preparations. 
This procedure gives important data on structures the nature of which 
in section is more or less doubtful. The paper strongly. supports the 
theory of His. The nerve fiber unites with the muscle before the de- 
velopment of the sarcolemma, which becomes so intimately fused with 
the sheath of SCHWANN that the boundary between the two structures 
is indistinguishable. Gee. 
Schlapp, M. G. The Microscopic Structure of Cortical Areas in Man and 

Some Mammals. Zhe American Journal of Anatomy, II, 2, pp. 259-281. 

A comparative study of functional centers according to structure 
and localization. Centers differ not so much in the characters of the 
individual cells as in the composition of the entire cortex of the re- 
gions. GaktG. 
Streeter, George L. Anatomy of the Floor of the Fourth Ventricle. 7 4e 

American Journal of Anatomy, Il, 3, pp. 299-314. 
The topographical markings of the floor of the fourth ventricle 


370 Journal of Comparative Neurology and Psychology. 


agree in the main with the descriptions by Rerzivs, but the author’s 
studies are concerned with the significance of these markings in rela- 
tion to the underlying structures of the medulla. Gs Ene: 


Mall, Franklin P. On the Transitory or Artificial Fissures in the Human 
Cerebrum. Zhe American Journal of Anatomy, 1, 3, pp. 333-340. 

The fissures are produced by the disintegration of the walls of the 
brain vesicles. A table is compiled from over fifty brains to show 
the relation of different hardening agents, especially formalin and al- 
cohol, to the occurrence of these fissures. G.iB.Ce 


Mellus, E. Lindon. Ona Hitherto Undescribed Nucleus Lateral to the Fas- 
ciculus Solitarius. The American Journal of Anatomy, II, 3, pp. 361- 
364. 

In the dog this nucleus consists of ‘‘large, oval or pear-shaped 
cells” extending upward 2 mm. from the level of the calamus scriptor- 
ius. A corresponding group of smaller cells occurs in man. 

G. Ese. 


Holmgren, Emil. Einige Worte zu der Mitteilung von Kopsch: ‘*Die Dar- 
stellung des Binnennetzes in spinalen Ganglienzellen und anderen KGrper- 
zellen mittels Osmiumsaure.”’ Anat. Anz., XXII, No. 17-18, pp. 374-381, 
Jan., 1903. 

The author reviews and, in certain points, corrects KopscH’s 
criticism of his work on intracellular canaliculi. By way of illustra- 
tion he introduces two new figures, with descriptions, of the ‘‘Tropho- 
spongium” and Saftkanalchen in the nerve cells of birds. . 

G. -B.0G: 


Holmgren, Emil. Ueber die sog. ‘‘intracellularen Faden’? der Nervenzellen 
von Lophius prscatorius. Anat. Anz., XXIII, No. 2-3, pp. 37-49, April 
8, 1903. . 

A review of the author’s previous publications on the nerve cells 
of Lophius with special reference to SOLGER’s paper on Zorpedo. The 
author denies the existence of a pericellular lymph space normally, 
and abandons the idea that the intracellular fibrils are nervous. 

G. E. & 


Wolff, Max. Ueber die Kontinuitat des perifibrillaren Neuroplasmas (Hyalo- 
plasma, Leydig-Nansen). Amat. duz., XXIII, No. 1, pp. 20-27. March 

17, 1903. 
The finer structure of the axone terminals upon the muscle sup- 
ports HeLp’s theory regarding the pericellular net of Gouat, and af- 
fords a morphological basis for the LEypIG-NANSEN theory of hyalo- 


plasm. GcEO IG 


Literary Notices. 371 
Kronthal, P. Zum Kapitel: Leuocyt und Nervenzelle. Amat. Anz., XXII, 
No. 20-21, pp. 448-454, Jan. 30, 1903. 

The author reviews his theory of the origin of the perikaryon and 
dendrites from leukocytes, with special reference to the GoLGi method, 
the histogenesis of the nerve, and the theory of FRAGNITO. 

Ce Oa Oe 
Zuckerkandl, E. Die Rindenbiindel des Alveus bei Beuteltieren. Anat. 
Anz., XXIII, No. 2-3, pp. 49-60, April 8, 1903. 
The dorsal part of the commissura superior receives fibers through 
the alveus from the pallium. It represents, therefore, the primitive 
corpus callosum. Ge BG. 
Zugmayer, Erich. Ueber Sinnesorgane an den Tentakeln des Genus Car- 
dium. Zeit. f. w. Zool., Bd. LNXVI, Heft 3, pp. 478-508, 1904. 

Agabow, A. Ueber die Nerven der Sclera. Archit f. mk. Anat., Bd. LXIII, 
Heft 4, pp. 701-709, 1904. 

Kallius, E. Sehorgan. Werkel u. Bonnet’s Ergebnisse. Bd. 12, (1902) pp. 348-441, 
1903. 

K6lliker, A. Die Entwicklung und Bedeutung des Glaskirpers. Zerts. f. w. 
Zool., Ba. 76, H. 1, pp: 1-25, 1904. 

Police, G. Sul sistema nervoso stomatogastrico dello Scorpione. Archivio 
Zoologico, Vol. I, Fasc. 2, pp. 179-198, 1903. 

Meigs, E. B. On the Mechanism of the Contraction of Voluntary Muscle of 
the Frog. Amer. Jour, Med. Scr., April, 1904. 

Attention is called to the resemblance that muscle fibers in water 
rigor have to those in tetanus. In both instances the fibers assume a 
beaded appearance and since in water rigor the form is dependent up- 
on the absorption of water, it is supposed that in tetanus a like absorp- 
tion takes place. That contraction would result from this is demon- 
strated by an ingenious model consisting of a closed rubber tube at- 
tached to an air-pump and encircled at short intervals by metal rings ; 
these are attached one to another by numerous longitudinal inelastic 
threads. When air is forced into the tube, the segments between 
pairs of rings become spherical and the inelastic threads change their 
form from straight to curved lines, thus shortening the fiber as whole. 

Ingenious as this hypothesis is, it scarcely touches the real prob- 
lems of muscle action. Why do muscle fibers at. rest fail to take up 
fluid which they are supposed to absorb when stimulated and how does 
a contracted muscle ever relax? These and like questions that must 
arise in the mind of the reader, show at once the incompleteness of Dr. 
Meics’ hypothesis and place it in unfavorable light in comparison with 
the older theories of muscle action such as those advanced by ENGEL- 
MANN and others. Go Bed Be 


372 Journal of Comparative Neurology and Psychology. 


Harti, J. Ueber den Einfluss von Wasser und anisotonischen Kochsalzlésungen 
auf die Grundfunctionen der Quergestreiften Muskelsubstanz und der mo- 
torischen Nerven. <Avch. f. (Anat. u.) Phystol., Jahrg..1904, Heft. 1-2, 


pp. 65-93, 1904. 
Motor nerves lose their irritability when placed in distilled water. 


This can be restored by placing the nerve for a time in hypertonic 
solution of NaCl (2-3%) and then bringing it. back into 0.5% NaCl. 
Similarly, if the irritability has been destroyed by placing the nerve 
in a strong (hypertonic) NaCl solution, it can be restored in from one- 
half to two hours by immersing the preparation in a hypotonic solution 
of the same salt (0.2-0.3%). R. P. 
Gotch, F. The Time-Relation of the Photo-electric Change produced in the 
Eyeball of the Frog by Means of Colored Light. Jour. PAystol., XXXI, 
No. I, pp. I-29, 1904. 

The excised eyeball of the frog gives photo-electric responses when 
it is subjected to the influence of colored light, however obtained. 
These responses fail or become very feeble in the infra-red or infra- 
violet regions of the spectrum. The range of light vibrations eliciting 
photo-electrie responses corresponds very closely with the range of vis- 
ion in man’s color sensations. The capillary electrometer gives records 
from which the time relation of the response to a given color may be 
determined. A response of the same general type as the illumination 
response is obtained when light is suddenly replaced by darkness. 
The excitatory process is of one fundamental type and is characterized 
electrically by a difference of potential between fundus and cornea of 
such character that a current flows through the eveball from the for- 
mer to the latter. There isa distinct difference in the latent periods 
of the response to different colored lights. The response to red 
light has the longest latent period (ca. 0.3 second); the violet light 
response has a shorter latent period (ca. 0.25 second); the latent 
period of the response to green light is the shortest (less than 0.2 sec- 
ond). The results are held to be in accordance with the YouNG- 
HELMHOLTZ theory as modified by MAxweELt. Re P. 
Nagel, W. A. and Schaefer, K. L. Ueber das Verhalten Netzhautzapfen 

bei Dunkeladaptation des Auges. Zert. f. Psv. u. Phys. d. Sinmesorgane, 
Bd. 34, pp. 271-285, 1904. 

The results presented in this paper complement very prettily the 
work already done by Piper. As is known, PIPER experimented upon 
the increase in the sensitivity of the larger retinal surfaces during the 
process of adaptation to darkness and found that, if the sensitivity of 
the retina adapted for light be compared with that of the retina thor- 
oughly adapted for darkness, the ratio of increase is from 1:2000 to 


Literary Notices. 373 


1:9000. The explanation for this enormous increase in sensitivity is 
to be found in the lack of rods in the central region of the retina. The 
rods are used in weak light, while the cones are used in strong lights. 

But it cannot be supposed that the stimulus threshold for the 
cones remains the same under all circumstances. Is not the sensitivity 
decreased by long activity and increased by rest? The difficulties in 
the way of a satisfactory answer to these questions are almost insur- 
mountable. According to the authors, however, there are are three 
possible methods of approach : 

1. One can arrange a fixation mark of minimal size and bright 
enough to be securely above the foveal threshold. A steadfast fixa- 
tion point is thus secured. ‘This is very necessary since at the moment 
of the onset of adaptation for darkness the greater sensitivity of the 
peripheral portion of the retina causes one to fixate with the periphery 
rather than with the fovea. 

2. One can make use of the fact that the adaptive increase in the 
sensitivity of the rod apparatus is least for pure red light; and is the 
smaller, the longer the wave length of the light. In consequence of 
this a foveal threshold can be determined without danger of the point 
of regard being turned towards the periphery. 

3. Since it takes 5 minutes for the process of adaptation for dark- 
ness (after the eye has been adapted for light) to set in, it is possible, 
in the first few moments after entrance into the dark room, to obtain a 
foveal threshold without the fixation mark being diverted either to the 
paracentral or to the peripheral portion of the retina. 

Summary of results obtained from all three methods. 

A. Investigations with red light. 

1. With foveal and paracentral region. 

a. When the adaptation for brightness is produced by strong arti- 
ficial light, the increase in sensitivity during the first minute is about 
thirty-two fold. From the end of the first 30 seconds to the end of 
the sixth minute we have the ratio of 1:16. 

b. When the adaptation for brightness is produced by bright sun- 
light, the increase in sensitivity, from first moment of entrance into 
the dark room, to the onset of adaptation for darkness, is in the ratio 
of 1:200. 

2. With the foveal region alone a fourtold increase in sensitivity 
is found. 

B. Investigations with green and blue lights. 

1. With the foveal region alone the increase in sensitivity is again 
fourfold. 


374 Journal of Comparative Neurology and Psychology. 


2. With the foveal and paracentral regions quantitative experi- 
ments could not very well be made because the green and blue lights 
mixed with the white of the idev-retinal light more easily than did the 
red light. Nevertheless, a marked increase in the sensitivity was 
found. jc Be we 


Nagel, W. A. Einige Beobachtungen iiber die Wirkung des Druckes und des 
galvanischen Stromes auf das dunkleadaptierte Auge. (Zum Teil nach 
Versuchen von Herrn. cand. med. BLECKWENN). Zest. f. Psy. ue. Vhys. 
d. Sinnesorgane, Bd. 34, pp. 285-291, 1904. 

This contributor first confirms the results of G. I Mutter, who 
has reported, in effect, that the sensitivity of the eyes for inadequate 
stimulation by the galvanic current is independent of the state of adap- 
tation of the eyes. The author’s next observations concern the differ- 
ences in the behavior of the pressure phosphenes when the eye is 
adapted for light and when adapted for darkness. It was found, that 
with a given position of the eye, and with a definite pressure on the 
eyeball, the same form of pressure phosphene could be recalled again 
and again. Having chosen, with eye adapted for light, a definite 
phosphene as a standard (in this case a bright ring with one or two 
concentric rings inside of it) Professor NAGEL made some comparisons 
when the eye was adapted to darkness. ‘The result was that the in- 
tensity of the pressure phosphene in the eye adapted to darkness was 
slightly increased. Qualitatively the appearance of the two phosphenes 
was very different. The ring in the eye adapted to the light) was yel 
lowish and small; in the eye adapted to the dark it was bluish-white 
and noticeably broadened. 

Since the author is dichromatic (a greenish tone in yellow and 
a violet tone in blue could not be perceived), it occurred to him that 
the color of the phosphene seen in the eye adapted tothe dark might be 
complimentary to the color of the phosphene seen in the eve adapted to 
the light. So he repeated the above experiment upon persons possess- 
ing normal color vision. ‘They stated that the phosphene seen in the 
eye adapted to the light appeared yellowish, inclining to red; the 
phosphene seen in the eye adapted to the dark appeared bluish or 
bluish-white. 

The author next tested the galvanic phosphenes in the eye adapted 
to the light and in the eye adapted to the darkness, to see if any differ 
ence in color could be found. The phosphenes produced in this way 
were always quantitatively and qualitatively alike in the two eyes. 

Numerous experiments were then made to test whether the senst- 
tivity of the eyes adapted to the darkness, is altered by the effect of an 


Literary Notices. 375 


electrical current passing through the eyes. A variation of the limen 
of the light stimulus was produced neither when the current flowed 
from the layer of nerve fibers to the layer of rods and cones, nor when 
the current owed in the opposite direction. 

Finally the author tested the effect of long continued pressure 
upon the visual process of adaptation for darkness. A threshold value 
Was taken, (1) after 30 minutes in the dark room, (2) after wearing, for 
30 minutes a light-tight bandage which exerted no pressure, and (3) 
after wearing a pressure bandage for 30 minutes All three cases gave 
exactly the same threshold value. Th Bow 
Abelsdorff, G. and Nagel, W. A. Ueber die Wahrnehmung der Blutbewegung 

in den Netzhautkapillaren. Zest. f. Psy. u. Phys. d. Sinnesorgane, Bd. 34, 
Pp. 291-300, F904. 

It one glances at the blue sky, one sees, as is well known, numer- 
ous small glittering particles moving in tortuous pathways across the 
field of view. ‘The particles are in constant motion, and since they 
never pass the point of clearest vision, it is impossible clearly to make 
out their form. ‘Fhe phenomenon is in some way connected with the 
circulation of the blood in the retina. If one presses lightly with the 
finger avainst the eyeball, the regular and uniform movement of the 
particles changes to one of a pulsating character, while a stronger 
pressure brings the particles almost to a standstill. “Phen after the re- 
lease of the pressure the particles hasten across the field of view even 
more rapidly than before. ‘That the phenomenon is not produced by 
the mechanical stimulation of the elements sensitive to light by the 
blood cells which circulate in the capillaries is proved by the fact that 
it is wholly lacking in darkness and weak lights, and even in strong 
lights the phenomenon can be seen only when the stimulating lights 
possess wave lengths lying within definite boundaries. 

Both Ruere and Roop have mentioned this phenomenon and re- 
marked that it can be best observed with the aid of blue glass. The 
present investigators finding, however, that the movement of the par- 
ticles cannot be seen with the aid of any and every blue light jointly 
undertook to make a more thorough investigation of the conditions 
under which this phenomenon appears. 

According to their view there are two possible ways of explaining 
the phenomenon: It may be a shadow phenomenon, similar to that 
of the vein-figures of PURKINJE, caused by the absorption of certain 
light rays by the blood corpuscles; or it) may be a phenomenon of 
light refraction, since conceivably the red and white corpuscles, acting 


as lenses, might focus the light on the sensitive layer or the retina. The 


376 Journal of Comparative, Neurology and Psychology. 


authors throw the latter supposition out of court, since one can think 
of no way in which. the corpuscles can act as lenses. 

Accepting, then, light absorption as the more probable manner of 
explanation they begin their experiments. As light absorbing ele- 
ments only the red corpuscles come into consideration. ‘These strongly 
absorb the blue and violet rays in the spectrum, ‘This explains why 
the phenomenon can be best observed in these lights, but since hae- 
moglobin also absorbs the yellow green rays considerably one would 
expect to find the phenomenon visible, at least to some extent, in this 
light. At first the investigators were unable to do this, but after nu- 
merous experiments with many light filters composed of different kinds 
of light absorbing mixtures they were enabled to show that the phe- 
nomenon is visible in all lights that are absorbed in the spectrum of 
the haemoglobin. 

The intensive absorption of the haemoglobin then tor indigo, blue 
and violet explains in a satisfactory way the appearance of the shadows 
of the corpuscles in these lights; it explains why the shadows are so 
much more intensive in the violet-blue than in the yellow-green. On 
the other hand, the permeability of the haemoglobin tor the cyan-blue, 
blue-green, red and orage harmonizes completely with the fact that in 
these lights the swarming of the corpuscles cannot be seen. 

J. B. W. 


Hall, G. Stanley and Theodate L. Smith. Keactions to Light and Dark- 
ness. American Journal of Psychology, Vol. 14, pp. 21-83, 1903. 


This report is based on questionnaire returns obtained from two 
normal schools, two colored schools, and one school for the blind. 
White pupils in the fifth grade, from ten to twelve years old, con- 
tributed also. The ages of the normal students lay mostly between 
eighteen and twenty-two, while those of the colored students ranged 
from ten toe twenty-eight. The investigation sought to discover the 
emotion reactions to darkness, dawn, twilight, artificial light, sudden 
transitions; and to learn the fancies connected with the sun, darkness, 
and light. No classification along lines of age or sex was attempted. 
As to race differences, the writers state that none specific occurred 
save those directly referable to degree of educational opportunity. 

The results of importance follow: (1) Longings tor dawn occur 
in 85% of 389 cases. Included are about 6% where a pleasurable 
event is anticipated. In the rest the character of the longing varies 
from mere restlessness to real light hunger. (2) Night fears occur in 
73% of 389 cases. In about 11% of these the fear is of darkness 
itself. In the remainder it is of specific live objects, natural or super- 
natural. The most frequent fear is of being seized or grabbed at. About 


Literary Notices. 377. 


6%, all adults and destitute of superstitious beliefs about darkness, 
still have these fears when in the dark or in aclosed space. (3) Blind 
children dread the night and, if they are to go about, desire compan- 
ions. ‘The reaction here may be due to stillness or loneliness; and 
one person so reports. (4) ‘Twilight hour is loved in 273 cases; 
shunned in 79, and indifferent in 32. Preference among whites was 
to be alone, while 80% of the returns for negroes showed desire for 
company. ‘The sentiments typical at sunset, given in order of their 
numerical importance, are moral and religious aspirations, sadness, lone- 
liness, rest, awe and reverence, quiet and thoughtfulness, peace, glad- 
ness, regret, sorrow and longing.” (5) Of 291 adults 197 had person- 
al experience of the exhilarating effect of artificial light—results that 
agreed with observations upon 32 children. ‘Che amount of this effect 
varies from a slight increase in mental and physical activity to cases of 
actual abandon. No effect had been noticed by 62 adults. (6) En- 
tering shade is followed by depression of spirit; entering sunlight 
rouses cheerful feeling. The blind are susceptible to these sudden 
changes, but not to the change from day to night. The direction of 
suceptibility is not stated. (7) The effects of a longer period of gloom 
appears in the poorer quality of mental work and its smaller quantity. 
So it seems to be with the blind. GrrkELy, the Arctic traveler, noted 
among his men insomnia, irritability, gloom, and indisposition to exer- 
tion as the winter wore on, leading to symptoms of mental disturbance 
even more serious. ‘Thermal effects must not be forgotten though 
where these differed widely, as in SraANLEY’s march through the great 
forest in Africa, this traveler noted similar reactions among his com- 
pany, and the strong revulsion of feeling on passing its confines. (8) 
The following examples of children’s phototropisms are frequently 
given: they play on the sunny side of the room or the street, disregard 
heat or cold to play in sunshine, babies creep toward the sun, children 
are always happier and more active in sunshine. (9) ‘This reaction at 
times becomes negative, apparently under conditions of fatigue. A 
child tired and sleepy with play in the sun usually craves the opposite 
condition for sleep. Travelers in lands of brilliant sunshine often re- 
report this as becoming positively paintul. Thermal effects here prob- 
ably offer complications, though GREELY found insomnia and restless- 
ness Consequent upon the long Arctic day. 

The richness of the fancies woven about light and darkness is 
taken as significant in favor of the theory of recapitulation. The value 
of such evidence ought to be questioned in view of the complicating 
effects of social heredity. - 


378 Journal of Comparative Neurology and Psychology. 


The general character of the evidence upon which this article is 
based is two-fold: reports of individuals about themselves and about 
others under their observation. Upon the second sort depend the 
chief facts in 6 to 9 above, and part of 5, as well as largely the facts 
about the blind. ‘To what extent this evidence is memory generalized 
does not appear. Original data are given merely for illustration. 

CHARLES ‘T. BURNETT. 
Zwaardemaker, H. Eine bis jetzt unbekannt gebliebene Eigenschaft des 
Geruchssinnes. Arch. f. (Anat. wu.) Phystol., Jahrg. 1904, Heft. 1-2, pp. 
42-48, 1904. 

Shows that if there is a periodical breaking of the air column 
within the nasal cavity (produced by alternate inspirations and expira- 
tions) an ¢vfermittent olfactory sensation results. If the air column is 
broken periodically ov/side the nasal cavity (i. e., in the olfactometer 
tube) a continuous olfactory sensation results. Ru Ps 


Cramer, W. On Protagon, Cholin and Neurin. Jour. PAysrol., XXNXI, pp. 
30-37, 1904. 

Physiological chemistry of the brain. K.P: 
Zwaardemaker, H. und Quix, F. H. Ueber die Emptindlichkeit des men- 
schlichen Ohres fiir T6ne verschiedener Hléhe. Arch f. (Anat. uw.) Physiol., 

Jahrg. 1904, Heft. 1-2, pp. 25-42, 1904. 

Muskens, L. J. J. Ueber eine eigenthiimliche compensatorische Augenbewe- 
gung der Octopoden mit Bemerkungen iiber deren Zwangsbewegungen. 

Arch. f. (Anat. u) Physrol., Jahrg. 1904, Heft. 1-2, pp. 49-56, 1904. 
Stuart, T. P. A. The Function of the Hyaloid Canal and some other New 


Points in the Mechanism of the Accommodation of the Eye for Distance. 
Jour. Physiol., XXX1, pp. 38-48, 1904. 


Delage, Y. Sur les mouvements de torsion de Poeil. Arch. a. 200l. exper. et 

gen. 4ser., T. 1, No. 3, pp. 261-306, 1903. 

Smallwood, Mabel E. The Beach Flea: Talorchestia longicornis. Cold 
Spring Harbor Monographs, 1. 27 pp., 3 pls., 3 text-figs. 1903. 

With this monograph a series of publications from the Biological 
Laboratory of the Brooklyn Institute of Arts and Sciences at Cold 
Spring Harbor is begun in which special attention will be given to the 
natural history of the animals in the region of the station, 

The present paper consists of an anatomical description of the 
beach flea, and an account of studies of its ethology. Breeding, moult. 
ing, habitat, burrowing, locomotion, phototropism, food and feeding, 
relation to water, and movements are in turn briefly considered in the 
light of observations made in nature or in the laboratory by the author. 
Review space does not permit the presentation of the facts of this in- 


Literary Notices. 379 


teresting paper, and it must therefore suffice to call attention to the 

importance, as a preparation for experimental work, of the study of an 

organism with respect to its habitat and behavior in its natural envi- 

ronment. R. M. Y. 

Wheeler, W. M. \ Crustacean-eating Ant (Leptogenys elongata Buckley). 
Biol, Bull., Vol. V1, pp. 251-259, 1904. 

WHEELER finds that under natural conditions the food of Lepéo- 
genvs clongata consists. very largely, if not exclusively, of the isopods 
Oniscus and Armadilidium. his is the only ant known to show so 
marked a preference for crustacean food; the other members of the 
same genus appear to feed for the most part upon termites. : 

The males of Z. elongata are winged, but the females are apter- 
ous, In appearance much resembling the workers. How the fertiliza- 
tion of the females takes: place is thus an interesting question. Of 
course a nuptial flight is precluded by the wingless condition of the 
females, and WHEELER considers it improbable that the males of one 
nest find their way into other nests and so fertilize the females there. 
If the females are fertilized by the males of the same colony, the author 
points out that this would be a most flagrant case of imbreeding, so it 
seems reasonable to suppose that the females issue from the nest at 
night as pedestrians and in this way meet the males of other nests, as 
the latter also go forth at night. The males are said to. be ‘‘high- 
ly heliotactic.” 1 5.7 OOLE; 
Marshall, Wm. S. The Marching of the Larva of the Maia Moth, Hemileuca 

maia. rol. bull., Vol. V1, pp. 260-265, 1904. 


A number of rather desultory experiments were made upon the 
marching columns of the recently hatched caterpillars of Afemiuca mata, 
It was found that when the leading caterpillar of a line was removed 
the procession was stopped and the larvee gathered into a bunch. — In 
nine out of twenty-one experiments the original leader when returned 
again took the lead and the line followed ; in the other eleven cases 
a new leader took the place of the one removed. No general conclu- 
sions are drawn, bedi: COLE: 


Adams, Chas. C. The Migration Koute of WKirtland’s Warbler Bulletin 
Michigan Ornith. Club, Vol. V, pp. 14-21, 1904. 


A study of the migration routes of this warbler, with maps and 
suggestions of conditions which influence migration. ed tee 


380 Journal of Comparative Neurology and Psychology. 


Ritter, Wm. E. and Davis, B. M. Studies on the Ecology, Morphology 
and Speciology of the Young of Some Enteropneusta of Western North 
America. Oniversitv of California Publications—Zoology., Vol. 1, pp. 171 
210, Pls. 17-20, 190}. 

The ecological portion of this report is concerned chiefly with the 
movements of fornarta, and the conditions which determine them. 
The organisms swim upward in the water because of a difference in 
specific gravity of the two ends. There is no satisfactory evidence of 
the importance of temperature or light in the orientation of the organ- 
isms. The stroke of the cilia is invariable in direction. R. M. Y. 
Ritter, Wm. E. Further Notes on the Habits of Autodax Lugubris. Amere- 

can Naturalist, Vol. XXXVII, pp. 853-886, 1903. 

This salamander lays its eggs in cavities in trees. The paper is an 

interesting contribution to our knowledge of the breeding habits. 
Ru Ma Ne 


Fisher, Walter K. On the Habits of the Laysan Albatross. The Auk, XXI, 
pp- 6-20, pls. II-VIII, Jan., 1904. 


This article gives an interesting account of the breeding habits of 
the birds, illustrated by excellent photographs, especially of a peculiar 


dance in which two or three birds take part. 
WALLACE CRAIG. 


Oldys, Henry. ~The Rhythmical Song of the Wood Pewee. 7%e -luk, XXTI, 
pp. 270-274, Apr., 1904. 

The author here adds a little to his very suggestive article on 
‘Parallel Growth of Bird and Human Music’ in Harper’s Magazine, 
CV, pp. 474-476, Aug. 1902. WALLACE CRAIG. 
Webster, F. M. Studies of the Life History, Habits and Taxonomic Rela- 


tions of a New Species of Obera (Obera ulmicola Chittenden). Audet 
Minors State Laboratories Natural History, Vol. VII, pp. 1-14, 1904. 


This paper contains several interesting facts concerning the natu- 
ral history of the insect. Re Mae 


The Journal of 


Comparative Neurology and Psycholog 


Volume XIV 1904 Number 5 


RETROGRADE DEGENERATION IN; THE -CORPUS 
Gx OSUM OF STEHE, WHITER AT: 


By S. WaLTeR Ranson. 
(from the Neurological Laboratory of the University of Chicago and the Anatomical 
Laboratory of St. Louis University.) 
With Plate VII 
SUMMARY OF THE LITERATURE. 


It was maintained by WALLER (6) and those who immedi- 
ately followed him that the end of the nerve fiber attached to 
the cell body did not degenerate as the result of section of the 
fiber Evidence has, however, been steadily accumulating to 
show that this view is incorrect. The facts bearing on this point 
have. been brought together by FLEmiInG (1), KitppeL and Dvu- 
RANTE (2), and vAN GEHUCHTEN (4). These authors review the 
literature in great detail; but only the briefest summary will be 
given here, and this will be based chiefly on the excellent re- 
view by VAN GEHUCHTEN. 

The first observations not in harmony with the law of 
WaLLER were made upon cases of long standing amputation. 
Atrophy of the ventral and dorsal root fibers and of the part of 
the spinal cord associated with the nerves of the amputated limb 
has been found in these cases. (DICKINSON, ’68, VULPIAN, ’68, 
Hayvem and GILBeErtT, ’84, MarINeEsco, ’92, and others). Ex- 
perimental amputations of the limbs of animals, involving sec- 
tion of the peripheral nerves, have confirmed these observations 
(VuLPIAN, ’69 and Haye, ’73), and shown the presence of fibers 
with fragmented myelin in the central ends of the cut nerves. 
Degenerating fibers were also found in the ventral and dorsal 
nerve roots and in the dorsal fasciculi of the cord. (Dark- 
SCHEWITSCH, ’92 and MoscHaeEw, '93). 


382 Journal of Comparative Neurology and Psychology. 


The second group of observations opposed to the state- 
ment formulated by WALLER has been derived from experiments 
intended to locate the nuclei of origin of the motor nerves. 
The tearing out of motor nerves is followed by atrophy or dis- 
appearance of their intramedullary roots and nuclei of origin. 
(Literature summarized by Foret, ’87.) A true degeneration 
of the central ends of these fibers can be demonstrated by the 
method of Marcu (BREGMANN, ’92, DARKSCHEWITSCH, 92). 

In the central nervous system a retrograde or cellulipetal 
degeneration has been observed in seven localities. A descend- 
ing degeneration has been seen in the optic radiation after ex- 
cision of its terminal ramifications in the occipital cortex (VvoN 
Monakow, ’84, MoE Lt, ’93) and in the medial lemniscus after 
injury to the central gyri (von Monakow, ’85, GREIWE, ’94, 
KiipreL and Durante, ’95). The retrograde degeneration in 
these tracts differs in some cases histologically from WaALLE- 
RIAN degeneration, the axis cylinder remaining intact while the 
myelin sheath disappears, although in most cases it resembles 
true secondary degeneration very closely. Often this cellulipe- 
tal degeneration is very extensive, involving the majority of the 
fibers of the tract. For these reasons, the downward degen- 
eration in the optic radiation and inthe lemniscus cannot be ad- 
duced as evidence for a double pathway. Similar observations 
have been made on the pyramidal tract, which in certain cases 
has degenerated cephalad after a transverse lesion of the spinal 
cord (WILLAMSON, ’93, RAYMOND, ’94). 

VAN GEHUCHTEN has shown that degeneration of the prox- 
imal part of injured nerve fibers may occur in the middle cere- 
bellar peduncle, in the fibers passing from the nucleus ruber to 
the lateral fasciculus of the spinal cord, in the fibers passing 
from the nucleus of Derirers to the anterior fasciculus of the 
cord, and in those from the cells of the formatio reticularis of 
the pons and medulla to the antero-lateral fasciculus of the cord. 
That retrograde degeneration occurs in these tracts and not 
merely the WALLERIAN degeneration of a second pathway, is 
supported by the facts that the changes in question do not ap- 


Ranson, Retrograde Degeneration. 383 


pear until fifteen days after WALLERIAN degeneration has begun 
and that the cells of origin of these tracts disappear. 


OBSERVATIONS ON THE WHITE RAT. 


Introduction and Summary. 


In a previous paper the writer (3) called attention to the 
complete degeneration of the splenium of the corpus callosum 
in a young rat after deep incision of the occipital lobe, and 
reference was made to a similar observation by von GUDDEN (5). 
If this degeneration had occurred according to WALLER’s law, 
about half the normal number of fibers should have been pres- 
ent on each side of the lesion. But in this case all the fibers 
had disappeared. This means that the fibers underwent seri- 
ous alterations in both directions from the point of injury. This 
observation taken by itself only shows the absence of the mye- 
lin sheath in the proximal portion of the injured fiber, as no 
stains were used which would demonstrate the presence or ab- 
sence of naked axis cylinders. Since there were no medullated 
fibers in the corpus callosum at the time of the operation the 
absence of myelin might be interpreted as due to an arrest of 
development. But further observations made on older rats 
have shown that a true degeneration closely resembling the 
WALLERIAN type may occur in the proximal portions of severed 
fibers. 

The chief difference between the changes in the proximal 
and the distal portions is that the latter pass more rapidly 
through the stages of fragmentation, solution and absorption, 
these changes affecting the whole extent of the severed portion 
at the same time; while in the proximal portions the changes 
occur somewhat later and may involve only the part of the fiber 
nearest the point of injury. Thus forty-five days after a wound 
is made in the medullated corpus callosum of young rats (21 to 
70 days of age) the ordinary WALLERIAN degeneration has run 
its full course and the resulting debris is entirely absorbed. But 
at this time fragmentation of myelin may be distinctly seen in 
the proximal portions of the severed fibers, affecting especially 
the part in the vicinity of the lesion. 


8 Journal of Comparative Neurology and Psychology. 
Pp rojo _ Ne 


Operative Technique. 


Through the occipital portion of the corpus callosum in 
rats of various ages (0.5, 3, 7, 21, 30, 40, 60, 70 days old), an 
incision was made in the left cerebral hemisphere about one milli- 
meter to the left of the great longitudinal sinus and two millimeters 
frontal to the lateral sinus, in such a way that a wound one and 
a half millimeters long and two or three millimeters deep was 
made in the posterior part of the occipital lobe, parallel to the 
midplane. The animals were killed forty-five days after the 
operation. In each case serial frontal sections through the left 
occipital lobe were prepared according to the PAL- WEIGERT 
technique. 


Results. 


In so simple an operation asepsis is not difficult to obtain. 
The wounds were covered with collodion and remained well pro- 
tected until healing had taken place. The animals recovered 
rapidly and after twenty-four hours appeared to be perfectly 
normal. During the entire subsequent period they were in ex- 
cellent physical condition, and equaled in weight the rats of the 
same age in the laboratory. In only one case did the post- 
mortem examination show any trace of inflammatory reaction. 
In this rat slight adhesions were present between the dura and 
the brain scar, but these produced no appreciable effect on the 
results. 

The mildest form of the cellulipetal degeneration is found 
in the brain of the oldest rat (seventy days old at the time of 
operation). Except for the comparatively narrow band of scar 
tissue, there is no area in which complete degeneration of all 
the fibers has taken place. Portions of many fibers must have 
been cut off from their cells of origin, and these portions have 
no doubt undergone complete WaALLERIAN degeneration, al- 
though the debris resulting from their disintegration has been 
entirely absorbed. Thus on each side of the cicatrix there is 
brain tissue which at first sight appears normal. But on closer 
examination many of the fibers in the immediate vicinity of the 
scar are found to differ from the normal in that they have an 


Ranson, Retrograde Degeneration. 385 


irregular contour, being very much constricted at certain points 
and swollen into beads at others. Most of these fibers stain 
well by the Pat-WeEIGERT method. Their myelin has not been 
gathered into droplets nor been to any appreciable extent ab- 
sorbed. These beaded fibers are not to be found more than 
two millimeters on either side of the line of incision since the 
cellulipetal degeneration had extended only a short distance 
along the fiber. 

Ina rat ten days younger (sixty days old at the time of 
operation) there are considerable areas of degeneration in the 
substantia alba. Figure 1, ‘‘a’’ shows a Y-shaped area of faint 
staining extending medialward from the scar. There is also a 
slender unstained band extending lateralward. In these areas 
the cellulipetal degeneration has progressed somewhat farther 
than in the case previously described. Near the line of incis- 
ion all the myelin has been absorbed, leaving only the faintest 
outline of the fibers visible. Figure 2 is a drawing of a small 
portion of the degenerated area represented at ‘‘@”’ in Figure 1. 
In addition to the beaded fibers described in the previous case 
there are many that are faintly stained, some of which contain 
minute droplets of myelin. There are also many large faintly 
stained drops of myelin which do not appear to be connected 
with fibers. 

In the rat which was thirty days old at the time of the op- 
eration, the process of cellulipetal degeneration has increased 
in intensity and extended farther along the fibers. Figure 3, 
“a, shows a comparatively wide band in the substantia alba 
faintly stained because of the disappearance of most of the 
fibers. Near the line of incision this disappearance of fibers is 
complete; only a few scattered drops of myelin are visible. 
Farther lateralward (Fig. 4) are fibers in the process of disinte- 
gration, some swollen and beaded, other faintly and irregularly 
stained. Still farther lateralward these give place to normally 
stained, smoothly contoured fibers. . 

Changes similar to those described above were found in 
the brain of a rat operated on when twenty-one days old; but 
here fibers were found degenerating at a much greater dis- 


386 Journal of Comparative Neurology and Psychology. 


tance from the point of injury. Fig. 5 shows that most of these 
fibers are in the last stages of degeneration. They are very irreg- 
ular in shape, and their outlines are only faintly visible. They 
stain faintly except in a few places, where there still remain 
minute globules of myelin. They are broken up into short 
segments, so that no fiber can be followed for any considerable 
distance. A few droplets of free myelin are still unabsorbed. 

In order to interpret these results it is necessary to bear in 
mind the condition of medullation in the corpus callosum of the 
young rat. Warson (7) has shown that medullation in this re- 
gion begins about the fourteenth day. Thus, fibers cut in the 
operation performed on the twenty-first day are both structur- 
ally and functionally very immature ; and the rapidity with which 
they degenerate is, no doubt, closely related to this condition. 
By the seventieth day the neurones have attained a greater de- 
gree of stability, which shows itself in the much more limited 
retrograde degeneration. When the operation was made on or 
before the seventh day of age no medullated fibers were cut, 
because there were none present. This would account for the 
fact that in examining the preparations of these brains no fibers 
with disintegrating myelin sheaths were found. There are, how- 
ever, areas which are almost devoid of fibers, although they ex- 
hibit a few that are slender, normally contoured and well stained. 
On the basis of the earlier experiments (3) these are to be ex- 
plained as having developed since the injury. Complete de- 
generation is best seen in the corpus callosum of the rat op- 
erated on when twelve hours old, which has been figured 
in the Journal of Comparative Neurology, Vol. XIII, Plate VII, 
Figures 4 and 7. Much the same condition is seen in the cor- 
pus callosum of the next older rat (3 days); but in this and the 
one operated on at the seventh day the wound is situated so far 
posteriorly, that the picture is complicated by the presence of 
fibers curving backward into the occipital lobe. These fibers, 
coming from in front and passing backward and outward, cross 
the zone which would otherwise be free from fibers. 

As has been already stated, this paucity of medullated 
fibers in the corpus callosum, so evident in the youngest rat, 


Ranson, Retrograde Degencration. 387 


might be interpreted as due to a failure of development of the 
medullary sheaths about the central portions of the severed ax- 
ones; or it might be due to the complete disappearance of these 
axones. But when one takes into consideration the retrograde 
degeneration seen in these fibers in the older rats, there can be 
little doubt that the degeneration is of the same nature in these 
younger animals and that the entire neurone has undergone dis- 
integration. 

If it is remembered that all these animals were allowed to 
live for one month and a half after the operation, it will be seen 
from what has been said that the intensity of the cellulipetal de- 
generation exhibited in any portion of the section depends upon 
two variables, the age of the animal and the distance between 
the point of observation and the point of injury. Inthe oldest 
rat the process was confined to a small portion of the fiber near 
the lesion. As we pass down the series from the oldest to the 
youngest animal, the degencration increases in intensity in the 
vicinity of the lesion, and extends to a greater distance from 
the point of injury. The complete degeneration of the fibers 
in the older rats takes place only in the immediate vicinity of 
the lesion, but in the youngest animal the fibers degenerate 
completely throughout their entire length. 

There are several respects in which the changes here de- 
scribed differ from the WALLERIAN degeneration. In typical 
secondary degeneration the myelin begins to liquify at the sixth 
day and is largely absorbed before the twentieth. But in the 
milder cases of the degeneration here described there are many 
fibers remaining after forty-five days which differ from the nor- 
mal only in the presence of a few beadlike swellings, the rest of 
the fiber remaining normal in contour and staining properties. 
And in these milder cases there are no fibers present in which 
the myelin has undergone liquefaction. It is evident that the 
secondary degeneration, which must have occurred in the por- 
tions of the fibers separated from their cell bodies, has run its 
full course and the resulting debris been entirely absorbed. 
Otherwise we could not account for the complete absence in 
some of these cases of fibers in the last stages of degeneration. 


388 Journal of Comparative Neurology and Psychology. 


The degeneration which is seen beginning in certain fibers 45 
days after the lesion is, therefore, a process commencing after 
the ordinary secondary degeneration is complete. Another 
feature which distinguishes retrograde degeneration from sec- 
ondary degeneration is the fact that the latter occurs simul- 
taneously throughout the entire length of the severed part, 
while the former may involve only a small part of a fiber in the’ 
immediate vicinity of the lesion. 

A word may be said regarding the nature and cause of 
this degeneration of the proximal part of injured fibers. Van 
GeHUCHTEN (4) has shown that associated with these changes 
in the fiber leading to its disintegration, there is a chromatolysis 
of the cells of origin resulting, in certain cases, in their complete 
destruction. In those neurones in which this occurs he believes 
that the degeneration of the fiber follows on the death of the 
cell and proceeds down the fiber toward its terminals. For 
this reason, he objects to the use of the term ‘‘retrograde” in 
designating this type of degeneration, because it indicates that 
the degeneration begins at the point of injury and proceeds to- 
ward the cell body. 

It is, however, quite conceivable that the evidence of this 
disintegration of the neurone should be found first in the por- 
tion of the neurone farthest separated from the nucleus, namely 
at the tip of the fiber near the lesion. Asa matter of fact 
many of the preparations upon which this paper is based show 
a degeneration in the end near the lesion while the rest of the 
fiber appears normal. In some cases beginning near the lesion 
and tracing the fiber toward the cell of origin one may see all 
the stages of degeneration ; at first the fiber stains faintly be- 
cause of the absorption of its myelin, then it is found to be well 
stained but of irregular contour and finally it takes on a per- 
fectly normal appearance. It seems clear, therefore, that in 
this case at least the process is a true retrograde or cellulipetal 


degeneration. 


Journal of Comparative Neurology and Psychology, Vol. XIV. PLATE VII 


Fig. 2 
(Point ‘a’ figure 1 enlarged) 


Fig. 4 
(Point ‘*a” figure 3 enlarged) 


Fig. 3 


A. B, STREEDAIN, DEL 


Ranson, Retrograde Degeneration. 389 


Bibliography. 


1. Fleming, R. A. 97. Edinburg Med. Jour., Vol. XLIII, pp. 49-279. 

2. Klippel et Durante. 795. Revue de Médecine, Vol. XV, pp. 1, 142, 343, 
574, 655. 

3. Ranson, S. W. 703. Jour. Comp. Neurol., Vol. XIII, p. 186. 

4. Van Gehuchten, A. 703. Le Névraxe, Vol. V, p. 3. 

5. Von Gudden, B. 89. Gesammelte und hinterlassene Abhandlungen, p. 
130. Konegl. Universitits- Druckeret in Wiirzburg. 

6. Waller. °52. Comp. Rend. del Académie des Sciences, Vol. XXXIV, p. 582. 

7. Watson, John B. 703. Animal Education: an experimental study on the 
psychical development of the white rat, correlated with the growth of its 
nervous system. Zhe University of Chicago Press, Chicago. 


DESCRIPTION OF PEATE Vil. 


The drawings, made by Mr. A. B. STREEDAIN, represent retrograde degen- 
eration in the corpus callosum of white rats, killed forty-five days after the mak- 
ing of an incision in the occipital lobe. They were made from PAL-WEIGERT 
preparations of frontal sections through the occipital lobe. 

Figure 1 is from a rat operated on when sixty days old. 

a and 6, degenerating areas. 
c, line of incision. 
m, medial surface of the hemisphere. 

Figure 2 is from the same preparation as the former drawing. It represents 
the appearance under the oil immersion lens of a small area designated by ‘‘a,”’ 
Figure 1. 

Figure 3 is from a rat operated on when thirty days old. The lettering is 
the same as in Figure I. 

Figure g is from the same preparation as Figure 3. It represents a small 
area at ‘‘a”’ seen under the oil immersion lens. 

Figure 5 was drawn with the aid of the oil immersion from the degenerat- 
ing corpus callosum of a rat operated on when 21 days old. 


THE. BARLY | HiStORY, Oy THE SOLEAGCTORS 
NERVE IN SWINE.’ 


By EpGar A. BEDFORD, S. M. 
With fourteen figures in the text. 


From 1862, the time of the first examination, from the 
standpoint of modern science, of the structure of the olfactory 
nerve by Max SCHULTZE,” up to the present time, various ob- 
servations have been made upon the structure and development 
of the olfactory nerve. 

Some of the views held by older investigators have been 
superseded. - There has been a growing tendency to depart 
from the earlier belief, that the olfactory nerve arises from the 
brain, to a belief that it originates in the periphery. This view 
is in harmony with the teachings of His that all sensory fibers 
originate in the periphery. However, since this nerve differs, 
in some respects, in histological structure from other nerves, 
_ too much dependence must not be placed upon analogies drawn 
from the development of other nerves. Our views concerning 
the development of this nerve, therefore, must be based upon 
the observations regarding its individual development. 

The anatomists of the middle of the 19th century looked 
upon the olfactory nerve as part of the brain, confusing it with 
the olfactory tractus and bulbus. Gradually this view began to 
be controverted and evidence was brought to show that both 
the optic and olfactory are true cranial nerves, although very 


1 Contribution from the Zoological Laboratory of Northwestern University, 
WILLIAM A. Locy Director. 


2 Max SCHULTZE. Untersuchungen iiber den Bau der Nasenschleimhaut. 
Adhandlungen der Naturforschenden Gesellschaft zu Halle, Bd. VII, 1862. 


BEDFORD, Olfactory Nerve in Swine. 391 


much modified. Up to very recent time, there has been con- 
fusion, even among writers of the highest merit. 

HErTwiG,' as late as 1892, says: ‘‘Finally in treating of 
the development of the cerebrum, there is still to be considered 
an appendage of it, the olfactory nerve. This part as well as 
the optic nerve is distinguished from the peripheral nerves by 
its entire development and must be considered as a specially 
modified portion of the cerebral vesicle. The older designation 
of nerve, therefore, is now more frequently replaced by the 
more appropriate name of olfactory lobe.” HErtwic then goes 
on to describe the development of the lobe of man, completely 
ignoring the development of the fibers which form the 
real olfactory nerve. The true condition is made clear by Ep- 
INGER.” ‘‘From the epithelium of the nasal mucous membrane 
long terminal fibrillae run backward. They are called fila olfac- 
toria and pass through the cribiform plate into the cranial cavity. 

The fila olfactoria pass to an anteriorly directed evagina- 
tion of the fore-brain vesicle. This evagination forms on the 
base of the brain a more or less elongated tube which, in most 
animals, remains hollow, tractus and bulbus  olfactorius.”’ 
Further he says that the tractus, which connects the bulbus 
with the remaining portion of the brain, in some animals, might 
easily be taken for the olfactory nerve, which, however, termi- 
nates at the olfactory bulbus. 

Legz,* Locy’ and others have directed attention to the true 
relation of the fila olfactoria and the tractus. It is with the 
development of these fila olfactoria that this paper is con- 
cerned. * 


1 Oscar HERTWIG. ‘Text-Book of the Embryology of Man and Mammals. 
Translation by Epwarp L. Mark, pp. 448-449. 

2 EDINGER. HALL’s Translation, p. 146. 

8’ Ler. Zur Kentniss des Olfactorius, Berichte Naturf. Gesellsch. Freiburg, 
Bd. VII, 1893. 


4Wmn. A. Locy. New Facts Regarding the Development of the Olfactory 
Nerve, Anat. Anz., XVI, pp. 273-290. _ 


392 Journal of Comparative Neurology and Psychology. 


Résumé of Literature. 


One of the earliest investigators to consider the development of 
the olfactory nerve was MitNes MarsHatv' (1878-1879). He describes 
the first appearance of the olfactory nerve in the chick, as ‘‘a small 
outgrowth of spherical or slightly fusiform cells, arising on either side 
from near the top of the forebrain.” ‘‘This small process,” MARSHALL 
claims, ‘‘may be traced for a short distance in successive sections run- 
ning downward and slightly outward, lying close to, but perfectly in- 
dependent of the external epiblast. At this period there is hardly a 
perceptible thickening of the epiblast at the spot where the olfactory 
pit will shortly afterwards appear. It is toward this point the growth 
is directed.” 

It is evident from reading MARSHALL’s papers that he began his 
work with the preconceived idea that the olfactory nerve arises from a 
continuation forward of the neural ridge. His observations are all 
made from that standpoint. It will be seen later how, by failing to 
observe the very first stages in the formation of the olfactory nerve, 
and by making a slight error in the observation of other stages, he 
might be led to believe that he had evidence of the origin af the olfac- 
tory nerve from the brain. In order to further support his attempt to 
homologize the olfactory with other nerves, he attempts to homologize 
the nasal pits with a pair of gill clefts. Mrvorv, in his textbook of em- 
bryology, points out that ‘“MarsuHa.t failed to attribute weight to the 
fact that the gill clefts are primarily evaginations of the endoderm 
while the nasal pits are invaginations of the ectoderm.” 

BALFouR? who preceded MARSHALL in the examination of the ol- 
factory nerve came to the conclusion that in the elasmobranchs 
it originates from the peripheral end of each olfactory lobe. Thus, 
BaALFour, as MARSHALL, believes in a cranial origin for the olfactory 
nerve. The only point in which he materially differs from MARSHALL 
is in the fact that he believes that the nerve arises from the olfactory 
lobe, while MarsHatt believes that, in both the elasmobranchs and 
the chick, it arises before an olfactory lobe has been formed. 


1 MILNES MARSHALL. The Development of the Cranial Nerves in the 
Chick, Quart, Journ. Micros. Sc., Vol. XVIII, 1878. 


Morphology of the Vertebrate Olfactory Organ, Quart, Journ. Micros. Sc., 
Vol. XIX, 1879. 


2 FRANCIS BALFOuR. Journal of Anatomy and Physiology, Vol. XI, 1878. 


BEDFORD, Olfactory Nerve in Swine. 393 


A. voN KO LLIKER’ is another able investigator who claimed a cen- 
tral origin for the olfactory nerve. His observations were made upon 
mammals. 

In 1890, however, he completely changed front and claimed a 
peripheral origin for the nerve in both the chick and mammals. In 
mammals he found (in the material at his disposal) the olfactory nerve 
always firmly attached to the epithelium of the olfactory pit. He 
found, however, no stage in which the olfactory nerve was connected 
with the olfactory pit without also being connected with the brain wall, 
yet he considers it evident that the olfactory netve arises in the olfac- 
tory epithelium and grows toward the brain. K6OLLIKER believes 
that the nuclei in the adult nerve belong to the nerve fibers themselves 
and that each fiber contains several nuclei. ‘‘Each fiber corresponds 
to a complex of nerve cells.”” The presence of mitoses within the an- 
lage is regarded as evidence that the cells lengthen and form fine 
fibers, while the nuclei divide several times. 

BEARD,? in his System of Branchial Sense Organs and their As- 
sociated Ganglia in Ichthyopsida, gives still another explanation of the 
origin of the olfactory nerve. He claims that the anlage of that nerve 
is made up of cells arising from both the brain and the nasal epithe- 
lium. A cell-mass grows from the forebrain, cells from the epithelium 
become connected with this and thus the ganglion is fully formed. 
BEARD’s observations were made upon the Torpedo. His general 
scheme of nerves is based upon conditions found in some of the more 
posterior nerves. He has found that in the selachians, the nerves that _ 
supply the gill arches are formed through the union of the two anlages, 
one arising from the brain and one arising as a thickening of the over- 
lying region of the integument. BEARD, in support of his view, at- 
tempts to homologize the nasal epithelium with a branchial sense 
organ. 

CHIARUGE agrees very closely with BEARD. He concludes that, 


1A. VON KOLLIKER. Entwickelungsgeschichte, 1879. 


Ueber die erste Entwickelung der Nervi olfactorii, Verhandl. d. physthaltsch 
mea. Ges. su Wirzburg, Sitz. von 6 Juli, 1890. 


2]. BEARD. The System of Branchial Sense Organs and their Associated 
Ganglia in Ichthyopsida, Quart. Journ. Micros. Sc., Nov., 1885. 


3’ CHIARUGI. Observations sur les premieres phases du developpement des 
nerfs encephaliques chez les mammiferes, et, en particulier, sur la formation du 
nerf olfactif, Archiv. Italiennes de Biologie, XV, 1891. 


394 Journal of Comparative Neurology and Psychology. 


in the guinea pig, the cellular anlage of the olfactory nerve is made 
up of cells arising both from the brain and epithelium of the olfactory 
pit. The evidence, however, which he presents is not very conclu- 
sive. CHIARUGI found a fibrillar stage following a purely cellular 
stage. He believes that more than one fiber may arise from one cell. 

His' was the first to affirm that the olfactory nerve arises exclu- 
sively from the periphery. Since his views have exerted such a great 
influence upon those held at present concerning the origin of the olfac- 
tory nerve, it will be well to examine his work in detail. 

He finds, first, in a four and one-half week old human embryo, a 
mass of cells lying near the olfactory plate, which he calls a ganglion, 
having apparently no connection with the brain. But even in earlier 
stages he finds in the olfactory plate, as in the medullary plate of the 
same period, two kinds of cells, one of which later becomes neuro- 
blasts with fibrillar processes, while the other contributes to the forma- 
tion of the supporting elements. 1s states that the cells which will 
form the neuroblasts, wander out of the olfactory epithelium, to form 
the ganglion. It is the processes of these cells which form the fibers 
of the olfactory nerve. The cells are bipolar, one process passing to 
the olfactory epithelium, the other passing toward the brain. Later 
the cell bodies pass toward the bulbus and are found in the cap-like 
covering of the bulbus. He believes that the nuclei lying in the 
course of the adult nerve do not belong to the fibers, but to the cellu- 
lar nerve sheath. 

Diss? applied Goua’s method to the study of the various stages 
in the development of the olfactory nerve in the chick. He agrees 
with His that the olfactory fibers arise from the neuroblasts that origi- 


1W. His. Ueber die Entwickelung der Riechlappens und des Reichgang- 
lions und iiber diejenige der verlangerten Marks, Verhandl. d. Amat. Ge- 
selischaft, 1889. 


Die Formentwickelung des menschlichen Vorderhirns, Aédhandl. d. math- 
phys. Klasse der Kgl. Stichs Gesellsch. d. Wissenschaften, Bd. XV, 1890. 


* DissE. Ueber die Erste Entwickelung des Riechnerven. Svtzungsberichte 
der Gesellschaft zu Beférderung der gesamten Naturwtssenschaften in Marburg, 
No. 7, October, 1896. 


Die Erste Entwickelung des Riechnerven, Amat. Hefte, 1 Abteilung, Heft 
9, 1897. 


On the Early Development of the Olfactory Nerve. Proceedings of the 
Anatomical Soctety of Great Britain and Ireland, published in the /Jourmal of 
Anatomy and Physiology, 1901. 


BEDFORD, Olfactory Nerve in Swine. 395 


nate within the olfactory epithelium. DissE, however, believes that 
the majority of the neuroblasts never leave their position within the 
olfactory epithelium. A very few do pass into the mesoderm separat- 
ing the olfactory epithelium from the brain and there undergo their 
transformation into bipolar ganglion cells. He also believes, as does 
His, that the cellular anlage of the olfactory nerve, which has been 
seen by various observers, arises from cells that migrate from the olfac- 
tory epithelium, but these cells, according to Dissr, instead of becom- 
ing neuroblasts are destined to form the cellular nerve sheath. Thus 
he believes that the cell mass, which by other investigators has been 
considered to be the anlage of the olfactory nerve, is of very slight 
importance in the tormation of that nerve. He failed to obtain satis- 
factory results from the use of the Goa: method in the study of 
mammalian embryos. 

Even if Dissr’s work be accepted as representing the true con- 
dition in the chick§ it does not necessarily follow that the course of the 
development of the olfactory nerve is precisely the same for mammals. 

The observations of His, voN KOLLIKER and CHIARUGI, only, are 
based upon the study of mammalian embryos. In BEarp, von Kox- 
LIKER, CHIARUGI, His and Dissz, whose work has been done since 
1884, we have five investigators, no two of whom are in entire 
agreement as to the origin of the olfactory nerve. CHIARUGI’s con- 
clusions, based upon the observation of mammalian embryos, differ 
very essentially from those arrived at by His and von K6LLIKER in 
the study of animals of the same class. His and von KOLLIKER in 
turn do not agree as to the relation of the cells to the fibers of the nerve 
and neither of these investigators employed the GoLa@1 method by the 
use of which Diss reached in the chick very different conclusions as 
to the position of the neuroblasts from which the fibers arise. 


Scope of This Paper. 


It is evident that there is need of more observations re- 
garding the origin of the olfactory nerve. It is especially de- 
sirable to ascertain whether the conclusions arrived at by DissE 
for the chick can be extended to mammals. 

Since the conclusions of the different investigators vary, 
the following pertinent questions have not, as yet, for mammals 
been conclusively answered. 

1. When and where do the first indications of the olfactory 
nerve appear ? 


396 Journal of Comparative Neurology and Psychology. 


2. If in the olfactory epithelium, is there also any indication 
of a portion of the anlage arising from the brain? 

3. Do the cells of the so-called anlage become ganglion 
cells. 

4. If these are ganglion cells, what is their location in the 
adult nerve ? 

5. If these cells are not ganglion cells, what is their fate 
and where are the true ganglion cells located ? 

The writer has undertaken to trace the history of the ol- 
factory nerve in swine, from its first indication onward to the 
sub-adult stage, and believes that in addition to giving a gen- 
eral history of its development, he is able to throw some light 
on all the above questions. But the fate of some of the cells 
of the so-called primitive anlage remains unsettled. 

The work was undertaken at the suggestion of Professor 
WitiiamM A. Locy of the Northwestern University, whom the 
writer has to thank for much valuable direction. 


Personal Observations. 


Methods. —Perfectly fresh material for fixation was obtained 
by plunging the embryos, removed from uteri of recently killed 
swine directly into the fixing fluid. At the time of their removal 
from the uteri, the hearts of the embryos were still normally 
beating. 

The most satisfactory results were obtained from material 
fixed in vom Ratn’s picro-platin-osmic mixture and stained with 
iron haematoxylin. Embryos fixed in corrosive-acetic and 
stained with either DELAFIELD’s haematoxylin or iron haema- 
toxylin gave good results. 

For Gotai preparations the rapid method was used. Some 
very good results were obtained with Gorci from material that 
had been preserved in ten percent formalin for a week or more. 

Formation of the Olfactory Pit.—Soon after the closure of 
the neural groove, a thickening, caused by the cells of the ecto- 
derm becoming elongated, appears well forward upon each side, 
of the head region. This is the olfactory plate. 

At this time the greatest thickness of the olfactory plate 


BEDFORD, Olfactory Nerve in Swine. 397 


is .075 millimeter. From the region of greatest thickness, it 
gradually thins out in every direction until the ordinary thick- 
ness of the general epithelium is reached, which is .oo1 milli- 
meter. Such a condition of the epithelium is found in a swine 
embryo of five millimeters length. Even at this time may be 
seen a slight indentation in the olfactory plate. In older em- 
bryos this indentation becomes deeper. This is due to the 
more rapid growth of the margins of the plate. 


Fig. 1. Section through the head of a swine embryo, 5 mm. long, in the 
plane indicated in the small figure,showing the thickening of the epithelium at 
future location of olfactory pit. A-B .o5 mm., C-D .075 mm., Z-F .025 mm., 
G-H .ool mm., A-Z .oo12 mm., F. B., forebrain, Mes., mesoderm, £ct., 
ectoderm, OQ. //., olfactory plate. 

As the deepening increases the pit comes to occupy a 
more ventral position and to lie relatively nearer the mid-line. 
In an embryo in which there is the earliest appearance of a pit, 
the distance between the two pits is practically the entire width 
of the head, while in an embryo of about eleven millimeters in 
length, the distance between the two pits constitutes only fifty- 
five percent of the entire width of the head. 

In a young embryo in which the pit is just beginning to 
form, the axis of the lumen is directed outward at a right angle 


398 Journal of Comparative Neurology and Psychology. 


to the lateral aspects of the head. As the embryo becomes 
older the axis of the lumen gradually shifts until it is directed 
ventrally, having passed through an angle of nearly go degrees. 
Up to the time of the first appearance of the nerve the 
pit has the form of a simple invagination. No folds as yet 
have appeared in its walls. Thus a well-formed pit has devel- 
oped before there is any indication of the olfactory nerve. 
Differentiation of the Cells of the Olfactory Epithelinm.— 
In embryos possessing an olfactory plate in which only a very 
slight indication of an invagination appears, two kinds of cells 
may be seen in the epithelum; first, the ordinary prismatic 
cells; second, large cells almost spherical in shape, whose cyto- 
plasm is not readily stained. The latter are usually located in 
groups of three or four. In embryos of this stage of develop- 
ment they are always situated near the external margin of the 
epithelium. In an embryo of six millimeters, in which the dif- 


LP. ce 
ane 
aad at 
oe" 919 6 6 a 

ages oo 
© @@6 VO) \ey sy Le 

OCle OIG a. 

aoe MX gt 8 
OF 
ae 
0, 


Fig. 2. Sections of olfactory epithelium showing germinating cells, G. C., 
located near lumen of the nasal pit; Z. P,, Lumen of Pit. Iron haematoxylin . 
A, from an embryo g millimeters in length; B, from an embryo 6 millimeters in 
length ee <415633° 


ferentiation of the cells was first observed, a number of these 
cells show different stages of karyokinetic division. The nuclei 


BEDFORD, Olfactory Nerve in Swine. 399 


of these cells are more nearly spherical than the nuclei of 
the prismatic cells, the nuclei of the latter being usually ellipti- 
cal, their long axes corresponding with the long axes of the 
cells. The nuclei of the rounded cells are not provided with a 
nuclear membrane and present a ragged outline. As has been 
often suggested, they are probably mitotic cells. 

Development of Neuroblasts.—In slightly older embryos, 
in addition to the spherical cells, cells of a slightly different 
shape are present, which, from their size, appearance and loca- 
tion, evidently belong to the same class of cells as the spherical 
cells described. They are pear-shaped with the pointed end 
directed away from the outer edge of the epithelium, toward 
that margin bordering the mesoderm. 


iW 


fig. 3. Various stages in the development of neuroblasts observed in the 
olfactory epithelium of a swine embryo 7 millimeters in length. The line above 
each figure represents boundary between epithelium and the lumen of the nasal 
pit. 800; iron haematoxylin. 

In a number of cases this pointed end passes into a fine 
fiber extending toward the mesodermal margin of the epithe- 
lium. In the majority of cases, the peripheral end is very 
slightly pointed, while in other cells a well developed, con- 


400 Journal of Comparative Neurology and Psychology. 


siderably elongated, conical elevation is present on the periphe- 
ral end of the cell. In these cases the cell body is removed 
somewhat from the outer margin of the epithelium and the cen- 
tral fiber is well developed. All intermediate stages, from a 
spherical cell through a pear-shaped cell, from the apex of which 
a fiber passes toward the central border of the epithelium, to a 


Fig. ¢. A, Longitudinal section of a swine embryo, 13 millimeters in 
length, through the nasal pit. Z, eye. x 8. 

&, Portion of olfactory epithelium of 4 (x) showing developing nerve cells 
(V) and supporting cells (S$). W. P., nasal pit. XX 93%. GOLGI preparation. 
bipolar cell, are found (Fig. 3). These cells conform very well 
to developing neuroblasts described by His, and called by him 
germinating cells. Not until some time after this is there any 
structure present between the epithelium of the olfactory pit 
and the brain wall, which might be considered to be the anlage 
of the olfactory nerve. 


Fig. 5. Section of olfactory epithelium of a swine embryo, 17 millimeters 
in length, showing developing nerve cells (V). GOLGI preparation. XX 93%. 


By the use of the Gore method, both the developing 
nerve cells and supporting epithelial cells are impregnated. 
The latter are quite irregular in outline, while each of the for- 
mer has an enlarged cell body which tapers at either the peri- 
pheral or the central pole of the cell or at both poles intoa 
slender unbranched process. In Gore! preparations, the de- 


BEDFORD, Olfactory Nerve in Swine. 401 


veloping nerve cells are seen to be located at different levels 
within the epithelium. & and 5’, Fig. 6, represent neuro- 
blasts whose cell bodies are located upon the margin of the 
epithelium bordering the lumen of the nasal pit. V, Figs. 4, 


Bry 


Fig. 6. A, Sagittal section through head of an embryo 17 millimeters in 
length. S&r., wall of forebrain. > 8. &, Portion of olfactory epithelium 
(X 93%) indicated in 4” by brace (x), showing developing nerve cells (7) and 
supporting cells (S). A’ represents a neuroblast that has migrated partially in- 
to the mesoderm. GOLGI preparation. 


Fig. 7. Developing nerve cells from the 

IVP. olfactory epithelium of a 15 mm. swine embryo, 
one with central process directed into an elevation 

of the epithelium. M4. P., Nasal pit. X I40. 


4 t / GOLGI preparation. 


5 and 6 represents developing nerve cells whose cell bodies are 
considerably removed from the margin of the epithelium bor- 
dering the lumen of the pit. MV’, Figs. 4 and 5 represents 
nerve cells whose cell bodies are located nearer the mesodermal 
margin of the epithelium. A’ of Fig. 6 represents a develop- 
ing nerve cell that is partially outside of the olfactory epithe- 
lium, lying partially within the mosoderm. The GoLei prep- 
arations were made from embryos of thirteen millimeters and 
upward in length. 

Beginning of Outgrowth from the Nasal Epithelium to- 
ward the Brain Wall.—In embryos from nine to twelve milli- 
meters in length, the median wall of the olfactory pit becomes 
relatively thicker than the lateral wall. At the same time, the 


402 Journal of Comparative Neurology and Psychology. 


margin of that portion of the wall bordering the mesoderm 
shows a slight waviness. Earlier stages show no indication of 
such a condition, nor do other portions of the olfactory wall in 
the same embryos (Figs. 8 and 9). 


Fig. 8. A, Section of olfactory epithelium of a swine embryo g millimeters 
in length. WW. ?., nasal pit; O. &., elevations of the olfactory epithelium. 
X 93%. 8B, Section through head, a portion of which (x) is represented by 4- 
F. 8., forebrain. X 7%. 

This waviness on the mesodermal margin of the epithe- 
lium develops into distinct elevations. These elevations appear 
to be caused by the pushing toward the mesoderm of the cells 
of the epithelium. Histologically, these cells seem to be, for 
the most part, the ordinary epithelial cells. In a few instances, 
they resemble the germinating cells found near the outer margin 


of the epithelium. 


OF. 
fig. g. Section through the walls of the olfactory pit of a 12 mm. em- 
bryo, showing at O. Z. the elevations mentioned in the text. 
The section shows also the variations in thickness of the epithelial walls. 


xX 93). 

In earlier stages the nuclei of those cells nearest the inner 
margin are arranged in a row ata definite distance (.00875 mm.) 
from the inner border. See Fig. 10, A. This arrangement is 
also to be noted in the later stages in those portions of the epi- 
thelium away from the elevations mentioned above. 


BEDFORD, Olfactory Nerve in Swine. 403 


This, however, is not found to be the case in those thick- 
ened portions of the epithelium of the same section where the 
waviness of the mesodermal edge and the elevations occur. 
By examination of Fig. 10, B it will be observed that some 
nuclei have passed beyond the general line of nuclei and have 
come to occupy a position much nearer the mesoderm. Fig. 
10, C shows an outpitting of the epithelium in which the nuclei 
lie upon the very border of the mesoderm, and a few lie only 


partially within the epithelium. Fig. 10, A and C are repre- 


HEypankgs 


Mie eh 


fig. ro. Three sections of the olfactory epithelium of a 12 mm. swine em- 
bryo. A shows the nuclei in a row, located at a definite distance from the inner 
margin; 4, nuclei that have moved slightly toward the mesodermal margin of 
the epithelium; C, nuclei in the act of migrating into the mesoderm from one of 
the elevations of the olfactory epithelium. 533%. Iron haematoxylin. 
sentations of different portions of the epithelium of the same 
section. The general line of the nuclei lies about .00875 mm. 
from the margin, while, as shown in Fig. 10, 2, some of the 
nuclei are within .0035 mm. of the mesodermal edge and in Fig. 
10, C the nuclei lie directly at the mesodermal margin. 
At the time the elevations appear, many cells, showing 
various stages of karyokinesis, are present. They are all lo- 


404 Journal of Comparative Neurology and Psychology. 


cated near the outer margin of the epithelium. In a few cases in 
GoLGI preparations, central processes of neuroblasts were seen 
extending towards the brain wall into elevations of the epi- 
thelium (Fig. 7). 

Formation of Connection between the Nasal Epithehum and 
the Brain Wall.—In slightly older embryos several cellular 
cords may be seen projecting a short distance into the meso- 
derm. The cords may be distinguished from the surrounding 
mesoderm by their compactness and their continuity with the 
epithelium. These cords are directed toward the brain (Fig. 11). 


Fig. 77. Section of a 12 mm. embryo, showing the development of the 
“elevations” into short cords (C@) projecting towards the brain wall. FF. B.; 
wall of forebrain; A¢., mesoblast; A’. P., lumen of nasal pit. 


In embryos of twelve or thirteen millimeters length, these 
cords become much longer. As yet, there is no connection 
with the brain. In none of the specimens stained by iron hae- 
matoxylin, have fibers been observed. However, dissections. 


BEDFORD, Olfactory Nerve wn Swine. 405 


of embryos of this age show that the cords are firmly attached 
to the nasal epithelium and exhibit considerable tensile strength 
(Fig. 12). This can hardly be accounted for unless we grant 
that this cord is not purely cellular but somewhat fibrous in 
character. 


Fig. 12. Partial dissection of the head of a 12 mm. swine embryo, show- 
ing cords in the position of the future olfactory nerve, extending from the wall 
of the olfactory cup toward the brain. 0. c., olfactory cup; Cd., cords; 4, 
lateral view ; &, lateral-dorsal view. 

I have been unable to find, in addition to this peripheral 
anlage, any evidence of a cerebral anlage as has been described 
by Bearp for the selachians and CuraruGi for mammals.  Evi- 
dently, at least at this stage, the development is entirely from 
the epithelium. 

At the time of the formation of the anlage of the olfac- 
tory nerve, the evagination of the forebrain to form the cere- 
bral hemisphere is well under way. However, at this time, 
there is no indication of an olfactory lobe. 

Establishment of the Olfactory Nerve.—In slightly older 
embryos, the cord may be traced tothe brain. Dissections, as 
well as a study of serial sections, show clearly that many sep- 
arate cords leave the epithelium (Fig. 14). I have counted four- 
teen on one side in one section (Fig. 13). These cords arise 
from various portions of the epithelium of the olfactory region. 
They run dorsally and slightly towards the mid-line. As they 
approach the brain, they converge to form a cellular mass, 

which, in later stages, appears as a kind of a cap over the end 
of the bulbus (Fig. 13). This cap remains chiefly cellular, 
even after the cord is almost completely fibrous. 


406 Journal of Comparative Neurology and Psychology. 


Cs 
Vo 


Fig. 73. <A series of sections of the olfactory nerve of a swine embryo 14 
mm. in length, to show convergence of cords into a cell mass which unites with 
the olfactory lobe. Thickness of each section 10 je. C85. Brey Brainywall 
NV. P., nasal pit. 

B. 50 u« higher than A. D. 110 4 higher than C. 
C. 20 # higher than B, E. 40 4 higher than D. 


BeprorD, Olfactory} Nerve in Swine. 407 


In stages of eighteen millimeters and over, the olfactory 
nerve is seen to be double and is connected with the olfactory bul- 
bus by means of two roots, median and lateral, from each of 
which arise a number of filaments passing to the olfactory epi- 


Fig. 14. Sagittal section of a swine embryo, 17 mm. in length, showing 
converging filaments (//a olfactorta) of the olfactory nerve. O. L., olfactory lobe 
XN. E., nasal epithelium; F. O., fila factoria; C. 4., cellular mass overlying the 
olfactory lobe. XX 93%. 
thelium. These main divisions are apparently homologous to 
the two divisions described by many observers for the sela- 
chians. 


Summary. 


1. At the time of the formation of the olfactory plate, 
there is no trace of either cerebral hemispheres or olfactory 
lobes. 

2. The olfactory plate shifts from a more dorsal to a more 
ventral position. 


408 Journal of Comparative Neurology and Psychology. 


3. The nasal pit is formed by a process of invagination. 

4. Ata very early period in the formation of the pit, two 
kinds of cells are present in the olfactory membrane ; first, 
columnar epithelial cells ; second, spherical cells, located near 
the outer margin of the epithelum. Many of these latter cells 
are in the process of karyokinetic division. 

5. These spherical cells develop into neuroblasts which, at 
first, are unipolar having only the central process developed, 
but later those which migrate from the outer margin become 
typical bipolar nerve cells. 

6. For the most part, the developing nerve cells retain 
their position near the outer margin of the epithelium, but, in 
some cases, the cell body comes to lie at a deeper level within the 
epithelium necessitating the lengthening of the peripheral pro- 
cess. 

7. Soon after the neuroblasts are formed cells from the 
inner part of the nasal epithelium push slightly into the meso- 
derm. This is indicated by a waviness of the margin of the 
epithelium, followed by distinct elevations extending towards 
the brain wall. Among the first indications of their outpush- 
ing, is a change in the arrangement of the nuclei of the cells of 
the epithelium. 

8. Distinct projections extend from the epithelium into 
the mesoderm. While these projections are chiefly cellular, 
dissections show that they are also somewhat fibrous. 

9g. A few of these cells seem to be migrating neuroblasts, 
while the majority are evidently epithelial cells which upon be- 
ing relieved of the pressure exerted upon them within the epi- 
thelium, take a more rounded shape. 

10. These projections, which may now be known as cords, 
become much longer. They converge and near the brain unite 
to form a cellular mass, which, however, as yet, has no connec- 
tion with the brain. 

11. At no stage have structures been observed originating 
in the brain that may be considered to take part in the forma- 
tion of the olfactory nerve. 

12. In still older embryos, the cellular mass, to form which 


* 
BEDFORD, Olfactory Nerve in Swine. 409 


the cords unite, is found to be in direct connection with the 
olfactory lobe of the brain forming a cap over the bulbus. 

13. When established, the nerve is seen to consist of two 
portions, a lateral and a more median one. 


From observations upon swine embryos, there seems to be 
no reason to question the peripheral origin of the cellular mass 
which is connected with the olfactory epithelium by cords, 
chiefly cellular. At no time, in the development, were any 
structures observed arising from the brain, which might con- 
contribute to the formation of this cell mass or to the cords. 

MARSHALL, VON KOLLIKER, BearD, His, and others have 
considered these cellular structures to constitute the anlage of 
the olfactory nerve. That these cellular cords represent, in po- 
sition, the olfactory filaments that arise later, there can be no 
doubt. Every stage can be traced from the first appearance of 
the cords as elevations of the epithelium up to the time of the 
presence of the olfactory filaments connecting the epithelium 
with the brain. 

It is quite evident, however, that the majority of the cells 
of the cords are not the cells from which the olfactory fibers 
arise. The latter arise from cells the majority of which retain 
their original position within the olfactory epithelium. Only a 
few of the neuroblasts migrate from the epithelium. The cen- 
tral processes of the neuroblasts, located within the epithelium, 
are seen to be directed toward the cellular cords. In the chick, 
DissrE has been able to trace the processes into the developing 
cords and finally to the bulbus where they end in glomeruli. 
My preparations show also some neuroblasts in the act of mi- 
grating from the epithelium into the adjacent mesoderm. GOLGI 
preparations do not show within the bulbus any indication of 
the development of neuroblasts which send processes periphe- 
rally to form olfactory filaments. Since it is known that nerve 
fibers are continuous with only one nerve cell, we must con- 
clude that the neuroblasts observed in the olfactory epithelium 
and which in some cases migrate into the mesoderm are the 


410 Journal of Comparative Neurology and Psychology. 


cells of origin for the fila olfactoria. Consequently it must be 
affirmed that the olfactory nerve has a peripheral origin. This 
view is supported by observations made by Enrticu,! RErztus,? 
Grass! and CaAstronovo,*? RaMon y CajAL,* JaGopowskr’ and 
others upon the adult nasal epithelium of mammals and other 
animals. 

The majority of the cells, therefore, that form the primi- 
tive cellular anlage of His and others do not develop into nerve 
cells. Disse has suggested that they constitute the cellular 
sheath of the nerve, that is, are comparable to neuroglia cells. 
Their fate I have not been able to ascertain. The majority of 
them, however, accumulate in the cap formed over the end of 
the bulbus. 

His’s contention that this cellular anlage constitutes a true 
ganglion is not supported by my observations. My conclusions 
on this point harmonize with those of Dissr, arrived at for the 
chick. At most, there is only a partial formation of a ganglion 
located between the olfactory epithelium and the brain. 

According to this view, the belief that the fibers of the 
olfactory nerve have the same relation to the olfactory cells as 
do fibers to sensory cells in the taste buds and tactile corpus- 
cles is not tenable. The olfactory cells constitute the cell bodies 
of neurones of the first order. 


' Enriicu. Ueber die Methylenblaureaktion der lebenden Nervensubstanz. 
Deutsche Med. Wochenschrift, 1886. 

? Rerzius. G. Zur Kentniss der Nervenendigungen in der Riechschleim- 
haut. &zol. Untersuchungen, Neue Folge, Bd. IV, 1892. 

3 GRASSI and CASTRONOVO. Beitrag zur Kentniss des Geruchsorgans des 
Hundes. Archiv f. mikros. Anatomic, Band XXXIV. 

* RAMON Y CAJAL. Origen y Terminacion de las fibras, nerviosas olfac- 
torias. Gazeta sanztaria municipal dai Barcelona, Dec., 1890. 

5 JAcopowskE1, K.P. Zur Frage nach der Endigung des Geruchsnerven 
bei der Knochenfischen. Azat. Anz., XIX, pp. 257-267. 


ire ATION: OF \ LEE CHORDA  ‘TYMPANE £O 
EAE VISCERAL ARCHES IN’ MIGROTUS. 


By Vicror E. EMMEL. 


(Contributed from the Biological Laboratory of Pacific University, under the 
devection of G. E. COGHILL). 


The mammalian chorda tympani is a branch of the facial 
nerve which passes over the tympanic cavity, underneath the 
auditory ossicles and joins the lingual branch of the trigeminus. 
It is generally accepted that the tympanic cavity and auditory 
ossicles are derivatives of the spiracular cleft and visceral arches 
of fishes. It would seem a natural conclusion, therefore, that 
the chorda tympani is also homologous with the pre-spiracular 
branch of the facial nerve of fishes and amphibians. Upon 
this point, however, authorities are not agreed. On the one 
hand, a large number of investigators regard the chorda tym- 
pani as the homologue of the pre-spiracular (pre-trematic) nerve 
of fishes, as, for example, BaLFour, in describing the anterior 
branch of the seventh nerve of Elasmobranchii, says: ‘‘This 
branch forms the prae-spiracular nerve of the adult and is 
homologous with the chorda tympani of mammals’ (Compara- 
tive Embryology, Vol. II, p. 459). Srrone, in his work on 
the .cranial nerves of Amphibia, interprets the r. mandibularis 
internus of fishes and Anura, and the r. alveolaris of Urodela, 
as homologous with the mammalian chorda tympani. On the 
other hand, Drtner denies that the r. alveolaris is the homo- 
logue of the chorda tympani (Zool. Jahrb., XV, 3); while Coc- 
HILL, in his work on the cranial nerves of Amblystoma, inter- 
prets the r. alveolaris,of Urodela as pre-spiracular, and takes 
the tentative position that the ‘‘most complete morphological 
and physiological representative (of the chorda tympani) in the 


412 Journal of Comparative Neurology and Psychology. 


Ichthyopsida is probably found in the r, alveolaris of Urodela”’ 
(Jour. Comp. Neurol., Vol. XII, p. 269). HERRICK questions 
whether Srrone’s r. mandibularis internus in the homologue of 
the chorda tympani. He finds no nerve in MZenzdza homolog- 
ous with the chorda tympani, and does not consider the r. pre- 
trematicus VII to be so homologous because it does not fuse 
with the r. mandibularis V and hence it does not distribute to 
the hyoid and mandibular arches in the way characteristic of 
mammals” (Jour. Comp. Neurol., Vol. IX, p. 324). And 
finally, in addition to the r. palatinus, r. pre-trematicus and r. 
post-trematicus, STANNIUS, as cited by Herrick (loc. cit.) de- 
scribes in Rajya and Sfzzax another branch of the seventh nerve 
which fulfills every condition for the chorda tympani. This 
conflict of opinion shows that the homology of the chorda tym- 
pani is far from being unquestionably established. 

A chief source of this disagreement lies in the fact that the 
morphological relations of the chorda tympani to the spiracular 
cleft throughout the ontogeny of mammals is not completely 
understood. It has been accepted by leading authorities that 
the chorda tympani is a pre-spiracular nerve in the mamma- 
lian embryo. Very recently Herrick ina literary notice of 
the work by VeRstuys on ‘‘Die mittlere und aussere Ohrsphare 
der Lacertilia und Rhynchocephalia” writes: ‘‘The detailed 
descriptions and figures make it very plain that the chorda 
tympani of reptiles is pretrematic and therefore morphologically 
pre-spiracular ; and in the absence of very definite proof to 
the contrary, we must assume the same condition to prevail 
among the mammals also” (Jour. Comp. Neurol., Vol. XIII, 
1). Lewis in giving “The Anatomy of a Twelve Milli- 
meter, Pig,” says that the seventh nerve ‘‘divides into a pre- 
trematic and post-trematic branch, but the division is under the 
spiracle or auditory cleft and not over it as in fishes” (Am. Jour. 
Anat., Vol. II, 2). In the last quotation it is not clear, how- 
ever, whether by ‘‘division under the spiracle’’ it is meant that 
the chorda tympani itself passes over or under the spiracular 
cleft: 

In the adult mammal the nerve in question clearly passes 


EmMEL, Chorda Tympani in Microtus. 413 


over and in front of the tympanic cavity, so that, in view of the 
confusion of ideas as noted above, the question now is whether 
the pre-tympanic position is primary and maintained throughout 
the embryonic life, or whether it is a position secondarily ac- 
quired in the development of the tympanum. Of course, the 
further questions of homology cannot be settled till this point 
in mammalian embryology is determined. It was for the purpose 
of contributing something to the solution of this question that 
the following study in the embryology of A/zcrotus was under- 
taken. 

The embryos used in this study were killed and preserved in 
formalin. To insure a correct conception of the relations of the 
nerves to all parts of the head a model of a 2.3 mm. embryo, 
magnified 50 diameters, was made by the Born method.  Re- 
productions of two older embryos, also, were made by Kast- 
CHENKO’S method of graphic projection. My observations were 
made from the same series of serial sections as were employed 
for the model and projections, and from several other series of 
slightly different ages and cut in different planes. 


First Embryo. 


The youngest of the embryos was used for the construc- 
tion of the model. The model and the sections from which it 
was made demonstrate clearly all the structures which are of 
importance for this study: the brain and all its flexures, the 
roots and ganglia of the fifth, seventh and eighth nerve, the 
mandibular and hyoid arches, and the posterior visceral arches 
as they are modified to form the sinus cervicalis. At this 
period the visceral arches are united only by a membrane com- 
posed of the two layers of epithelial cells, and the nerve trunks 
can be traced only a short distance into the mesenchyme of the 
arches. 

Second Embryo. 

From this embryo, more advanced than the first, two 
eraphic projections were made, one of the exterior of the head and 
the other of the brain, fifth and seventh nerves and pharyngeal 
cavity. The mandibular and hyoid arches are still conspicuous 


414 Journal of Comparative Neurology and Psychology. 


as typical visceral arches. The formation of the mandibular 
and hyoid cartilages has not begun, and these regions are filled 
with primitive mesenchyme cells. 

The Spivacular Cleft.'—In the dorsal part of the external 
groove between the mandibular and hyoid arches a small pit is 
found. From the apex of this pit the lumen of the spiracular 
cleft passes inwards and cephalad, and opens into the pharynx. 
Beginning in its most external part the lumen is very narrow for 
a distance of about .0o7 mm., then it broadens out into a flat 
cavity with its shortest diameter, as seen in the sagittal sec- 
tion, in a dorso-ventral direction. In the extreme lateral region 
of the cleft its epithelial walls approach each other in such a 
manner that the lumen is reduced to a small circular canal, un- 
til, finally, for an extremely short distance they come into close 
contact with each other, so that the lumen seems to be oblit- 
literated. The epithelium of the cleft, however, ts perfectly con- 
tanuous wth the epithelium of the skin. 

This relation of the visceral arches and the pharyngeal 
cavity to this cleft, and the continuity of the inner and outer 
epithelial plates are essential characteristics which establish its 
homology with the spiracular cleft of fishes. 

The Chorda Tympani and Related Nerves.—The Gasserian, 
geniculate and auditory ganglia and their roots are clearly de- 
fined. The rr. ophthalmicus, maxillaris superior and mawillaris 
inferior are easily identified in their usual relations. Near its 
ganglion the r. maxillaris inferior gives off the buccal nerve, 
and, passing into the mandibular arch, divides to form the in- 
ferior dental and the lingual nerves. The latter can be traced 
into the base of the tongue. 

From the geniculate ganglion the facial nerve passes out- 
ward and slightly caudad for some distance. Just back of the 
spiracular cleft it makes a slight turn ventrad. At this angle it 
gives off the chorda tympani from its anterior border. The 


1 The term sfzvacular cleft is used here as HERTWIG uses the term szdcus 
tubo tympanicus. This usage is justified by the relations as they are described 
farther on in this paper. 


EmMEL, Chorda Tympani in Microtus. 415 


chorda tympani then passes directly forward beneath the spirac- 
ular cleft and close to its ventral edge. It soon turns inward 
and passes a considerable distance nearly parallel with the an- 
terior wall of the cleft. Near the rudiment of the tongue it 
meets and fuses with the lingual brach of the trigeminus. 

At this stage of the embryonic development of Microtus, 
therefore, the primitive continuity of the epithelium of the 
spiracular cleft and the skin still persists, and the chorda tym- 
pani passes behind and underneath the cleft and unites in a 
typical manner with the lingual nerve. 


Third Embryo. 


In the oldest of the three embryos, from which projections 
were made as from the second embryo, the pinna has begun to 
form, the mandibular and hyoid arches no longer appear as vis- 
cerial arches and have assumed in a general way the adult con- 
ditions. The skeletal regions are still for the most part filled 
with mesenchyme cells, but the fundaments of MEcKEL’s car- 
tilage and of the hyoid cartilage are distinguishable. 

The Sptracular Cleft and External Auditory Meatus.— 
The comparatively large orifice of the external auditory meatus 
is bordered by the ridges or fundaments of the pinna. The 
meatus soon narrows into a flattened cavity with its shortest 
diameter lying in the dorso-ventral plane, as seen in sagittal sec- 
tion. Its course is ina cephalo-ventral direction. It terminates 
as a blind tube. Ina plane about .075 mm. outward from the 
blind end of the external auditory meatus, and dorsal of the 
meatus at a distance about equal to the greatest diameter of the 
meatus at this region, lies the blind end of the cleft which in 
the second embryo was identified as the spiracular. This cleft 
is also a flattened cavity with its longest diameter, as seen in 
sagittal section, lying in nearly the horizontal plane. It passes 
inward for a short distance, then takes a cephalo-ventral direc- 
tion and opens into the pharynx. It is an important fact that 
in this embryo there is no continuity between the epithelium 
of the spiracular cleft and the skin. 

The Chorda Tympant.—The ganglia and the main trunks 


416 Journal of Comparative Neurology and Psychology. 


of the nerves are essentially the same as described for the sec- 
ond embryo. In addition to the inferior dental and lingual 
branches of the submaxillary, the mylo-hyoid and masseter 
branches are clearly defined. The lingual occupies a position 
along the inner side of MEcKEL’s cartilage and can be traced 
forward into the lateral region of the tongue. Of the facial 
nerve, also, the supra-maxillary and auriculo-temporal are easily 
traced in their usual positions. The chorda tympani is easily 
traced from its point of origin from the facial trunk. It passes 
behind MerckeEt’s cartilage, takes the same general direction 
that it does in the earlier embryo, and joins the lingual nerve 
near the point of separation of the latter from the inferior den- 
tal. But the relation of the chorda tympani to the spiracular 
cleft is distinctly different from that found in the earlier embryo. 
In its course in front of the hyoid cartilage and behind the 
proximal end of MrcKEL’s cartilage, it passes over the extreme 
lateral end of the spiracular cleft and close to its dorsal edge. 
It remains a question whether this lateral end of the spiracular 
cleft is the primary end of the cleft or a secondary evagination 
from it. It might be the latter, since it is generally accepted 
that the closed end of the ceft by evagination outward towards 
the external auditory meatus and upward around the chorda 
tympani and auditory ossicles, forms the tympanic cavity of the 
adult. 

We find, then, at this stage of development that the chorda 
tympani no longer lies underneath the spiracular cleft but that 
it passes over the closed end of the cleft, or over the funda- 
ment of the tympanum. ‘This is the morphological position 
the nerve holds in the adult. 


Conclusions. 


The results of this study of the embryological development 
of the chorda tympani in Mzcrotus lead to the following con- 
clusions : 

1. In the earlier stages of development the chorda tym- 
pani passes behind and underneath the spiracular cleft. 2. In 


EmMEL, Chorda Tympani in Microtus. Ary 


later stages this nerve occupies a position over and in front of 
the closed end of the spiracular cleft which is generally accept- 
ed to be the fundament of the tympanum. 3. The chorda 
tympani is, therefore, a post-spiracular nerve, and is to be con- 
sidered as the homologue of a post-trematic nerve of fishes and 
amphibians. 


EDITORIAL: 


NATURE STUDY. 


Energetic, enthusiastic and intelligent efforts are being 
made to introduce Nature Study into the American public school 
curriculum. The efforts themselves are not new, but enthusi- 
asm and intelligence in.connection with them perhaps are. 
HUXLEy’s insistence upon the use of that which is vitally and 
practically related to human activities rather than conventional 
hereditary materials for the purposes of educational training, 
and AGassiz’s pleas for the study of Nature before books are 
giving evidence of their influence. 

With the year 1905 there will appear a journal devoted to 
Nature Study in the elementary schools. The founding of this, 
the Nature Sindy Review, is encouraging evidence of the recog- 
nition of the place and values of the study of Nature in our 
schools, and of the active interest of scientifically trained men. 
The editorial committee of the Review consists of L. H. Bat- 
LEY of Cornell University, H. W. Farrsanxs of Berkeley, Cal- 
ifornia, C. F. Hopce of Clark. University, J. F. WoopHULL 
and M. A. BicELtow of Teacher’s College, New York City. 
These men, and such as they, are intelligently introducing the 
materials of natural science into our public schools. They are 
effecting just the kind of utilization of the materials of their 
own sciences that‘ HuxLrey devoted so much of his energy and 
enthusiasm to encouraging. Grounded in genuine interest in 
scientific work as a source of knowledge which will promote 
the progress of the race, they are reaching beyond the narrowly 
circumscribed sphere of scientific investigation with the purpose 
of making Nature contribute directly to the education which is 
an important condition of human happiness and efficiency. 


Editorial. 419 


Perhaps no other book so well voices the judgment of 
those who stand close to the American school system as 
Hopce’s Nature Study and Life.’ It is a book which reveals 
the nature lover as well as the trained scientist in itsauthor. It 
presents a sensible, highly practical scheme for the study of 
animals and plants in the graded school, while at the same time 
filling the reader with faith in the possibilities of the work for 
training, and with enthusiasm for Nature Study. Enter into the 
spirit of the life about you; do not live to search for truth, no 
matter what kind, but search for knowledge, understanding and 
sympathetic appreciation of Nature in order that life may be 
fuller, freer, and more nearly perfect—this is the injunction of 
the book. Learn to know the living beings as thoroughly as 
does the scientist, and to love and sympathize with them as he 
too often does not. There is inspiration for the reader in this 

book, for the author’s faith in his cause and his enthusiasm are 
7 contagious. No one should read it who does not care to have 
his interest in Nature Study, both in and for itself and asa 
means of training the child, greatly increased. 

Great depth of insight into the significance of the signs of 
the times in natural science is not necessary in order that one 
should be able to say that the next generation of Americans is 
to be a generation of naturalists. Interest in Nature is rapidly 
increasing and the introduction of Nature Study in the schools 
is now going to equip our future scientific specialists with an 
intimacy of acquaintance and sympathetic appreciation of Na- 
ture that will enable them to live the better and enter the more 
fully into the truth of their subjects. The important thing is 
that this general interest in Nature Study be made to contribute 
truly earnest investigators rather than dilettanti. 

The study of animal behavior, of the life-histories, habits, 
instincts, and intelligence of organisms, of their relations to hu- 
man industries, is only a small part of Nature Study, to be 
sure, but for those of us whose interests center about the func- 

\ 
'C. F. Hopce. Nature Study and Life. Gian & Company, Boston, 1902. 
$1.50. 


420 Journal of Comparative Neurology and Psychology. 


tions of the nervous system it is an important part. It is our 
duty to keep ourselves alive to the possibilities of adapting the 
results of our special investigations to the needs of Nature 
Study courses. 

Furthermore, it is to our interest and for the good of our sct- 
ences that we make as much of our material available for the pur- 
poses of elementary training as possible, and that immediately, 
for thus will be implanted in the lives of those who are to ad- 
vance scientific knowledge in the future a love of animals and a 
desire to know the truth that will lead them to constant and 
patient research. 

When we thus in a journal devoted to pure science call at- 
tention to an apparently unrelated aspect of educational work 
and to a journal which is practical and pedagogical in its aims, 
it is not to be supposed that we are hopeful ef direct contribu- 
tions from Nature Study to pure science, but rather that we be- 
lieve the introduction of the intelligent study of animals and 
plants into our elementary schools will indirectly and ultimately 
affect our scientific work importantly. What we are concerned 
about is that this shall bea desirable influence. That it will be 
desirable in many senses is guaranteed at present by the fact 
that men who know science in its research as well as its educa- 
tional aspects are leading the Nature Study movement. 

ROBERT M. YERKES. 


RECENT CONTRIBUTIONS TO THE BODY-MIND: CON- 
VERSY.! 


The present article does not attempt to review with any degree of 
completeness the field indicated by the title. Comprehensive digests 
have been given in the works by Professors SrRoNG and BussE quoted 
below and, to avoid misunderstanding, the writer desires to avow 
his purpose in advance, viz. 1) to submit to somewhat careful 
analysis the original view expressed in Dr. Strona@’s book; 2) to 
bring into effective contrast therewith those statements of recent writers 
which may prove illuminating, and 3) to attempt a critical and con- 
structive statement of the solution of this general problem offered by 
Dynamic Realism. By this frank avowal the reader may be prepared 
to excuse the anomaly that this paper may seem as much a pleading 
as a review. 

At the outset we can do no less than express our hearty recogni- 
tion of the merit of Dr. Srrone’s work, which, for clearness of pre- 
sentation, thoroughness of research, as well as candor and courage of 
treatment, is entirely admirable. Its usefulness will be especially ap- 
parent to those who find greatest difficulty in agreeing with all of the 
conclusions. It is assumed that the reader of these lines will also 
peruse the book and thus absolve us from the obligation of making a 
comprehensive digest of the contents, which consist so largely of the 
statement of conflicting theories as to leave too small space for a con- 


1C. A. Stronc. Why the Mind Has a Body. New York, Macmillan, 
1903. 

Lupwic Bussr. Geist und Kérper. Letpzizg, 1903. 

J. Mark Batpwin. Mind and Body from the Genetic Point of View. 
Princeton Contributions, III, 2, Dec., 1903. 

H. HeatH BAWDEN. The Functional Theory of Parallelism. Phzlos. Rev. 
XT; 35° 1903: 


Necessity from Standpoint of Scientific Method of a Re- 
construction of the Ideas of Psychical and Physical. Journ. Philos. Psych. Sct. 
Methods, I, 3, 1904. 

HarTLey B. ALEXANDER. The Concept of Consciousness. Journ. Philos. 
Psych. Sci. Methods, I, 5. 

WILLIAM JAMES. Human Immortality, 1goo. 

W. OstwaLp. The Philosophical Meaning of Energy. Jxtermat. Quart., 
Wile, TOOR: 


422 Journal of Comparative Neurology and Psychology. 


nected statement of the author’s own position, which must, therefore, 
be assembled to a large extent from the critical portion of the work. 

Professor STRONG classifies the theories, in so far as they are em- 
pirical, into 

I. Interactionism: Psychophysical dualism and Psychophysical 
phenomenalism (interactionist type). 

II. Automatism: Psychophysical materialism and Psychophys- 
ical phenomenalism (automatist type). 

III. Parallelism: Psychophysical monism and Psychophysical 
idealism (the last being the author’s position). 

By the title chosen the author intentionally prepares his reader 
for the panpsychist view advocated, as he explains in the preface. For 
his theory he claims that ‘‘its difficulties are of the nature of obscuri- 
ties, not of contradictions. Hence I think that panpsychists are justi- 
fied in maintaining that with their principles they are able to explain 
the connection of mind and body.” The author hopefully proposes 
‘¢a settlement of the controversy between the parallelists and the inter- 
actionists,” a hope which we fear few of his readers will be able to 
share. 

The problem for the author, resolves itself into an ‘‘issue between 
interactionism and automatism, the former regarding the brain as an 
instrument used by the mind in dealing with the external world, while 
the latter conceives of brain-process as the physical basis or condition 
of consciousness, which simply accompanies the brain-process without 
exerting any influence upon it.” One may argue with Huxtey that 
consciousness is an effect of the brain-process, or with CLIFFORD that 
the two processes are parallel, the brain being no more responsible for 
consciousness than consciousness is for what happens in the brain. 

In the introduction Professor STRONG effectively sets forth the re- 
sults of the denial of casual relations which seems to be involved in 
any of these views. ‘‘Parallelism involves the denial of the physical 
efficiency of mind, and automatism the denial of its general efficiency.” 
«‘Thus a whole series of scientific and philosophical conceptions of the 
first order—the principle of the conservation of energy, the mechan- 
ical theory of life, the biological doctrine of evolution, the philosoph- 
ical conceptions of mechanism, efficiency, free will—all converge and 
come to a focus in the problem of the relation of mind and body. 
Not only so, but every one of these conceptions is vitally engaged, 
and will be found to stand or fall or suffer total transformation, accord- 
ing as we espouse interactionism, automatism, or parallelism.” 

We may reassure ourselves soffo voce that the case is not so bad as 


Herrick, Body-Mind Controversy. 423 


it appears. We cannot agree that these are the only possible solutions 
of the problem, and we may add that any form of parallelism, sezsu 
stricto, is simply an evasion of the issue. To say that brain-event 
and mind-event are cotemporaneous or consecutive is to offer no ex- 
planation of a fact of observation. It produces no scientific convic- 
tion that the next brain-event will be accompanied by a mind-event. 
It is no sense a theory—it is but a denial of the possibility of a theory. 
Many things that pass as parallelistic theories really go further and 
produce or assume a real tie between the two series, perhaps va some 
other element. This is especially true of functional theories. In the 
approach of the discussion of causation, which is evidently crucial in 
this connection, the necessity of determining what is meant by matter 
is encountered and frankly met: ‘‘For if at the present day there is 
a point on which philosophers show some approach to agreement it is 
that matter does not exist, in any such sense as the plain man supposes ; 
that it has no existence independently of the mind.” We think that 
this statement is true only as to the first clause, or that the second 
statement is at least misleading. There are very few philosophers who 
would deny the existence independent of the mind of something corre- 
sponding to the concept of matter in the mind; certainly the author 
himself does not consistently do so and yet he will not carry all phil- 
osophers with him to the extreme of identifying the thing back of 
matter with mind as such. What philosophy and modern science tend 
so generally to agree upon is that the matter concept as such is 
erroneous in so far as it sets up a category of creation incongruous 
with all else in the universe and places it outside of the sphere of ex- 
perience. 

After spending forty-five pages in discussing ‘‘The Facts,” the 
author confesses that ‘‘In the course of this study, nothing has been 
established to the advantage or detriment of any particular casual the- 
ory. We carry away from it a single positive result: the law of psy- 
chophysical correlation.” This law states that consciousness as a 
whole never occurs except in connection with a brain-process, and 
that particular mental states never occur except in connection with 
particular brain-events. It would seem that important limitations may 
be necessary even in the application of this ‘‘law.” Brain processes 
must be taken in a very wide sense and the ‘‘mental states” of course 
refer to those of human experience and would not prejudice the possi- 
bility of ‘‘psychic modes” corresponding to other types of what may be 
called intrinsie aspects of other physical processes. 

‘¢Any view which ascribes physical action to the mind, no matter 


424 Journal of Comparative Neurology and Psychology. 


what that action, can be reconciled with the principle of conservation 
of energy on the hypothesis that the mind is itself a form of energy.” 
‘The interactionist who shrinks from making consciousness a form of 
energy has, therefore, a single course left: to attack the universality 
of the principle of conservation directly.” Here it is to be feared ex- 
ists an unhappy confusion between consciousness and the extrinsic 
form of energy variously called ‘‘soul”’ or even ‘‘experience” (ALEX- 
ANDER) though Professor STRONG expressly says ‘‘the existence of 
consciousness is our existence. The soul is a dark and mysterious 
source from which consciousness in some unintelligible manner flows” 
though ‘‘insensibly we are drawn to picture it by the aid of that ille- 
gitimate notion of matter existing with all its materiality apart from 
consciousness—in short, as a mind-atom.” What then are we to do 
with the whole infra-conscious part of life as well as the past unre- 
membered stream of consciousness which we are wont to believe, 
with more reason than any other fact whatever, accounts forand makes 
intelligible the present consciousness? Such exclusion shuts us out from 
the teleology which alone accounts for our individuality upon the con- 
fession of idealists themselves. The idealist indeed holds ‘‘that we 
can have immediate knowledge only of our mental states ;” to which 
the realist replies that this statement does violence to a fundamental 
dictum of science that with action there must be reaction. A purely 
spontaneous activity or energic manifestation is impossible in a created 
universe (it would be a miracle and there are no miracles in philosophy, 
however it may be in theology). To say that my mind created reality 
out of nothing as a spontaneous fiat is to misapprehend the nature of 
reality. The fact that I experience a phenomenal universe demands 
something other than the simple subject of experience. For, as we 
like to say, reality is the affirmation of attribute and involves subject 
and object, energy and limitation, action and reaction, and so is zpse 
. facto proof of extraneous somewhat. ‘This reality does not necessarily 
vindicate our interpretation of it as object but it implies something to 
be interpreted. The author himself, however, provides a corrective 
in various places and admits that ‘‘the need in question (1. e., of ex- 
plaining perceived events by means of preceding events not perceived) 
can only be met by some form of realism.” ‘‘Though the objects 
themselves we percive cannot continue to exist when we no longer 
perceive them, it is consistent with idealism that they should have ex- 
tramental causes which continue to exist and of which the perceived 
objects are symbolic.” Now if this be idealism it is idealism in terms 
of realism—an idealism with the sting extracted so that it is harmless 


HERRICK, Lody-Mind Controversy. 425 


even to the most naive form of common sense. Later we somehow 
discover to our chagrin that this extra-mental something is also mental. 

There will be pretty general agreement that, ‘‘if we come to ad- 
mit things-in-themselves, we shall have to conceive them as non-ma- 
terial.” But why in the same connection add that ‘‘If things-in-them- 
selves exist, their exisence cannot be immediately known, but only in- 
ferred. The broadest of distinctions separates such extra-mental re- 
alities, which in the nature of the case can never be immediately given, 
the hypothesis of which is consequently unverifiable, from the empirical 
objects, such as matter and motion, thoughts and feelings, which we 
know by immediate experience’ (italics mine). This is most reasonably 
explained as a simple lapse but such lapses occur throughout. | Surely 
Professor StrRONG does not mean that an object is given in experience. 
Or, if he does, he cannot mean the metaphysical postulate of matter 
already admitted to be illegitimate, is known by immediate experience. 
If we know matter and motion by direct experience, that is the end of 
it. Is there no difference between knowledge and experience? 
Dynamic realism insists that we know external objects in the 
same indirect or secondary way that we know self. Genetic psychology 
traces the origin of both from an earlier ‘‘protoplasmic” condition of 
consciousness. The objective and subjective are both given in ex- 
perience and the act of judgment (or intuition) recognizing an exter- 
nal object is as valid a process as that which recognizes the individual 
self. Experience gives us neither; all simple realities imply both but 
the partition is made in thought and gives us knowledge equally of 
the two elements. This individualizing peculiarity of human mind is 
implicate of limitation. 

Professor STRONG, however, defines reality as ‘‘something which 
exists of itself and in its own right and not merely as a modification of 
something else.” But would this not make the ‘‘Absolute” the only 
reality ? for obviously only It can exist ‘‘of itself.” But this necessary 
result is not perceived by the author and to some extent will go far to 
invalidate the chapter on consciousness, etc. 

The distinction made between soul and self is interesting and sug- 
gestive. Soul is a metaphysical entity back of self much as some en- 
tity exists behind matter. Mind and soul are two different conceptions, 
the former corresponding to the soul of empirical psychology. ‘‘Con- 
sciousness is empirically a thing so mutable and transitory that we can- 
not conceive it except as supported by some more durable underlying be- 
ing, and our choice lies between making it dependent on the brain and 
on the soul,” and ‘‘since the brain, as material, cannot treasure up what 


426 Journal of Comparative Neurology and Psychology. 


is spiritual, the treasure-house must be the soul.” It seems quite im- 
possible for this writer to escape from the nave form of materialism in 
his discussion. In spite of his explicit statement of the non-existence 
of matter, he eveywhere sees it as assumed till he, by its destruction, 
has proved his triumphant point. He says: ‘‘As there cannot be 
motion without an object to move, so there cannot be thought without 
a thinker.” But this is a false analogy. The ‘‘object” which moves 
exists only as a judgment compounded of varieties of activities. So far 
as physical science knows, the movements of an object is the moving 
of other sorts of movement. In other words, we simply establish re- 
lations between different orders of activities or energetic complexes. 

In the course of the chapter devoted to the possibility of ‘‘things- 
in-themselves,” after stating that no argument from analogy can possi- 
bly prove the existence of things extra-mental, ‘‘The utmost it can 
do is to indicate their nature, when their existence is known from some 
other source,” and ‘‘it is in the nature of the case, impossible that 
consciousness should supply rational grounds for the inference of reali- 
ties beyond itself.” Dr. STRONG goes on to state as a categorical and 
‘striking fact” that something to which neither the external nor 
the internal senses lend the slightest testimony may yet with perfect 
certainty be kown to exist.” It is to him a matter of surprise ‘‘that it 
never occurred them (all other philosophers) that we might have a 
kind of knowledge less rational than either, a kind founded on neither 
reason nor experience, but solely on instinct. It never occurred to 
them that neither experience nor reason can fully account for the 
knowledge of other minds.” How this is made to agree with a later 
statement that ‘‘through our mental states, which alone are immediately 
given, we may obtain knowledge of non-empirical existences, as we 
see in the case of other minds,” we must leave to the author. 

A different point of view sometimes appears, as where it is said 
‘The reality of an object signifies its membership in an order in space 
and time existing for all similarly organized percipients.” 

As to Professor STRONG’s distinction between brain process and 
mind process, the former a possibility of perception, the latter forever 
beyond it (transcendent), it must be remembered that the distinction is 
made in our own experience before it can be predicated of another. 
So far as the mind process of another becomes knowledge it is inferred 
in exactly the same way that brain process is, but we project the sub- 
ject-object dualism of experience into another. 

As Dewey remarked in a recent lecture, ‘‘states of consciousness 
have been made either a mythological monster eating up the whole of 


Herrick, Body-Mind Controversy. 427 


reality (subjective idealism)—panpsychism, or the other way is to say 
that atoms and molecules are the real thing and states of conscious- 
ness only an accidental phosphorescence or epiphenomena.” ‘‘Mental 
states are not different stuff from the objects, but the attitudes, the in- 
dividual attitudes, necessary for reconstruction of the experience and 
thus the counterpart of the objects in this process of construction. 
The subjective is real, as an attitude, etc.” 

Coming finally to the author’s statement of the Psychophysical 
Idealism for which the book stands, it reduces to the statement that 
‘‘brain-process is a manifestation of the accompanying mind.” The 
mind is manifested directly through the brain. We have supposed 
that our thoughts are given directly; but not so, we only know we 
think when we discover changes in the brain cortex. But we would 
not do the author injustice. We are now astonished to discover that 
‘‘by brain event we mean the actual modification of another or the 
same consciousness—and this is the only natural or strictly defensible 
meaning of the word.” This identification of brain-event and mind- 
event would seem to reduce the matter to a question of identity and 
we might have been spared the rest of the book. (Yet in the next 
sentence we return to ‘‘nerve currents passing from eye to brain” and 
‘perception of the brain event”). 

Behind a mass of contradictory and inconsequent statements we 
frequently get glimpses of a genuine realism. ‘‘The phenomenal 
causal relation between sensory stimulus and sensational brain event is 
the symbol of a real causal relation between the extramental event and 
the sensation, the phenomenal causal relation between the volitional 
brain event and yoluntary motion the symbol of a real causal relation 
between volition and an extra-mental event.” The link between this 
idealism and modern realism must be found, we believe, in the inter- 
pretation of energy as potentially capable of mentality as a manifesta- 
tion of all or some of its modes. In this sense the two systems agree 
in holding ‘‘the universe to be in all parts mental in nature.” 

Panpsychism will offend the scientific mind by what seems an un- 
warrantable assumption that all things in themselves are mental in 
their nature. They will ask with Professor Srumpr ‘‘How can we 
conceive of a crystal, a dew drop, or a molecule as possessing any- 
thing analogous to sensation and will as we know them in ourselves ?” 
This difficulty Dynamic Realism meets by assuming a unitary nature 
underlying all things. They have in common an energic character 
which implies, on the face of it, nothing more than efficiency or power 
to act,. and this, of course, a fundamental philosophical necessity of all 


428 Journal of Comparative Neurology and Psychology. 


being. The individuaiiziug character is mode. There is the widest 
variety and there are compatibles and non-compatibles among modes. 
There is for each unit (complex, energic center) a form peculiarly its 
own to which there attaches an intrinsic as well as an extrinsic value 
(action and reaction). ‘The intrinsic value would be a ‘‘genetic mode” 
incapable of being translated directly in terms of any other kind of be- 
ing (but about which descriptions may be formulated in psychological 
language). This is revealable directly only in itself but is the condi- 
tion of the reflection of the external world into self. Such a mode is 
every form of consciousness, instinct, affinity, habit, attraction (and 
what-not unknown to us in the lower types of energic centres). There 
is no such thing as a general consciousness, only various conscious 
modes. The line between the conscious and unconscious in the in- 
trinsic sphere is vague. In its earlier simpler form consciousness may be 
but a longing, instinct, impulse or attraction. Each such genetic mode 
is the intrinsic side of a definite kind or form of energy which is also 
capable ef becoming an object of observation extrinsically by influenc- 
ing other energic centres. 

The real self in the case of man is not the sum of his conscious 
acts at any one time or all times, nor of his bodily activities, but the 
energic complex which, viewed intrinsically, forms the one, and 
viewed extrinsically forms the other. The real self is the ‘‘metaphys- 
ical soul” referred to by Dr. Srronc which is not only panpsychical 
but panphysical. 


In this connection it is interesting to trace with Professor BaLp- 
WIN genetically the origin of zdeas of mind and body. Assuming that 
experience is at first protoplasmic or undifferentiated, the first distinc- 
tions are of the ‘‘projective” order and do not give us self and not-self 
as usually stated, but personsand things. Self is recognized later and 
is divided into a body part and mind part. 

It is also important to consider that the ‘‘procedure which in- 
volves treating other minds as objective phenomena, and at the same 
time maintaining the psychic point of view with reference to one’s own 
mind is illegitimate.” ‘The fallacy of the subjectivists is in saying 
that in contrasting body and mind we may mean the thought of a body 
which is a constructed object subject to analysis, and a thought of mind 
which is not an object at all.” (Of this fallacy the work entitled ‘“‘Why 
the Mind has a Body” is an illustration, as already pointed out.) 

The fallacy of the materialists, according to Professor BaLDwIn, 
has its roots in ‘‘taking the spontaneous standpoint for one term of 


HeErRIck, Body-Mind Controversy. 429 


the antithesis, body, and the reflective standpoint for the other, 
mind.” The nature of Professor BALDWIN’s answer to the question : 
‘‘How can body and mind, being what we have come to think them 
to be, live hospitably housed together in one phenomenal group of 
facts?” is only vaguely foreshadowed under the term, ‘‘Esthonomic 
Idealism” and the ‘‘hope for a theory of correlation” is precisely what 
inspires the dynamic realist in the energic postulate. 

We cordially assent to Dr. ALEXANDER’S criticism (Of. cit.) of 
James’ ‘‘stream of consciousness” which he wishes had never been in- 
vented, for ‘‘It could hardly have arisen except in connection with a 
parallelist, psychological view, and in metaphysics it is certainly harm- 
ful.” For the rest, the most important point in ALEXANDER’s article 
is his discrimination of experience and consciousness. ‘‘Experience 
means just the as yet unanalyzed and unclassified facts and happenings 
encountered in the course of a natural human life.” But this is not 
the usual view; it implies a soul other than the mind corresponding 
to the ‘‘life’” or complete being of the dynamic school, or, as LorzE 
would say, ‘‘the life of a soul,” coming into intelligibility in conscious- 
ness. Consciousness is only an illumination of experience and it may 
be a very partial illumination. The very appreciative allusion to Pro- 
fessor MAcH’s View is interesting, for MAcH, more than most writers, 
solves the puzzle by denying its existence, stating that, in last resort, 
the data of physics and of psychology are the same. But (inconse- 
quently, as it seems to us) Professor ALEXANDER seems to imply that 
we havea means of knowing certain realities to be ‘‘wholly inanimate 
and quite unconscious.” 

Professor BAWDEN’s earlier paper, ‘‘The Functional Theory of Par- 
allelism,” also quotes with approval Macu’s view that ‘‘the boundary line 
between the physical and the psychical is solely practical and conven- 
tional.” ‘‘I see, therefore, no opposition of physical and psychical, 
but simply identity. In the sensory sphere of my consciousness 
everything is at once physical and psychical.” Professor BAWDEN 
considers that ‘‘the mental lite is a continual synthetic construction. 
It is simply the name for the orderly continuous functioning of an or- 
ganism under conditions of tension in adaptation.” ‘‘Mind is not an 
entity behind the process of consciousness ; it is that process itself.” 

In several places the materialistic view is verbally allowed, as 
where the statement is made that ‘‘mind is here viewed as the totality 
of the functioning matter.” But ‘‘The psychical is the meaning of the 
physical.” ‘‘Consciousness represents what, comparatively, we may 
call the tensional equilibrium of the organism, whereas habit represents 
its relatively stable equilibrium.” 


430 Journal of Comparative Neurology and Psychology. 


It would appear, therefore, that a man is a whole both to the 
child and to the philosopher, but to the psychologist who stands be- 
tween, there exists the dualism of mind and body. ‘‘It appears a 
problem only because of the fact that our experience is not yet com- 
pleted, that, as Professor BALDWIN says, it still has a career before it.” 

In a later paper (The Necessity from the Standpoint, etc.) Pro- 
fessor BAWDEN states the energic view, ‘‘Under the name of energy, 
motion is now regarded as itself the essence of reality, and the idea of 
brute, lump matter drops away. In place of the static we get the 
dynamic theory of the nature of reality.” ‘‘This is the dynamic or en- 
ergist’s view quite generally held by philosophical physicists today.” 
‘‘The solution of the paradox (that time is built up in consciousness 
while the latter is an evolution in time) lies in seeing that conscious- 
ness, taken apart from the organism which is conscious, is not an entity 
or thing or even a process, it is only a meaning or significance.” A 
meaning to what or whom? To the organism? Professor BAWDEN 
claims that the dualism of consciousness and organism is simply meth- 
odological not ontological. ‘‘Consciousness is not an entity or thing; 
it is a function, a meaning.” But if the being of the organism be its 
activity, consciousness resolves into the function of an activity and we 
reach a conclusion like that of Macu referred to. In fact, the word 
function is perhaps unfortunate and could hardly be used in a strict 
way if we held to a materialistic construction of physical being. Evi- 
dently by ‘‘function” is not meant the doing that constitutes the being 
of things, but the interpretation of this doing or its revelation in the 
act of doing. It would seem to be nearer the conception intended by 
all the writers last mentioned if we conceive of energy or activity as 
the ground of all being and admit that the specific meaning of each 
form depends on its mode,form or type. Each type has its intrinsic mean- 
ing, but whether it shall be what we call consciousness or not depends 
on the exact form which the energy assumes. 

This sketch would be incomplete without reference to Professor 
James ‘‘Barrier Theory” of mind. It would interesting to know how 
far the author was influenced by his well-known leaning toward occult- 
ism and the mystical in general in putting forth this theory. Starting 
from the statement (to which we are asked to subscribe in advance) of 
the ‘‘great psychophysical formula: Thought is a function of the 
brain,” Professor JAMEs considers that the difficulty so generally felt 
in the acceptance of this statement is due to an unnecessary limitation 
in the meaning of the word ‘‘function.” 


Herrick, Body-Mind Controversy. 431 


Professor JAMEs thinks that, when we speak of the power of the 
functioning of a moving waterfall, etc., ‘‘the material objects have the 
function of creating or engendering their effects and their function 
must be called productive function.” But we also have releasing or 
permissive functions and we have transmissive functions. ‘‘When we 
think of the law that thought is a function of the brain, we are not re- 
quired to think of productive function only; we are entitled also to 
consider permissive or transmissive function.” The universe of ma- 
terial things may be but a surface-veil of phenomena, hiding and keep- 
ing back the world of genuine relations. Our brains are half-trans- 
parent places in the veil. The genuine reality, the life of souls as it 
is in its fulness, will break through our several brains in all sorts of re- 
stricted forms, with all the imperfections and queernesses that charac- 
terize our finite individualities here below. Through the weak spot 
in us, namely, our brains (appropriate conception) ‘‘Gleams, how- 
ever finite and unsatisfying, of the absolute life of the universe, are 
from time to time vouchsafed. Glows of feeling, glimpses of insight, 
and streams of knowledge and perception float into our finite world.” 
Those writers who envy Professor JAMES his superb mastery of En- 
glish style may piously express their gratitude that they escape the 
temptation to sin with impunity against logic which that mastery con- 
fers. It is hard to think at the same time in tropes and syllogisms. 

The forms of consciousness (thoughts, etc.) are either predeter- 
mined before they leave the great universal sea of all consciousness or 
else they are individualized and determined by the nature of the hole 
through which they pass. If the former, there is some determinant 
either in that sea or between it and the brain. But evidently Professor 
JAMEs believes the brain to be the determinant for he uses the figure 
of the glottis determining the sounds by limiting air currents passing 
through it. Only on this presumption could the thoughts be ours. 
Only on this theory could there be any explanation of the curious fact 
that we have brain at all. But on this assumption the brain has just 
as productive a function as any in the world. Surely no one, unless 
it be some kind of a panpsychist, contends that new energy is created 
by thinking. The figure of the water power used by James aptly 
illustrates this. The form of the aperture in the turbine determines 
(produces) the modification of energy constituting the work of the mill. 
The waterfall ‘‘creates or engenders its effects” only by modifying the 
form of existing energy. Creation itself is only such a modification 
(self-limitation). The difference between a productive and permissive 
function is a play of words only. C. L. HERRICK. 


LITERARY NOTICES: 


His, W. Entwickelung des menschlichen Gehirns wahrend der ersten Monate. 
Leipzig, S. Hirzel, 1904. Price M. 12. 

Neurologists are to be congratulated that before his death Pro- 
fessor His was able to bring the present work to completion—a beau- 
tifully illustrated volume of 176 pages. After the appearance of his 
paper on the development of the medulla oblongata the publication of 
this series of researches was interrupted, as the author tells us in the 
preface of the present work, during the period of active reconstruction 
of morphological conceptions represented by the labors of FLECHsIG, 
Gouci1, RAMON y CaJAL, etc. In the meantime Professor His had 
been continuing his investigations and now at the close of the research 
period just referred to presents an installment which covers the histo- 
genesis and morphogenesis of the entire central nervous system in its 
earlier stages, including a revised summary of much that is contained 
in the earlier papers. 

In the review of the histogensis of the nerve tube, the term syn- 
cytium is applied for the first time, I believe (p. 13), to the spongio- 
blastic framework as it appears in the earliest form of the ‘‘ Randschlier” 
a conception which has been abundantly confirmed and enlarged by 
Harpesty in his latest contribution. He abandons his former view 
that mesodermal elements enter with the blood vessels and share in the 
formation of neuroglia, while HaRpesty, in the work just cited, admits 
a still more extensive participation of mesoderm in the neuroglia by 
means of a fusion of the spongioblastic syncytium with the enveloping 


connective tissue syncytium. 

The germinative cells are again described as a distinet category, 
though from the brief reference it appears that, as contended by re- 
cent critics, they are probably nothing other than undifferentiated cells 
in a state of mitosis. For the recognition of neuroblasts there is no 
criterion save their connection with a nervous process (p. 21). 

The section devoted to the longitudinal zones of the central nerv- 
ous system is disappointingly brief. Recognizing the inadequacy of 
the original terms basal plate (Grundplatte) and alar plate (//igelplatte), 


Literary Notices. 433 


it is proposed to substitute the terms hypencephalic area (including 
the hypothalamus, etc.) and epencephalic area (cerebral and cerebellar 
hemispheres, thalamus, corpora quadrigemina, brachium conjunctivum, 
olive and part of the pontile nuclei). 

His combats vigorously (p. 29, ff.) the idea of the origin of con- 
duction paths from a primitive nervous syncytium as expressed by 
BETHE in his recent book. 

Summarizing the development of the brain in the first month, we 
find that the regional differentiation of the medullary tube is begun, but 
not far advanced. There is formed a separate mantle layer containing 
neuroblasts whose neurites form motor root fibers, arcuate fibers and 
in the ventral zones longitudinal funicles directed caudad into the 
spinal cord. ; 

The chapter on the development of the cerebral hemispheres com- 
prises 96 pages. The earlier contributions on the form relations are 
reviewed and thoroughly worked over. The histogenesis of the cere- 
bral cortex as it occurs during the third and fourth months is given in 
detail, followed by the development of the blood vessels and commis- 
sures. Finally, 75 pages are devoted to#he sequence of development 
of the intra-medullary fiber pathways. Caml aa 
Wilder, Burt G. The Brain of the Sheep. Phystology Practicums, Part IV, 

pp- 49-76. Published by the Author, 1904. 

A copy of the latest revision of Dr. Burr G. WiLpeEr’s Practi- 
cum devoted to ‘‘The Brain of the Sheep,” indicates that this 
veteran neurologist is still employing the familiar methods which have 
served so good a purpose in his hands. The revision chiefly concerns 
details and the author cannot refuse a plaintive yet hopeful protest 
against a ‘‘reactionary tendency” as regards nomenclature in America. 

C.-L. 
Harrison, Ross Granville. Experimentelle Untersuchungen iiber die En- 
twicklung der Sinnesorgane der Seitenlinie bei den Amphibien. Archiv 

f. mtk. Anat., Bd. LXIII, H. 1, pp. 35-149, 1903. 

The results of numerous cutting and grafting experiments per- 
formed upon frog embryos at the time of the growth of the lateral lines 
show that the lateral line An/age follows definite paths formed by the 
surrounding tissues, that its growth is determined by forces within itself 
and not from stimuli received from surrounding tissues, and that the 
differentiation of the An/age into the sensory and supporting cells of the 
sense organs is likewise free from the influence of the surroundings ex- 
cept that adequate space is necessary for the development of typical 
organs. Fy Basle 


434 Journal of Comparative Neurology and Psychology. 


Mills, C. K. The Physiological Areas and Centers of the Cerebral Cortex of 
Man, with New Diagrammatic Schemes. Untv. of Penna. Medical Bulle- 
tin, XVII, 3, pp. 90-98, May, 1904. 
The history and theory of cortical localization are briefly re- 
viewed and the new features of the author’s diagrams commented upon. 
oy Me: 


McCarthy, D. J. The Formation of Bone Tissue within the Brain Substance. 
A Contribution to the Inclusion Theory of Tumor Formation. Univ. of 
Penna. Medical Bulletin, XVII, 3, pp. 120-121, May, 1904. 

Report of a small tumor containing true bone tissue which ap- 
peared in the cerebral hemisphere of a young cat subsequent to an ex- 
perimental lesion. Chee 


Piper, H. Das elektromotorische Verhalten der Retina bei Eledone moschata. 
Aarchiv fiir Anatomie und Physiologie, pp. 453-474, 1904. 

The author starts out from the observation that water, and especi- ' 
ally the water of the Mediterranean Ocean, strongly absorbs red and 
yellow rays of light so that the sunlight which reaches moderate depths 
below the surface is strongly tinged with blue and green. HIMsTEDT 
and NaGeEt had discovered*in rgo1 that the action currents of the 
frog’s retina are stronger for intense yellow light (natrium) than for any 
other intense colored stimulations which they applied. Now the yel- 
low portion of the solar spectrum as measured bolometrically has a 
greater energy than any other part, so that these authors referred the 
greater action currents for yellow light to an economical adaptation of 
nature, whereby the light most predominant in nature has also the 
greatest stimulation value. The human eye receives the most intense 
sensation from the yellow part of the spectrum, so that they further 
concluded that the action currents of the retina are a fair measure of 
the intensity of the sensation being carried to the brain. And in con- 
firmation of this they actually discovered that a frog’s retina when 
adapted to ‘‘rod vision” before being removed, would then give greater 
action currents for blue-yellow light than for the yellow light to which 
the unadapted retina best responds; just as the human adapted eye 
sees the blue-yellow part of the spectrum as brightest (PURKINJE phe- 
nomenon). 

Now Dr. Piper inquires whether animals living some distance be- 
low the level of the sea will give the strongest retinal action currents 
for that color of light to which they are most exposed ; and more par- 
ticularly, whether animals living in the depths of the Mediterranean 
Ocean will have the strongest retinal currents for that blue light by 
which they are always surrounded. In fact, the author finds this to 


Literary Notices. ; 435 


be the case with the Cephalopod Lledone moschata. He demonstrates 
this admirably by tables and curves. Whereas the action currents of the 
frog’s retina, for he was careful himself to repeat the experiments of H1m- 
STEDT and NAGEL, are the greatest for spectral light of about 590 uu 
wave-length (yellow), those of the cephalopod’s retina are greatest 
around the wave-length 500 wy (blue-green). For considerably weaker 
intensities of light the frog’s retina gave the strongest currents for the 
wave-length 560 uu (yellow-green); that is, when the retina was more 
less adapted to darkness the position of maximum currents shifted from 
the yellow toward the yellow-green. This isin precise agreement 
with Himsrept and NAGEL. 

For both animals the author used a dispersion spectrum from the 
Nernst lamp; and he bases his conclusions on experiments with 13 
specimens of £&. moschata. In view of the extreme similarity of the 
results from the several individuals, this number seems quite sufficient 
to establish the author’s point. The author used this species alone, 
because it was the only one which could be easily obtained and of 
which the eye on being removed retains vitality enough to make ex- 
perimentation possible. It is interesting to note that the action cur- 
rent both attains its maximum and subsides very rapidly. Dr. PIPER 
does not confirm the results of Beck as regards the direction of the 
action current. 

The paper is written with exemplary clearness and conciseness, 
and cannot fail to convince the careful reader; and this the more in 
view of the rare and delightful modesty with which the author claims 
to have established his interesting and important point. 

By OB: HL 


Keeble, Frederick, and Gamble, F. W. The Color-Physiology of Higher 
Crustacea. Phil. Trans. Roy. Soc. London, Ser. B, Vol. 196, pp. 295-388, 


1904. 

Notwithstanding the fact that color patterns and color changes 
have always interested naturalists greatly, and that much has been 
written concerning ‘‘protective” coloration and ‘‘color mimicry,” it is 
only recently that color phenomena in animals have been subjected to 
any very close and accurate scientific investigation, looking toward an 
explanation of their origin. The work of SremnacH, RasL and CHUN 
on mollusks, and of KEEBLE and GAMBLE on Crustacea not only clears 
up many points that were uncertain before, but will also doubtless stim- 
ulate to further investigation in a field of inquiry that promises to be 
most fruitful. 

The present monograph by KrEsL_E and GAMBLE is one which de- 


436 Journal of Comparative Neurology and Psychology. 


lights the eye by the excellence of its form and arrangement, and 
rejoices the heart with the thoroughness and accuracy of the work and 
the far-reaching importance of its results. It is really a continuation 
and amplification of the investigation by the same authors on ‘‘Hippo- 
lyte varians: a study in color-change’’,' extending the observations 
made on this species and including a study of Crangon, Palaemon, 
Carcinus, Portunus and Galathea, based upon Aacromysis as a funda- 
mental type. 

In Macromysis the authors observe that the color units, the chro- 
matophores, are arranged in three main groups and one accessory 
group. The three main groups are (1) the neural, in relation to the 
brain and nerve-cord; (2) the visceral, connected with the alimentary 
tract, liver and gonad; (3) the caudal group on the upper surface of 
the tail. These three groups are so related that they may be conceived 
as forming a system, the primary system of chromatophores. The acces- 
sory group, on the other hand, is related to outlying structures, and 
may be considered as an ¢zncipient accessory system. The chromato- 
phores are not simple cells, as they are widely considered, but consist 
of a protoplasmic, pigmented center, enclosed in a spherical thin-walled 
bag, which is pierced by the proximal ends of a number of cells vary- 
ing from five to nine. ‘These cells have their nuclei in, or close to, the 
chromatophore center, and extend outward in branched, fibrillated 
processes, the whole being not unlike the branching of a tree. Some 
of these branches are 2 mm. and over in length. 

The chromatophore centers of AZacromysis contain two kinds of 
pigments, a brown pigment, which turns red and is finally decolorized 
under the influence of oxydizing agents, and a small quantity of pig- 
ment which is bright yellow or white by reflected light, but has a gray- 
ish color in transmitted light. It is the brown pigment that gives the 
characteristic color pattern to the animals, giving them a dark brown 
tint when expanded, i. e., when the pigment migrates to the branches, 
and leaving them colorless or gray when the pigment contracts to the 
center. 

In deecapod Crustacea the situation is much more complex. The 
color-marking of the adult decapod is determined by the development 
of the secondary system of chromatophores, which completely covers 
up the first and differs from it in having much shorter branchings 
and being much more decentralized. In the larval stages, however, 
through the Mysis stage, the primary system remains in the ascend- 


“Keeble, Frederick, and Gamble, F. W. Hippolyte varians: a Study in 
Color-change. Quart. Journ. Micros. Sctence, Vol. 43, pp. 589-698, 1900. 


Literary Notices. 437 


ency, so that the larva is more like dZacromysis than it is like the adult 
form. ‘This primary system persists unchanged in the adult but is 
overlaid by a secondary, and sometimes even by a tertiary, system of 
chromatophores. The pigments of this secondary system are either 
absorbing or reflecting; the former, red, yellow, brown, violet and 
diffuse blue, are the same in transmitted and reflected light, the latter 
are only effective in reflected light, and appear white, yellow, greenish 
or blue, as the case may be. 

The question is raised whether these chromatophore systems and 
the color patterns resulting from them are inherited or acquired. After 
marshalling the evidence the authors conclude that the primary sys- 
tem, owing to its appearance in the earliest larval stages, and its per- 
sistence in the adult, is inherited in all cases. In Crangon and Palae- 
mon there is a steady, constant development of the secondary pattern 
from the embryo to the adult, and hence the secondary system is 
thought to be inherited in these forms. In //pfolyte, however, there 
does not seem to be any such constancy of development, but the dom- 
inant color-pattern is rather a result of the action of the environment. 

Regarding the mechanism of pigment migration the authors hesi- 
tate to express themselves. They are not inclined, however, to accept 
PocHEt’s view that it is due to the active amoeboid movement of cell 
processes, but prefer to account for it by the turgidity of the constitu- 
ent cells of the centers, caused chiefly by the action of light, and con- 
trolled to a greater or less extent by the nervous system. ‘This view is 
strengthened by the fact that in old dZyszds ‘‘the pigment at times 
bursts the frondose extremities of the chromatophores and exudes into 
the surrounding tissues.” Moreover, the origin of the chromatophores is 
to be found, not in connective, but in glandular tissue, and their action 
seems to be like that of a gland, continually secreting or transforming 
pigment substances. 

In Aippolyte varians there is a regular alternation of the diurnal 
color-pattern, due to red and yellow pigments, with the nocturnal, 
which is blue. Under appropriate light stimulation the red and yel- 
low pigments flow out through the branches, and when the stimulation 
is withdrawn, these pigments contract and there is a diffusion of blue. 
The authors think, however, that the blue pigment does not serve any 
protective purpose, but is rather a by-product obtained by the trans- 
formation of the yellow and red pigments, and ‘‘exudes from the 
chromatophores, permeates the tissues and subsequently disappears.” 

Perhaps the most interesting portion of the paper is the last sec- 
tion, which deals with the influence of light on littoral Crustacea. 


438 Journal of Comparative Neurology and Psychology. 


During the day, Palacmon and /fippolvie are quiet and sluggish, but in 
the evening they become very active and restless, many throwing 
themselves out of the shallow pans in which they are kept. Hence 
the authors think that these animals should be considered nocturnal. 
Experiments on phototropic reactions (going toward or away from the 
light) showed that the animals experimented on formed a series, Pa/- 
aemon being negatively phototropic (light-shunning), //7ppolvfe positive 
(light-seeking), and Macromysis negative on a white ground but posi- 
tive on a black ground. The zoeae of Palaemon, however, are posi- 
tive, and if given a choice of ground select the white. The adult 
Palaemon and Macromysis choose the black, while /7pfolvre in all stages 
prefers the white. A test was made to determine whether the posi- 
tively thigmotropie Palaemon could be driven from the bottom of a 
bottle, whose upper portion was darkened, by its negative phototrop- 
ism. As long as there was nothing in the upper part of the bottle to 
cling to, the animal returned to the bottom after a short swim above. 
When an inclined stick was placed in the upper end of the bottle, 
Palaemon remained clinging to it in the shadow. 

The effect of light upon pigment migration is discussed in great 
detail. ‘The effect of light stimulation was found to be in part direct, 
and in part indirect, i. e. through the eyes and the nervous system. 
The indirect response is the most important for color display, but its 
action is slower, so that the direct response often gets a start, and then 
is checked by the indirect. The direct response is determined not by 
the background but by the incident light, whereas the indirect re- 
sponse is determined by the background entirely, a white ground caus- 
ing contraction of pigments, and a black ground expansion. ‘*There 
is a close agreement between the phototropic reaction and the pigment- 
movement reaction; both depend on the eye and both are determined 
by ‘background’”’. 

“A monochromatic light in conjunction with a scattering (white) 
or absorbing (black) background, produces the same ultimate effect on 
pigment movement as does a white light in conjunction with the same 
background. The fact of background must be taken into con- 
sideration in all experiments on phototropism.” 

In conclusion let it be said that the work is well supplied with 
summaries, an appendix of 17 tables, a bibliography of 62 numbers 
and seven splendid plates. J. CARLETON BELL. 


Literary Notices. 439 


Porter, James P. A Preliminary Study of the Psychology of the English 
Sparrow. Amer. Jour. Psychology, Vol. XV, pp. 313-346, 1904. 

As the author remarks, the psychology of the sparrow is of special 
interest because of the remarkable degree of success which this 
bird has attained in its struggle for existence in America. If adapta- 
bility is taken as a measure of intelligence the sparrow certainly ranks 
well in the psychic scale. 

Porvrer’s preliminary paper is characterized by admirable clear~ 
ness and accuracy of statement. His experiments are thoroughly sci- 
entific in plan and execution, and his results, although as yet limited 
to only one or two individuals, are as valuable as they are interesting. 

The present paper contains observations on general behavior and 
characteristics, and reports of experiments to test association and per- 
ception of number, form, color and design. 

The association tests, with food boxes and a maze, indicate that the 
bird is able to profit by experience very rapidly. In fact the habit 
curve given by the author’s tests is strikingly like those of the rat and 
monkey. The sparrow evidently learns by trial and error; there is 
some evidence of imitation, but ‘‘no sign of reason or looking ahead 
and suiting of means to an end.” There is notable persistency in the 
efforts to obtain food, whether it be by opening the door of a food box 
or finding the way through a maze. Memory appears to be good. 

There is evidence of perception of number similar to that of 
monkeys. As the author suggests this may be ‘‘sense of position” 
rather than ‘‘sense of number.” The few experiments described indi- 
eate little ability to distingush forms; but colors and designs were dis- 
tinguished readily by the single individual tested. 

A comparative study of bird psychology is promised by PORTER 
as a continuation of this preliminary paper. R.M. Y. 


Uexkiill, J. v. Studien iiber den Tonus. II. Die Bewegungen der Schlangen 
Sterne. Zerschrift f Brologre. Bd. 46, 1904. 

This paper is noteworthy as evidence of the value of kinematograph- 
ic photography in the study of animal reactions. ‘The author succeeded 
in obtaining series of photographs of the serpent star (Op/zoglypha lacer- 
tosa) which show splendidly the manner of locomotion, of turning 
over, of taking food, of freeing members from encumbrances, etc. 
One is able to see clearly in these series of pictures the different phases 
of movement, and to determine precisely what part each member 
plays in the reaction, as well as the way in which the movements of 
the parts are codrdinated. 

In addition to descriptions of the normal activities of the organ- 


440 Journal of Comparative Neurology and Psychology. 


ism v. UEXKULL gives accounts of certain experiments which had to 
do with food taking and various forms of behavior which are appar- 
ently intelligent, and with the forms of reaction of one, two, three or 
four armed animals. 

The descriptions of the reactions, which cannot be summarized 
within the few sentences of this notice, are followed by a consideration 
of the structure of the animal in its relation to reaction. ‘The mechanics of 
movement are discussed. In connection with an examination of the 
principles of action in the nervous system the author takes occa- 
sion to show that the nerve impulse always passes in the direction of 
the expanded muscle (p. 28). The paper is a valuable contribution to 
our knowledge of the workings of the nervous and muscular systems 
in this form. 

Considering the great possibilities of the kinematographie method 
for the investigation of reactions and their reproductions on paper or 
on a screen, it is surprising that it is not more widely used. Photo- 
graphs taken at the rate of 20 to 30 per second make possible the 
careful analysis of movements which are too rapid for the naked eye 
to follow satisfactorily. Moreover, a series of photographs will often 
make clear at a glance what pages of description may fail to make in- 
telligible. R. M. Y. 
Binet, A. L’Année Psychologique. Tenth year, 1904. Parts, Masson et Cie, 

Editeurs. 

The tenth issue of the Arée contains the Bibliography for 1903 
(about 3000 titles) and the annual abstracts of the more important 
works. ‘The original memoirs include several of interest to our read- 
ers, notably the paper by LecAILLon, ‘‘La biologie et la psychologie 
dun araignée” and ZWAARDEMAKER’S ‘‘Sur la sensibilité de Voreille 
aux différentes hauteurs des sons.” Besides these features, we have 
the announcement of systematic annual digests of cytology, anatomy, 
physiology, pathology, anthropology and a number of other collateral 
fields, each by a specialist, which promise to be of great value. Twelve 
such digests are given in this issue. Attention should be called to 
the fact that the publisher of the Année has been changed since the 
last issue. Col panrle 


Smallwood, W. M. Notes on the Natural History of Some of the Nudi- 
branchs. Audletin of Syracuse University, Series IV, No. 1, pp. 14-17, 
Oct. 1, 1904. 
Data on the copulation and eges. Cae 


The Journal of 
Comparative Neurology and Psychology 


Volume XIV 1904 Number 6 


THE BEHAVIOR OF PARAMECIUM. ADDITIONAL 
FEATURES AND GENERAL RELATIONS. 


By H. S. JeNNINGs. 


Assistant Professor of Zoolagy in the University af Pennsylvania. 


With 17 figures in the text, 


CONTENTS. 


INTRODUCTION: Object and Methods : 2 r 2 2 p- 442 
I. THE ACTION SYSTEM . 2 , : . 4 : P- 443 
1. The Usual Movements; Spiral Swimming, p. 443. 

2. Modification ef ue ae ua under Stimulation ; 

Reaction Types, p. 450. The Avoiding Reaction, 

Dar 4 50-4 she ecidinge Reaction as a Factor in Be- 

havior; the Method of Trial and Error, p. 458 


11. NATURE OF STIMULATION : - ; - : p. 464 
HII. REACTIONS ro CERTAIN STIMULI, WITH SPECIAL REFER- 

ENCE TO THE PART PLAYED BY THE ACTION SYSTEM . : p- 468 

A. Reactions Produced through the ‘‘ Avoiding Reaction.” p. 408 
1. Reactiens to Water-Currents; Rheotaxis, p. 468. 2. 
Reactions to Gravity ; Geotaxis, p. 473. Summary, p. 479- 


hb. Behavior during Conjugation. p = p. 480 
C. Responses to Stimuli not Brought about ‘th es) the 

<‘ Avoiding Reaction.” . 2 % 3 a - “ p. 483 
1. lorward Movement as a Response to Stim- 

ulation. = z A e : c : p- 483 

2. Reaction to Electricity . z : : p. 484 


Part played by the Action System, p. 
484. Peculiarity of the Reaction to Elec- 
tric Current, p. 488. Cause of Backward 
Swimming in Strong Currents, p. 494. Re- 
lation between Contact Reaction and Re- 
action to Electric Current, p. 496.  Irreg- 
ularities of Reaction to the Electric Cur 
rent, p. 503. Reaction of Paramecia to 
Electricity when in solutions of Chemicals, 
p- 504. ; 

EV. PRESENT POSITION OF INVESTIGATION OF THE BEHAVIOR 


OF PARAMECIUM . 2 : - : 5 p- 506 


442 Journal of Comparative Neurology and Psychology. 


Since Paramecium is usually taken as a type for the study 
of unicellular animals, it is desirable to have its reactions to 
stimuli as fully known as possible. In attempting to put to- 
gether the results of numerous investigations made during the 
last fifteen years on the behavior of this animal, | have found 
that there are still a number of reactions which have not been 
described, or have been described incorrectly, and that certain 
general relations running through the behavior have never been 
brought out. The present paper attempts to fill, so far as 
possible, these gaps in our knowledge, supplementing and uni- 
fying previous accounts of the behavior of Paramecium. The 
writer tries to point out omissions or errors in his own pre- 
vious work with the same impartiality as in the works of others. 

The chief subjects dealt with are, in the first place, what 
we may call the action system of Paramecium; in the second 
place, the fundamental character of the stimulations to which the 
animal responds. In the third place an account is given of cer- 
tain imperfectly or incorrectly known reactions, with particular 
reference to their relation to the ‘‘action system” of Parame- 


yy 


cium. The chief reactions thus taken up are ‘‘rheotaxis, 
“ocotaxis sand. ‘electrotaxis. * 
Methods.—A word should be said here as to certain meth- 


ods of work. Throughout the following paper accounts are 


given of the direction of the effective beat of the cilia. This 
was determined in every case by mingling finely ground India 
ink with the water containing the Paramecia, thus observing 
the direction of the currents caused by the cilia. By using 
such a method one is not reduced to conjecture as to the really 
effective direction of the ciliary beat, as has been the case in 
certain papers on this subject, but this effective direction ts de- 
termined immediately by observation. I have supplemented 
this method by observing the cilia of animals partly confined in 
a gelatin solution, in the usual way, and of animals partly stu- 
pefied with chloretone. These methods gave especially good 
results when combined with the use of India ink, to show the 
currents. Owing to its fineness, blackness, and absolute lack 
of chemical action, I have found the use of India ink (or Chi- 


Jennincs, Behavior of Paramecium. 443 


nese ink) much preferable to that of carmine or indigo. The 
ink is procured in sticks and rubbed up with water in the usual 


way. 
J. THe Action System. 


By the behavior of an organism we mean essentially the 
regulation, by means of movement, of its relations to environ- 
mental conditions. The characteristic complex of movements 
by which the relations of Paramecium to its environment are 
determined may be called the ‘‘action system” of the organism. 
Most animals have certain peculiar methods of action, depend- 
ing largely upon their structure—upon what von UEXK@LL 
(1903, p. 269) calls the ‘‘biologische Bauplan’’—by which most 
of their behavior is brought about. These characteristic ways 
of acting are usually few in number and form a unified system, 
providing a definite reaction combination for any stimulus. The 
reaction systems of different animals vary as much as de 
their structures. Thus many different agents acting on a given 
animal may produce the same set of movements, while on the 
other hand the same agent acting on organisms of different 
“action systems” produces in each case different movements. 
The method of reaction then depends as much on the action 
system of the organism in guestion, as upon the physical or 
chemical action of the stimulus. The usual relation between 
the two factors may be expressed as follows: The action sys- 
tem supplies a limited number of methods of action, the char- 
acter of the stimulus (including its localization) determines 
which of these methods shall be set in operation. 

In dealing with the action system of Paramecium, we have 
to consider, first, the usual movements and the environmental 
relations which they induce; second, the typical modifications 
of these movements (the reaction types), under the influence of 
stimulation. 

t. Lhe Usual Movements ; Spiral Swimming.—As is well 
known, Paramecium continually swerves toward the aboral side 
and revolves on its long axis as it swims through the water, so 
that its course is a spiral one (Fig. 3). The revolution, so far 


444 Journal of Comparative Neurology and Psychology. 


as I have observed, is always over to the left, when the anterior 
end is directed away from the observer. That is, the upper 
surface is continually passing to the observer's left (the lower 
surface of course to his right). Before using the stereoscopic 
binocular I supposed that the revolution was sometimes over 
to the right, sometimes over to the left (JENNINGS, 1899, p. 
316). But observation of thousands of cases since this instru- 
ment was used has never shown a single exception to the revo- 
lution over to the left. I have repeatedly known observers 
working with the usual monocular microscope to assert that 
part of the Paramecia in a given culture weré revolving over to 
the right, but on examination with the stereoscopic binocular 
they invariably became convinced that there was no exception 
to the revolution over to the left. The appearances shown by the 
monocular microscope are very deceptive in such phenomena, 
and I do not believe that observations with it even by practiced 
observers are reliable on this particular point. 

The revolution is still over to the left when the animals are 
swimming backward. This is contrary to the statement made 
in the second of my ‘‘Studies”’ (JENNINGS, 1899, p. 316), when 
I was working with the monocular microscope. But the binoc- 
ular leaves no doubt upon this point. When the forward move- 
ment is reversed, the direction of rotation is of reversed. 

The oral groove of Paramecium always passes, if the oral 
side is down and the anterior end away from the observer, from 
the right behind to the left in front (as represented in BUTSCHLI, 
1889, Pl. 63, Fig. 1 a). Many observers have reported Para- 
mecia in which the direction of the groove is ‘‘reversed,”’ running 
from the middle obliquely to the right instead of to the left. 


'There is no general agreement as to the designation of the direction of a 
spiral. ‘The above method seems most convenient for free swimming organisms, 
since it gives the results of immediate observation, and other methods of desig- 
nation usually have to be translated, for practical purposes, into this one. If we 
used the method of designation proposed by N&GELI (1860), the spiral of Para- 
mecium rises from south to west. If we designate the direction of rotation by 
the method used in spiral cleavage, imagining a small observer situated in the 
long axis of Paramecium with head toward the anterior end (NOFOID, 1894, p,. 
180), then we must say that the rotation is to the right. 


Jennincs, Behavior of Paramecium. 445 


But the monocular is deceptive on that point. An investigator 
who was certain that in a particular culture many of the individ- 
uals were thus ‘‘reversed’’ made at my request a careful exam- 
ination of a large number, after killing them with an excellent 
fixing solution. Nota single reversed specimen was found. If 
such exist, they are certainly extremely rare. 

The obliquity of the oral groove—from right behind to 
left in front—appears to be the opposite of that which would 
assist the revolution over to the left. If the groove should act 
like the groove of a screw, moving along a solid ridge, the ani- 
mal would revolve over to the right instead of over to the left. 
It is of course known that the revolution on the long axis is in- 
dependent of the groove, since when the animal is cut in two 
in such a way that no part of the groove remains on the pos- 
terior half, this half nevertheless continues to revolve on its 
long axis when moving forward (JENNINGS and JAMIESON, 1902). 
The significance of the direction of the oral groove is probably 
to be sought in its relation to the stream of water which it leads 
to the mouth. 

The width of the spiral path of Paramecium varies much. 
The spiral is narrowest when the animal is progressing most 
rapidly, through water which presents no stimuli; its width is 
then equal to about one-half the length of the animal. Usually 
the spiral is wider than this; the length of the animal is per- 
haps a fair measure of the average width. In many cases, as 
after stimulation, the width is much greater ; it may be several 
times the length of the animal. Paramecium as a rule makes 
one turn of the spiral, reaching a corresponding phase or posi- 
tion, in about four times its length; but this relation is also 
variable. 

The spiral motion is compounded of three factors: (1) 
the forward movement; (2) the swerving toward the aboral 
side; (3) the revolution on the long axis. Each of these fac- 
tors depends on certain peculiarities in the stroke of the cilia. 
The forward motion is due of course to the fact that the cilia 
strike in a general way backward. The revolution on the long 
axis is due to the fact that the stroke is not directly backward, 


446 Journal of Comparative Neurology and Psychology. 


but is oblique. This obliqueness in the stroke of the cilia is 
easily rendered evident by mounting the animals in water con- 
taining a large quantity of India ink in suspension, as described 
above. After the violence of the movement has subsided, 
specimens may be studied that are restrained by coming in con- 
tact with a solid, or by swimming into a crevice. In such speci- 
mens, still revolving on the long axis, it may be seen that the 
particles of India ink on the upper surface of the animal pass 
backward and, when the anterior end is directed away from 
the observer, to the observer’s right. That is, on the right 
side of the animal the particles pass toward the oral groove, 
on the left side away from the oral groove (Fig. 1). This 


‘ig. 1. Diagrams showing the direction of the water currents caused by 
the cilia, in different positions of the animal. a, aboral surface; 4, right side; ¢, 
left side; d, oral surface. 
movement is indicated in a transverse section of the animal by 
Fig. 6, a. It is evident that the ciliary motion thus indicated 
would turn the animal in the opposite direction from the cur- 
rents—that is, over to the left. In the oral groove the cilia 
strike more nearly directly backward, with but a slight oblique- 
ness that is opposite that of the body cilia) This is shown by 
the fact that a current runs within the groove from its anterior 
to its posterior end (Big.. 15.8; ¢, 2). 

The swerving toward the aboral side is due, in the normal 
swimming, largely to the more powerful stroke of the cilia in 


Jennincs, Behavior of Paramecium. 447 


the oral groove. It may be increased, under stimulation, by a 
change in the beat of the body cilia of the anterior end at the 
left side of the oral groove, by which they strike toward the 
oral groove instead of away from it. On the number and 
strength of action of the cilia showing the changed beat depends 
the amount of swerving toward the aboral side. 

All the three factors in the spiral course may vary more 
or less independently of each other, and on the amount of such 
variations depends the width of the spiral, the number of turns 
in a given distance, and the like. The effects of stimuli consist 
largely, as we shall see, in changing the proportional parts 
played by these various factors—decreasing or stopping one, 
increasing another, etc. 


Fig. 2. A Paramecium swims toward an area containing India ink; before 
it reaches the boundary of the area a cone of the ink is drawn out by the action 
of the oral cilia, reaching the anterior end and oral side. 

Owing to the stronger and more direct backward beat of 
the oral cilia, in swimming forward a current of water is caused 
to pass from in front in the form of a cone to the oral side and 
mouth. This is rendered evident when a cloud of India ink is 
added to the water containing many Paramecia. The cloud 
has for a time a definite boundary surface. When the Para- 
mecia swim toward this surface, the latter may be seen to ex- 
tend out in the form of a cone, to meet the advancing animal 
(Fig. 2). As soon as this black cone comes in contact with the 
anterior end of the Paramecium, the latter stops and turns in 
another direction—this occurring some distance from the gen- 


448 Journal of Comparative Neurology and Psychology. 


we 


a 


Ss 


—— 


AA 


Se 
= 


~ 


SS 


Gs) 


Se ie) 
ee ae eee 


=. 


Fie 


eral boundary surface of 
the cloud. This explains 
the observation often made 
that Paramecia and other 
infusoria react and turn 
away seemingly some dis- 
tance before reaching the 
agent causing the reaction. 
Thus, on approaching a 
bubble or the free surface 
of the water, infusoria of- 
ten react and turn away 
when still separated by a 
marked interval from the 
air surface. A little of the 
water next: to the airehas 
been drawn out to meet the 
animal, which then reacts 
to any modification the 
water may have undergone 
by contact with the air. 
Thus in its forward 
course the animal is contin- 
ually receiving ‘‘samples’’ 


Fig. 3. Spiral course of Para- 
mecium, showing how the animal 
is subjected through this method 
of swimming to many changes in 
its relation to the environment. 
The arrows at the right indicate 
some agent (light, gravitation, a 
water current or the like) acting 
from a definite direction: the re- 
lation of the animal to this agent 
is continually changing; at 6 the 
body is nearly transverse, at d 
nearly parallel to the arrows. The 
dotted areas x show the currents 
of water carried to the anterior end 
by the movements of the oral cilia. 


JENNINGS, Behavior of Paramecium. 449 


of the water in front of it, and reacting to these samples. In 
its spiral path Paramecium becomes pointed successively in 
many different directions, so that it ‘‘samples’”’ the water from 
many directions (Fig. 3). When the spiral is very narrow, the 
animal swimming rapidly forward, these samples all come from 
near the axis of the spiral and therefore show little variation. 
But in most cases the direction from which they come is contin- 
ually changing. Thus we may say that Paramecium, through 
its spiral course, is continually ‘‘trying’’ the water in various 
directions. Or, to express the same thing in a more objective 
way, through the spiral course the most sensitive portion of 
the organism is subjected successively to water coming from 
many different regions. 

In another way the spiral course subjects the organism to 
varied experiences. Suppose that a force which acts in straight 
lines from a definite direction is operating on the swimming organ- 
ism from one side; for example, light, or the electric current, 
or gravity, or a current of water. By its spiral course the or- 
ganism is brought successively into different relations with this 
agent (Fig. 3). In one phase of the spiral, as at d, it swings 
more nearly into paralellism with the lines of action of the agent ; 
in another it is becoming more nearly transverse, as at 0. In 
the case of light the anterior end is becoming more illuminated 
in one phase, less in another; in other words, the anterior end 
is subjected to continual variations in the intensity of illumina- 
tion. With gravity, or a water current, the swinging is assisted 
in one phase of the spiral, resisted in another, so that the ani- 
mal is subjected to continual variations in the resistance it meets. 
These changes give opportunity for directive or regulative stim- 
ulation. It is only when the axis of the spiral course is in the 
lines of force—in other words, when the organism is ‘‘orient- 
ed’’—that such changes cease. These relations will be brought 
out in detail later in describing the reactions to certain stimuli. 

Altogether, we see that the ‘‘action system” of Parame- 
cium contains elements of such a nature as to subject the animal 
to the greatest possible number of changes in the environment, 
thus giving it opportunity to react to all such changes. 


450 Journal of Comparative Neurology and Psychology. 


2. Modification of the Movements under Stimulation ; 
Reaction Types.—In the behavior of Paramecium under the ac- 
tion of stimuli we may recognize a certain number of distinct 
reaction types. (1) The chief one of these is that which I have 
in former papers called the ‘‘motor reflex’ or ‘‘motor reaction,”’ 
and which I shall call here, for reasons given later, the ‘‘avoid- 
ing reaction.’’ The others are (2) the movement forward from 
the resting condition ; (3) the coming to rest of a moving indi- 
vidual; (4) certain features of the reaction to the electric cur- 
-rent; (5) local contractions: of ‘the body, and possibly (6) the 
discharge of trichocysts. The list of reaction types thus rises 
to a considerable number, but the last three named play almost 
no part in the regulation of the relations of Paramecium to its 
environment under natural conditions. We shall deal zz extenso 
here only with the most important reaction type—the ‘‘avoiding 
reaction.’ 

3. The Avoiding Reaction.—Through this reaction type 
occur most of the marked reactions of Paramecium that have 
often been spoken of as ‘‘tropisms”’ or ‘‘taxes;”’ in other words, 
the reactions to stronger stimuli of all sorts. The avoiding re- 
action consists, when well marked, of the following: the ani- 
mal swims backward, turns toward the aboral side, then resumes 
the forward motion. I have called this in former papers the 
‘motor reaction” or the ‘‘motor reflex.’’ But the former is a 
general term, properly used for any movement that takes place 
as a response to a stimulus, and hence not fitted for character- 
izing a special reaction type. To the second, objection has been 
raised on thé ground that the word veflex should be used only 
when a nerve cell is concerned; there are perhaps other and 
better grounds for leaving open the question whether the move- 
ment in this reaction is in the nature of a reflex or not. For 
these reasons I have sought for a simple expression which shall 
bring out the essential character of the reaction without preju- 
dice to its nature in other respects. The most general effect of this 
reaction is to remove the reacting organism from the source of 
stimulation and direct it elsewhere; it may, therefore, be ap- 
propriately called the ‘‘avoiding reaction.’’ By this reaction, 


Jennincs, Behavior of Paramecium. 451 


fig.4. Backward spiral cours 
of Paramecium in reacting to a 
stimulus. d, c, 4, a, successive po- 
sitions occupied. The turning is 
to the left, in the same direction 
as in Fig. 3. 


as I have shown in previous pa- 
pers, Paramecium responds to heat, 
cold, mechanical stimuli, chemicals 
of all sorts, osmotic stimuli—in 
fact, to stronger stimuli of almost 
all classes. 

The avoiding reaction is brought 
about through certain modifica- 
tions of the three factors in the 
spiral swimming. The first phase 
of the reaction is a slowing, suspen- 
sion or reversal of the forward com- 
ponent in the spiral course. Ina 
very pronounced reaction, caused 
by a powerful stimulus, the for- 
ward course is reversed, while the 
revolution on the long axis and the 
swerving toward the aboral side 
continue as before. The animal 
therefore swims spirally backward 
for a distance (Fig. 4). When the 
stimulus is weaker, the forward 
course is merely suspended for a 
moment—the revolution and swerv- 
ing toward the aboral side contin- 
uing. Finally, in some cases the 
forward course is merely made 
slower. The backward swimming 
or stoppage is brought about by a 
reversal of the forward compo- 
nent in the stroke of the cilia. In 
a pronounced reaction all the cilia 
are reversed (Fig. 4); in a less 
marked reaction the body cilia are 
reversed while the oral cilia are not 


(Fig. 5). Inthe latter case the effect on the currents in the 
water, as shown by the movements of particles of India ink, is 


452 Journal of Comparative Neurology and Psychology. 


peculiar. The currents pass forward everywhere, save in the 
oral groove, where they pass backward. Since the animal at 
the same time revolves on its long axis, the particles in a given 
region close to the Paramecium at first dart forward, then later 
backward, depending on whether the body surface or the oral 
groove is directed toward the region in question. 

The second feature in the 
avoiding reaction is the increased 
turning toward the aboral side. 
This is due to two changes in 
the stroke of the cilia. \The first 
and less important is the fact, 
mentioned above, that after a 
stimulus of not very great inten- 
sity the body cilia are reversed, 
while the oral cilia continue to 
beat backward. This of neces- 
sity turns the anterior end toward 
the aboral side. The second and 
more important factor is a change 
in the stroke in the body cilia of 
the left side,in the anterior por- 
of a reaction to a strong stimulus. tion of the animal. In the ordi- 
The animal moves backward: the MNary swimming, as we have seen, 


body cilia are reversed, the oral cilia the cilia of the right side strike 
are not. The arrows show the direc- 


tion of the water currents. 


Fig. 5. Currents in the reaction 
to a weak stimulus, or near the end 


toward the oral groove (Fig. I, 
6), those of the left side away 
from the oral groove (Fig. 1, c). But in*the avoiding reaction, 
both while the swimming backward continues and after it has 
ceased, the cilia of both right and left sides strike toward the 
oral side. This of course drives the body of the animal toward 
the aboral side. The difference between the stroke of the cilia 
in the usual course, and in the avoiding reaction is shown in 
sectional views in Fig. 6. 

Thus the cilia to the left of the oral groove play a most 
important part in the avoiding reaction, reacting by a reversal 
of the direction of the usual stroke—at least by a reversal of 


JenNnINGS, Behavior of Paramecium. 453 


the transverse or oblique component of the stroke. They thus 
play a part similar to the large cilia at the left of the peristome 
in the Hypotricha, and to the cilia which WALLENGREN (1902) 
designates as the ‘‘Drehungswimpern’ in Opalina. It is to their 
reversal that the most characteristic features of the reaction 
are due. 

The change in the stroke of these cilia 
of the left side explains the third feature 
of the avoiding reaction; namely, the 
modification of the revolution on the long 
axis. The turning toward the aboral side 
in the reaction involves an increase in the 
swerving found in the normal swimming, 
in proportion to the rate of revolution. 
The change in the stroke of the cilia of the 
left side causes, as we have seen, the in- 
creased swerving ; it likewise causes a de- 
crease or stoppage in the revolution on the 
long axis. In the usual swimming, the cilia 
of both right and left sides tend to turn the 
body over to the left (Fig. 6, a); in the 


fig. 6. Diagram of cross sections of Paramecium (viewed trom the anterior 
end), showing the obliquity of the ciliary stroke. a, condition in the usual for- 
ward progression: the body cilia all strike toward the right side ; 6, condition 
while turning toward the aboral side, in reacting to a stimulus: the cilia of the 
left side have changed the direction of their stroke; 7, lett side; 7, right side ; 
o, oral grdove. The arrows show the direction in which the cilia tend to turn 
the body. 
avoiding reaction the cilia of the left side tend to turn the body 
to the right, those of the right side to turn it to the left (Fig. 
6, 6). Thus the cilia of the two sides oppose each other so far 
as revolution is concerned, but co-operate in causing the body 
to swerve toward the aboral side. 

The effectiveness of the changeof beat of the cilia of the 
left side varies much, apparently as a result of the fact that the 
number of cilia having the changed stroke varies. On this 
point it is exceedingly difficult to determine numerical or pre- 
cise quantitative relations. But if the stimulus is weak, appar- 


454 Journal of Comparative Neurology and Psychology. 


ently only a few of the cilia at the anterior tip of the left side 
change their direction of stroke; with a stronger stimulus the 
number is greater. It is possible further that the amount of 
change in the stroke of individual cilia is variable; from some 
of my observations I believe this probable. But whatever the 
nature of the variation, the following results are produced. If 
the effective beat of these left cilia is only slightly changed, the 
anterior end then describes but a small circle, as in Fig. 8, a. 
As the effective beat of these cilia changes farther, the swerv- 
ing becomes stronger and the revolution slower, so that the an- 
terior end swings in a larger circle (Fig. 8, 0). Finally all the 
cilia beat toward the oral side; the revolution on the long axis 
has then entirely ceased, while the swerving toward the aboral 
side is very rapid. Asa result the anterior end describes the 
circumference of a circle, in the radii of which lies the long 
axis of the body (Fig. 9). Thus the swerving toward the 
aboral side varies inversely as the rate of revolution on the long 
axis. In the unstimulated swimming the revolution is rapid 
and the swerving slight; in the strongest reaction the revolution 
is zero and the swerving is strong, while between these two ex- 
tremes an indefinite number of gradations exist. The change 
in the forward stroke of the cilia seems more nearly independ- 
ent of the two interconnected sets of changes just described. 
The rapid forward swimming may be combined with the mini- 
mum of swerving and the maximum of rotation; the animal 
then shoots rapidly forward. On the other hand, the forward 
swimming may either entirely cease, or be converted into a 
backward movement, in combination with the same minimum 
of swerving and maximum of rotation. In the former case the 
animal merely rotates rapidly on its long axis, neither advanc- 
ing nor retrograding; in the latter case it shoots rapidly back- 
ward. But whenever the swerving toward the aboral side be- 
comes largely increased, the longitudinal motion seems to de- 
crease; this is probably a necessary consequence of the fact 
that the effective stroke of many of the cilia is in this case lat- 
eral, so that only a comparatively weak component is left for 
movement along the long axis. While swerving strongly, how- 


Jenninos, Behavior of Paramecium. 455 


ever, the longitudinal motion may be either forward, or zero, 
or backward. 

As our analysis thus far shows, it is quite inadequate to 
conceive the cilia as having merely forward and backward strokes 
phases. The effective stroke 


” 


—‘‘expansive”’ and ‘‘contractile 
may be nearly straight backward or forward; or obliquely back- 
ward or forward, with various grades of obliqueness; or 
transverse. © Purthermore,. the cilia’ gof different ‘parts. “of 
the body may vary independently in their effective stroke. 
Thus, we have above distinguished the following conditions: 

1. All the cilia strike almost directly backward (forward 
course, Pig: 3): 

2. All the cilia strike almost directly forward (backward 
Course,» hie. 4): 

3. All the cilia strike obliquely backward and to the 
right, save the oral cilia, which strike nearly di- 
rectly backward (forward course, with much 
swerving toward aboral side). 

4. All the cilia strike obliquely forward and to the right, 
save the oral cilia, which strike nearly directly 
forward (backward course with much swerving). 

5. All the cilia strike transversely to the right (rotation 
on the long axis, without progression or retro- 
gression. ) 

6. The cilia of the right side strike obliquely to the 
right and backward; the cilia of the left side 
strike obliquely to the left and backward (for- 
ward course, swerving to the aboral side, with- 
out rotation). 

7. The cilia of the right side strike obliquely to the 
right and forward; the cilia of the the left side 
strike obliquely to the left and forward (backward 
course, swerving to the aboral side). 

8. All cilia strike obliquely forward, save those in the 
oral groove, which strike backward (backward 
course after a weak stimulus, or after the effect 
of a strong stimulus has nearly expired, Fig. 5). 


456 Journal of Comparative Neurology and Psychology. 


It must be added that the extent of body surface on which 
the cilia show any of the characteristic strokes mentioned is ex- 
ceedingly variable. Often, for example, the body cilia of only 
the anterior tip. or the anterior half, show the transverse stroke, 
while posterior to this they do not. Farther, the cilia of the 
posterior half of the body frequently cease beating effectively, 
showing only a slight quivering, while the anterior cilia are still 
very active. As a result of a long study of the ciliary move- 
ments, one retains the impression that almost any combination 
of forward, reversed, oblique or transverse strokes is possible 
among the different areas of the body, and that those mentioned 
above are only typical combinations, produced under more or 
less definite conditions. As a rule a combination is produced 
such as brings about a well ordered movement of some sort, 
but under certain conditions the movements of the cilia are 
such as to produce only a disordered quivering or jerking, with- 
out movement in any definite direction. This is sometimes the 
case for example when the animal is immersed in a strong chem- 
ical. Under some conditions a similar result is produced also, 
as we shall see later, by the electric current. 

What are the conditions on which depends the direction of 
the effective stroke of the cilia in any given region of the body ? 
The question is a very difficult one. According to the tropism 
theory, the direction of the effective stroke of the cilia—that 
is, whether the ‘‘contraction phase”’ or ‘‘expansion phase’ was 
the effective one in producing movement—depended on the di- 
rect action of stimuli on the part of the body bearing the cilia 
in question. Certain agents impinging on any given region of 
the body caused the ‘‘contraction” or backward stroke to be 
more effective; others had the opposite effect. But we now 
know that this conception was far too schematic. Asa result 
of a stimulus applied to a single definite region of the body, 
certain cilia beat effectively in one way, others in a different 
manner, and the first effect is soon followed by a second one, 
equally complicated. Thus, a touch at the anterior end with a 
glass rod, or a chemical acting on the surface, (1) produces re- 
versal of the stroke of the cilia over the entire body; (2) then 


Jenninos, Behavior of Paramecium. 457 


a return of the oral cilia to the backward stroke, the others re- 
maining reversed ; (3) then causes the body cilia of the left side to 
strike toward the oral groove (whereas before they struck in the 
opposite direction), while the forward stroke of the body cilia 
becomes converted into a backward one. There is a co-ordi- 
nated system of movements, producible in many ways, a sys- 
tem that is variable in many respects, yet as a rule varies in 
such a way as to retain throughout its co-ordination. 

The change in the stroke of the cilia is correlated in many 
cases with certain other phenomena. Paramecium still retains 
to a very slight degree the power of contraction that is so 
marked in many other ciliates. The anterior end especially 


fig. 7. Relation of reversal of the ciliary stroke to contraction. a, usual 
condition: over the entire surface of the slender body the cilia strike backward ; 
6, the body is contracted, becoming short and thick: all the cilia are reversed ; 
¢, anterior end alone contracted, and cilia reversed in this region alone.; @, con- 
traction on the aboral side, curving the body: cilia reversed in the contracted 
region. 
may be shortened and thickened, or narrowed and lengthened, 
or bent to one side, to an appreciable degree. These move- 
ments are hardly to be observed in specimens swimming freely 
through the water. But if the movements are impeded and 
the animals partly flattened out between the slide and cover, 
partial contractions are very evident. It is then to be observed 
that whenever contraction takes place, the cilia of the contracted 
region become partly or entirely reversed (Fig. 7, 0), beating 
no longer forward, but backward or transversely. At times the 
whole body contracts, becoming shorter and thicker; at the 


458 Journal of Comparative Neurology and Psychology. 


same time it begins to swim backward. The moment the more 
slender form is restored, the animal begins to swim forward. 
Frequently only the anterior half or anterior tip is contracted 
(Fig. 7, ¢); then the cilia are reversed in this region alone. 
Again, one often sees the aboral side contract strongly, so that 
the animal curves toward this side. At the same time the cilia 
are reversed on this side, while they continue to strike as usual 
on the oral side; the animal then of course turns toward the 
aboral side (Fig. 7, d). Is this coincidence of the reversal of 
ciliary movement with contraction to be considered a necessary 
relation, so that whenever contraction occurs, the cilia must be 
reversed ? STATKEWITSCH (1903) shows that the same relation 
exists in the reaction to induction shocks, so that the general- 
ization seems very probable. 

4. The Avotding Reaction as a Factor in Behavior.— 
Let us now leave the detailed physiology of the avoiding reac- 
tion, and consider it asa factor in behavior; that is, its effect 
on the relation of Paramecium to the environment. We may, 
for the sake of a vivid realization, put the conditions in the 
form of a problem, with a slightly subjective tinge. The Para- 
mecium has been swimming forward without stimulation; on 
reaching a certain region it is stimulated. What is to be done 
in order to avoid or escape the stimulation ? 

The first feature of the reaction—the swimming backward 
or stopping—of course either removes the animal from the re- 
gion where it is stimulated, or prevents it from entering farther. 
This reaction is, logically if we may so express it, an abso- 
lutely correct one. Since the animal was not stimulated till a 
certain point is reached, then was stimulated, in order to avoid 
the stimulation it is sound practice to retrace the course; in 
other words, to restore the condition which did not stimulate. 
With the swimming backward the direction of the water cur- 
rents is likewise reversed, so that no more of the water from 
the stimulating region is brought to the mouth. 

The next problem is, in what direction shall the Parame- 
cium now swim forward so as to avoid further stimulation? To 
determine this, it would be well if a trial could be made of the 


Jennincs, Lehavior of Paramecium. 459 


different conditions immediately in advance. This is exactly 
what the Paramecium does. It begins to turn toward the aboral 
side, at the same time continuing to revolve slowly on the long 
axis. In this way the anterior end swings about in a circle and is 
pointed successively in many different directions (Fig. 8). From 
each direction a little water is brought to the anterior end and 
mouth by the oral cilia. Thus the Paramecium is given oppor- 
tunity to ‘‘try” the water in many different directions. When 
the water coming from a certain one of these directions does 
not show the conditions which acted asa stimulus, the ani- 


fig. 8. Diagrams of the way in which Paramecium swings its anterior end 
about in a circle, in reacting to stimuli. a, reaction to weak stimulus; 4, reac- 
tion to a stronger stimulus. From each different direction a current of water is 
brought to the anterior end. (The forward or backward component of the mo- 


tion is omitted from the diagram). 


mal may move forward in that direction, since now there is no 
further cause for reaction. If the original stimulus was weak, 
the anterior end is swung about ina small circle, ‘‘trying” the 
water ‘from a number of directions varying only a little from 
the original one (Fig. 8, a). If the stimulus was very strong, 
after swimming backward a long distance the animal swings its 
anterior end about a larger circle, a circle of which the longi- 
tudinal axis forms one of the radii; thus directions are ‘‘tried”’ 
which diverge as much as possible from the original one (Fig. 9). 
If in any of these ‘‘trials’’ the stimulus is again strongly re- 
ceived, the animal may repeat the whole reaction from the be- 
ginning—retracing its course anew, and beginning a new set of 
“trials. 


460 Journal of Comparative Neurology end Psychology. 


With avery powerful stimulus, such asa strong chemical, 
this reaction makes the impression of being violent and dis- 
ordered, as indeed may the reactions of a human being under 
similar conditions. But with a moderate stimulus the reaction 
may be very delicate. This may be illustrated by the behavior 
of Paramecia within an area of water containing carbon diox- 
ide. Part of the reaction under these conditions was described 


fig. 9. Diagram of the swinging of the anterior end about a large circle, in 
reacting to a strong stimulus. The revolution on the long axis has entirely ceased. 
in one of my earlier paper (JENNINGS, 1899, p. 331), though 
without a full appreciation of its real significance. The Para- 
mecium, swimming slowly within the area of carbon dioxide, 
comes near to the edge of the area, where it receives water 
containing none of the gas in solution. This change acts asa 
very mild stimulus; the organism merely stops and swings its 
anterior end gently toward the aboral side, ‘‘trying’’ a new di- 
rection. If the water now received is still without the carbon 
dioxide, the Paramecium swings its anterior end still farther, 
at the same time continuing to revolve on the long axis, which 
changes the direction of swinging. As soon as the water it re- 
ceives contains carbon dioxide, it swims ahead, changing its 


‘ 


Jennincs, Behavior of Paramecium. 461 


course only when it again receives water without the gas in so- 
lution. The reaction under such conditions is a very delicate 
one, keeping the animal in close touch with the environmental 
conditions. The behavior does not impress one as a definite 
‘‘reflex’’; the Paramecium is seen merely to change its course a 
little after trying several slightly differing directions. 

The behavior of Paramecium in swinging its anterior end 
about in a circle is essentially similar to the ‘‘feeling about,” 
“searching,” or ‘‘trial’” of a higher organism. We know, of 
course, no more of subjective qualities in any organism outside 
the self than we do in Paramecium. If we describe the ‘‘feel- 
ing about” or ‘‘searching” of any higher animal in a purely ob- 
jective way, we shall find that the description takes essentially 
the same form as for Paramecium. Under certain conditions 
the organism performs certain movements, which subject it to 
certain environmental changes. As long as the conditions re- 
main of essentially the same character, it continues these move- 
ments. As soon as these movements induce conditions differ- 
ing in acertain way, the movements stop. This description 
fits equally well the movements of a cat trying to escape from 
a cage (see THORNDIKE, 1898), of a dog searching for a bone, 
and of Paramecium reacting to carbon dioxide. In its method 
the behavior seems fundamentally similar throughout. 

The behavior of Paramecia under such ‘‘repellent’’ stimuli 
follows then, perhaps, as effective a general formula as could 
be devised. When stimulated it performs movements which 
take it away from the source of stimulus, and direct it success- 
ively in many ways, until the stimulation ceases. Reaction of 
this character is essentially that of ‘‘trial and error’ as we find 
it in higher animals. From this standpoint the behavior may 
be summed up as follows: When there is ‘‘error’ the organ- 
ism ‘‘tries’’ various directions or methods of action till one is 
found in which the ‘‘error” ceases. These relations have been 
brought out by the author for lower organisms in general in a 
previous paper (JENNINGS, 1904, 0). 

We must ask here the question whether the reaction 
method of Paramecium above described should or should not 


462 Journal of Comparative Neurology and Psychology. 


be called a veflex—a term which I have applied to it in previous 
papers. The question which interests us here is not whether 
an act performed without the intervention of a nervous system 
may properly be called a reflex; it may be strongly doubted 
whether the anatomical structure of organisms forms a proper 
basis for classification of types of behavior. But does the re- 
action method described fall in the concept of a reflex, judged 
merely as a type of behavior ? 

A reflex is commonly described as a fixed and invariable 
method of response to a definite stimulus. It is rare, however, 
that such definitions are found to be rigidly maintainable for 
given instances; the excellent discussion of HOBHOUSE (1g01) 
shows how the reflex concept must be modified and its limits 
effaced, till it flows easily into other behavior types, before it 
can be applied to the phenomena actually found in animal be- 
havior. Such a process of softening down is certainly neces- 
sary before we can make the reflex concept apply to the avoid- 
ing reaction of Paramecium. This reaction is composed of 
three factors, which may vary more or less independently of 
one another, in such a way that an absolutely unlimited number 
of combinations may result, all fitting the common reaction 
type. The possible variations may be expressed as follows: 
If the Paramecium be taken as a center about which a sphere 
is described, with a radius several times the length of the ani- 
mal, then as a result of the avoiding reaction the Paramecium 
may traverse the peripheral surface of this sphere at any poznt, 
moving at the time either backward or forward. In other 
words, the reaction may carry it in any one of the unlimited 
number of directions leading from its position as a. center. 
While the direction of turning is absolutely defined by the 
structure of the animal, yet the combination of this turning 
with the revolution on the long axis permits the animal to reach 
any conceivable position with relation to the enviroment. In 
other words, Paramecium, in spite of its curious limitations as 
to method of movement, is as free to vary its relations to the 
environment in response to a stimulus as an organism of its 
form and structure cowld conceivably be. 


JENNINGS, Behavior of Paramecium. 463 


Again, the reaction at times keeps the organism in the 
closest possible touch with the environment, continuing as long 
as certain conditions continue, increasing in effectiveness as the 
conditions causing it increase in intensity, and ceasing when the 
conditions causing it cease, maintaining the organism through- 
out in certain relations with the source of stimulation. Alto- 
gether, I believe that the following admission must be made. 
If we consider the reaction of Paramecium a reflex, it is because 
we are convinced beforehand that such an organism caz show 
only reflexes. If the actions of Paramecium did belong to some 
higher type of behavior, there could be little objective evidence of 
this, beyond what we already have. 

In Paramecium the reaction has not been shown to be 
modifiable by previous experience, so that from this criterion 
the behavior retains the characteristics of a reflex. But ina 
close relative, Stentor, such modification by experience has 
been demonstrated (JENNINGS, 1902), so that it may be presumed 
that technical difficulties alone have thus far prevented our ob- 
serving it in Paramecium. 

The effectiveness of the method of reacting by ‘‘trial and 
error’ that we have described above for Paramecium depends 
upon the power of discrimination of the reacting organism. 
By ‘‘discrimination” of stimuli we mean, in an objective study 
of behavior, that the organism reacts differently to the different 
stimuli in question. In this sense Paramecium discriminates 
acids from alkalies and salts, and these again from sugar. Fur- 
thermore, it discriminates different strengths of solution, react- 
ing differently, for example, with relation to weak and to strong 
acids. On the other hand, it does’ not effectively discriminate 
different acid substances, save in so far as one is stronger than 
another. Thus it swims into weak carbonic acid, which is harm- 
less, and likewise into weak sulphuric acid and copper sulphate, 
which kill it. It does not markedly discriminate a ten per cent 
sugar solution from water, hence it swims readily into such a 
sugar solution and is killed by the osmotic action.’ Thus in re- 


1 Details as to the facts cited are given in my previous papers on Paramecium 
here we are concerned only with the interpretation of these facts. 


464 Journal of Comparative Neurology and Psychology. 


gard to powerful acid substances and to sugar solution it makes 
what we would call in ourselves a ‘‘mistake.’’ In higher ani- 
mals we recognize that the power of accurate discrimination is 
one of the ‘‘higher’’ powers, becoming more secure as develop- 
ment progresses. We cannot, therefore, be surprised that it 
should not be perfect in so low an organism, nor that such or- 
ganisms, through lack of discrimination of injurious and non- 
injurious agents, often react in a way that leads to their de- 
struction. Any organism reacting by the method of ‘‘trial and 
error’ is subject to the possibility of destruction in some of the 
“trials.” 

This method of ‘‘trial and error,”’ based on the ‘‘avoiding 
reaction’ above described, plays a large part in the behavior of 
Paramecium. Through it are produced the ‘‘negative’’ reac- 
tions to agents of all sorts, as well as the collections formed in 
certain chemicals, in regions of optimum temperature, and the 
like. On the other hand, there exist certain reactions in which 
the final relation to the environment is brought about in amore 
direct way—notably ‘‘positive thigmotaxis” and certain features 
of the reaction to the electric current. These reactions will be 
taken up later. 


II. NATURE OF STIMULATION. 


Just what is the nature of the stimulation which produces 
this reaction by ‘‘trial and error’ in Paramecium? An exam- 
ination of the facts shows that asa general rule the effective 
stimuli consist of some change in the conditions, or, what is the 
same thing to the organism, of some change in the relation of 
the organism to the conditions. Change is the essential feature 
in producing the chief reactions of Paramecium. : 

This statement requires of course some qualification in de- 
“tail. A change may be nearly instantaneous, while the conse- 
quent reaction of the animal of course requires time, and must, 
therefore, continue for a certain period after the change has 
been completed. If the animal is suddenly subjected to a one- 
fourth per cent solution of common salt, it continues to react 
for a short time after the instant of the change, though if the 


JenniNGS, Behavior of Paramecium. 465 


conditions now remain constant, it soon ceases to react. The 
length of time the reaction may continue after the change is 
completed varies with different agents, becoming longer as the 
agent is more powerful. The phenomena may be expressed in 
the following somewhat indefinite way: the animal reacts to the 
change as long as @¢s effect as a change continues. In the limit- 
ing case of a stimulus so powerful as to be destructive, the re- 
action may continue for a considerable period, till death inter- 
venes. In such cases we have then a continued reaction to a 
condition that remains constant for some time. But with de- 
structive agents, the action of the agent seems progressive, so 
that there is really a continual change in the relation of the or- 
ganism to the agent, till the progressive series of changes ends 
in death. Whatever the explanation in these rare cases of de- 
structive conditions, change is elsewhere the fundamental fea- 
ture of the stimuli producing the chief reactions in Paramecium. 
This is the result which stands out clearly from all my work on 
stimulation in Paramecium. 

A change from one condition to another produces a reac- 
tion when neither the preceding nor the following condition, 
acting continuously, produces any such effect. Thus, Parame- 
cia may live and behave normally in water at 20° or at 30°, yet 
a change from one to the other, or a very much less marked 
change, produces the avoiding reaction. Paramecia may live 
without reaction in tap water or in water containing one-tenth 
per cent sodium chloride, but the change from the former to 
the latter produces the avoiding reaction. This relation could 
be illustrated by innumerable cases, taken from my earlier pa- 
pers on Paramecium. 

In all cases of course a certain amount of change is required 
in order to produce reaction; in other words, there is a certain 
necessary threshold of stimulation. Since the change itself is 
the real cause of the reaction, it is probable that the amount of 
change necessary will bear some definite relation to the inten- 
sity of action of the agent in question before the change. In 
other words, it is probable that ‘the reactions are subject to 
WepbeEr’s law, as they are known to be in bacteria (PFEFFER, 


466 Journal of Comparative Neurology and Psychology. 


1904, p. 625). The corresponding quantitative relations have 
not been worked out for Paramecium. 

The fact that change is the essential feature in causing re- 
action is of course correlated with the fact that organisms 
become acclimatized, so far as reaction is concerned, to a cer- 
tain strength of stimulus. To say that the organism becomes 
thus acclimatized is indeed little more than to say that it reacts 
only to changes. 

The change which produces stimulation may be a direct 
alteration in the environment, as when a chemical is brought 
near a specimen, or when it is touched at the anterior end with 
a glass rod, or when the temperature is raised or lowered from 
without. But under natural conditions the change is more usu- 
ally produced by the movements of the animal itself. In its 
rapid swimming the animal passes from one region to another, 
the conditions in one region changing to those in the next, and 
thus causing reaction. Further, as we have seen, the spiral 
course gives opportunity for frequent changes to act upon the 
organism; the anterior end is pointed successively in many di- 
rections, receiving ‘‘samples’” of water from each direction. 
The greater the swerving in the spiral course the greater the 
opportunity for frequent changes to affect the animal. The 
avoiding reaction, with its swerving in many directions, may in- 
deed be looked upon asa method of subjecting the organism 
successively to many changes. 

It is, however, not mere change fer se that causes the re- 
action, but change of a certain kind or in a certain direction. 
Of two opposite changes, one usually produces the reaction, 
while the other does not. Paramecium reacts wnen it passes 
out of a weak acid, not when it passes in; it reacts when it 
passes into an alkali, not when it passes out. A. Paramecium 
at 28° reacts at passing toa higher temperature, not at passing to 
a lower one; a Paramecium at 20° shows the opposite relations. 
The direction of change which produces the avoiding reaction 
may be briefly characterized-as that leading away from the optt- 
mum, while change leading toward the optimum produces none. 
It is thus clear that in most cases the actual determining factor 


Jennincs, Behavior of Paramecium. 467 


in the reactions is the direction of movement of the animal, not 
the mere orientation, as has sometimes been held. The signifi- 
cance of these relations in connection with the theory of gen- 
eral ‘‘pain reactions’ I have considered elsewhere (JENNINGS, 
1904, 6). Here we may point out, asa relation of some in- 
terest, that in Paramecium it is an injurious or negative stimulus 
that primarily induces motor reactions. This is not at all in 
agreement with the theory sometimes set forth, that the effect 
of such stimuli is to cause a cessation of activity. 

In no case, so far as I am aware, has it been shown that 
the reaction in Paramecium is due to the difference in intensity 
of a graduated stimulus on the two sides or ends of the animal, 
as is assumed by the orthodox tropism theory. In most cases 
it has been demonstrated that the determining features of the 
reaction are not of this character. 

I have above illustrated the fact that in reactions to chem- 
icals and in temperature reactions, it is a change that causes the 
response; details are given in my previous papers. In the re- 
actions to changes in osmotic pressure, a very marked change 
to a higher pressure is required to produce reaction ; the oppo- 
site change, even to distilled water, is without effect. In the 
reaction to mechanical stimulation, sudden contact of the anter- 
ior end with a solid produces the reaction, though continuous 
contact is of no effect. Paramecium is not, so far as known, 
sensitive to light. But in other infusoria the writer has recently 
shown (JENNINGS, 1904) that it is the change in light intensity, 
at the sensitive anterior end, that induces reaction. The reac- 
tion occurs when the change is due to an actual alteration in the 
source of. light, or when it is due to a movement of the organ- 
ism. Orientation is produced through the fact that in the spi- 
ral course the anterior end of an unoriented organism is repeat- 
edly subjected to changes in illumination. To these changes it 
reacts, by the method of ‘‘trial and error,’’ above described, till 
it comes into a position where such changes no longer occur ; 
such a position is found only when the animal is oriented. The 
reactions to light are particularly instructive for the part played 
by the spiral course, with its. swerving from side to side, in 


468 Journal of Comparative Neurology and Psychology. 


causing changes in the intensity of the stimulus, and hence in 
determining the reactions. While in Paramecium there is no 
reaction to light, certain other reactions are produced in the 
manner just set forth. These reactions we shall analyse in the 
next section of this paper. 


III. Reactions To CERTAIN STIMULI, WITH SPECIAL REFER- 
ENCE TO THE PART PLAYED BY THE ‘‘ACTION SYSTEM.” 


A. Reactions Produced through the ‘‘Avoiding Reaction.” 


I. Reactions to Water Currents ; Rheotaxis.—Under rheo- 
taxis is usually understood the orientation of the organism in 
line with a water current, and movement with or against the 
current. I have come across a reference to such a reaction to 
water currents in Paramecium only in two papers dealing pri- 
marily with reactions to the electric current—namely the papers 
of DaLE (1901) and STATKEWITSCH (1903, a). DaLe says: ‘‘It 
is sufficient to watch the behavior of Paramecium in water con- 
tained in a tall jar in which convection currents have been pro- 
duced, in order to be convinced of its tendency to swim with a 
Stream”of water” (DALE, 7. ¢:,"p. 354). ‘Hel attempts *tovuse 
this tendency to swim with the current in explaining the move- 
ment to the cathode in the reaction to electricity, but has no 
farther observations on rheotaxis itself. STATKEWITSCH (1903, 
@, pp. 102-104) likewise observed that Paramecia swim with 
currents caused by the absorption of water by porous sub- 
stances, but showed that this has nothing to do with the move- 
ment to the cathode, since the latter occurs in the same way, 
whatever the direction of the water currents. 

I have carefully examined the reaction of Paramecium to 
water currents under various conditions. The reaction varies 
with different individuals, and it is difficult to arrange the con- 
ditions in such a way as to make the reaction a very precise 
one. But in all my experiments a large majority of the ani- 
mals showed the opposite relation to the direction of the current 
from that mentioned by DaLeE and StaTKeEwitscH. They turned 
the anterior end up stream and moved against the current. 
There were usually a number of individuals, however, that 


Jennines, Behavior of Paramecium, 409 


showed the opposite relation, and I can well believe that in 
some cultures the majority may conduct themselves in this man- 
ner, and that this was the case with the Paramecia observed by 
the authors named. But certainly as a rule most of the organ- 
isms swim against the current, not with it. The phenomena 
may best be observed by placing Paramecia in a tube which is 
narrowed in the middle and open at both ends. Only the cen- 
tral part of the tube is filled with water, the two ends contain- 
ing only air. Over the two ends are fitted rubber caps, such 
as are used for medicine droppers (Fig. 10). By compressing 


Fig. ro. Tube for study of the reaction to water currents. See text. 


one of these caps the water is forced through the narrow part 
of the tube with any desired velocity, and is always under com- 
plete control. With a certain velocity of current most of the 
animals are seen to become oriented and to swim against the 
current. The tube must not be too narrow, since in this case 
many of the individuals strike against the side of the tube, and 
then no longer respond well to the current, the contact reaction 
interfering with ‘‘rheotaxis” as well as with many other reac- 
tions. In any case, many individuals show no orientation or 
are oriented in the opposite direction, yet the phenomenon is 
sufficiently general to show clearly that we have here a real re- 
action of the organism. 

How is this reaction to water currents brought about? If 
we direct a fine current of water fora moment upon a Para- 
mecium that is swimming quietly, we find that it gives the 
‘avoiding reaction” in a not very pronounced form. That is, 
it stops, or begins to progress more slowly, and swerves more 
strongly toward the aboral side, appearing thus to swing from 
side to side, the anterior end really describing circles of consid- 
erable size, as in Fig. 8, 6. The effect of this current on the 
animal is of course to change in some way the resistance it 


470 Journal of Comparative Neurology and Psychology. 


meets in swimming, or the pressure of the water upon it. Such 
an environmental change produces, then, lke many other 
changes, the avoiding reaction, with its ‘‘trial” of different di- 
rections. The same result is produced by setting the water in 
motion in other ways, as by causing the vessel containing the 
animals to vibrate back and forth. 

If now we produce a more extensive current, and allow it 
to continue, as in the experiment shown in Fig. 10, we find 
the same result produced. The animals at first pause, then 
swing the anterior end about in acircle, thus ‘‘trying’ many 
different directions. They then swim forward in one of these 
directions. The reaction is then repeated, and this occurs as a 
rule several times, until they have come into a position with 
anterior end directed up the stream. The reaction then ceases ; 
the animals swim forward in the usual spiral manner. 
They have become oriented by the method of ‘‘trial and error,”’ 
the ‘‘trials’’ continuing till the position of orientation was 
reached. 

We have seen that the original cause of the reaction wasa 
change in the environment—the movement of the water— 
causing a change in the resistance or pressure the Paramecium 
meets. But why does the reaction continue till orientation is 
reached, then cease? Consideration of the relation of the cur- 
rent to the spiral course followed by the animal shows that this 
is exactly what we should expect from all that we know of the 
behavior of the animal and the cause of the present reaction. 
Consider a specimen that is swimming transversely or obliquely 
to the current, asin Fig. 11. In its spiral course it swings the 
anterior end first against the current, to the point a, then with 
the current to the point 4. In the swing toward a the move- 
ment is resisted by the current; in the swing toward @ it is aid- 
ed by the current.’ Its relation to the current thus changes 
during each turn of the spiral; in. one phase the movement is 
‘‘easier”’ from being aided, in the next more difficult, from be- 


1 The upward and downward movement of the swing may be neglected for 
our present purpose. 


JENNINGS, Behavior of Paramecium. 471 


ing resisted. As we know, exactly such changes act as stim- 
uli, and the animal reacts, as we have seen, in the usual way. 
It swings its anterior end about in a circle, so that the body 
axis occupies successively many positions, and continues or re- 
peats this reaction as long as it is subjected to the changes men- 
tioned But when it comes into a position such that its rela- 
tion to the current remains. constant, it no longer reacts, for to 
constant conditions, unless destructive, Paramecium soon be- 
comes acclimatized. Such a position is found only when the 
axis of the spiral path coincides with the direction of the cur- 


Qn oi 


eer nee it 


Fig. 11. Diagram to illustrate the cause of the reaction to currents of 
water. The straight arrows indicate the direction of the current. The 
swinging of the unoriented Paramecium in its spiral course from the position 6 
to a is resisted by the current, while the movement from a to 4 is assisted. (The 
same diagram illustrates the conditions in the reaction of gravity, if the straight 
arrows represent the direction of gravity). : 


rent. In this position the animal of course still swims ina 
spiral, the anterior end describing circles about the axis of the 
spiral. But in every phase of the path the axis of the body 
forms the same angle with the axis of the spiral, and hence 
with the direction of the water current, so that its relation to 
the current remains constant, and there is no farther cause for 
reaction. Orientation has been attained through the ‘‘method 
of. trial and error.” 

But why do the majority of the animals become oriented 
with anterior ends against the current? Our description thus 
far accounts for the position of the body axis, but not for the 
more usual direction of the anterior end. We know that asa 
rule when Paramecium is subjected to changes of opposite char- 


472 Journal of Comparative Neurology and Psychology. 


acter, such as may be called plus and minus, it reacts to one of 
these changes, but not to the opposite one (above, p. 466). 
In its spiral course the unoriented organism is subjected, under 
the action of a water current, to plus and minus changes in re- 
sistance. Asa rule it is the minus change that induces the re- 
action, while the plus does not. This is perhaps intelligible, 
from the fact that Paramecium normally receives some resist- 
ance in its swinging toward the aboral side, so that when the 
pressure of the current comes from the oral side, driving the 
animal toward the aboral side, the change from the usual con- 
dition is a very marked one. Therefore, whenever the Para- 
mecium swings from @ to 6, Fig. 11,a reaction is induced, caus- 
ing strong swerving toward the aboral side. This is effective 
in the next phase of the spiral, causing the animal to swing far 
in the direction —a (since the aboral side is now toward a); thus. 
the animal becomes more nearly oriented. Since this movement 
from 6 to a involves only a plus change, it causes no reaction ; 
the ordinary spiral swimming is resumed, so that in the next 
phase the animal swerves only a short distance toward 6. But 
this involves the minus change, inducing reaction again; so in 
the next phase of the spiral the animal swings still farther in 
the direction 6—a, and is now nearly oriented. This process 
continues, the animal swinging far in the direction 6—a and 
only slightly in the direction a—é@, until the axis of its path co- 
incides with the direction of the current; then the plus and 
minus changes cease, and there is no cause for further reaction. 
The general principle on which the orientation depends is this : 
whenever moving in a certain direction causes increased swerv- 
ing, this increased swerving must show itself chiefly in the suc- 
ceeding phase of the spiral, thus causing the animal to swerve 
farther than usual in the opposite direction. 

In cases where it is the plus change which induces the re- 
action, the organism must, in the way just described, finally 
come into orientation with anterior end directed down stream. 
If both plus and minus changes induce reaction, then the ant- 
mals become oriented in either direction, the essential point be- 
ing only that the axis of the spiral coincides with the current 


Jennines, Behavior of Paramecium. 473 


direction. This condition is apparently found in a number of 
specimens in any given culture. 

2. Reaction to Gravity; Geotaxis.—The general features 
of the reaction of Paramecium to gravity have been described 
by JENSEN (1893). JENSEN further proposed a theory to ac- 
count for the reactions; but at the time his work was done, the 
‘action system’’—the general complex of structural relations, 
movements and reactions, by which most of the behavior is 
brought about—was not known. JENSEN’s theory could there- 
fore take no account of this system, and I believe that in view 
of the known facts and of those which I shall bring forth in the 
present account, it can be no longer maintained. My present — 
purpose is to describe the method by which the reaction to 
gravity occurs, and to show the relation of this to other reac- 
tions and to the ‘‘action system” of Paramecium. 

The gross facts are as follows: When Paramecia are 
placed in a vertical tube, fairly free from other sources of stim- 
uli, they swim upward, to the upper end of the tube. Control 
experiments show that gravity is the real directive influence. 
But usually some individuals in any culture show the opposite 
effect, swimming downward, while others do not become oriented 
at all. In certain cultures the majority of the individuals 
swim downward, or are indifferent. The reaction to gravity is 
easily overcome or modified by the action of other agents (Sos- 
NOWSKI, 1899, Moore, 1903). 

JENSEN’S theory to account for the reaction to gravity was 
as follows: The cause of the reaction is the difference in 
pressure upon the two sides or ends of the animal; the lower 
end or side is in a region of greater pressure than the upper. 
The greater pressure acts as a stimulus to cause the cilia on the 
lower side of the body to beat more strongly. As a result, 
the anterior end must be turned in the opposite direction (that 
is, upward), until it points in the direction of least pressure. 
The two sides are now similarly affected by the pressure, so that 
there is no cause for further turning. JENSEN’s theory is thus an 
application of the typical tropism schema to the reaction to 


474 Journal of Comparative Neurology and Psychology. 


gravity, the difference in pressure on two sides or ends of the 
animal being the determining factor. 

Does the unoriented animal react as JENSEN supposed, by 
turning azvectly toward the side of least pressure? This ques- 
tion is not to be answered from a fyior7 considerations; only 
actual observations of the movements of the animal in becom- 
ing oriented can give usa reliable answer. With the Braus- 
DRUNER stereoscopic binocular such observations can be made 
without great difficulty. The best plan of experimentation 
that I have found for giving many opportunities to observe the 
animals at the time orientation takes place is as follows. The 
animals are placed in a long U-tube (Fig. 12). The two open 
ends are covered with rubber 
caps, and the tube is at first 
placed with free ends upward. 
The Paramecia collect at the free 
ends. Now the tube is inverted; 
the clouds of Paramecia at the 
two ends move upward, toward 
the cross piece of the y which 
is now ‘above (Fig./"12). sAu- 
riving here, most of them do 


not cease swimming, but move 


fig. 12. Tube for study of the : 
across. the’ eross- “piece: ofrethic 


reaction to graviy. 2x, place where 
the change of direction of movement M and even start obliquely down- 
case ward. Here the reaction oc- 
curs; they turn around and swim upward again. At this point 
(x, Fig. 12) one has at any instant a large number of speci- 
mens in the process of becoming oriented with anterior ends 
upward. The binocular is now brought to bear upon this re- 
gion, and the method of reactionisevident. The spiral course 
becomes wide, the animals swerve strongly toward the aboral 
side, so that the anterior end is moving about in a circle; the 
Paramecia appear to oscillate irregularly back and forth. In 
other words, they are reacting in the usual ‘‘trial and error” 
way—'‘‘trying’”’ successively many different positions. This is 
continued till they have gradually worked around into a posi- 


Jennincs, Behavior of Paramecium. 475 


-tion with anterior end upward. The strong swerving then 
ceases; the animals swim upward in the usual spiral path. 

Thus, observation shows that the reaction is not brought 
about in accordance with the tropism schema, as was supposed 
by JENSEN. The animal does not turn a@rectly into orientation, 
as that theory requires, but the turning is throughout toward the 
aboral side, and the orientation is attained by the ‘‘method of 
trial and error.”’ 

What is the cause of the reaction? JENSEN’s theory that 
it is the difference in pressure on the two sides of the animal 
loses whatever plausibility it may have had, when the nature of 
the reaction itself is known. As we have seen, the turning in 
the reaction is not due to differential action on upper and lower 
sides, but to swerving toward a side that is structurally defined 
—the aboral side—whatever the position of the latter with 
reference to gravity. Thus the difference in pressure certainly 
does not act in the direct way supposed by JENSEN. 

Furthermore, as we have seen above (p. 467), in no other 
reactions of Paramecium is the difference in intensity of a grad- 
uated stimulus on the two sides or ends of the animal known 
to be the determining factor in the reaction. 

On many other grounds it is highly improbable that this dif- 
ference in pressure is the effective agent. The difference in 
pressure between the two sides is so excessively minute in pro- 
tion to the total pressure acting on the animal, that it is almost 
inconceivable that this difference should be perceived. The in- 
fusorians are of course under atmospheric pressure; this is 
equal to the pressure of a little more than 10,000 millimeters 
of water. As JENSEN shows, the difference in pressure between 
the two sides of certain of the infusoria which show the reac- 
tion to gravity is only that of 0.01 mm. of water. Hence the 
difference in pressure between the two sides of the organism is 


1 : 
only mon Of the pressure acting everywhere on the surface. 


Furthermore, JENSEN showed that the reaction still occurs when 
the atmospheric pressure is more than doubled; the effective 


; : 1 
difference in pressure would then be less than s;;7p the general 


476 Journal of Comparative Neurology and Psychology. 


pressure. When we consider the large threshold differential re- 


quired for the perception of differences in pressure in known 


1 


cases—for example, about => in man—we can hardly believe 


that a differential of Wom is perceptible by infusoria. JENSEN 
did not calculate this threshold differential, but said in general 
that the great sensitiveness here shown agreed well with 
the great sensitiveness to chemical, thermal and other stim- 
uli. But the great sensitiveness assumed to exist for chem- 
cals and heat was based on the theory that the reaction was 
due to the difference in intensity of the agent in question on 
the two sides or ends of the animals. This I have shown in 
previous papers not to be the cause of the reactions in question ; 
they are due to changes in intensity brought about by the 
movements of the Paramecia from one region to another. The 
degree of sensitiveness required is therefore much less than 
would be necessary on JENSEN’s theory, and does not approach 
remotely such a minuteness of threshold differential as J ENSEN’S 
view requires for the reaction to pressure. 

Further, JENSEN assumes that the reaction is brought about 
when there is a difference of a similar order of magnitude to 
that above mentioned, between the anterior and posterior ends 
of Parameciuin. Now, we know that the anterior end is much 
more sensitive than the posterior; this has been shown pre- 
cisely for mechanical pressure. A Paramecium touched with a 
glass hair at the anterior end reacts violently, while the same 
touch or a stronger one on the posterior half of the body pro- 
duces no reaction. Thus it may be considered practically cer- 
tain than an increase of pressure on the posterior end such as 
JENSEN’S theory assumes to be the effective agent would cause 
no reaction whatever; any reaction to the existing pressure 
which might occur would be due to that at the anterior end. 

JENSEN makes one attempt to differentiate experimentally 
between the direction of gravity and the direction of decrease 
of pressure, and to show that the Paramecia follow the latter 
instead of the former. He placed Paramecia in a tube inclined 
to the perpendicular, and observed that, while often the Para- 


Jennines, Behavior of Paramecium. mee Vey 


mecia first swim vertically upward against the inclined wall, then 
turn away, and again swim vertically up till they strike it, etc., 
in other cases they swim obliquely upward along the wall. 
From this latter fact he concluded that they swim in the direc- 
tion of decrease of pressure, instead of in the direction of ac- 
tion of gravity. It is difficult to imagine from what data or by 
what process of reasoning this conclusion was reached. The 
decrease in pressure of course takes place in an inclined tube 
in the same direction as in a perpendicular one, and coincides 
in both cases with the direction of gravity. JENSEN’S experi- 
ment was not of the least value in differentiating the two direc- 
tions; indeed, so long as the pressure is due to gravity the two 
directions in question must coincide. If, therefore, the obser- 
vations mentioned speak in the least against the view that the 
organisms tends to move in the lines of the direction of gravity 
(which, as DAVENPORT, 1897, p. 123, has shown, they do not), 
then they speak equally against the view that the movement is 
in the direction of decrease of pressure. 

What then is the effective stimulus in the reaction to grav- 
ity? In the other reactions of Paramecium we have found that 
the effective stimulus is due to some change in the conditions, 
or, what amounts to the same thing, in the relation of the or- 
ganism to the conditions. In the reactions to gravity exactly 
the conditions are present for the production of such changes, 
and the reaction is of precisely the character that might be ex- 
pected from such changes as occur. The conditions are quite 
parallel to those found in the reactions to water currents. The 
changes in question are brought about through the fact that 
Paramecium swims in a spiral, swinging successively in many 
directions. In an unoriented specimen the upward phase of 
the swerving is resisted by gravity, making the motion more 
difficult ; the downward phase is assisted, making the motion 
easier. The effect of these repeated changes in resistance or 
the ease of swimming is similar to the effect of repeated streams 
of water directed on a quiet animal. The result of such en- 
vironmental changes is, as we know, to produce the ‘‘avoiding 
reaction,’’ and this is what we see in the reaction to gravity. 


478 Journal of Comparative Neurology and Psychology. 


The animal swerves farther toward the aboral side, and this, 
with the revolution on the long axis, causes it to occupy suc- 
cessively many different positions. When asa result of these 
repeated ‘‘trials’’ it comes into such a position that the changes 
causing the reaction no longer occur, the reaction ceases. Such 
a position is found only when the axis of the spiral course co- 
incides with the direction of gravity. It this position the body 
of the animal, maintaining a constant angle with the axis of 
the spiral, maintains also a constant angle with the direction of 
gravity ; changes in the relation of its swerving to the direction 
of gravity, therefore, no longer occur. ‘To constant conditions 
Paramecium quickly becomes acclimated, so now reaction no 
longer takes place. 

Whether the anterior end is directed upward or downward 
depends upon whether the plus or minus change in resistance 
induces the reaction. If the minus change—the change from 
the greater resistance of the upward swing to the less resistance 
of the downward swing—is the effective stimulus, then the ani- 
mal will become oriented with the anterior end upward, for 
every time it swerves downward the reaction is induced, causing 
it to ‘‘try’’ many new positions, while when it swerves upward 
no reaction is induced, and it retains the position reached. This 
is apparently the usual condition of affairs. On the other hand, 
if it is the plus change—the change from less resistance to greater 
resistance—that causes the reaction, the animal will become 
oriented with anterior end downward. To both cases we could 
apply the detailed analysis given in the account of the reactions 
to water currents, above. 

Thus as to the nature of the effective stimulus in gravita- 
tion, our analysis leads to results agreeing with the conclusions 
of Davenport (1897). This author holds that the reaction to 
gravity is due to the fact that the organism ‘ ‘experiences greater 
resistance (friction + weight) in going upward even to the 
slightest extent than in going downward (friction — weight)” 
(/. c., p. 122). What I have set forth above is the way in 
which this difference in resistance acts in orienting the or- 


ganism. 


Jennines, Behavior of Paramecium. 479 


The stimulus induced by the variations in the resistance 
due to gravity is of course a very light one, and observation 
shows that it is easily modified or masked by other stimuli. 
Chemical, mechanical and electrical stimuli overcome the reac- 
tion to gravity, hence the necessity of having the Paramecia in 
nearly pure water and in a clean tube if the reactions to gravity 
are to be seen clearly. If these conditions are not fulfilled, the 
Paramecia may collect in any part of the tube, through reac- 
tions to chemical stimuli, and to contact with solids. It may 
perhaps be said in general that the reaction to gravity shows 
itself only when the animal is not subjected to other effective 
stimuli. 

JENSEN (/ c.) showed that when placed on the centrifuge 
Paramecium reacts with regard to the direction of the centri- 
fugal force in the same way as to gravity. The animals orient 
themselves and swim in the direction opposite to that in which 
the centrifugal force tends to carry them. In these experiments 
the conditions are of course present for the same sort of reac- 
tions that we find under the action of water currents and of 
gravity. In one phase of the spiral course the movement of 
the unoriented animal is assisted by the centrifugal force, in an- 
other resisted; the changes thus produced lead to reaction and 
orientation in the way already described. 

Summary.—The reactions to water currents (‘‘rheotaxis’’), 
to gravity (‘‘geotaxis’’) and to centrifugal force are in Parame- 
cium essentially the same, and due to similar conditions; they 
may be summed up as follows: The unoriented individual is 
subjected, owing to its spiral course, to repeated changes of 
pressure and of the resistance to its movements; in one phase 
of the spiral the motion is assisted, in another resisted. These 
changes induce the usual reaction; through the consequent in- 
creased swerving toward the aboral side, with the revolution on 
the long axis, the animal occupies successively many different 
positions, till one is found in which these changes no longer 
occur, when there is no further cause for reaction. Such a po- 
sition, in which the relation of the movement to the resistance 
remains constant, is found only in orientation with the axis of 


480 Journal of Comparative Neurology and Psychology. 


the spiral path coincident with the direction of the force in 
question. Under the action of the three agents named, as a 
rule it is the minus change that induces reaction; hence the 
animal directs itself against the operation of the forces at work. 


B. Behavior during Conjugation. 


The behavior during conjugation is not brought about 
through the avoiding reaction, yet the conditions determining 
it seem of the same character as those determing behavior pro- 
duced through the reaction named, so that it should be consid- 
ered in relation with the latter. It is not my purpose to 
give here a full account of the behavior during conjugation, but 
merely to point out the part played in this behavior by the 
usual ‘‘action system’ of Paramecium, above set forth. 

Paramecia during a period of conjugation are perhaps in 
a ‘‘physiological state’’ differing from the usual state, so that 
they react differently from usual, uniting in pairs. Yet it is re- 
markable how much of their behavior at such times is due to 
precisely the same features that are always present, taken in 
connection with a physical modification of the body substance. 
I have not thus far been able to observe at such times any 
method of reaction differing from the usual ones. The factors 
bringing together two individuals seem to be chiefly the follow- 
ing. 

1. At these periods of conjugation the oral surface of Para- 
mecium is adhesive, through some physical modification of the 
protoplasm. Asa result of this modification other Paramecia 
coming in contact with the oral surface become attached. The 
position of the two Paramecia is of no consequence, nor the 
way in which the contact is brought about, provided only that 
one animal comes in contact with some part of the oral surface 
of another. Asa result of this fact, the individuals ina crowded 
culture become stuck together in all sorts of bizarre ways, and 
evidently’ without any previous definite reaction on the part of 
the individuals concerned. Two specimens will be seen feed- 
ing on the bacterial zoogloea and moving in opposite directions 
over its surface; one crosses by chance the path of the other, 


Jennincs, Behavior of Paramecium. 481 


and in passing its posterior end drags across the oral surface of 
the latter. Thereupon they stick together, and a struggle en- 
sues, each individual trying to pursue its forward course and 
not succeeding, till one finally drags the other one backward 
(Fig. 13, at the upper left hand corner). The second speci- 


Fig. 13. Irregular adhesion of individuals, observed ig cultures of Para- 
mecia in which conjugation was taking place. These groups move about irregu- 
larly, remaining attached, in spite of the struggles of the individuals. 
men may be dragged about through the water or over obstacles 
of all sorts, till finally the adhesion gives way and they sep- 
arate. Specimens thus become adherent in every possible way, 
provided merely that some part of the oral surface of one of 
the individuals enters into the adhesion. Many such cases are 
clearly not early stages of any ordered conjugation, and they. 
often separate after one individual has been dragged about for 
some time much against his struggles. 

Again, often more than two individuals thus adhere; 
groups of three, four or five are seen, adhering in all sorts of 
irregular ways, and apparently struggling to free themselves. 
A number of such cases of irregular adhesion are shown in 
Fig. 13, from a culture in which conjugation was taking place 
freely. It is evident that such groups as are shown in this fig- 
ure cannot be interpreted as due to any will or desire of the 


482 Journal of Comparative Neurology and Psychology. 


animals, and this becomes still more evident when one observes 
the accidental manner in which they are formed, the way in 
which the individuals are dragged about against their efforts, 


and their struggles to free themselves—at times resulting suc- 
cessfully. I have even seen moribund individuals, and individ- 
uals undergoing fission thus attached irregularly to the oral sur- 
face of other specimens. 

2. A second important factor in bringing about conjuga- 
tion is found in the usual ciliary movements of the animals and 
in the currents produced by these movements. As we have 
seen in the foregoing pages, there is a strong current passing 
backward along the oral side of Paramecium, so that there is a 
tendency for all sorts of objects suspended in the water to be 
carried to the oral groove. This tendency is of course opera- 
tive on other Paramecia in the neighborhood as well as upon 
lifeless objects. In the case of two Paramecia close together 
this tendency is of course reciprocal; each tends to draw the 
other to its own oral groove. Thus if two Paramecia are swim- 
ming along close together, there is a strong tendency, through 
their usual movements, for them to come together with oral 
surfaces in contact. Under ordinary conditions this is often 
seen, but does not lead to conjugation, because the oral sur- 
faces are not adhesive. But when the oral surfaces are adhe- 
sive, as we know them to be at periods of conjugation, then 
the animals stick together. The remainder of the process falls 
outside the field of ‘‘behavior.’’ The relations just pointed out 
show why in a conjugating culture so many more individuals 
are found in contact by their oral surfaces than in the irregular 
ways shown in Fig. 13; the irregular adhesions occur only 
through unusual accidents. 

Thus when the oral surfaces of Paramecia become adhesive, 
the usual movements lead to attachment by these surfaces, such 
as we find in conjugation. All the phenomena seem to be in- 
telligible on the basis o1 these factors alone, though it may be 
possible that there are certain modifications of the usual be- 
havior in periods of conjugation. 


Jennincs, Behavior of Paramecium. 483 


C. Responses to Stimuli not brought about through the ‘*Avotd- 


” 


ing Reaction. 


The behavior which we have thus far considered is brought 
about chiefly through the avoiding reaction ; the general method 
is that of ‘‘trial and error.’’ Though the most important fea- 
tures of the behavior of Paramecium are produced in this way, 
there are certain other reactions in which the method of ‘‘trial 
and error’ does not play the chief, or at least the only part; 
in these the relation of the direction of movement to the source 
of stimulus is, in certain features at least, more direct. These 
reactions we shall take up next, though only with the reaction 
to the electric current shall we deal here in detail. A list of 
these reactions was given on page 450. Local contraction of 
the body as a response to stimulation has been dealt with suff- 
ciently above (page 457), and in the paper of STATKEWITSCH 
(1903). MassarT (1901) gives a thorough study of the dis- 
charge of trichocysts asa response to various stimuli, while 
STATKEWITSCH (1903) gives details as to the production of this 
reaction by induction shocks. The reaction to contact by com- 
ing to rest has been described in detail in a previous paper by 
the present author (JENNINGS, 1897), and in a more recent pa- 
per by PUrrer (1900). These matters, then, we need not con- 
sider further here. 


1. Forward Movement as a Response to Stimulation. 


In a previous paper (JENNINGS, 1900) I showed that many 
Infusoria respond to a stimulus which affects only some other part 
of the body than the anterior end, by moving forward. I did 
not succeed in showing this for Paramecium, owing to diffi- 
culties of technique in working with so small an animal. In 
the meantime ROESLE (1902) has observed that when a speci- 
men is stimulated at about the middle of the body by col- 
lision with another specimen, it responds by moving forward. I 
have recently been able to confirm this result experimentally. 
A small glass rod may be drawn out so fine that the tip is hard- 
ly visible under a magnification such that the differentiations in 
the body of Paramecium are conspicuous and cilia are plainly 


484 Journal of Comparative Neurology and Psychology. 


seen. With the tip of sucha rod it is possible to stimulate 
Paramecium locally, without jarring the animal as a whole. It 
is then found that a mechanical stimulus back of about the an- 
terior one-third causes a movement forward. It is notable that 
at the anterior end the lightest touch produces a strong avoid- 
ing reaction, whereas an equally light stimulus elsewhere pro- 
duces no reaction whatever. I was not able to confirm with 
the rod RoEsLe’s view that the region about the mouth is espe- 
cially sensitive, but this seems highly probable on general prin- 
ciples, as well as in view of RogESLE’s results; the technical 
difficulties of reaching precisely the region about the mouth 
with the rod are very considerable. 

A very powerful stimulus even on the posterior part of the 
body induces the avoiding reaction. But this may be due to 
the mechanical transmission of the shock to the anterior end. 

Apparently a very light, unlocalized stimulus likewise pro- 
duces forward swimming, as I noted in a previous paper (1899, 
a, p. 104). This is true of a slight jarring of the vessel con- 
taining resting individuals. RoESLE (1902) states that an in- 
duction shock sometimes has the same effect, though as StTat- 
KEWITSCH (1903) shows, this stimulus usually produces the 
avoiding reaction. 


2. Reaction to Electricity. 


Part Played by the Action System.—The reaction to the 
electric current presents certain features not found in the reac- 
tions to other stimuli. According to the account of this reac- 
tion in the foundational paper of LupLorr (1895), the cilia on 
the cathode half of the body of Paramecium strike forward, 
those on the anode half backward. The inevitable result is 
that any specimen not in line with the current will be turned 
directly around, until the anterior end is toward the cathode. 
The reaction seems, according to this account, to be much sim- 
pler and more schematic in character than the reactions to other 
stimuli, the characteristic ‘‘action system’ seeming to play no 
differential part. But the recent papers of PEARL (1900), PUtT- 
TER (1900) and WALLENGREN (1902, 1903) show that the reac- 


Jennincs, Behavior of Paramecium. 485 


tion to the electric current is in many ciliates more complex and 
less schematic than had been supposed. Avs first brought out 
in the paper of PEARL (1900), there seems to be an attempt by 
the animal to react in the same way to the electric current as 
to other stimuli (PEARL’s ‘‘reflex factor’’), but this is modified 
or masked by certain effects peculiar to the current (PEARL'S 
“forced movements’). Cilia of different parts of the body un- 
der the influence of the current thus differ in their method of 
action and force of stroke. WALLENGREN (/. c.) shows that 
whether anodic, kathodic or transverse electrotaxis is produced 
depends upon the peculiar action of the cilia of certain regions 
of the body. Thus the ‘‘action system” of the organisms does 
play a part in determining the reaction to the electric current, 
though not so exclusive a part as in the reactions to the stimuli 
met under natural conditions of life. The corresponding rela- 
tions have never been brought out for Paramecium ;' this I shall 
try to do in the following. 

PEARL (1900) confirmed Luptorr’s schematic account of 
Paramecium, though at the same time he showed, as noted 
above, that in certain other ciliates the ‘‘action system”’ (his 
“reflex factor’) does play an important part in determining the 
reaction to the electric current. Though the results of Lup- 
LOFF and PEARL on Paramecium are correct so far as they go, 
they are incomplete. The ‘‘action system”’ does in reality play 
a much larger part in determining the reactions to the electric 
current than would appear from the accounts of the two authors 
named. ‘This is most clearly seen in the fact that when the an- 
terior end is directed toward the anode at the moment the cur- 
rent is made (Fig. 14, 0) the animal always reaches the position 
of orientation with the anterior end to the cathode by turn- 
ing toward the aboral side, as in the reactions to other stimuli. 
Under these conditions the cilia of both the oral and aboral sides 
beat backward in the anterior half of the body (Fig. 14, 0); since 
the cilia of the oral groove are more powerful than the opposing 


1 Tt is somewhat peculiar that these relations are not dealt with in the recent 
extensive and valuable paper of STATKEWITSCH (1903, @). 


486 Journal of Comparative Neurology and Psychology. 


aboral ones, they turn the organism toward the aboral side. 
But this is aided by the fact that the cilia of the aboral side of 
the anterior half of the body strike obliquely toward the oral 
side. So far then as the anterior half of the body is concerned, 
this reaction is the same as that produced by other stimuli. In 
the posterior half, directed toward the cathode, another factor 
plays a part, to be taken up later; but this has under the pres- 
ent conditions no effect on the reaction. 


Fig. 74. Diagram representing the action of the cilia and the direction of 
turning in Paramecia occupying different positions with relation to the electric 
current. The small arrows within the outlines of the body represent the direc- 
tion in which the cilia of the different regions tend to turn the animal; the 
larger external arrows represent the actual direction of turning. In all positions 
from a to d the turning is toward the aboral side; at e it is toward the oral side. 


Even when the animal lies in a very slightly oblique position, 
so that orientation would be reached somewhat more quickly 
by turning toward the oral side (Fig. 14, a), the turning is 
still toward the aboral side, the strong oral cilia striking back- 
ward and driving the animal toward the aboral side. Further, 
when the animal is transverse to the current and the aboral side 
is toward the cathode (Fig. 14, c), the turning is of course to- 
ward the aboral side, as inspection of the figure shows it must 


Jennines, Behavior of Paramecium. 487 


be. Indeed, in any position from a through 6 and ¢ to d, Fig. 
14, the animal attains orientation by turning toward the aboral 
side, as in reactions to other stimuli. These results follow even 
when the movements of the cilia are precisely those described 
as typical by Luptorr, the greater effectivess of the oral cilia 
determining the direction of turning. 

On the other hand, if the animal is transverse to the cur- 
rent with the oral side toward the cathode (Fig. 14, e), it turns 
directly toward the ora/ side, until the position of orientation is 
reached. In this turning toward the oral side the electrotactic 
reaction differs from the motor reactions to other stimuli, the 
factor peculiar to the action of the electric current playing here 
the essential part. In the typical case where the cilia act as 
described by Luptorr, all the cilia tend to produce the turning 
toward the oral side, as Fig. 14, e, shows. 

Between the position shown in Fig. 14, e, in which the 
animal turns toward the oral side, and thatin Fig. 14, a, in 
which it turns toward the aboral side, there is of course an in- 
termediate position in which the tendencies to turn in the oppo- 
site directions are in equilibrium. In such cases the animal retains 
its position until the normal revolution on the long axis has 
occurred, bringing the body into the position shown in Fig. 14, 7, 
with aboral side to the cathode. The animal then of course 
turns at once toward the aboral side, into the position of orien- 
tation. A similar method of reaction in certain positions has 
been described by PEaRL (1900, p. IoI, ‘‘type IID’) for Col- 
pidium, and by WALLENGREN (1902, p. 365) for Opalina. The 
tendency to turn in two opposite directions at once, as it were, 
so that the animal no longer reacts in a co-ordinated way, 1s 
very characteristic for the reaction to the electric current, dis- 
tinguishing this reaction from all others. 

Altogether, in nearly three-fourths of all possible positions 
the animal attains orientation by turning toward the aboral 
side; that is, the ‘‘action system’ of Paramecium—PEARL’S 
“reflex factor’’—determines to this extent the reactions to elec- 
tricity, as it does still more completely the reactions to other 
stimuli. In practical experimentation with free swimming Para- 


488 Journal of Comparative Neurology and Psychology. 


mecia the turning toward the aboral side plays even a larger 
part than is indicated in the discussion just given. Thus, if the 
current is frequently reversed, the Paramecia practically always 
become re-oriented by turning toward the aboral side, since 
after the reversal the anterior end is directed to the anode as in 
Fig. 14, 6; in this position, as we have seen, the turning is al- 
ways toward the aboral side. It is only by taking special pains 
to close the current when the animal is in such a position as is 
shown in Fig. 14, e that it can be caused to turn toward the 
oral side. “ The results then due’tq’ an effect peculiar “to the 
current, which will be taken up later. 

The ‘‘action system” in Paramecium further plays a part 
in the reactions to electricity in the fact that the response on 
breaking the circuit, and the response to a single induction 
shock, take the character of the typical ‘‘avoiding reaction.” 
This response at the breaking of the circuit is described by 
PEARL (1900, p. 113); the response to induction shocks by 
STATKEWITSCH (1903, p. 48). 

Again, the ‘‘action system” of Paramecium plays a part 
in the fact that the path followed during the reaction to the 
constant current is a spiral of the usual sort, the animal revolv- 
ing to the left and swerving toward the aboral side. Thus there 
is during the reaction to the current an obliqueness in the stroke 
of the cilia similar to that found under usual conditions.  Cer- 
tain variations in the spiral path under the action of the electric 
current will be taken up later. 

Pecuharity of Reaction to the Electric Current.—On the 
other hand, it is clear that a factor exists in the reaction to the 
electric current which is not found, so far as known, in the re- 


actions to other stimuli—a factor not supplied in the ‘‘action 
system” as observed in the movements under the natural con- 
ditions of existence. This is the factor shown in the turning 
toward the oral side under certain conditions ; the factor that 
causes the animal to try at times to turn in two opposite direc- 
tions at once—PEARL’s ‘‘forced movement factor.’’ What is 
its nature ? 


The characteristic phenomenon of the reaction to the elec- 


Jennincs, Behavior of Paramecium. 489 


tric current is the contrasted action of the cilia in the cathode 
and anode regions of the body (Fig. 14), as described by Lup- 
LOFF (1895). But it is to be observed that the action of the 
cilia in the anode region is identical with that which occurs un- 
der the influence of any other stimulus. The work of RoESLE 
(1902) and STATKEWITSCH (1903) shows that under induction 
shocks the stimulation is primarily at the anode, and that the 
effect of this stimulation is similar to that of stimulation by 
other means; the cilia are reversed for a short time, so that the 
animal swims backward; then it starts forward in a new direc- 
tion (STATKEWITSCH, 1903). Under the constant current, after 
the circuit has been closed and the conditions have become con- 
stant, the anode cilia are directed backward, as under usual con- 
ditions, so that so far as they are concerned the animal swims 
forward in the normal way. It is then in the continued rever- 
' sal of the cathode cilia that the peculiar action of the current 
manifests itself; these cilia oppose the normally acting anode 
cilia, giving rise to the conflict in direction of turning and of 
progression that is so striking a factor in the reactions to elec- 
tricity. LUDLOFF’s account of this peculiar action of the cathode 
cilia is excellent, but certain points brought out by LUDLOFF 
are not included in the schema usually copied from his work, 
and this has given rise to certain misconceptions. This has 
been shown in the recent valuable paper of STATKEWITSCH 
(1903 2). My own results confirm those of STATKEWITSCH on 
this point; since they were obtained quite independently of the 
work of STATKEWITSCH,' and by a different method of experi- 
mentation, I will set them forth. The essential point is that 
the reversal of the cilia in the cathode region of the body does 
not typically include just half the body, as is usually set forth. 
On the contrary, it begins in a weak current with a very slight 
effect limited to the point of the cathode end of the body, and 
as the current becomes stronger it spreads gradually backward, 
until it finally includes almost the entire body. SraTKEWITSCH 


1 My experimental work was completely finished and the first draft of this 
paper written when STATKEWITSCH’s paper appeared. 


490 Journal of Comparative Neurology and Psychology. 


(1903 a, p. 92) determined this by direct observation of the 
cilia on animals in viscous media of various sorts, inventing a 
number of new media for this purpose. My own results were 
obtained by observation of the currents produced by the cilia. 
These observations were made by the use of India ink in the 
water containing the animals, as set forth above (p. 442); they 
add certain features to the results set forth by STATKEWITSCH. 


Fig. 15. Currents of water produced by the action of the cilia in the reac- 
tion of Paramecium to the electric current. a, electric current weak, water cur- 
rents reversed only at the anterior tip—most markedly in the oral groove; 4, 
electric current strong. The arrows show the direction of the water currents. 


With a weak electric current the ciliary currents, after ori- 
entation is reached, are everywhere backward. At the very 
anterior tip (directed to the cathode) the currents are perhaps a 
little less strongly backward than when the animal is not sub- 
jected to electricity. This agrees with the results of LUDLOFF 
and of STATKEWITSCH (1903 a), who found that in a weak cur- 


Jenninecs, Lehavior of Paramecium. 491 


rent only the cilia at the cathode tip are reversed (Fig. 16, 7). 
An additional feature, to be observed from the movements of 
the ciliary currents, is that in the oral groove the cathode effect 
is more marked than elsewhere, and shows itself by repeated 
reversals of the ciliary current in the anterior part of this re- 
gion, lasting but an instant. 

With a stronger current the effective stroke of a part of 
the cilia of the anterior region of the body is reversed, so as to 
be forward. At first this includes only a small part of the an- 
terior region of the body, and this result is reached first in the 


| 
fA 

fig. 76. Different stages of the reaction of the cilia to the electric cur- 
rent, after STATKEWITSCH (1903 a). The cathode is conceived to be above, the 
anode below. Ina weak current, only a few cilia at the tip of the cathode end 
are reversed (1). As the current becomes stronger (2, 3, 4, 5, 6) more and more 


of the cilia are reversed, until in the strongest currents practically all of the cilia 


strike forward. 


oral groove, where a water current 
passes continually forward even 
y when the electric current is so weak 
( that over the remainder of the an- 


terior part of the body the water 
currents are still backward or at 
resti(ig. 15,94), ~s the electric 
current is made stronger, the cur- 
rents pass forward over the entire 
anterior half of the body. This is 
the stage usually considered typi- 
cal, though as STATKEWITSCH (1903 
a, p. 93) points out, it is only one 


point in a series of continuous 


changes. At this stage there is still an alternation at intervals 
in the direction of the effective beat of the cilia of the anterior half 
of the body, giving the movement a jerky character. As the 
electric current is made stronger the forward water currents on 
the anterior half of the body become constant and more pow- 
erful; the currents on posterior and anterior halves separate at 
about the middle of the body, and water is drawn from all sides 


492 Journal of Comparative Neurology and Psychology. 


to supply them, making the animal the center of a sort of 
cyclonic disturbance in the water (Fig. 15, 4), which gives a 
most extraordinary appearance. At this stage the forward 
movement of the animal is much retarded, owing to the strong 
backward stroke of the cilia on the anterior half of the body. 

With a still stronger electric current the forward ciliary 
currents in the anterior (cathodic) region of the body become 
still more powerful and extensive, seeming to begin even be- 
hind the middle, though the precise boundaries of the two sets 
of currents are very difficult to determine by this method of ob- 
servation. ‘There comes a period when the effect of the two 
sets of currents are equal, and the animal neither advances nor 
retreats, but retains its position, revolving rapidly on the long 
axis. It is clear that the forward stroke of the anterior cilia 
just balances the backward stoke of the posterior cilia. Often 
the two sets of cilia alternate in obtaining the upper hand; the 
animal is driven backward a distance, then forward again. If 
the electric current is made still more powerful, the forward 
currents in front become still stronger and more extensive; they 
gain the upper hand permanently, and the animals are driven 
backward toward the anode. 

For stronger electric currents it is not possible to determ- 
ine by observation of the ciliary currents the distribution of for- 
ward and backward striking cilia. But this has been determined 
from direct observation by STaTKEWITSCH (1903, a); his re- 
sults are shown in Fig. 16. The reversal of the cilia, begin- 
ning with a weak electric current at the cathodic tip, extends 
backward as the current becomes stronger till it finally includes 
practically the entire body surface. 

In view of these results, the known factsas to the reaction 
to the electric current may be formulated at follows. First, the 
current stimulates in the same manner as any other stimulus; 
this stimulation has origin at the anode. Second, the results 
of this stimulation are interfered with or overcome by an effect 
peculiar to the electric current, and having origin at the cathode. 
This peculiar effect is shown in a progressive reversal of the 
cilia, beginning with a weak current at the cathode tip, and 


Jennincs, Behavior of Paramecium. 493 


gradually extending toward the anode end, until with a strong 
current it affects almost or quite the entire body. Without this 
second factor, the reaction to the electric current would appar- 
ently take place in the same way as the reaction to gravity or 
to currents of water. The first factor mentioned corresponds 
to PEAaRL’s ‘‘reflex factor,” the second to his ‘‘forced movement 
factor.” 

Thus in the reaction to the electric current the point espe- 
cially demanding explanation is the cathodic reversal of the 
cilia; it is this which distinguishes this reaction from all others. 
As STATKEWITSCH (1903, @, p. 79) has emphasized, ‘‘the reac- 
tion of the cilia is the first and fundamental phenomenon of 
galvanotropism.’’ <Any theory of the reaction to the electric 
current is of value just in so far as it promises to aid us in under- 
standing the peculiar action of the current on the cilia. Theo- 
ries which attempt to account for electrotaxis on certain general 
considerations, without taking into account the effect on the 
cilia, are at the present time anachronisms; they close their 
eyes to the real problem that needs solution. 

As to the fundamental nature of the change in the proto- 
plasm that induces the cathodic reversal of the cilia, which 
forms the distinctive feature of the reaction to the electric cur- 
rent, the conclusions drawn from the thorough and extensive 
work of STATKEWITSCH (1903, @) are most worthy of consid- 
eration. For details reference must be made to the original 
work of STATKEWITSCH ;' we may say here that the author 
comes to the conclusion, after extensive experimentation as to 
the chemical and physical effects of the electric current on the 
organisms, that the current disturbs the usual equilibrium of 
the processes of metabolism in such a way as to produce a change 
in the normal backward stroke of the cilia, in the manner de- 
scribed above (/. ¢., p. 158)—this change beginning at the 
cathode end, and progressing, as the current is made stronger, 
over the entire body. 


} A German translation of parts of STATKEWITSCH’s Russian text is to ap- 
pear, I understand, in VERWORN’S Zeitschrift fiir Allgemeine Physiologie. 


494 Journal of Comparative Neurology and Psychology. 


Cause of Backward Swimming in Strong Currents.—The 
observations described above on the direction of the effective 
beat of the cilia as the current becomes stronger throw light on 
the disputed question as to the cause of the swimming back- 
ward toward the anode in a strong current. LUDLOFF (1895) 
explained this backward movement as due to the fact that in a 
strong current the effectiveness of the reversed stroke of the 
anterior (cathodic) cilia becomes increased, till it overcomes the 
forward effect of the posterior cilia. According to LUDLOoFF's 
view, then, the animal swims actively backward in a strong 
current, just as it swims actively forward in a weak current. On 
the other hand Peart (1900, p. 123) holds that in a strong cur- 
rent the animals are borne passively backward to the anode by 
the cataphoric effect of the current—the electrical convection— 
while their active movements tend to carry them to the cathode. 
In other words, he holds that in a strong current the electrical 
convection becomes more effective than the stroke of the cilia, 
thus carrying the animal backward. Date (1goOl, p. 354) holds 
the same view. WALLENGREN (1902) adopts this explanation, 
for Opalina, without expressing an opinion in regard to Para- 
mecium. Which of the two explanations is correct? 

As the account given on preceding pages (pp. 490 492) 
shows, the observations on the direction of the effective beat 
the cilia are throughout in accordance with the explanation 
given by Luptorr, and no other factor is required to account 
for the phenomena which actually occur. When the animal is 
swimming backward to the anode the effective beat of a large 
portion of the cilia is demonstrably forward, producing currents 
equal or superior to those due to the backward stroke of the 
other cilia. This forward stroke of the anterior cilia must in- 
evitably tend strongly to drive the animal backward, so that at 
the best only a very small part in the phenomena could 
possibly be attributed to the electrical convection. The direct 
impression from observations is that the result is fully accounted 
for without bringing the electrical convection into the matter 
at all. 

The further question arises as to whether the electrical 


Jennincs, Behavior of Paramecium. 495 


convection is competent to produce the effect ascribed to it on 
the view of Peart and Date. With the strength of current 
used, is the electrical convection sufficiently powerful to carry 
the bodies of Paramecia, considered merely as pieces of ma- 
terial of a certain size and weight, toward the anode at the rate 
at which the Paramecia move backward? Observation shows 
that even smaller, non-living particles are not carried toward 
either pole at any such rate. Further, Paramecia that have 
been killed in ether, chloroform, chloretone or formalin are not 
moved to either electrode by the electrical convection. Brru- 
KOFF (1899), who maintains the efficacy of electrical convec- 
tion, endeavors to explain the fact last cited as follows. The 
dead Paramecia do not remain suspended, but sink to the bot- 
tom, and it is a necessary condition for the effective operation 
of electrical convection that the solid particles in question should 
remain in suspension. 

Obviously then in order to test this matter we must ar- 
range experiments in such a way that the dead Paramecia shall 
remain for some considerable time suspended. This is easily 
done by placing them in a vertical tube, or by placing the slide 
bearing the Paramecia in a vertical position. The electrodes 
are then introduced at the upper and lower ends of the tube or 
preparation. The Paramecia sink slowly through the water, 
and thus remain a long time suspended, not being in contact 
with any solid objects till they reach the bottom. 

With living specimens under these conditions the reactions 
are identical with those in horizontal preparations. If a weak 
current is used, the Paramecia hasten to the cathode, both when 
this is at the upper, and when it is at the lower end of the tube. 
If a stronger current is used, and the upper end of the prepa- 
ration is made the anode, the infusoria swim backward against 
the pull of the gravity to the anode, at the upper end. With 
lifeless Paramecia on the other hand no such effects are pro- 
duced. The dead animals simply sink steadily, whatever the 
strength of the current, in spite of electrical convection toward 
cathode or anode. 

Thus whatever it is that causes the Paramecia to move 


496 Journal of Comparative Neurology and Psychology. 


backward to the anode in a strong current is competent to lift 
the animals against the force of gravity. The electrical con- 
vection is not competent to produce this result. It is therefore 
evident that the electrical convection is not the essential agent 
in producing the movement of Paramecium backward to the 
anode. The observations previously detailed show clearly what 
zs the agent producing this result. 

BiRUKOFF (1899) held even that the usual movement to 
the cathode was produced by the cataphoric effect, or electrical 
convection. This had of course been disproved long before 
the paper of BrRUKOFF was written. As an additional disproof, 
we may note that the experiments just described show that the 
electrical convection is not competent to produce the effect ob- 
served in the movement to either cathode or anode. It is to 
the movements of the cela brought about by the electric current 
that we must turn for the real factors producing the movements 
to cathode or anode. 

Relations between Contact Reaction and Reaction to Elec- 
tric Current.—In a previous paper (1897) I described what I 
called an interference between the contact reaction (‘‘thigmotax- 
is’) and the reaction to the electric current, and in a later paper 
Pitrer (1900) considerably extended our knowledge of the 
phenomena in question. The interference described consisted, 
so far as Paramecium is concerned, essentially in the fact that 
specimens showing the contact reaction respond less readily to 
the electric current than do free specimens, and the response, 
when it occurs, is intermittent. For Stylonychia, PUrrerR held 
that a further effect was evident, in the fact that thigmo- 
tactic specimens take up a transverse position with respect to 
the electric current, while the free specimens swim directly to 
the cathode. 

I wish to bring out here certain further points in’regard to 
the interference between the contact reaction and the reaction 
to the electric current. These are the following : 

1. In my previous paper I described this interference only 
for the case of Paramecia in contact with a mass of detritus. 
But the Paramecium need not be in contact with such a mass in 


Jenninos, Behavior of Paramecium. 497 


order to show the interference described. It occurs also when 
the animals are in contact with a clean glass surface, or the 
surface film of water. This is particularly evident when the 
Paramecia are subjected to a moderately strong current on the 
slide in a thin layer of water, without a cover. They swim as 
usual toward the cathode. But when a specimen in its spiral 
course comes against the glass slide or the surface film, it at 
once stops. It may stop only an instant, or it may remain at 
rest for some time; or it may show certain peculiar movements, 
to be described later. 

2. The effect of thigmotaxis appears not merely in a de- 
crease in sensitiveness to to the current, but in a change in the 
method of reaction to the current. PUTTER (1900) showed that 
in various Hypotricha individuals in contact with a surface take, 
in the current, a nearly transverse position with the left side 
(bearing the peristome) to the cathode, while free swimming in- 
dividuals become oriented with anterior end to the cathode. 
Similar relations are to be obser- 
ved in Paramecium, though less 
frequently than in the Hypotri- 
cha, because Paramecium its less 
often in contact with the surface. 
But when a large number of 
individuals are subjected to the 


current in a thin layer of water 
Fon Aaianeverse” of Sbliqué (with or without a cover glass), 
orientation of Paramecium to the the phenomena are evident. 
electric current when in contact with The free specimens swim as 
aruince: usual, with anterior ends to the 
cathode. Those that come in contact with the surface film or 
the glass, stop, as described above. If they do not quickly re- 
sume the forward course, they soon take up a position nearly 
transverse to the current, with the oral side or peristome direct- 
ed toward the cathode (Fig. 17). In this position they may 
either remain quiet, or may move forward transversely (or ob- 
liquely) to the current, keeping in contact with the surface. 


The effective beat of the cilia, as determined by the movements 


498 Journal of Comparative Neurology and Psychology. 


of the particles of India ink, is now everywhere backward, save 
in the oral groove, where it is usually forward. though at inter- 
vals it here passes backward for a moment. 

If while in this position the direction of the current is re- 
versed, so that the oral surface is toward the anode, the oral 
cilia strike strongly backward. This has one of two effects. 
Sometimes it causes the animal to be detached from the surface ; 
in this case it turns toward the aboral side until the anterior end 
is directed to the cathode, then it swims forward in that direc- 
tion, like other free swimming specimens Or the animal may still 
remain in contact with the surface; in this case it turns toward 
the aboral side, until the peristome or oral surface is again di- 
rected toward the cathode. Then it remains quiet, or resumes 
its forward movement transverse to the current In cultures 
where the specimens are much inclined to be thigmotactic, one 
often observes in this way marked transverse electrotaxis in a 
large number of individuals; by repeatedly reversing the cur- 
rent they can be driven from one side of the preparation to the 
other and back again, always transversely or obliquely to the 
current. 

ROESLE (1902) observed that Paramecium reacts much 
more readily to induction shocks when the peristome is directed 
toward the anode than in other positions. ROESLE interprets 
this as showing that the peristome is more sensitive than other 
parts of the body surface. While this conclusion is @ priori 
very probable, I am not sure that the facts cited really demon- 
strate it. When the constant current is made, the animal lying 
against a surface with peristome to the cathode, there is a reac- 
tion, which is, however, ineffective in causing a movement of 
the animal’s body. The reaction consists in a weak reversal of 
stroke of the oral cilia, as is shown by the forward movement 
of the particles of India ink in the oral groove. This forward 
stroke of the oral cilia has very little locomotor effect, 
and does not overcome the attachment of the animal to 
the surface; it could not be observed without the presence of 
the particles of India ink. It is possible that this reaction oc- 
curs also with induction shocks, and escaped observation, owing 


Jennincs, Behavior of Paramecium. 499 


to the fact that RoESLE used no method of rendering the cur- 
rents visible. When the circuit is closed with the peristome to 
the anode, on the other hand, the oral cilia strike strongly 
backward, and this has a powerful locomotor effect, driving the 
animal forward, or, if the current continues, turning it toward 
the aboral side. RorEsLE’s observations are then fully explica- 
ble on the basis of the known action of the current on the cilia, 
as described first by LupLorr, together with the stronger loco- 
motor effect of the oral cilia when striking backward, a difference 
that is evident in many ways. I must then agree with the con- 
clusion of STATKEWITSCH (1903), reached on other grounds, 
that the results of RoEsLE do not demonstrate the greater sen- 
sitiveness of the peristome. 

Thus we find under certain circumstances a ‘‘transverse 
electrotaxis’” of Paramecium under the action of the constant 
current, as in many other infusoria. This transverse orienta- 
tion is of course of an entirely different character from that ob- 
tained by STATKEWITSCH (1903 a, pp. 24-32), with rapidly 
alternating currents. 

3. Ina strong electric current the contact reaction causes 
not merely a stoppage of the forward course, but actual swim- 
ming backward. If the Paramecia are in athin layer of water, 
through which a rather strong current is passed, all the speci- 
mens that are not in contact with upper and lower surfaces 
swim forward, in the somewhat cramped manner, as if against 
resistance, that is characteristic of the swimming in a strong 
current. But when a specimen comes in contact with the glass 
surface below or the surface film above, it begins to swim back- 
ward. This may last for but an instant, while the accidental 
contact continues, or if the animal remains in contact the back- 
ward swimming continues a long time. If a very thin layer of 
water is used, so that the Paramecia can hardly avoid coming 
in contact with a surface, most of them swim backward, though 
as soon as a specimen becomes free from the surface, it darts 
forward. With a slightly thicker layer of water, often about 
half the individuals are free and swim forward, while the other 
half are in contact and swim backward. The same individual 


500 Journal of Comparative Neurology and Psychology. 


may alternate frequently in the direction of swimming, accord- 
ing as it comes in contact with the surface, or becomes free 
from it. To obtain these results in a sharply defined way, it is 
necessary to vary the strength of current until exactly the 
proper intensity is found. 

The cause of this peculiar effect of contact seems to be as 
follows: PUTreR (1900) has shown that one effect of the con- 
tact reaction is to cause the cilia of the region posterior to the 
place of contact to cease effective action. In the strong cur- 
rent the cilia of the anterior half of the body tend to drive the 
animal backward, while the posterior cilia force it forward; the 
latter are a little the more effective, so that the animal on the 
whole moves forward. Inthe spiral course the body, swerv- 
ing toward the aboral side, comes in contact with the surface 
at about its middle. Thereupon, in accordance with the ob- 
servation of PUTTER, above mentioned, the cilia behind this 
spot, driving the animal forward, cease to beat, while the cilia 
in front of this spot, driving it backward, continue their action. 
Hence the anterior cilia now gain the upper hand, forcing the 
animal backward. 

In his recent valuable papers (1903, pp. 46-47; 1903 a, 
pp. 46-56), STATKEWITSCH maintains that there is no real in- 
terference between the contact reaction and the reaction to the 
electric current, but that the animal in contact with a solid is 
reached only by a weaker current than the free swimming indi- 
viduals, hence it reacts less markedly. Animals showing the con- 
tact reaction are usually in contact with a heap of detritus; 
STATKEWITSCH holds that the electric current divides, a portion of 
greater intensity passing through the water, a weaker portion 
through the heap of detritus and the Paramecium. 

This simple physical theory would of course be very satis- 
factory if it explained the observed facts, but this it does not 
do. It is based on the assumptions (1) that the so-called inter- 
ference is shown only when the animal is in contact with a heap 
of detritus; (2) that the interference appears only as a 
weakening of the reaction, not asa change in its character. 
Both of these assumptions, as I have shown above, are 


Jennincs, Behavior of Paramecium. SOL 


incorrect. As to the first one, the Paramecia, as we have seen, 
show the interference described even when the animal is in con- 
tact only with a clean glass surface, or with the surface film of 
the water. It is evident that this cannot be explained as due 
to the dividing of the current and the passage of a weaker por- 
tion through the object with which the animal is in contact. 
STATKEWITSCH’S observations on this phenomen (1903 a, pp. 
45-52) were made only on individuals in contact with a bit of 
detritus, and he assumes that this is a necessary condition for 
the production of the supposed interference. 

As the second assumption mentioned, I have shown above 
that the contact reaction produces not a mere weakening of the 
effect of the electric current, but actual changes of a most de- 
cided character in the way the reaction occurs. Paramecia 
in contact with a glass surface or the surface film take up a 
transverse position, or move backward, in the same current 
which produces forward movement in free swimming specimens. 
These effects cannot possibly be explained as due to the divid- 
ing of the current into weaker and stronger portions, as sup- 
posed by STATKEWITSCH. 

PUTTER (1900) had already set forth that in Stylonychia 
the contact reaction has the effect of producing a transverse 
orientation in the electric current. STATKEWITSCH, however, 
tries to show that this transverse orientation is merely the effect 
of a weak current. But when one examines attentively his 
evidence for this (1903 @, pp. 43-44) it seems apparent that all 
the specimens which showed transverse orientation were in con- 
tact with a surface, and he does not mention the existence of 
transverse orientation in free swimming specimens. Thus his 
results are equally well explained on PUTTER’s view that the 
transverse orientation is due to the contact reaction. In Para- 
mecium STATKEWITSCH expressly states repeatedly (for exam- 
ple, 1903 a, p. 57) that the effect of the weak current is to cause 
movement toward the cathode, and he never in his extensive 
and thorough study of the reaction of Paramecium to electric- 
ity observed transverse orientation to the constant current. The 
transverse orientation of Paramecia that are in contact, described 


502 Journal of Comparative Neurology and Psychology. 


above, cannot then be accounted for as due to the weakening 
of the current affecting them. This is true a fortorz of the 
swimming backward of individuals that come in contact with a_ 
surface, for such swimming backward occurs under other condi- 
tions only in stronger, not in weaker, currents. There is no 
escape from the conclusion that the contact reaction interferes 
with and modifies in a striking manner the reaction to the elec- 
tric current. 

STATKEWITSCH’S view that the supposed interference be- 
tween the effects of the two stimuli is to be explained in the 
simple physical way he sets forth seems based largely on an a pri- 
ort conviction that the electric current est always produce the 
same reaction when it acts upon the same organism with the 
same strength (see for example STATKEWITSCH, 1903, p. 46). 
This conviction appears in a most curious way in his attempts 
to demonstrate the correctness of his view. In his earlier pa- 
per (1903, p. 47) he promises to demonstate in his final paper 
that the supposed’ interference. does not exist, but is to be ex- 
plained by the division of the current, in the way above set 
forth. In the final paper this promised demonstration takes 
the following form:  ‘‘For demonstration of this condition it is 
not necessary to search out any methods of registration ; for 
this purpose the very objects on which we are experimenting 
can serve most excellently ; a more sensitive galvanometer than 
Paramecium, indeed, one need not demand. Its reactions to 
the current present unchanging. definite phenomena, taking 
place in accordance with law, dependent on the strength of the 
acting current. The orientation with relation to the cathode, 
the increase in the rapidity of progression up to a definite limit, 
the changes in the form of the body—all these appear at a 
definite intensity of the current, which demonstrates in an im- 
mediate way that through the bit of detritus andthe protist at- 
tached to it passes a current of less intensity than in the neigh- 
boring fluid, where the reactions of the infusoria are more pro- 
nounced”’ (1903 @, p. 55, translation). Now, the question at 
issue was whether the electric current of a given strength does 
as a matter of fact always produce the same reaction on the 


JENNINGS, Behavior of Paramecium. 503 


‘same organism, as STATKEWITSCH holds, or whether on the con- 
trary the contact reaction may interfere with it, as set forth by 
PUTrER and myself. In attempting to demonstrate the former 
alternative in the. manner given above, I submit that SraTKe- 
WITSCH merely assumes its truth, and uses this assumption for 
disproving the second alternative—after which disproof the first 
alternative of course emerges triumphant. We have herea 
clear case of reasoning in a circle. 

The general fact that the reaction toa certain defined stim- 
ulus may be modified by the reaction of the organism to other stim- 
uli, present or past, is perfectly well established for the behavior 
of lower organisms. Ina recent paper (1904, a) I have devel- 
oped this point in detail, and have adduced many examples 
from the reactions of the Ciliata. The contact reaction is espe- 
cially effective in modifying the reactions to other stimuli. This 
appears in the reactions to many agents besides electricity. 
PUTTER (1900) has shown that the contact reaction interferes 
largely with the reaction to heat, a result which I have con- 
firmed, especially for Stentor. I have often observed that the 
contact reaction inhibits to a large degree the reaction to me- 
chanical shock. Paramecia and other infusoria when free swim- 
ming react strongly to a light touch with a glass point at the 
anterior end, giving the ‘‘avoiding reaction” in a pronounced 
form. But when thigmotactic they often do not respond at all 
to such a touch. Again, attached specimens of Stentor caeru- 
lus do not react to light in any way, while unattached individu- 
als react decidedly (JENNINGS, 1904). STATKEWITSCH surely 
cannot expect us to take seriously in opposition to such well 
defined facts his objection that the concept of the contact reac- 
tion is indefinite, and that we cannot measure its effect (1903 a, 
p. 56). The effect of the contact reaction on the cilia has been 
described in a perfectly definite way by, PUrrER (1900) and by 
myself (1897), and we certainly cannot be asked to shut our 
eyes to the existence of such striking phenomena because no 
one has devised means of measuring them. 

Irregularities in the Reaction to the Electric Current.— 
There are certain irregularities in the reaction to the electric 


504 Journal of Comparative Neurology and Psychology. 


current that deserve mention. First, one often observes that 
while most of the specimens in a preparation are reacting pre- 
cisely and strongly, a few specimens do not react at all, swim- 
ming about at random. Second, one at times observes single 
specimens that swim toward the anode, while all the others go 
toward the cathode. This is most likely to be observed after 
the current has been reversed several times, though it is some- 
times seen at the beginning of the experiment. After repeated 
reversal of the current, one sometimes makes the following ob- 
servation. A specimen is oriented and swimming toward the 
cathode; on reversal of the current it retains its orienta- 
tion and continues to swim forward—now of course toward the 
anode. <A third very peculiar irregularity that is less unusual 
than the others is the following. Ina ratner strong current the 
animals are swimming slowly and in a rather cramped way to- 
ward the cathode. Now the current ts reversed, whereupon, 
without .turning around, they swim rapidly backward to the 
cathode. By repeatedly reversing the current, the animals may 
sometimes be caused to alternate several times, first swimming 
forward, then backward, retaining throughout the same posi- 
tion. But usually after swimming backward a short time to- 
ward the cathode, the animal turns around and swims to the 
cathode in the usual way. All these irregularities are so com- 
paratively unusual that I have not been able to determine pre 
cisely the nature of the ciliary movements. 
Reaction of Paramecia to Electricity when in Solutions of 
Chemicals. —GREELEY (1903) has recently raised anew the ques- 
tion as to the significance of certain peculiarities of the reaction 
to the electric current when the animals are in solutions of cer- 
tain chemicals. He points out that in acid solutions Paramecia 
move to the anode, whereas, under usual conditions, where the 
solution is alkaline or neutral, they move to the cathode. This 
he attempts to bring into relation with the observations of Lir- 
LIE (3903), who shows that cell constituents containing much 
nucleic acid migrate to the anode as an effect of electrical con- 
vection, and that the tendency to migrate to the anode decreases. 
with the decrease in acidity. In this way we seem to be on. 


Jennines, Behavior of Paramecium. 505 


the road to a direct physical explanation of electrotaxis. In 
criticism of the views of GREELEY, so far as hitherto brought 
out, the following must be said : 

1. All thorough work thus far shows that the essential 
point in the reaction to the electric current is the method in 
which the current affects the cilia. No attempt has been made 
to show how the known effects on the cilia could be produced 
through the factors emphasized by GREELEY, and it would un- 
doubtedly be difficult or impossible to bring the two into relation. 

2. The movement toward the anode is not limited to acid 
solutions, but is known to take place in a still’ more striking 
way in various salt solutions, especially in a solution of sodium 
chloride. I have observed it even in a solution of sodium bicar- 
bonate, having of course an alkaline reaction. 

3. The movement to the anode in such solutions is back- 
ward. It has been so described by Lorpand Buncerr (1897, p. 
532), by PUTTER (1900, p. 297), and so far as I am aware, by 
every one who has described it carefully, and I can myself con- 
firm this fact. The organisms thus become oriented in the same 
manner, with anterior end to the cathode, as under usual con- 
ditions. Further, these same solutions produce backward swim- 
ming even without the use of the electric current. We have 
then all the existing features of the reaction fully accounted for 
without taking into consideration the factor considered essential 
by GREELEY. The electric current taken by itself accounts for 
the orientation in the usual way; the chemical stimulation 
taken by itself accounts for the swimming backward; the com- 
bination of the two accounts for the swimming backward to 
the anode. 

4. The swimming to the anode continues only as long as 
the chemical stimulation exists. As soon as the organism has 
had time to become acclimatized to the chemical, z¢ swzms as 
usual to the cathode. This has been shown by PUTTER (1900), 
and by STATKEWITSCH (1903 a), andI can confirm it. Often it is 
but a few moments that the swimming backward to the anode 
continues. 


In view of all these facts, it cannot be held on the evi- 


506 Journal of Comparative Neurology and Psychology. 


dence thus far brought forth, that the phenomena observed in 
acid solutions, as described by GREELEY (1903), have any spe- 
cial significance for the theory of electrotaxis, such as that au- 
thor assumes. The known facts point to the following general 
statement of the phenomena. Immersion in chemicals, of vari- 
ous characters, causes the organism to swim backward. If at 
this time the Paramecia are subjected to the electric current, 
they continue to swim backward, and, becoming oriented, there- 
fore pass to the anode. This movement to the anode ceases as 
soon as the stimulating action of the chemical ceases. 

In order to make out a case for the theory advanced by 
GREELEY, it will be necessary to show clearly that this general 
statement is incorrect.' 


IV. PRESENT POSITION OF INVESTIGATION OF THE BEHAVIOR 
OF PARAMECIUM. 


I believe it may be said that we are now able to make a 
general, qualitative survey of the chief facts and factors in the 
behavior of this representative of the unicellular animals. There 
are doubtless still some dark points; the reaction to the electric 
current, for example, is still hard to place in the general scheme 
of behavior, though recent researches have gone far toward 
clearing up this matter. But it is true that we know, ina 
general way, most of the chief methods of action of this ani- 
mal, and the way in which these are affected by the chief classes 
of external conditions. There still remains the investigation of 
the intimate physiological processes underlying the gross fea- 
tures of the reactions, and especially the quantitative study of 
the phenomena which the qualitative examination has brought 
out. Our present knowledge, then, amounts to a preliminary 
survey, showing us in the gross the phenomena which require 
investigation in detail. Attempted quantitative study of 
phenomena of which the qualitative, purely descriptive, features 


' Since the above was written, GREELEY’s final paper has appeared (Avo/. 
Bull., Vol. 7, pp. 3-32). It raises many interesting questions, which I hope to 
touch upan later. (Note added during correction of proof.) 


Jennincs, Behavior of Paramecium. 507 


are uncertain, is likely to be misleading and worthless; this has 
been too often illustrated in the investigations on the reactions 
of unicellular animals. We cannot measure things till we at 
least know what we are measuring ; if we attempt it our results 
have only the appearance of accuracy, and are likely to fall to 
the ground as soon as the qualitative’ nature of the phenomena 
is worked out and found to be different from what we had as- 
sumed. It is for this reason that the present writer has limited 
himself thus far almost entirely to qualitative work. Now that 
the qualitative survey has been made, I believe that if its re- 
sults are held clearly in mind, quantitative work can be done 
with some hope of understanding the significance of the data 
which our measurements bring out. But in view of the pecu- 
liar and complicated action system of Paramecium, quantitative 
results will always have to be interpreted with the greatest care, 
and it must be realized that that method of investigation which 
examines only the beginning and end of an experiment, with- 
out troubling itself as to what the organism does in the mean- 
time, is likely to be most misleading, Further, in view of the 
peculiar character of the action system of Paramecium, and the 
large part it plays in determining the behavior under stimula- 
tion, the utmost caution is necessary in transferring the 
conclusions obtained with this animal to other organisms having 
a different action system. 


The work on which the present paper is based was done 
at the Naples Zoological Station while the author was a Re- 
search Assistant of the Carnegie Institution of Washington. It 
is a pleasure to acknowledge my indebtedness to the Carnegie 
Institution for making the work possible, and for permission to 
publish the present paper. 

Pozzuoli, Italy. April 26, 1904. 


508 Journal of Comparative Neurology and Psychology. 


LITERATURE CITED. 


Birukoff, B. 
1899. Untersuchungen iiber Galvanotaxis. Arch. f. d. ges. Physiol., Bd. 
LXXVII, pp. 555-585. 
Biitschli, O. 
1889. Protozoa. III. Abth. Infusoria. Bronn’s Klassen und Ordnungen 
des Thierreichs, Erster Band. 
Dale, H. H. 
1901. Galvanotaxis and Chemotaxis of Ciliate Infusoria. Part I. Journ. 
of Physiol., Vol. XXVI, pp. 291-361. 
Davenport, C. B. 
1897. Experimental Morphology, Vol. I, 280 pp. Mew York. 
Greeley, A. W. 
1903. The Reactions of Paramecia and other Protozoa to Chemical and 
Electrical Stimuli. Sczence, Vol. XVII, pp. 980-982. 
Hobhouse, L. T. 
1g0l. Mind in Evolution. 415 pp. London. 
Jennings, H. S. 
1897. Studies on Reactions to Stimuli in Unicellular Organisms. I. 
Reactions to Chemical, Osmotic and Mechanical Stimuli in the 
Ciliate Infusoria. Journ. of Physiol., Vol. XXI, pp. 258-322. 
1899. Studies, etc., Il. The Mechanism of the Motor Reactions of Par- 
amecium. Amer. Journ. Physrol., Vol. 11, pp. 311-341. 
1899a. The Behavior of Unicellular Organisms. Biol. Lectures from 
the Marine Biol. Lab. at Woods Hole, for 1899, pp. 93-112. 
1909. Studies, etc., V. On the Movements and Motor Reflexes of the 
Flagellata and Ciliata. Amer. Journ. Physiol., Vol. III, pp. 
229-260. 
1902. Studies, ete., IX. Onthe Behavior of Fixed Infusoria (Stentor 
and Vorticella), with special Reference to the Modifiability of 
Protozoan Reactions. Amer. Journ. Physiol., Vol. VIII, pp. 
23-60. 
1904. Reactions to Light in Ciliates and Flagellates. Contributions to 
the Study of the Behavior of Lower Organisms, Second Paper, 
pp. 29-71. Publications of the Carnegie Institution, No. 16, 
Washington, D. C. 
1904a. Physiological States as Determining Factors in the Behavior of 
Lower Organisms, /é7d., Fifth Paper, pp. 109-127. 
19044. The Method of Trial and Error in the Behavior of Lower Organ- 
isms. J/é¢d, Seventh Paper, pp. 235-252. 
Jennings, H. S. and Jamieson, Clara. 
1902. Studies, etc., X. The Movements and Reactions of Pieces of Cil- 
iate Infusoria. 4zo/. Bull., Vol. III, pp. 225-234. 
Jensen, P. 
1893. Ueber den Geotropismus niederer Organismen. Arch. f. ad. ges. 
Phystol., Bd. LIII, pp. 428-480. 


Jenninos, Behavior of Paramecium. © 509 


Kofoid, C. A. 

1894. On Some Laws of Cleavage in Limax. Proc. Am. Acad. Arts and 

Scz., Vol. XXIX, pp. 180-202. 
Lillie, R. S. 

1903. On Differences in the Electrical Convection of Certain Free Cells 

and Nuclei. Amer. Journ. Physiol., Vol. VIII, pp. 273-283. 
Loeb, J. and Budgett, S. P. 

1897. Zur Theorie des Galvanotropismus. IV. Mittheilung. Ueber 
die Ausscheidung electropositiver Ionen an den ausseren Anoden- 
flache protoplasmatischer Gebilde als Ursache der Abweichungen 
vom Pfliiger’schen Erregungesetz. Arch. f. d. ges. Physiol., Bd. 
LXVI, pp. 518-534, Pl. 16. 

Ludloff, K. 

1895. Untersuchungen iiber den Galvanotropismus. drch. f. d. ges. 

Phystol., Bd. LIX, pp. 525-554. 
Massart, J. 

tgo1. Recherches sur les organismes inferieurs, IV. Le lancement des 
trichocystes (chez Paramecium aurelia). Bz’. Acad. roy. de 
Belgique, Classe des Sct., pp. 91-106. 

Moore, Anne. 
1903. Some Facts Concerning the Geotropic Gatherings of Paramecia. 
Amer. Journ. Phystol., Vol. 1X, pp. 238-244. 
Naegeli, C. 
1860. Rechts und Links. SAedtr. z. wiss. Botanik, Heft. 2, pp. 53-58. 
Pearl, R. 

1900. Studies on Electrotaxis. I. On the Reactions of certain Infusoria 
to the Electric Current. Amer. Journ. Phystol., Vol. IV, pp. 
96-123. 

Pfeffer, W. 
1904. Pflanzenphysiologie, zweiter Ausgabe, zweiter Band. 
Pitter, A. 

1900. Studien iiber Thigmotaxis bei Protisten. Arch. f. Anat.u. Physiol., 

Physiol. Abth., Supplementband, pp. 243-302. 
Roesle, E. 

1902. Die Reaktion einiger Infusorien auf einzelne Induktionsschlage. 

Zeitschr. f. Allg. Physiol., Bd. U1, pp. 139-168. 
Sosnowski, J. 

1899. Untersuchungen iiber die Veranderungen der Geotropismus bei 

Paramecium aurelia. Az//, Acad, Sct. Cracovie, pp. 130-136. 
Statkewitsch, P. 

1903. Ueber die Wirkung der Inductionsschlage auf einige Cillata. 
Le Physrologiste Russe, Vol. Ill, nr. 41-47, pp. 1-55. 

1903a. Galvanotropism and Galvanotaxis of Organisms. Part First. 
Galvanotropism and Galvanotaxis of Ciliate Infusoria. Disserta- 
tion. 160 pp. Moscow. (Russian). 

Thorndike, E. L. 

1898. Animal Intelligence. Psychological Review, Monograph Supple- 

ment, Vol. II, No. 4. 


510 Journal of Comparative Neurology and Psychology. 


Uexkiill, J. v. 
1903. Studien iiber den Tonus. I. Der biologische Bauplan von Sipun- 
culus nudus. Zettschr. f. Biol., Bd. XLIV, pp. 269-344. 
Wallengren, H. 
1902. Zur Kenntnis der Galvanotaxis. I. Die anodische Galvanotaxis. 
Zettschr. f. Allg. Phystol., Bd. Il, pp. 341-384, Pl. 11. 
1903. Zur Kenntnis der Galvanotaxis. II. Eine Analyse der Galvano- 
taxis bei Spirostomum. Zeztschr. f. Allg. PAystol., Bd. Il, pp- 


516-555. 


EDITORIAL: 


PHYSIOLOGY AND PSYCHOLOGY. 


The recognition in daily life as well as in scientific descrip- 
tion of two classes of reaction, the psychic and the non-psychic, 
is the basis of the separation of the science of organic functions 
into physiology and psychology. Without any assumptions as 
to the relations of consciousness to organic processes we may, 
and in fact constantly do, deal with the reactions of organisms 
according to certain characters which are commonly spoken of 
as indicative of automatism or intelligence. It is true that we 
can no more draw a sharp line between the psychic and the 
non-psychic in reaction than we can between the reflex and the 
instinctive. Certain aspects or relationships of reactions are so 
prominent as to furnish the basis of types. Modifiability in 
high degree is said to be a mark of the psychic, yet no one 
would deny that the non-psychic reaction is also modifiable. 
There is surely a difference of degree, but by whom and how is 
the point at which this characteristic passes from an indication 
of one type to that of the other to be fixed ? 

Some physiologists and psychologists have chosen ability 
to learn as the criterion of the psychic reaction, but 
this if used alone is evidently of limited and uncertain value, for 
all reactions, it is safe to assume, change with repetition; organ- 
isms profit by experience more or less rapidly. Thus far the 
critical point which those who have implicit faith in the applica- 
bility of this criterion necessarily posit—the point at which ability 
to learn appears as a distinctive character of the organism, or in, 
the light of the criterion, the point at which the psychic reaction 
appears in the animal series—has not been discovered. The 
important question is, Does such a critical point exist ? 


512 Journal of Comparative Neurology and Psychology. 


Few will venture to deny probability to the assumtion that 
modifability of reaction varies in degree, not in kind; yet, if 
ability to profit by experience is to be a satisfactory criterion 
of the psychic there must be either reference to a difference in 
kind of modifiability, “or the choice, by those who attempt to 
use the criterion, of an arbitrarily selected degree or rapidity 
of change in reaction as indicative of the transition from the 
non-psychic to the psychic. 

At this point there are at least two possibilities: either we 
may choose a certain standard of modifiableness as indicative of 
the psychic reaction, or we may seek for other characteristics 
in addition to modifiability as means of distinguishing the 
psychic from the non-psychic in organic reaction. That the 
latter alternative is the more desirable of the two all who have 
attempted to use the criterion of ability to profit by experience 
will grant more or less freely, according to their various preju- 
dices. 

Although the physiologist deals primarily with the non- 
psychic, he is no more able to ignore the psychic than is the 
chemist to avoid the use of physical concepts and terms, Similarly 
the psychologist is dependent upon the physiologist, and in turn 
upon the chemist and physicist, as is the physiologist himself. 
Granting validity and scientific value to the separation of reac- 
tions into the psychic and non-psychic, the existence of physi- 
ology and psychology as coordinate sciences needs no justifi- 
cation. Both are natural sciences; both deal with organic re- 
actions. From certain points of view the psychic reaction is 
more difficult of description than the non-psychic, but the same 
methods of investigation apply to the two classes of reaction. 
Physiologists and psychologists must cooperate in discovering, 
and must agree upon the distinguishing characteristics of the 
psychic and the non-psychic reaction. By mutual agreement 
they must fix the limits of their sciences. 

The most keenly felt need at present in the science of or- 
ganic reaction is for careful, detailed, patient, and extensive 
study of the forms and modifications of reaction. Whether 
physiologists or psychologists, we must know our materials 


Literary Notices. 513 


thoroughly before we can classify them or profitably consider 
their relations to the materials of allied sciences; in fact even 
before we can distinguish physiology from psychology in any 
accurate sense we must know the possible methods of classifica- 
tion of reaction, and be able, in the light of accurate and ex- 
tensive knowledge of the peculiarities and unimportant varia- 
tions of reactions as well as their fundamentally important differ- 
ences, to select as criteria those characters which are most con- 
stant and which taken together form the most valuable working 
basis for the sciences of reaction. 

There is a tendency among physiologists—among natural 
scientists generally—to look upon psychology with distrust, if 
not with indifference or scorn. The average German physiolo- : 
gist uses very different tones of voice for the ‘‘Physiolog’”’ and 
the ‘‘Psycholog.”’ Some of them apparently feel that psycho- 
ogy is too near akin to metaphysics to be a safe favorite for the 
natural scientist, while others are evidently satisfied in their own 
minds that the psychic is not and cannot be material of a natu- 
ral science. In America too there is a strong prejudice against 
psycnology, among the natural scientists especially, or, if not 
prejudice, there is a distrustful curiosity which makes the life of 
the truly scientific student of psychic reactions at-times un- 
pleasant. This general distrust and ridicule of psychology is 
doubtless due, first, to the fact that the naturalistic movement 
of the last century was accompanied by a wide speading and 
deep distrust of the speculative sciences of which psychology 
was then, and is still by many, reckoned as one; and second, 
perhaps almost as largely, to the semi-scientific and too often 
carelessly used methods of that new psychology which calied 
itself experimental. Even the honest and sincere defender of 
psychology, or of the possibilities of such a science, cannot 
deny that much work which has been placed upon record as 
experimental psychology is pure rot. But, admitting this with 
regret, he well may ask, What of the early stages in the devel- 
opment ofastronomy, of chemisty, of physics, of anthropology, 
of sociology? Natural sciences are not born to perfection of 
“method, they develop; and psychology is even now approach- 


514 Journal of Comparative Neurology and Psychology. 


ing a stage of development which will justify its recognition by 
the most timid, narrow, or prejudiced naturalist as an increas- 
ingly exact natural science. Sciences differ widely in degree 
of exactitude; at present, forexample, the biological sciences 
are far less exact than the physical, but one may reasonably 
argue that this is due to inherent difficulties in dealing with the 
materials rather than to the impossibility of applying exact 
methods. Psychology as a natural science, or rather psychology 
in so far as it is considered as anatural science, is in its infancy. 
As physiology gradually approaches the standard which physics 
has set for it, so psychology approaches, and will the more 
rapidly approach as those in allied fields recognize its progress, 
this same standard. 

For those of us who have at heart the establishment and 
advancement of comparative psychology as a science coordinate 
with physiology there is the clear duty to make our work emi- 
nently worthy of scientific recognition and reliance. Casting philo- 
sophical implications aside, so far as our scientific work is in ques- 
tion, we should apply ourselves to the study of psychic reactions 
with intent to place our knowledge of them ona level with or 
above that of the non-psychic as represented by the condition 
of present day physiology. In attempting to do this we should 
ever be willing and eager to take advantage of the assistance 
which the closely allied biological and less directly related phys- 
ical sciences can give us. ‘Speculative sciences have their 
place, but we shall accomplish most for the science of psychic 
reactions if we keep our metaphysical longings in the back- 
ground and strive ceaselessly for accurate and complete descrip- 
tions of the reactions with which we are concerned—reactions 
which are the most complex and interesting of biological phe- 
nomena. | ROBERT M. YERKES. 


CLARENCE LUTHER HERRICK 


We are called upon with the present issue of the Journal 
to lament the sad and untimely death of its founder and editor- 
in-chief at Socorro, New Mexico, on the 15th of September. 
For the past ten years, dating from his last connection with 
Denison University, he has struggled heroically against tuber- 
culosis of the lungs, together with other complications, which 
at last cut him off in the midst of his labors and in the prime 
of life. Untimely as his death must seem when regarded from the 
point of view of his plans and hopes, yet Dr. Herrick had 
done an amount of scientific research and philosophical writing, 
some of which he was preparing for the press when he was 
taken, which assures him an enduring name in the world of 
thought. 

The end came in accordance with his own most earnest 
wish—he fell fighting for the truth. As one of those who 
were near him when he passed away has said: ‘‘He was taken 
literally in the harness. His laboratory and study tables 
showed the unfinished tasks. His morning mail brought its 
usual load of duties. He had contributed an article to the 
September number of the dsmerican Geologist, and his mail on 
the morning of his death, brought a request from Dr. N. H. 
WINCHELL for some further contributions to the October num- 
ber. Thus in the midst of his labors he passed into the larger 
sphere.” 

Very early in his career he seems to have laid out, at least 
in a general way, a plan of action, including for the first part of 
his life miscellaneous research and study under direction in the 
broad field of general natural history. Upon the basis of this 
foundation, was to follow a period of intense specialization in a 
circumscribed field of zoological work leading up to a mastery 


516 Journal of Comparative Neurology and Psychology. 


of the anatomy and physiology of the nervous system. Finally 
the ripest years were to be devoted to physiological and com- 
parative psychology on the basis of the mechanics of the nerv- 
ous system and to philosophical correlation. 

His life may be roughly divided into four periods. While 
these were marked by extraneous events and were apparently 
purely artificial and arbitrary, yet it may be said that the ideal 
scheme was in the end fairly achieved, though with great devia- 
tion in the details of the working. 

Dr. HERRICK was born near Minneapolis, June 21, 1858. 
He grew up ina home far from neighbors, a solitary child 
with few playmates, and very early showed his bent as a natu- 
ralist. While still in the Minneapolis High School he collect- 
ed extensively and left at graduation a case of over a hundred 
mounted bird skins and other specimens to the high school. It 
was during this period that his father, despite his poverty, got 
him an eight dollar microscope. With this crude instrument 
and without guidance or library facilities he worked over the 
fresh water fauna of the neighboring brooks and pools so thor- 
oughly that before graduation from the University of Minne- 
sota in 1880 he had published several articles of value on the 
fresh water crustacea of Minnesota and four years after gradu- 
ation, with somewhat better facilities, published a report on the 
micro-crustacea of Minnesota, which is still standard. The 
materials for this report were elaborated before he graduated 
from college. 

These years were filled with many bitter struggles, not the 
least of which was with poverty and the consequent lack of 
material for study. But, notwithstanding, he completed the 
college course in three years, at the same time partly sup- 
porting himself by assisting on the staff of the Geological 
and Natural History Survey of Minnesota. He had also showed 
so obvious a native gift with his pencil that upon his graduation 
the president of the university said to his father that he was 
uncertain whether to advise the young man to devote his life 
to science or to art. But there was no uncertainty in the mind 
of the graduate. Continuing his work on the Geological and 


Clarence Luther Flerrick. . 517. 


Natural History Survey of Minnesota, he published many pa- 
pers in rapid succession on the fauna of the state and began an 
extensive report, the first volume of which was completed in 
1885. This was a Jarge quarto on the Mammals of Minnesota, 
fully illustrated with many colored plates and pen drawings. 
It was accepted for publication, but for lack of funds in the 
Survey never saw the light. Years afterwards, in 1892, a small 
octavo was published by the Survey made up of the more pop- 
ular parts of this work. The remainder is still buried in the 
vaults of the Survey in Minneapolis. The season of 1881-2 
was spent at the University of Leipzig, and in 1883 he was 
married to Miss Alice Keith of Minneapolis. This, roughly, 
may be said to constitute the first period of his life, from 1858 
to 1884. 

He was called tothe chair of Geology and Natural History 
of Denison University in the summer of 1884. He spent the 
fall of that year at Denison, then returned to Minneapolis to 
complete the work in progress in the Minnesota Survey, and in 
the fall of 1885 moved with his family to Granville. Meanwhile, 
in 1885, he took the degree of M.S. from his alma mater. It had 
been his intention to continue his zoological work, and there 
was great activity in this line during the entire period, but the 
routine excursions made in the course of the instruction of his 
geology classes showed him so much of interest in the local 
strata that his chief labors while in Granville were upon the 
fossils and stratigraphy of the Waverly free stones and_ shales 
of Ohio. This work was abruptly cut short by his removal 
from Granville in 188g and, while never rounded out as he 
would have liked, is probably his most important geological 
work. In 1885 he founded the Bulletin of the Scientific La- 
boratories of Denison University, in which the greater part of 
his researches, and those of his pupils, on Ohio geology were 
published. 

His phenomenal success as a teacher during this and the 
subsequent periods was due to factors, some of which are easily 
seen—others are harder to define. After his attractive personal 
qualities and magnetic enthusiasm, I should place his deep philo- 


518 Journal of Comparative Neurology and Psychology. 


sophic insight and the fearless way in which he disclosed his 
profoundest thinking to the least initiated of his pupils. The 
ability to do this without befogging the air was an exceedingly 
rare gift and was stimulating even to a dullard. He knew the 
philosophical classics thoroughly from original sources and the 
trend of his thinking was very early foreshadowed in the trans- 
lation of Lorzr’s Outlines of Psychology published in 1885 in 
Minneapolis, with his own appended chapter on the structure of 
the nervous system. 

Upon his removal to the University of Cincinnati in 1889, 
with which the third period of his life may be said to begin, 
the geological studies with which the preceding five years had 
been so fully occupied were summarily brought to a close and 
he threw himself with renewed energy into the study of the 
nervous system. Extensive papers on the brains of different 
animals appeared in rapid succession, of which the most valu- 
able are two series, one on the brains of various fishes, the 
other on those of reptiles. In 1891 the Journal of Comparative 
Neurology was founded and served as the medium of publication 
for most of these researches. The founding of this Journal 
can best be designated as a piece of characteristic audacity. It 
was a purely private enterprise, with no fund to defray the ex- 
penses and very little outside cooperation promised. But with- 
out counting the cost he plunged boldly in, expecting a con- 
stiuency to be developed as the work went on. In this he has 
not been disappointed, though recognition of financial needs has 
lagged sadly behind that of the scientific value of the Journal. 

At the close of 1891 he resigned his chair in the Univer- 
sity of Cincinnati to accept a chair of biology in the University 
of Chicago, then being reorganized. The early part of 1892 
was spent in Europe, chiefly Berlin. Upon his return the ad- 
justment at the University of Chicago presented unexpected 
difficulties and after a series of misunderstandings he finally 
withdrew from that institution, declining an offer to return to 
Germany for further study on full salary. He was im- 
mediately elected to his old post in Denison University with 
an assistant and the privilege of devoting only a part of his 


Clarence Luther Hlerrick. 519 


time to teaching, the remainder, either at home or abroad, to 
the further prosecution of his research. A year and a half of 
great productiveness followed. He bought a small tract of land 
adjacent to the college campus, built a residence upon it and 
planned to devote the remainder of his days to breeding animals 
on an extensive scale and studying the laws of heredity, com- 
parative psychology and allied problems. But before this pro- 
ject was fully under way his health broke down completely and 
he was forced to abandon his home in the fight for life. 

In December, 1893, he had a severe attack of la grippe, 
but, as was his custom in illness, went on with his work as 
usual. Upon completion of the last examination of the term 
he came home too ill'to correct the papers, and in course of 
the following night was attacked by a severe hemorrhage from 
the lungs and for weeks his life hung in the balance. With 
the return of spring his strength increased sufficiently to enable 
him to remove to New Mexico, where the local physicans told 
him that he had a fighting chance for a few years. He accept- 
ed the challenge bravely and for more than ten years held the 
disease in check. During the spring of 1894 his college dedi- 
cated the Barney Science Hall, which had been built largely un- 
der the stimulus of his presence in the faculty; but he was never 
permitted to work in it. 

The fourth period, from 1894 to 1904, covers the remain- 
ing years of his life. 

This decade, filled with bodily pain and the worse torture 
of anxiety and mental unrest, is yet one of the most productive 
periods of his life. Much of the time was spent in the open 
with covered wagon and camp kit, and with the return of 
strength scientific interests again absorbed his attention. Nat- 
urally in this case he again turned to geology and an extensive 
series of articles on the geology of New Mexico bears testi- 
mony to the industry of these apparently aimless wanderings. 
The first scientific work done in the Territory, however, was a 
revision of his earliest important work, the Crustacea of Minne- 
sota. As soon as his geological knowledge became known his 
services were in demand as a mining expert and during the later 


520 Journal of Comparative Neurology and Psychology. 


years of his life in the Territory he supported himself and his 
family chiefly by practicing this profession as strength permitted. 
In 1898 he took the degree of Ph.D. from the University of 
Minnesota. For four years (1897-1901) he was president of the 
territorial university at Albuquerque, though at the close of the 
third year it became evident that the strain of the executive work 
and confinement were too hard for him, and the connection dur- 
ing the fourth year was mainly one of supervision and general 
control. 

During his last year there was an obvious failing of physi- 
cal strength, so that long field trips had to be abandoned. But 
the more quiet life gave opportunity for a thorough recasting 
of many questions and formulation of matters which had been 
in his mind all his life. So that before his death much of 
the philosophical correlation, of which mention has been 
made, was effected. A number of articles have already 
been published in the philosophical serials bearing on these 
matters and there is a considerable collection of MSS. remain- 
ing, much of which can doubtless be edited for publication. 
It is gratifying to know that he had the satisfaction of seeing 
this work so well rounded out before his death and that the 
latest months of his life were much more restful than those pre- 
ceding, some of which were marked by extreme suffering. He 
continued in about the usual health until September 8, when 
he again had a series of uncontrollable hemorrhages, daily be- 
coming weaker until on the morning of the 15th he peacefully 
passed away. 

One essential feature of his success must receive mention 
here—the devoted heroism of his wife. His work was always. 
stimulated by her interest and cooperation; but during the last 
decade his life was unquestionably preserved by her self-sacri- 
ficing care. She often accompanied him for weeks on wagon 
trips far from settlements in order to see that he had proper 
food and comforts, sometimes enduring severe hardships and 
sacrificing her own health for his welfare. 

So much for a brief sketch of Professor HEkkRIck’s life. 
Of his relation to the various institutions with which he was. 


Clarence Luther Flerrtck. 521 


connected and the great stimulus which he gave to education 
by his connection with them, an account will be given in other 
biographical notices soon to appear in the Bulletin of the Sci- 
entific Laboratories of Denison University, which he founded. 
It remains here to say something of Dr. Herrick, first, as an 
investigator and thinker, and secondly, as a teacher and as a 
man. 

In estimating the character of his work it is difficult to say 
whether he was primarily an investigator or a philosopher. 
And this is to his great credit for he combined in a remarkable 
degree the qualifications of an expert in both of these lines. 
He had at once acute perceptions, and keen insight for scientific 
details, and a broad philosophic horizon and perspective which 
peculiarly fitted him for the work he undertook of throwing 
light upon the nature of consciousness from the neurological 
side. A glance at the appended bibliography will show that a 
philosophic scope as well as a scientific specialization character- 
ized all his work. 

His work in every line was extremely suggestive, and it 
should be added, seldom exhaustive, though certain of his neu- 
rological and geological papers reveal his power of accurate 
and detailed research. But his thought ever was moving for- 
ward, and he was impatient of the routine details which would 
put any check upon his richly developing insight. 

His scientific labors fall in three states—Minnesota, Ohio, 
and New Mexico. Of his work in geology during the first and 
second periods of his life we have already spoken. His neuro- 
logical work was done mostly during the second and third peri- 
ods, while connected with the University of Cincinnati and 
with Denison University. 

The first contribution in neurology was the elementary 
chapter on the nervous system appended to the translation of 
Lorze’s Outlines of Psychology, published in Minneapolis, in 
1885. This is significant not so much for its content (though 
here the dynamic point of view is dominant) as for its context. 
The juxtaposition, in a manual designed for an elementary text- 


522 Journal of Comparative Neurology and Psychology. 


book, of Lorze’s lectures and original lectures on the mechan- 
ism of the brain was a decided novelty in those days. 

In 1889 he began work in earnest on the nervous system 
and immediately there appeared a series of papers in rapid suc- 
cession, some of great length and others mere jottings. The 
first long paper was published with Professor W. G. Ticur in 
the Denison University Bulletin in 1890, and was entitled ‘:The 
Central Nervous System of Rodents.’’ This paper contains. 
nineteen double plates and a vast amount of observation; and 
was designed as a preliminary survey of the field, the plates to 
form the basis of further detailed observations and correlation. 
But he soon became convinced that this correlation could best 
be attempted after a thorough study of several types of lower 
brains and the series was interrupted. Atthe time of his break- 
down in 1894 he was just about to take up again by the degen- 
eration methods a more thorough study of the mammalian 
brain. Thus this rodent paper stands now as an unfinished 
fragment. 

This, however, illustrates well his plan of work, a plan 
which must be clearly understood in order to put a proper esti- 
mate on his published researches. He found correlation im- 
possible and at once saw that only in primitive types could the 
key be found, and that too not in any one series, but only in the 
common features of many lower types. Accordingly he un- 
dertook to examine in rapid succession as material offered a 
large number of lower brains, taking voluminous notes and 
publishing the observed data as fast as they were ready. All of 
this work was fragmentary and much of it contained but little 
correlation. But the mass of facts gathered and recorded was 
enormous. He realized that the incessant strain on his eyes 
could not always be kept up, and planned to accumulate fact 
as rapidly as possible until failing eyes should impair his eff- 
ciency in this field. Zex he hoped to review the whole field 
of vertebrate neurology systematically, using his own observa- 
tions as the skeleton on which to build by study of literature 
and further research of his own on critical points, until the whole 
should take shape as a unity. When he settled in Granville 


Clarence Luther Flerrick. 523 


the second time in 1893 he expected to begin that work of cor- 
relation, and this is doubtless the special significance of the an- 
nouncement published at that time of a text-book on compara- 
tive neurology. But this period of work he was not able to 
enter far and the text-book is still unpublished. This manu- 
script, together with that of several other projected works on 
psychology and ethics, remains. It is yet too early to state 
how much of this matter can be edited for publication. If the 
last ten years of his life could have been spent in Granville, as 
was his plan, results of moment in the way of correlation would 
undoubtedly have followed. As it is, none of the papers in neu- 
rological lines were regarded by him as other than fragments. 

The first important paper in neurology was published in 
the Journal of the Cincinnati Soctety of Natural History—‘‘Notes 
upon the Brain of the Alligator.’’ This is an elaborate descrip- 
tive article illustrated with nearly a hundred of the beautiful 
pen drawings which he used so freely in all of his work. 

The second neurological paper of special importance was 
the leading article in the first .issue of this Journal, on the his- 
togenesis of the cerebellum in correlation with its comparative 
anatomy. This paper was ignored largely by the workers im- 
mediately following, but its main points have been fully con- 
firmed by later students. It is really, though very brief, one of 
his best contributions. 

Of the remaining neurological papers, the most important 
were published in this Journal, those in the Axatomischer An- 
geiger, American Naturalist, etc., being for the most part sum- 
maries of the longer articles. These were descriptive articles, 
in most cases, devoted mainly to the brains of fishes and 
reptiles, with some atrention to amphibians. 

The greater part of his descriptions of the fish brain have 
since been worked over with the same sections which he used 
in hand, and his descriptions have been found to be very exact, 
though often so brief as to make it difficult to understand them 
without reference to the preparations. Furthermore they stand 
the test of control by the more recent neurological methods 
very well, though of course not always in detail. His method 


524 Journal of Comparative Neurology and Psychology. 


of pushing a given research through rapidly enabled him to 
cover a great deal of ground with surprising fidelity to the facts 
of his material. But the method results in a positive hardship 
to his readers, since the matter was not fully digested and cor- 
related before publication. While, therefore, this matter is of 
great value, it is hard to read and will not be used fully save by 
a few specialists until it is worked over and correlated within 
itself and with other more recent work. It is hoped that this 
may be done soon. The facts as stated must necessarily serve 
as the basis for any future work on the types which he studied. 

After his departure for New Mexico a few brief neurolog- 
ical articles were published, but only fragments remaining from 
his earlier work or critical articles. This period was devoted 
chiefly to geology and other studies which could be pursued 
out-of-doors, and more recently to philosophical writing. 

In 1892 he contributed a short paper to the LEUCKART 
Festschrift. In 1893 he wrote four articles for the supplement 
to Wood’s Reference Handbook of the Medical Sciences. He 
also wrote a few articles for the second edition of the Hand- 
book, beginning in 1900. In conjunction with C. Jupson 
Hexrick, he prepared the neurological articles for the BALD- 
win Dictionary of Philosophy and Psychology, some of these 
being encyclopedic articles of considerable length. 

The best years of his life were devoted to his neurological 
work and it is all of a high order of merit, yet one feels that in 
very little of it did he do himself justice. His impetuous tem- 
perament and phenomenal ability to turn off research rapidly is 
partly responsible for this; but its unsatisfactory character is 
largely due to the fact that it was cut off prematurely. He 
never had the patience to polish his work as some like to see it 
done, and it would have been much more accessible if he had 
put even the unfinished reports of progress into more syste- 
matic form. Yet, even as it is, the aggregate is a monumental 
work to stand as the out-put of only about half a decade of 
productive work. 

Of his work in New Mexico one who had first-hand 
knowledge writes as follows: 


Clarence Luther Flerrick. 525 


“He first resided, with his family, in Albuquerque, and 
while gaining strength, began to study the local fauna and flora. 
Perbaps it may be allowable to give an incident from this per- 
iod of his life, for it is most typical of: him. 

“While recovering strength he was accustomed to lie upon 
a couch in the open air. His microscope was close at hand, 
and he began at once the study of our fresh water crustaceans. 
For a few minutes he would study his creature under the micro- 
scope, make his exquisite drawings, write out his description, 
when, being seized with a coughing spell, he would be forced 
to his couch completely exhausted, to remain there perhaps 
half an hour before he could resume his study. 

‘This incident illustrates two characteristics. It illustrates 
first, his unremitting labors. Only when necessity compelled 
did he cease his labor. True, he had his recreations, but these 
were often of such a character as to be downright labor for most 
men. The incident also illustrates, secondly, his deep thirst 
for knowledge. Only he who has drunk at the fountain of in- 
spiration could labor so incessantly under conditions so unfavor- 
able. 

‘‘After some months spent in Albuquerque, Professor Her- 
rick and his family moved to Socorro. There he became inter- 
ested in geological stidies, and also collected a considerable 
herbarium of native plants. He contributed occasional articles 
to the Journal of Comparative Neurology. In the spring of 1897 
he, in company with his son Harry and Dr. MAtrsy, made an 
exploring trip to the Tres Marias Islands, off the western coast 
of Mexico, where a large natural history collection was made. 

“Upon his return from Mexico, Professor HERRICK was 
elected President of the University of New Mexico, and began 
his new labors in 1897. His wide experience, having been 
connected with three universities, viz., Minnesota, Cincinnati 
and Denison, his several trips to Germany, where he met and 
worked with the leaders in the biological sciences, his national 
reputation in fields of zoology, geology, neurology, psychology 
and philosophy, gave him an ideal preparation as a college presi- 
dent. No wonder, then, that he drew to him immediately a 


526 Journal of Comparative Neurology and Psychology. 


number of advanced students who were inspired by his genius 
and broad knowledge, and who fairly worshiped him. 

‘In passing, it may be mentioned that under him the 
policy of the University was completely reversed. From a lit- 
erary academy, it became a scientific school; from a prepara- 
tory school it developed into a college with a post-graduate de- 
partment. In three short years the institution was placed where 
it belonged—at the head of the school system of New Mexico. 

‘“‘Upon entering his new duties, Dr. HERRICK commenced 
the biological and geological survey of the territory. 

‘‘Two volumes of original investigations in these lines speak 
for themselves. In addition, contributions were made to some 
of the leading journals of America, especially to the Journal of 
Comparative Neurology, the American Geologist and tne Psycho- 
logical Review.”’ 

Of Professor HerRIck’s contributions to philosophy a 
word should be said. That his interest was a deep and abid- 
ing one is abundantly evident from a glance at his writings 
which include many articles and discussions dating from the 
publication in 1882 of his translation of Lorze’s lectures on 
psychology to the series of articles on ‘‘Dynamic Realism” 
which he had begun to publish in the Journal of Philosophy, 
Psychology, and Scientific Methods, at the time of his death. 
He made frequent short contributions to the Psychological Re- 
view, besides publishing various articles of a psychological and 
philosophical character in the columns of his own /owrnal. His 
interest in problems of ethics and religion is evidenced by 
divers articles in certain of the religious periodicals as well as 
by much unpublished MS. 

Of his metaphysical writings it should be said that they 
were always inspired by his scientific researches. He never 
was Satisfied with the easy philosophy of the ‘‘anti-metaphys- 
ical” standpoint of many fellow scientists. Psycho-physical 
parallelism he regarded as ‘‘the Great Bad.’’ The aim of his 
life was to throw light upon just such so-called insoluble prob- 
lems as the relation of consciousness to the brain. ‘*Ignorabi- 
mus’’ is a word which never fell from his lips. The unity of 


: Clarence Luther Herrick. 527 


the material and the mental is a truth upon which he came to 
lay increasing stress in his later years. Starting from a Lotzean 
spiritualistic idealism he never lost hold of the monism which 
characterizes that philosophic world-view, though in many re- 
spects he worked beyond it, his scientific studies serving to cor- 
rect any tendency to an exclusive emphasis upon the mental. 
This is seen in the title under which his latest writings appear 
—‘‘Dynamic realism’’—in which many will find hints of a com- 
ing philosophic movement which is to reinterpret the fixed 
ontological categories of a past metaphysics in more dynamic 
and organic terms. 

Of his contributions to the theory as to the nature of con- 
sciousness (equilibrium theory ot consciousness), the physiolog- 
ical basis of the emotions, theory of pleasure-pain (summation- 
irradiation theory of pleasure-pain), his discussion of the reflex 
arc or organic circuit under the terms of his own coining 
(‘‘aesthesodic’’ and ‘‘kinesodic’’), and in general his interpreta- 
tion of experience in dynamic and energic terms, we may not 
here speak in detail. But the attention of the readers of this 
Journal should be called to this side of his work as it is em- 
bodied in his various published writings and especially in cer- 
tain writings which are yet to appear. 

In the memory of his pupils Professor HERRICK was great- 
est asa teacher. This statement can only be appreciated by 
those who knew him personally and were in his classes. There 
was no display or oratory. He was not what would be called 
a gifted public speaker, though he was often called upon for 
such services. It was in the class-room or about the seminar 
table or in general conversation that the inexhaustible fertility 
of his thought and fine suggestiveness of his language ap- 
peared. In his lectures one always knew that he was getting 
the best, the latest, the deepest results of his scientific research 
and philosophic reflection. Never was any work slighted in 
which his students were involved. Other things might be sacri- 
ficed—time, money, convenience, even health itself, but never 
the student. The result was that his teaching was not confined 
to the class-room or laboratory. There never was an occasion 


= 


528 Journal of Comparative Neurology and Psychology. 


upon which he was not ready to suggest, advise, assist the grop- 
ing mind in its search for the truth. 

He was extraordinarily versatile in the class-room. He 
would lecture with a piece of chalk in each hand, sketching at 
the same time ambidextrously upon the blackboard the figure 
he was describing. Never did the lecture degenerate into a 
mere description of the figure. The figure he was describing 
was the figure in his mind, the figure that he was thereby sug- 
gesting in the student’s mind. Such description and all the other 
instrumentalities of the class-room and laboratory were always 
kept in their proper place and proportion as means to the end 
of knowledge and insight. His artistic sense was too fine to 
allow them ever to degenerate into mere ends in themselves ; 
the technique of his teaching was in itself a work of art, the 
more that it was unconscious on his part. His courses in neu- 
rology, embryology, and histology were primarily courses in 
thinking. This is no doubt the reason why so many of his 
students look back upon his teaching as the period of their in- 
tellectual awakening. 

One of his colleagues at Denison University says of him: 
‘‘All who knew Professor HERRICK loved him. Different friends 
had different reasons for loving him, but all agreed in loving. 
Christian people loved him because he wasa loyal Christian man. 
Intellectual people loved and admired him because of his bril- 
liant and keen intellect; and men in general loved him because 
they saw in him a true and noble man loving the truth and liv- 
ing it out in his daily life.”’ 

As has been said of another: ‘‘He did his work with a 
quietness which concealed its power. He contributed to science 
our best example of the scientific temper. He was a profound 
thinker. He was a successful teacher. He wasa lover, in- 
spirer, and leader of youth.” 

H. HEATH BAWDEN. 


Clarence Luther Herrick. 529 


BIBLIOGRAPHY OF C. L. HERRICK. 


1877. 

The Trenton Limestone at Minneapolis. Amer. Nat., 11, 247-248. 

Ornithogical Notes. /7/th Ann. Rep. Geol. and Nat. Hist. Survey of Minn., 
for 1876, 230-237. 

A New Cyclops. Fifth Ann. Rep. Geol. and Nat. Hist. Survey of Minn., 
for 1876, 238-239, 2 figs. 

‘ 1879. 

Microscopic Entomostraca. Seventh Ann. Rep. Geol. and Nat. Hist. Survey 
of Minn., 81-164, 21 pl. 

Fresh Water Entomostraca. Amer. Nat., 13, 620-624, 4 pl. 

1882. 

Papers on the Crustacea of the Fresh Waters of Minnesota. I. Cyclopidae 
of Minnesota. II. Notes on Some Minnesota Cladocera. III. On Notadromas 
and and Cambaras. Tenth Ann. Rep. Geol. and Nat. Hist. Survey of Minn., 
for 1881, 219-254, 11 pl. 

Habits of Fresh Water Crustacea. Amer. Nat., 16, 813-S16. 

A New Genus and Species of the Crustacean Family of Lyncodaphnidae. 
Amer. Nat., 16, 1006-1007. 

1883. 

Types of Animal Life, Selected for Laboratory Use in Inland Districts. 
Part Il. Arthropoda. Minneapolis, 33 pp., 7 pl. 

Heterogenetic Development in Diaptomus. Amer. Nat., 17, 381-389. 

Heterogenesis in the Copepod Crustacea. Amer. Nat., 17, 499-505. 

A Blind Copepod of the Family Harpacticidae. Amer. Nat., 17, 206. 

1884. 

[Abstract of ] Minnesota Laws Relating to Mines and Mining. Eleventh Ann. 
kep. Geol. and Nat. Hist. Survey of Minn., for 1882, 195-212. 

A Final Report on the Crustacea of Minnesota Included in the Orders 
Cladocera and Copepoda. ‘Together with a Synopsis of the described Species in 
North America and Keys to the known Species of the more Important 
Genera. Twelfth Ann. Kep. Geol. and Nat. Hist. Survey of Minn., for 1883, 
Part V, 1-192, 30 pl. 

1885. 

Notes on the Mammals of Big Stone Lake and Vicinity. Zhirteenth Ann. 
hep. Geol. and Nat. Hist. Survey of Minn.,for 1884, 178-186. 

Outlines of Psychology: Dictations trom Lectures by Hermann Lotze. 
Translated with the addition of a Chapter on the Anatomy of the Brain. Mn- 
neapolis, x +-150 pp., 2 pl. 

The Evening Grosbeak, Hesperiphona vespertina, Bonap. Bul. Scz. Lad. 
Denison Univ., 1, 5-15, 2 pl. 

Metamorphosis and Morphology of Certain Phyllopod Crustacea. Bud. Sez. 
Lab. Denison Univ., 1, 16-24, 5 pl. : 

Mud-Inhabiting Crustacea. Bud. Sct. Lab. Dentson Univ., 1,37-42, 1 pl. 

Notes on American Rotifers. Bul. Sct. Lab. Denison Univ., 1, 43-62, 4 pl. 

A Compend of Laboratory Manipulation [Lithological]. Aud. Sct. Lad. 
Denison Univ., 1, 121-136, 1 pl. 


530 Journal of Comparative Neurology and Psychology. 


Tables for the Determination of the Principal Rock-Forming Minerals. 
Translated and Modified from Hussak’s Tabellen zur Bestimmung der Min- 
eralien. Bul. Sct. Lab. Denison Univ., 1, 39 pp. 


1886. 
Certain Homologous Muscles. Sczence, 7, 396. 
1887. 


Contribution to the Fauna of the Gulf of Mexico and the South. List of 
the Fresh-Water and Marine Crustacea of Alabama, with Descriptions of the 
New Species and Synoptical Keys for Identification. Memozrs of the Denison 
Sct. Assoc., Granville, O., 1, No. 1, 1-56, 7 pl. 

A Sketch of the Geological History of Licking County Accompanying an 
Illustrated Catalogue of Carboniferous Fossils from Flint Ridge, Ohio. Bud. Scé. 
Lab. Denison Univ., 2, Pt. 1, 4-70, 6 pl. 

Geology and Lithology of Michipicoten Bay. Bud. Sc?. Lab. Denison Untiv., 
2, Pt. 2, 119-143, 4 pl. (With W. G. Tight and H. L. Jones). 

Sketch of the Geological History of Licking County. No. 2. Bul. Sez. 
Lab. Denison Univ., 2, Pt. 2, 144-148, 1 pl. 

1888. 

Science in Utopia. Amer. Nat., 22, 698-702. 

Some American Norytes and Gabbros. Amer. Geologist, 1, No. 6, 339-346, 
I pl. (With E. S. Clark and J. L. Deming). 

The Geology of Licking County, Ohio. Parts [III and] IV. The Subcar- 
boniferous and Waverly Groups. Aud. Sez. Lab. Denison Uni., 3, Pt. 1, 13- 
OSs 2sp ll. 


Geology of Licking County. Part IV. List of Waverly Fossils, Continued. 
Bul Sct. Lah, Denison Univ., 4, Pt. 1, 11-60, 97-123, 11 pl. 
1889. 
Educational Briefs. Bz. Sc?. Lab. Denison Univ., 4, Pt. 2, 135-138. 
Lotze’s Ontology—The Problem of Being. Bu/. Sez. Lab. Denison Univ., 
4, Pt. 2, 139-146. 
Notes upon the Waverly Group in Ohio. Amer. Geologtst, 3, 50-51, 94-99, 
4 pl. 
A Contribution to the Histology of the Cerebrum. The Cincinnati Lancet- 
Clinic. 
1890. 
Additions and Corrections to Miller’s North American Palaeontology. 
Amer. Geologist, 5, No. 4, 253-255. 
Notes upon the Brain of the Alligator. Journ. Cincinnatt Soc. Nat. Hist., 
12, 129-162, 9 pl. 
Suggestions upon the Significance of the Cells of the Cerebral Cortex. 
The Microscope, 10, No. 2, 33-38, 2 pl. 
The Central Nervous System of Rodents. Preliminary Paper. Axl. Sc7. 
Lab. Denison Univ., 5, 35-95, tg pl. (With W. G. Tight). 
The Philadelphia Meeting of the International Congress of Geologists. 
Amer. Geologist, 5, 379-388. 
1891. 
The Cuyahoga Shale and the Problem of the Ohio Waverly. Bul. Geolog- 
ical Soc. of America, 2, 31-48, 1 pl. 


Clarence Luther Herrtck. 531 


The Commissures and Histology of the Teleost Brain. Anat. Anz., 6 
676-681, 3 figs. 

Biological Notes upon Fiber, Geomys and Erethyzon. Sul. Sc. Lab. 
Denison Univ., 6, Pt. 1, 15-25. (With C. Judson Herrick). 

The Evolution of the Cerebellum. Sczence, 18, 188-189. 

Contributions to the Comparative Morphology of the Central Nervous Sys- 
tem. I. Illustrations of the Architectonic of the Cerebellum. /ourn. Comp. 
Neur., 1, 5-14, 4 pl. 

Contrtbutions to the Comparative Morphology of the Central Nervous 
System. II. Topography and Histology of the Brain of Certain Reptiles. 
Journ. Comp. Neur., 1, 14-37, 2 pl. 

Laboratory Technique. A New Operating Bench. /ourn. Comp. Neur., 
i, Stet 

Editorial. The Problems of Comparative Neurology. /ourn. Comp. Neur., 
1, 93-105. 

Notes uponechnique. Journ. Comp. Neur., 1, 133-134. 

Contributions to the Comparative Morphology of the Central Nervous Sys- 
tem. III. Topography and Histology of the Brain of Certain Ganoid Fishes. 
Journ. Comp. Neur., 1, 149-182, 4 pl. 

Editorial. Neurology and Psychology. /ourn. Comp. Neur., 1, 183-200. 

Contributions to the Morphology of the Brain of Bony Fishes. (Part I by 
C. Judson Herrick). Part Il. Studies on the Brains of Some American Fresh- 
water Fishes. /Journ. Comp. Neur., 1, 228-245, 333-858, 5 pl. 

1892. 

The Mammals of Minnesota. A Scientific and Popular Account of their 
Features and Habits. Azdlletin No. 7, Geological and Nat. Hist. Survey of 
Minn., 300 pp., with 23 figures and 8 plates. 

Notes upon the Anatomy and Histology of the Prosencephalon of Teleosts. 
AEN, 26.) NO.2, 112-120, 2) pl: 

Additional Notes on the Teleost Brain. Anat. Anz., 7, Nos. 13-14, 422- 
431, 10 figs. 

Notes upon the Histology of the Central Nervous System of Vertebrates. 
Festschrift zum siebenzigsten Gebutrstage Rudolf Leuckharts, 278-288, 2 pl. 

The Cerebrum and Olfactories of the Opossum, Didelphys virginica. /ourn. 
Comp. Neur., 2, 1-20; and Bul. Sct. Lab. Denzson Univ., 6, Pt. 2, 75-94, 3 pl. 

Contributions to the Morphology of the Brain of Bony Fishes. Part II. 
Studies on the Brain of Some American Fresh-water Fishes (Continued). /owrz. 
Comp. Neur., 2, 21-72, 8 pl. 

Neurologists and Neurological Laboratories. No. 1. Professor Gustav 
Fritsch. With portrait. /ourn. Comp. Neur., 2, 84-88. 

The Psychophysical Basis of Feelings. /ourn. Comp. Neur., 2, 111-114. 

Instances of Erronious Inference in Animals. /ourn. Comp. Neur., 2, 114. 

Editorial. Instinctive Traits in Animals. Journ. Comp. Neur. 2, 115-136. 

Histogenesis and Physiology of the Nervous Elements. Journ. Comp. Neur., 
2, 136-149. 

Intelligence in Animals. Journ. Comp. Neur., 2, 157-158. 

Embryological Notes on the Brain of the Snake. /ourn. Comp. Neur., 2, 
169-176, 5 pl. 


532 Journal of Comparative Neurology and Psychology. 


Localization in the Cat. Journ. Comp. Neur., 2, 190-192. : 
1893. 

Observations upon the so-called Waverly Group of Ohio. Oh?o Geological 
Survey, 7, 495-515. 

The Scope and Methods of Comparative Psychology. Denzson Quarterly, 
1, 1-10; 134-141; 179-187; 264-281. 

Articles in Woods Reference Hand-book of the Medical Sciences, 9, Suppl., 
as follows: (1)-The Comparative Anatomy of the Nervous System; (2) The 
Histogenesis of the Elements of the Nervous System; (3) The Physiological and 
Psychological Basis of the Emotions; (4) Waller’s Law. ; 

The Evolution of Consciousness and of the Cortex. Scéence, 21, No. 543, 
351-352. 

The Development of Medullated Nerve Fibers. Journ. Comp. Neur., 3, 
II-16, 1 pl. . 

Editorial. The Scientific Utility of Dreams. Journ. Comp. Neur., 3 
17-34. 

The Hippocampus in Reptilia. _/owrn. Comp. Neur., 3, 56-60. 

Contributions to the Comparative Morpology of the Central Nervous Sys- 


tem. II. Topography and Histology of the Brain of Certain Reptiles (Con- 
tinued). Journ. Comp. Neur., 3, 77-106, 119-140, 11 pl. 

Report upon the Pathology of a Case of General Paralysis. /Journ. Comp. 
Neur., 3, 141-162, and Bulletin No. 1 of the Columbus State Hospital for the 
Insane, 5 pl. 

The Callosum and Hippocampal Region in Marsupial and Lower Brains. 
Journ. Comp. Neur., 3, 176-182, 2 pl. 

1894. 
The Seat of Consciousness. /ourn. Comp. Neur., 4, 221-226. 
1895. 


Synopsis of the Entomostraca of Minnesota, with Descriptions of Related 


, 


Species, Comprising all Known Forms from the United States Included in the 
Orders Copepoda, Cladocera, Ostracoda. Geological and Nat. Hist. Survey of 
1-525, 81 pl. (With C. H. Turner). 

Microcrustacea from New Mexico. Zool. Anz., 18, No. 467, 40-47. 

Modern Algedonic Theories. Journ. Comp. Neur., 5, 1-32. 

The Histogenesis of the Cerebellum. /ourn. Comp. Neur., 5 

Notes on Child Experiences. Journ. Comp. Neur., 5, 119-123. 

Editorial. The Cortical Optical Center in Birds. Journ. Comp. Neur., 5 
208-209. 


Menn., Zoological Series, 2 


J 


66-70. 


, 


, 


Editorial. Neurology and Monism. /ourn. Comp. Neur., 5, 209-214. 
1896. 

Suspension of the Spatial Consciousness. /sych. Rev., 3, 191-192. 

Focal and Marginal Consciousness. /sych. Rev., 3, 193-194. 

The Testimony of Heart Disease to the Sensory Facies of the Emotions. 
fsych. Kev., 3, 320-322. 

Hlustrations of Central Atrophy after Eye Injuries. Journ. Comp. Neur., 
G.i-45 0) ple 

Lecture Notes on Attention. An Illustration of the Employment of Neu- 
rological Analogies for Psychical Problems. Journ. Comp. Neur., 6, 5-14. 


Clarence Luther Terrick. 533 


The Psycho-sensory Climacteric. Psych., Rev., 3, 657-661. 

The Critics of Ethical Monism. Denzson Quarterly, 4, 240-252. 

The So-called Socorro Tripoli. Am. Geologist, 18, 135-140, 2 pl. 

UIST Ac 

Editorial. The Ethics ef Criticism. Jorn. Comp. Neur., 7, 71-72. 

Psychological Corrollaries of Modern Neurological Discoveries. Journ. 
Comp. Neur., 7, 155-101. 

Inquiries Regarding Current Pendencies in Neurological Nomenclature. 
fourn. Comp. Neur., 7, 162-165. (With C. Judson Herrick). 

The Propogation of Memories. fsych. Rev., 4, 294-296. 

The Geology of a Typical Mining Camp. Am. Geol., 19, 256-262, 2 pl. 

The Waverly Group of Ohio. mal Rep. Geol. Survey of Ohio, 7, 256- 


1898. 
The Geology of the Environs of Albuquerque, New Mexico. Am. Geol., 
21, 26-43, 1 pl., 5 figs. 
Occurrence of Copper and Lead in the San Andreas and Caballo Moun- 
tains, New Mexico. Am. Geol., 22, 285-291, 1 fig. 
Papers on the Geology of New Mexico. Buwd/. Sct. Lab. Denison Untv., 11, 
75-92, 4) pl- 
The Geology of the San Pedro and Albuquerque Districts. Ba/. Sez. Lad. 
Denison Univ., 11, 93-116. 
Physiological Corollaries of the Equilibrium ‘Theory of Nervous Action and 
Control. Journ. Comp. Neur., 8, 21-31. 
The Sematic Equilibrium and the Nerve Endings in the Skin. Part I. 
Journ. Comp. Neur., 8, 32-56, 5 pl. (With G. E. Coghill). 
The Cortical Motor Centers in Lower Mammals. Journ. Comp. Neur., 8, 
92-98, 1 pl. 
The Vital Equilibrium and the Nervous System. Sczence, N.S., 7, No. 
181, 813-818. 
1899. 
Notes on a Collection of Lizards from New Mexico. A#u/. Ser. Lab. Denison 
Uniw., 11, 117-148, 11 pl. (With John Terry and H. N. Herrick, Jr-.). 
The Material Versus the Dynamic Psychology. Psych. Rev., 6, 180-187. 
Editorial. Clearness and Uniformity in Neurological Descriptions. Journ. 
Comp. Newur., 9, 150-152- 
Geography of New Mexico. A chapter in the Natural Advanced Geog- 
raphy. Mew York, Am. Book Co., 6 pp., map and 9g figs. 
1900. 
The Geology of the White Sands of New Mexico. Journ. Geol., 7, 112- 
128, 3 pl. 
The Geology of the Albuquerque Sheet. Bz. Sct. Lab. Dentson Univ., 11, 
175-239, 1 map and 32 pl. (With D. W. Johnson). 
Report of a Geological Reconnaissance in Western Socorro and Valencia 
Counties, New Mexico. Am. Geol., 25, 331-346, 2 pl. 
Identification of an Ohio Coal Measures Horizon in New Mexico. Am. 


Geol., 25, 234-242. (With T. A. Bendrat). 


534 Journal of Comparative Neurology and Psychology. 


1901. 
Neurological Articles for Baldwin’s Dictionary of Philosophy and Psychol- 
ogy. Mew York, The Macmillan Co. (With C. Judson Herrick). 
Article on The Development of the Brain in Woods Reference Hand-book of 
the Medical Sciences. Second Edition, 2, 268-282. 
1903. 
Secondary Enrichment of Mineral Veins in Regions of Small Erosion. 
Mining and Scientific Press, San Franctsco, 87, 97. 
1904. 
Laws of Formation of New Mexico Mountain Ranges. Am. Geol., 33, 
301-312, 2 pl. 
Block Mountains in New Mexico: A Correction. Am. Geol., 33, 393. 
The Clinoplains of the Rio Grande. Am. Geol., 33, 376-381. 
Lake Otero, an Ancient Salt Lake Basin in Southeastern New Mexico. Am. 
Geol., 34, 174-189, 2 pl. 
A Coal Measure Forest near Socorro, New Mexico. Journ. Geol., 12, 237- 
252. 
The Logical and Psychological Distinction betwee the True and the Real. 
Psych, Rev., 11, 204-210. 
Fundamental Concepts and Methodology of Dynamic Realism. /ourn. 
Phil., Psy., Sct. Methods, 1, 281-288. 
The Dynamic Concept of the Individual. Journ. Phil., Psy., Sc?. Methods, 
1, 372-378. 
Editorial L’Envoi. Journ. Comp. Neur. and Psych., 14, 62-63. 
The Beginnings of Social Reaction in Man and Lower Animals. Journ. 
Comp. Neur. and Psych., 14, 118-124. 
Color Vision (a critical digest). /vurn. Comp. Neur. and Psych., 14, 274- 
281. 
Recent Contributions to the Body-Mind Controversy. Journ. Comp. Neur. 
and Psycth., 14, 421-432. 
The Law of Congruousness and its Logical Application to Dynamic Real- 
ism. Journ. Phtl., Psy., Sct. Methods, 1, 595-604. 
Mind and Body—The Dynamic View. Psych. Rev., 11, 395-409. 


Volume XIV 


MARCH, 1904 


»% 

Pe 

YY 
a 


SS “Number I 


The Journal of Comparative 


Neurology and Psychology 


(Continuing the Journal of Comparative Neurology.) 


EDITORS 


C. L. HERRICK, Socorro, New Mexico. / 


C. JUDSON HERRICK, Manager, 
Denison University, 


ROBERT M. YERKES, / 
Harvard University. 


ASSOCIATED WITH \ 


OLIVER S, STRONG, 
Columbia University. 


HERBERT S. JENNINGS, \ 


University of Pennsylvania. 


/ 


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J. MARK BALDWIN, Johns Hopkins University 
FRANK W. BANCROFT, University of California 
LEWELLYS F, BARKER, Wniversity of Chicago 
H. HEATH BAWDEN, Vassar College : 
ALBRECHT BETHE, University of Strassburg 
G, E COGHILL, Pacific University 

FRANK J. COLE, University of Liverpool 

H. E. CRAMPTON, Columbia University 

C. B. DAVENPORT, University of Chicago 

W.M. HARPER DAVIS, Columbia University 
HENRY H. DONALDSON, University of Chicago 
LUDWIG EDINGER, Frankfurt a-M, 

8. 1. FRANZ, Dartmouth College 

A. VAN GEHUCHTEN, University of Louvain 

R. G. HARRISON, Johns Hopkins University 

C. F. HODGE, Clark University 

S. J. HOLMES, University of Michigan 

EDWIN B. HOLT, Harvard University 

G. CARL HUBER, University of Michigan 
JOSEPH JASTROW, University of Wisconsin 

J. B. JOHNSTON, West Virginia University 


B. F, KINGSBURY, Cornell University 
FREDERIC 8S. LEE, Columbia University 
JACQUES LOEB, University of California 
ADOLF MEYER, N. Y. State Pathological Inst, 
THOS. H. MONTGOMERY, Jr., Univ. of Texas 
WESLEY MILLS, McGill University 

C. LLOYD MORGAN, University College, Bristol 
T. H. MORGAN, Bryn Mawr College 

A. D. MORRILL, Hamilton College 

HUGO MUENSTERBERG, Harvard University 
W. A. NAGEL, University of Berlin 

G. H. PARKER, Harvard University 
STEWART PATON, Johns Hopkins University 
RAYMOND PEARL, University of Michigan 
C. W. PRENTISS, Western Reserve University 
C.S. SHERRINGTON, University of Liverpool 
G. ELLIOT SMITH, Gov’t. Medical School, Cairo 
EDWARD L.THORNDIKE, Columbia University 
JOHN B. WATSON, University of Chicago 
W.M,. WHEELER, Am. Museum of Nat. History 
0.0. WHITMAN, University of Chicago. 


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The Royal Prussian Academy of Science, 
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Dr. N. L. Britton. 

Education and Industry. Professor Edw. 
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Evolution Not the Origin of Species. O. F. 
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Volume XIV 


APRIL, 1904 


Number 2 


The Journal of Comparative 


, Ladies 
par 


Neurology vad | 


D 


<ychology 


(Continuing the Journal of Comparative Neurology.) 


EDITORS 
C. L. HERRICK, Socorro, New Mexico. 


C. JUDSON HERRICK, Manager, 
Denison University 


ROBERT M. YERKES, 
Harvard University 


ASSOCIATED WITH 


OLIVER S. STRONG, 
Columbia University 


HERBERT S. JENNINGS, 


University of Pennsylvania 


COLLABORATORS 


J. MARK BALDWIN, Johns Hopkins University 
FRANK W. BANCROFT, University of California 
LEWELLYS F, BARKER, University of Chicago 
H. HEATH BAWDEN, Vassar College 
ALBRECHT BETHE, University of Strassburg 
G. E COGHILL, Pacific University 

FRANK J. COLE, University of Liverpool 

H. E. CRAMPTON, Columbia University 

Cc. B. DAVENPORT, University of Chicago 

WM. HARPER DAVIS, Columbia Univeisity 
HENRY H. DONALDSON, University of Chicago 
LUDWIG EDINGER, Frankfurt a-M. 

S. I. FRANZ, Dartmouth College 

A. VAN GEHUCHTEN. University of Louyain 

R. G. HARRISON, Johns Hopkins University 

C. F. HODGE, Clark University 

S. J. HOLMES, University of Michigan 

EDWIN B. HOLT, Harvard University 

G. CARL HUBER, University of Michigan 
JOSEPH JASTROW, University of Wisconsin 

J. B. JOHNSTON, West Virginia University 


B. F. KINGSBURY, Cornell University 
FREDERIC 8, LEE, Columbia University 
JACQUES LOEB, University of California 
ADOLF MEYER, N. Y. State Pathological Inst. 
THOS. H. MONTGOMERY, Jr., Univ. of Texas 
WESLEY MILLS, McGill University 

C. LLOYD MORGAN, University College, Bristol 
T. H. MORGAN, Bryn Mawr College 

A. D, MORRILL, Hamilton College 

HUGO MUENSTERBERG, Harvard University 
W. A. NAGEL, University of Berlin 

G. H. PARKER, Harvard University 
STEWART PATON, Johns Hopkins University 
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C, W. PRENTISS, Western Reserve University 
©.S SHERRINGTON, University of Liverpool 
G. ELLIOT SMITH, Goy’t. Medical School, Cairo 
EDWARD L. THORNDIKE, Columbia University 
JOHN B. WATSON, University of Chicago 

W. M, WHEELER, Am. Museum of Nat. History 
Cc. O. WHITMAN, University of Chicago 


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Aerial Navigation. O. Chanute. 

The Metric System: Shall it be Compul- 
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The Conservation of Energy in Those of 
Advancing Years. Dr. J. Madison Taylor. 

The Royal Prussian Academy of Science, 
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The Tropical Station at Cinchona, Jamaica. 
Dr. N. L. Britton. 

Education and Industry. Professor Edw. 
D. Jones. 

Evolution Not the Origin of Species. O. F. 
Cook. 

Some Historical Aspects of Vegetarianism. 
Professor Lafayette B. Mendel. 

Tokyo Toikoka Dragaku (The Imperial Uni- 
versity of Tokyo). Nachide Yatsu. 


THE PopuLAR SCIENCE MONTHLY has had few rivals and no equal in the 
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CONTENTS, 


Physiological Evidence of the Fluidity of the Conducting Sub- 
stance in the Pedal Nerves of the Slug—Ariolimax colum- 
bianus. By O. P. Jenkins and A. J. Cartson. From 
the Physiological Laboratory of Leland Stanford, Jr., Uni- 
versity. With one figure. . : : 4 ee (4 


The Nervous Structures in the Palate of the Frog: the ce 
eral Networks and the Nature of their Cells and Fibers. 
By C. W. Prentiss, lustructor of Biology, ee Re- 
serve University. With 12 figures. s : : -. 3Q@3 


The Beginnings of Social Reaction in Man and Lower Animals. 
By C. L. Herrick, Socorro, New Mexico. . ; / 118 


Inhibition and Reinforcement of Reaction in the Frog, Rana 
clamitans. By Robert M. Yerxes. yom the Harvard 
Psychological Laboratory. ; : . : : » cee 


On the Behavior and Reactions of Limulus in Early Stages of its 
Development. By RayMonD PEARL. From the Zoological 
Laboratory of the te of oe With one 
figure. ; ‘ : : Cia 


Editorial. ; : : ; é : : ; : . 165 


Recent Studies on the Finer Structure of the Nerve Cell. By 
G. E. Cocuitt, Professor of Biology, Pacific University. 171 


Literary Notices. : ; : : j ‘ i . 203 


THE JOURNAL OF COMPARATIVE NEUROLOGY AND PSY- 
CHOLOGY is published bi-monthly. The annual volume of six numbers 
comprises about 500 pages, with plates and text-figures. The subscription price 
is $4.00 a year, strictly net (foreign subscription, $4.30, 18 s., M. 18, 22 fr., 
L. 22), postage prepaid. 

Authors receive 50 reprints of their papers gratis and additional copies 
are supplied at cost. All MSS. and matter for review relating to the Structure 
of the Nervous System and all business correspondence should be addressed 
to the ManacinGc EpITOR AT DENISON UNIVERSITY, GRANVILLE, OHIO. 
Editorial Matter relating to Comparative Psychology and the Physiology of the 
Nervous System should be sent directly to Dr. Ropert M. YERKES, PsyCHO- 
LOGICAL LABORATORY, HARVARD UNIVERSITY, CAMBRIDGE, MASss. 


Entered as second-class matter in the Postoffice at Granville, O. 


3.5 Shor 


Volume XIV JUNE, 1904 Number 3 


The Journal of Comparative 


Neurology and Psychology 


(Continuing the Journal of Comparative Neurology) 


EDITORS 


Cc. L. HERRICK, Socorro, New Mexico. 


C. JUDSON HERRICK, Manager, ROBERT M. YERKES, 
Denison University Harvard University 


ASSOCIATED WITH 
HERBERT 


OLIVER 5S. STRONG, 
Columbia University 


S. JENNINGS, 
University of Pennsylvania 


COLLABORATORS 


J. MARK BALDWIN, Johns Hopkins University 
FRANK W. BANCROFT, University of California 
LEWELLYSF, BARKER, University of Chicago 
H. HEATH BAWDEN, Vassar College 
ALBRECHT BETHE, University of Strassburg 
G.E COGHILL, Pacific Univ ersity 

FRANK J. COLE, University of Liverpool 

H. E. CRAMPTON, Columbia University 

Cc. B. DAVENPORT, University of Chicago 

WM. HARPER DAVIS, Columbia University 
HENRY H. DONALDSON, University of Chicago 
LUDWIG EDINGER, Frankfurt a-M. 

S, I. FRANZ, McLean Hospital, Waverly, Mass, 
A, VAN GEHUCHTEN, University of Louvain 
R. G. HARRISON, Johns Hopkins University 

C. F. HODGE, Clark University 

Ss. J. HOLMES, University of Michigan 
EDWIN B. HOLT, Harvard University 

G. CARL HUBER, University of Michigan 
JOSEPH JASTROW, University of Wisconsin 

J. B. JOHNSTON, West Virginia University 


B. F. KINGSBURY, Cornell University 
FREDERIC S, LEE, Columbia University 
JACQUES LOEB, University of California 
ADOLF MEYER, N. Y. State Pathological Inst. 
THOS. H. MONTGOMERY, Jr., Univ. of Texas 
WESLEY MILLS, McGill University 

C. LLOYD MORGAN, University College, Bristol 
T. H. MORGAN, Bryn Mawr College 

A. D, MORRILL, Hamilton College 

HUGO MUENSTERBERG, Harvard University 
W. A. NAGEL, University of Berlin 

G. H. PARKER, Harvard University 
STEWART PATON, Johns Hopkins University 
RAYMOND PEARL, University of Michigan 

C. W..PRENTISS, Western Reserve University 
Cc. Ss. SHERRINGTON, University of Liverpool 
G. ELLIOT SMITH, Gov't. Medical School, Cairo 
EDWARD L. THORNDIKE, Columbia University 
JOHN B. WATSON, University of Chicago 
W.M, WHEELER, Am. Museum of Nat. History 
C. 0. WHITMAN, University of Chicago 


Published bi-monthly 
CENISON UNIVERSITY, GRANVILLE, OHIO 


The American Naturalist 


A Monthly Journal Devoted to the Natural Sciences 
in Their Widest Sense. 


Since its foundation in 1867 by four of the pupils of Louis Agassiz, 
THE AMERICAN NATURALIST has been a representative Amer- 
ican magazine of Natural History and has played an important part in 
the advancement of science in this country. 

The journal aims to present to its readers the leading facts and dis- 
coveries in the fields of Anthropology, General Biology, Zodlogy, 
Botany, Paleontology, Geology, and Mineralogy, and the various subdi- 
visions of those subjects. 


Annual Subscription, $4.00 net, in advance. Single Copies, 
35 cents. Foreign Subscription, $4.60. 


IMPORTANT SCIENTIFIC BOOKS 


BERGEN’S MILLIKAN’S 
Foundations of Botany Mechanics, Molecular 
YOUNG’S Physics, and Heat 


Manual of Astronomy licGREGORY’S 
MILLER’S Manual of Qualitative 
Laboratory Physics Chemical Analysis 


GINN & COMPANY, Publishers, 


29 Beacon Street, Boston, Mass. 


H. Kiwopic, Editeur, 11, Corraterie, GENEVE. 


Archives de Psychologie 


PUBLIEES PAR 


Th. Flournoy Ed. Claparéde 
Dr en médecine. Dr en médecine. 
Prof. de Psychologie expérim. Privat-Docent de Pyschologie. 


a la Faculté des Sciences de l’Université de Genéve. 


Les Archives de Psychologie paraissent 4 époque indéterminée. Chaque 
fascicule se vend séparément et le prix en est fixé suivant sa grosseur et le nom- 
bre des figures. On peut toutefois souscrire d’avance au prix de 15 francs 
pour un volume (d’au moins 400 pages); avec le dernier fascicule du volume, 
les souscripteurs recoivent le titre et les tables des matiéres.—Les fascicules 


sont envoyés franco de port aux souscripteurs. 


Tome let, vol. broché de 424 pages et 57 figures . . . . . . - 15 fr. 
Tome il, 73 a3 “s 404 “é ““ 28 ce Z c 2 e ‘ 15 a3 
Tome III, (En cours de publication) . 2. 2. 2 ee ee ee 15 


Aux nouveaux souscripteurs du tome III, les tomes [er et II sont laissés a 
leur ancien prix, soit 12 fr. chaque (frais de port compris). 


International Instrument Co., 


MAKERS AND DEALERS IN 


HIGH GRADE SCIENTIFIC 


LABORATORY APPARATUS. 


oe 


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Stand 
with 
Universal Adjustable 
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1e Psychological Keview 


EDITED BY 
J. MARK BALDWIN HOWARD C. WARREN 
AND 
Jouns Hopkins UNIVERSITY PRINCETON UNIVERSITY 


WITH THE CO-OPERATION OF 


A.C. ARMSTRONG, Wesleyan University, Middletown, Conn.; ALFRED BINET, 
Ecole des’ Hautes-Etudes, Paris; W. L. Bryan, Indiana University, Blooming- 
ton, Ind.; MAry W. CALKINS, Wellesley College, Wellesley, Mass.; JoHN DrEwey, 
H. H. Donatpson, University of Chicago; C. LADD FRANKLIN, Baltimore; G. 
S. FULLERTON, University of Pennsylvania; H. N. GARDINER, Smith College, 
Northampton, Mass.; G. H. Howtson, University of California; JosEPH 
JAsTRow, University of Wisconsin; ApoLF Mryer, N. Y. Pathol. Institute, 
Ward's Island, N. Y.; HuGo MUNSTERBERG, Harvard University; E. A. Pace, 
Catholic University, Washington; G. T. W. Parrick, University of Iowa, Iowa 
City, lowa; CARL Strumpr, University, Berlin; R. M. WENLEY, University of 
Michigan, Ann Arbor, Mich.; and a special board for The Psychologecal Bulleten., 


THE PsYCHOLOGICAL REVIEW, New Series, is issued in two sections; the 
Article Section, containing original contributions, appears bimonthly, on the first 
of January, March, May, July, September and November, the six numbers com- 
prising a volume of at least 4oo pages; the Literary Section (Psychological Bulle- 
tm) containing critical reviews notices of books and articles, psychological news 
and notes, university notices, announcements. and shorter discussions, appears 
on the fifteenth of each month, and forms aseparate volume of at least 300 pages. 


Annual Subscription to Both Sections, $4.00 (Postal Union, 
$4.30); Bulletin alone, $2.00 (Postal Union, $2.20); 
Single Numbers of Article Section, 50c. 

(58e.)3; of Bulletin, 25¢. (27¢.). 


In connection with THE ReEviEw there is published annually 
THE PSYCHOLOGICAL INDEX 


a bibliography of books, monographs, and articles upon psychological and cog- 
nate topics that have appeared during the year. The /zdex is issued in March, 
and may be subscribed for in connection with THE RKrviEw, or purchased sep- 
arately (/zuex and Rervirw, $4.50 per annum; Postal Union, $4.85. /dex 
alone, 75 cents; Postal Union, 8o cents.) 

In connection with THE Review there is also published a series of 

MONOGRAPH SUPPLEMENTS 

consisting of longer researches or treatises which it is important to publish 
promptly and as units. The A/onographs appear at irregular intervals and are 
gathered into volumes of about 500 pages, with a uniform subscription of $4.00 
(Postal Union, $4.30). The price of single numbers varies according to the 
size. Five volumes have already been issued. 

Subscriptions, orders and business communications may be sent direct to 


Professor H. C. WARREN, Business Manager, Princeton, New Jersey, U.S. A.,, 
or forwarded through the publishers or agent. 


PUBLISHED BY 
THE MACMILLAN COMPANY, 
41 N. QUEEN ST., LANCASTER, Pa. 66 FirrH AVENUE, NEW York. 
AGENT: G. E..STECHERT, London (2\Star Yard; Carey St., W.€,): 
Leipzig (Hospital St., 10); Paris (76 rue de Rennes). 


Che Popular Science Monthly 


The Contents of the March Number include the fol- 
lowing articles: 


Aerial Navigation. O. Chanute. 

The Metric System: Shall it be Compul- 
sory? Professor W. Le Conte Stevens. 

The Conservation of Energy in Those of 
Advancing Years. Dr. J. Madison Taylor. 

The Royal Prussian Academy of Science, 
Berlin. Edward F. Williams. 

The Tropical Station at Cinchona, Jamaica- 
Dr. N. L. Britton. 

Education and Industry. Professor Edw. 
D. Jones. 

Evolution Not the Origin of Species. O. F. 
Cook. 

Some Historical Aspects of Vegetarianism. 
Professor Lafayette B. Mendel. 

Tokyo Toikoka Dragaku (The Imperial Uni- 
versity of Tokyo). Nachide Yatsu. 


THE PoPULAR SCIENCE MONTHLY has had few rivals and no equal in the 
educative service it has done for the American people. A complete set of the 
volumes thus far published is both a history of science for the period covered 
and at the same time a pretty complete cyclopedia of natural science. ‘here is 
nothing to fill its place, and to carry it on is a benefaction to the public.—W. le 


Harris, U. S. Commissioner of Education. 


The Popular Science Monthly, 


SUB-STATION 84, NEW YORK CITY. 
$3.00 per year. 30 cents per copy. 
3 I y 3 I P) 
fesPTHE PoruLAR SCIENCE MONTHLY wrl/ be sent for six months for 


one dollar to new subscribers mentioning The Journal of Comparatiwe Neurology 


and Psychology. 


CAMBRIDGE UNIVERSITY PRESS. 


The British Journal of Psychology 


Edited by James Warp and W. H. R. RIvERs. 


With the Collaboration of W. McDoucaut, C.S. Myers, A. F. SHAND, 
C. S. SHERRINGTON, W. G. SMITH. 


NOW READY. Vol. |. Part |. January, 1904. Price 5s. net. 


CONTENTS. 


Editorial. 

WARD, JAMES. On the Definition of Psychology. 

SHERRINGTON, C. S. On Binocular Flicker and the Corre- 
lation of Activity of ‘‘Corresponding” Retinal 
Points. (Two Figures and Twelve Diagrams.) 

McIntTyrk, J. Lewis. A Sixteenth Century Psychologist, 
Bernardino Telesio 

McDoucGAaLL, W. The Sensations excited by a Single Mo- 
mentary Stimulation of the Eye. (Six Figures 
and Plate I (Five Figures) ). 

McDouGati, W. Note on the Principle underlying Fech- 
ner’s ‘Paradoxical Experiment” and the Predom- 
inance of Contours in the Struggle of the two 
Visual Fields. 


Proceedings of the Psychological Society. 


The Journal will be issued in parts at irregular intervals. Four parts will 
(usually) constitute a volume of about 450 pages Royal 8vo. The price to 
subscribers, payable in advance, will be 15s. net per volume (post free). The 
price for each part sold separately will be ss. net. The first number will be 
published in January, 1904. 

Subscribers may send their names to any Bookseller or to the Publishers, 
Messrs. C. J. Ctay & Sons, Cambridge University Press Warehouse, Ave Maria 
Lane, London, E. C. 

Papers for publication should be sent to Dk. Warp, 6, Selwyn Gardens, 
Cambridge, or to Dr. W. H. R. Rivers, St. John’s College, Cambridge. 

The Proceedings of the Psychological Society will also be published in 
the Journal. 


London: C. J. Clay & Sons, Cambridge University Press Warehouse, 
Ave Maria Lane. 


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CONTENTS, 


An Enumeration of the Medullated Nerve Fibers in the Ventral 
Roots of the Spinal Nerves of Man. By Cuarzes E. 
InGBERT. rom the Neurological Laboratory of the Unt- 


versity of Chicago. With 38 Figures in the text. . . 209 
Editorial. : : i: 29% 
Color Vision. By C. L. Herrick. : : : ‘ 27a 
Literary Notices. : ; ; : : : Ok 


The Mark Anniversary Volume, 281. 


THE JOURNAL OF COMPARATIVE NEUROLOGY AND PSY- 
CHOLOGY is published bi-monthly. The annual volume of six numbers 
comprises about 500 pages, with plates and text-figures. The subscription price 
is $4.00 a year, strictly net (foreign subscription, $4.30, 18 s., M. 18, 22 fr., 
L. 22), postage prepaid. 

Authors receive 50 reprints of their papers gratis and additional copies 
are supplied at cost. All MSS. and matter for review relating to the Structure 
of the Nervous System and all business correspondence should be addressed 
to the Manacinc Epiror aT DENISON UNIVERSITY, GRANVILLE, OHIO. 
Editorial Matter relating to Comparative Psychology and the Physiology of the 
Nervous System should be sent directly to Dkr. Ropert M. YERKES, PsycHo- 
LOGICAL LABORATORY, HARVARD UNIVERSITY, CAMBRIDGE, Mass. 


Entered as second-class matter in the Postoffice at Granville, O. 


The University of Chicagn 


FOUNDED BY JOHN 1). RoCKEFELLER 


The Associative Processes of the Guinea Pig. A Study 
of the Psychical Development of an Animal with 
2 Nervous System Well Medullated at Birth 


A DISSERTATION SUBMITTED TO THE FACULTIES OF THE GRADUATE 
SCHOOLS OF ARTS, LITERATURE AND SCIENCE, IN CANDIDACY 
FOR THE DEGREE OF DOCTOR OF PHILOSOPHY 


(DEPARTMENT OF PHILOSOPHY) 


BY 


JESSIE BLOUNT ALLEN 


Reprinted from the Journal of Comparative Neurology and Psychology, Volume 
XIV, Number 4, July, 1904 


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Volume XIV 


SEPTEMBER, 1904 


Number 5 


The Journal of Comparative 


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logy and Psychology 


(Continuing the Journal of Comparative Neurology) 


EDITORS 
C. L. HERRICK, Socorro, New Mexico. 


C. JUDSON HERRICK, Manager, 
Denison University 


ROBERT M. YERKES, 
Harvard University 


ASSOCIATED WITH 


OLIVER S. STRONG, 
Columbia University 


HERBERT S. JENNINGS, 


University of Pennsylvania 


COLLABORATORS 


J. MARK BALDWIN, Johns Hopkins University 
FRANK W. BANCROFT, University of California 
LEWELLYS F, BARKER, University of Chicago 
H. HEATH BAWDEN, Vassar College 
ALBRECHT BETHE, University of Strassburg 
G.E COGHILL, Pacific University 

FRANK J. COLE, University of Liverpool 

H. E. CRAMPTON, Columbia University 

Cc. B. DAVENPORT, University of Chicago 

WM. HARPER DAVIS, Lehigh University 
HENRY H. DONALDSON, University of Chicago 
LUDWIG EDINGER, Frankfurt a-M. 

S. I. FRANZ, McLean Hospital, Waverley, Mass. 
THOMAS H. HAINES, Ohio State University 

A. VAN GEHUCHTEN, University of Louvain 

R. G. HARRISON, Johns Hopkins University 

C. F. HODGE, Clark University 

S. J. HOLMES, University of Michigan 

EDWIN B. HOLT, Harvard University 

G. CARL HUBER, University of Michigan 
JOSEPH JASTROW, University of Wisconsin 

J, B. JOHNSTON, West Virginia University 


B, F. KINGSBURY, Cornell University 
FREDERIC S. LEE, Columbia University 
JACQUES LOEB, University of California 

E. P. LYON, St. Louis University 

ADOLF MEYER, N. Y. State Pathological Inst. 
THOS. H. MONTGOMERY, Jr., Univ, of Texas 
WESLEY MILLS, McGill University 

C. LLOYD MORGAN, University College, Bristol 
T. H. MORGAN, Bryn Mawr College 

A. D, MORRILL, Hamilton College 

HUGO MUENSTERBERG, Harvard University 
W. A. NAGEL, University of Berlin 

G. H. PARKER, Harvard University 
STEWART PATON, Johns Hopkins University 
RAYMOND PEARL, University of Michigan 

C. W. PRENTISS, Western Reserve University 
C. 8. SHERRINGTON, University of Liverpool 
G. ELLIOT SMITH, Goy’t. Medical School, Cairo 
EDWARD L. THORNDIKE, Columbia University 
JOHN B. WATSON, University of Gece 

W. M. WHEELER, Am, Museum of Nat. History 
C. O. WHITMAN, University of Chicago 


Published bi-monthly 
DENISON UNIVERSITY, GRANVILLE, OHIO 


The American Naturalist 


A Monthly Journal Devoted to the Natural Sciences 
in Their Widest Sense. 


Since its foundation in 1867 by four of the pupils of Louis Agassiz, 
THE AMERICAN NATURALIST has been a representative Amer- 
ican magazine of Natural History and has played an important part in 


the advancement of science in this country. 
The journal aims to present to its readers the leading facts and dis- 


coveries in the fields of Anthropology, General Biology, Zodlogy, 
Botany, Paleontology, Geology, and Mineralogy, and the various subdi- 


visions of those subjects. 
Annual Subscription, $4.00 net, in advance. Single Copies, 
35 cents. Foreign Subscription, $4.60. 


IMPORTANT SCIENTIFIC BOOKS 


BERGEN’S MILLIKAN’S 
Elements of Botany (Revised Mechanics, [Molecular 
Edition) Now Ready Physics, and Heat 
Se aaiial of Astronomy Boe eS eS 
> Manual of Qualitative 
MILLER’S Chemical Analysis 


Laboratory Physics 


GINN & COMPANY, Publishers, 


29 Beacon Street, Boston, Mass. 


H. Kitwnpic, Editeur, 11, Corraterie, GENEVE. 


Archives de Psychologie 


PUBLIEES PAR 

Ed. Claparéde 

Dr en médecine. 
Privat-Docent de Pysehologie. 


Th. Flournoy 
Dr en médecine. 


Prof. de Psychologie expérim. 
ala Faculté des Sciences de l’Université de Genéve. 


Les Archives de Psychologie paraissent 4 époque indéterminée. Chaque 
fascicule se vend séparément et le prix en est fixé suivant sa grosseur et le nom- 
bre des figures. On peut toutefois souscrire d’avance au prix de 15 francs 


pour un volume (d’au moins 400 pages); avec le dernier fascieule du volume, 
les souscripteurs recoivent le titre et les tables des matiéres.—Les fascicules 


sont envoyés franco de port aux souscripteurs. 


Tome ler, vol. broché de 424 pages et 57 figures . . . . . . . 15 fr. 
Tome ll, 6 ‘6 6e 404 “é «7 28 6 A 3 NLT eR RAT Umi Hpk 
Tome Ill, ‘‘ ss i AR Ot ASS $¢330 (48° eb Siplanchescs 3 ars Aes 

Zit gt aoa Ny Ont al RHR ANG eal as Ry tenner eth ag eae 


Tome IV, (En cours de publication) 
Aux nouveaux souscripteurs du tome IV, les tomes Ier 4 ITI sont laissés 
au prix, de 39 fr. (frais de port compris). 


International Instrument Co., 


MAKERS AND DEALERS IN 


HIGH GRADE SCIENTIFIC 
LABORATORY APPARATUS. 


Elevating Tripod 
Stand 
with 
Universal Adjustable 
Stationary 
Supports. 
Send for Bulletin on 


this. 


International Instrument Co., 


23 Church St., Cambridge, Mass. 


1e Psychological Keview 


EDITED BY 
J. MARK BALDWIN HOWARD C. WARREN 
AND 
Jouns Hopkins UNIVERSITY PRINCETON UNIVERSITY 


WITH THE CO-OPERATION OF 


A. C, ARMSTRONG, Wesleyan University, Middletown, Conn.; ALFRED BINET, 
Ecole des Hautes-Etudes, Paris; W. L. Bryan, Indiana University, Blooming- 
ton, Ind.; MAry W. CALKINs, Wellesley College, Wellesley, Mass.; JOHN DEWEY, 
H. H. DoNALDSON, University of Chicago; C. LADD FRANKLIN, Baltimore; G. 


S. FULLERTON, University of Pennsylvania; H.N. GARDINER, Smith College, 


Northampton, Mass.; G. H. Howtson, University of California; JosEPH 
Jasrrow, University of Wisconsin ; ADOLF Meyer, N. Y. Pathol. Institute, 
Ward's Island, N. Y.; HuGo MUNSTERBERG, Harvard University; E. A. Pacr, 


Catholic University, Washington; G. T. W. Patrick, University of Iowa, Iowa 
City, lowa; CARL Srumpr, University, Berlin; R. M. WENLEY, University of 
Michigan, Ann Arbor, Mich.; and a special board for The Psychological Bulletin. 


THE PSYCHOLOGICAL REviEW, New Series, is issued in two sections; the 
Article Section, containing original contributions, appears bimonthly, on the first 
of January, March, May, July, September and November, the six numbers com- 
prising a volume of at least 400 pages; the Literary Section (Psychological Bulle- 
tm) containing critical reviews. notices of books and articles, psychological news 
and notes, university notices, announcements. and shorter discussions, appears 
on the fifteenth of each month, and forms aseparate volume of at least 300 pages. 


Annual Subseription to Both, oreo $4.00 (Postal Union, 
$4.50); Bulletin alone, $2.00 (Postal Union, $2.20); 
Single Numbers of Article Section, 50c. 
(53c.)3 of Bulletin, 25e. (27¢.). 
In connection with THE REVIEW there is published annually 
THE PSYCHOLOGICAL INDEX 
a bibliography of books, monographs, and articles upon psychological and cog- 
nate topics that have appeared during the year. The /nzdex is issued in March, 
and may be subscribed for in connection with THE REVIEW, or purchased sep- 


arately (/uwex and REVIEW, $4.50 per annum; Postal Union, $4.85. Lndex 
alone, 75 cents; Postal When So cents.) 


In connection with THE REVIEW there is also published a series of 


MONOGRAPH SUPPLEMENTS 


consisting of longer researches or treatises which it is important to publish 
promptly and as units. The A/onographs appear at irregular intervals and are 
gathered into volumes of about 500 pages. with a uniform subscription of $4.00 
(Postal Union, $4.30). The price of single numbers varies according to the 
size. Five volumes have already been issued. 

Subscriptions, orders and business communications may be sent cites! to 
Professor 11. C. WARREN, Business Manager, Princeton, New Jersey, U.S. A,, 
or forwarded through the publishers or agent. 


PUBLISHED BY 
THE MACMILLAN COMPANY; 
41 N. QUEEN ST., LANCASTER, PA. 66 FIFTH AVENUE, NEW YorRK. 


AGENT: G. E. STECHERT, London (2 Star Yard, Carey St., W. C.); 
Leipzig ({lospital St. y 10); Paris (76 rue de Kennes). 


Che Popular Science Monthly 


The Contents of the March Number include the.«fol- 
lowing articles: 


( 
ce 


Aerial Navigation. O. Chanute. 

The Metric System: Shall it be Compui- 
sory? Professor W. Le Conte Stevens. 

The Conservation of Energy in Those of 
Advancing Years. Dr. J. Madison Taylor. 

The Royal Prussian Academy of Science, 
Berlin. Edward F. Williams. 

The Tropical Station at Cinchona, Jamaica: 
Dr. N. L. Britton. 

Education and Industry. Professor Edw. 
. Jones. 

Evolution Not the Origin of Species. O. F. 
Cook. 

Some Historical Aspects of Vegetarianism. 
Professor Lafayette B. Mendel. 

Tokyo Toikoka Dragaku (The Imperial! Uni- 
versity of Tokyo). Nachide Yatsu. 


THE POPULAR SCEENCE MONTHLY has had few rivals and no equal in the 
educative service it has done for the American people. A complete set of the 
volumes thus far published is both a history of science for the period covered 
and at the same time a pretty complete cyclopedia of natural science. ‘There is 
nothing to fill its place, and to carry it on is a benefaction to the public.—W. T- 


Harris, U. S. Commissioner of .Education. 


The Popular Science Monthly, 


SUB-STATION 84, NEW YORK CITY. 
$3-00 per year. 30 cents per copy. 


Ree’ THE POPULAR SCIENCE MONTHLY wll be sent for six months for 
one dollar to, new subscribers mentioning The Journal of Comparative Neurology 


and Psychology. 


The Journal of Comparative 
Neurology and Psychology. 


PUBLISHER’S ANNOUNCEMENT. 


Complete sets and separate volumes of back numbers of THE 
JOURNAL OF COMPARATIVE NEUROLOGY (volumes I to XITI) are for 
sale at this office at the rate of $3.50 per volume unbound, carriage 
pre-paid. Single numbers are also sold at prices varying with the 
contents. The new series began with January, 1904. Contents of 
the four numbers already issued follows. 


Volume XIV, Number 1, March, 1904. 


The Relation Zs the Motor Endings on the Muscle of the Frog to Neigh- 
boring Structures. By JOHN GORDON Ww ILSON. ‘Two plates. 

Space Perception of Tortoises. By Roperr M. YERKEs. 

A Note on the Significance of the Form and Contents of the Nucleus in the 
Spinal Ganglion Cells of the Foetal Rat. By SHINKIsHI Harat. Two plates. 

An Establishment of Association in Hermit Crabs. By E, G. SPAULDING. 

Editorial. 

The Mid-Winter Meetings. 

Literary Notices. 


Volume XIV, Number 2, April, 1904. 


Physiological Evidence of the Fluidity of the ees Substance in the 
Pedal Nerves of the Slug—Ariolimax columbianus. By O. P. JENKINS and A. 
J. CARLSON. One figure. 

The Nervous Structures in the Palate of the Frog: the Peripheral Net- 
works and the Nature of their Cells and Fibers. By C. W. PRENTISS. Twelve 
figures. 

The Beginnings of Social Reaction in Man and Lower Animals. By C. L. 
HERRICK. 

Inhibition and Reinforcement of Reaction in the Frog, Rana clamitans. 
By Rosperr M. YERKES. 

On the Behavior and Reactions of Limulus in Early Stages of its Develop- 
ment. By RAYMOND PEARL. One figure 

Editorial. 

Recent Studies on the Finer Structure of the Nerve Cell. By G. E, Coc- 
1g 0063 Dy 

Literary Notices. 


Volume XIV, Number 3, June, 1904. 


An Enumeration of the Medullated Nerve Fibers in the Ventral Roots of 
the Spinal Nerves of Man. By CHARLES E. INGBERT. Thirty-eight figures. 

Editorial. 

Color Vision. By C. L. Herrick. 

Literary Notices. 


Volume XIV, Number 4, July, 1904. 


The Associative Processes of the Guinea Pig. <A Study of the Psychical 
mi! elopment of an Animal with a Nervous System Well Medullated at Birth. 
By Jesse ALLEN. Two plates and twelve figures. 

Editorial. 

Literary Notices. 


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CONTENTS, 


Retrograde Degeneration in the Corpus Callosum of the White 
Rat. By S. WaLtTerR Ranson. (from the Neurological 
Laboratory of the University of Chicago and the Anatomt- 
cal Laboratory of St. Louts University. With Plate VII. 381 


The Early History of the Olfactory Nerve in Swine. By Ep- 
GAR A. BEpFoRD, S.M. With fourteen figures. . eg OD 


The Relation of the Chorda Tympani to the Visceral Arches in 
Microtus. By Victor E. EMMeL. (from the Biological 


Laboratory of Pacific University. . ‘ : Se 
Editorial . : ; : . : : i : . 418 
Recent Contributions to the Body-Mind Controversy. By C. 

L; HERRICK. 2: : : i : : : Ae 
Literary Notices. : : Re eh os : a Ag2 


THE JOURNAL OF COMPARATIVE NEUROLOGY AND PSY- 
CHOLOGY is published bi-monthly. The annual volume of six numbers 
comprises about 500 pages, with plates and text-figures. The subscription price 
is $4.00 a year, strictly net (foreign subscription, $4.30, 18 s., M. 18, 22 fr., 
L. 22), postage prepaid. 

Authors receive 50 reprints of their papers gratis and additional copies 
are supplied at cost. All MSS. and matter for review relating to the Structure 
of the Nervous System and all business correspondence should be addressed 
to the Manacinc EpIToR aT DENISON UNIVERSITY, GRANVILLE, OHIO. 
Editorial Matter relating to Comparative Psychology and the Physiology of the 
Nervous System should be sent directly to Dr. RoperT M. YERKES, PsycHo- 
LOGICAL LABORATORY, HARVARD UNIVERSITY, CAMBRIDGE, Mass. 


a 


Entered as second-class matter in the Postoffice at Granville, O. 
\ 


Volume XIV NOVEMBER, 1904 Number 6 


The Journal of Comparative 


Neurology and Psychology 


(Continuing the Journal of Comparative Neurology) 


EDITORS 
C. L. HERRICK, Socorro, New Mexico. 
C. JUDSON HERRICK, Manager, ROBERT M. YERKES, 
Denison University Harvard University 


ASSOCIATED WITH 


OLIVER S. STRONG, HERBERT S. JENNINGS, 
Columbia University University of Pennsylvania 
COLLABORATORS 


J. MARK BALDWIN, Johns Hopkins University b. F. KINGSBURY, Cornel! University 
FRANK W. BANCROFT, University of California FREDERIC S. LEE, Columbia University 
LEWELLYS F, BARKER, University of Chicago JACQUES LOEB, University of California 
H. HEATH BAWDEN, Vassar College E. P. LYON, St. Louis University 


ALBRECHT BETHE, University of Strassburg ADOLF MEYER, N. Y. State Pathological Inst. 
G. E COGHILL, Pacific University THOS. H. MONTGOMERY, Jr., Univ. of Texas | 
FRANK J. COLE, University of Liverpool WESLEY MILLS, McGill Davee 

H. E. CRAMPTON, Columbia University C. LLOY D MORGAN, University College, Bristol 
Cc. B. DAVENPORT, University of Chicago T. H. MORGAN, Bryn Mawr College 

WM. HARPER DAVIS, Lehigh University A. D, MORRILL, Hamilton College 


HENRY H. DONALDSON, University of Chicago HUGO MUENSTERBERG, Harvard University 
LUDWIG EDINGER, Frankfurt a-M. W. A. NAGEL, University of Berlin 


§. I. FRANZ, McLean Hospital, Waverley, Mass. G. H. PARKER, Harvard i ookc doles 

THOMAS H. HAINES, Ohio State University STEWART PATON, Johns Hopkins University 
A. VAN GEHUCHTEN, University of Louvain RAYMOND PEARL, University of Michigan 

R. G. HARRISON, Johns Hopkins University C. W. PRENTISS, Western Reserve University 
C. F. HODGE, Clark University C. 8. SHERRINGTON, University of Liverpool 
8. J. HOLMES, University of Michigan G. ELLIOT SMITH, Gov’t. Medical School, Cairo 
EDWIN B. HOLT, Harvard University EDWARD L. THORNDIKE, Columbia University 
G. CARL HUBER, University of Michigan JOHN B. WATSON, University of Chicago 
JOSEPH JASTROW, University of Wisconsin W. M. WHEELER, Am. Museum of Nat. History 
J. B. JOHNSTON, West Virginia University Cc. O. WHITMAN, University of Chicago 


7 Published bi-monthly 


i dagy Me DENISON UNIVERSITY, GRANVILLE, OHIO 


2 


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ie Psychological Keview 


EDITED BY 


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WITH THE CO-OPERATION OF 


A. C, ARMSTRONG, Wesleyan University, Middletown, Conn.; ALFRED BINET, 
Ecole des Hautes-Etudes, Paris; W. L. Bryan, Indiana University, Blooming- 
ton, Ind.; Mary W. CALKINS, Wellesley College, Wellesley, Mass.; JoHN DEWEY, 
H. H. Dona.pson, University of Chicago; C. LADD FRANKLIN, Baltimore; G. 
S. FULLERTON, University of Pennsylvania; H. N. GARDINER, Smith College, 
Northampton, Mass.; G. H. Howison, University of California; JosepHn 
JAsTROw, University of Wisconsin; ADoLrF MEYER, N. Y. Pathol. Institute, 
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City, lowa; Cart Stumpr, University, Berlin; R. M. WENLEY, University of 
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The Contents of the March Number include the fol- 
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Aerial Navigation. O. Chanute. 

The Metric System: Shall it be Compul- 
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The Conservation of Energy in Those of 
Advancing Years. Dr. J. Madison Taylor. 

The Royal Prussian Academy of Science, 
Berlin. Edward F. Williams. 

The Tropical Station at Cinchona, Jamaica: 
Or. N. L. Britton. 

Education and Industry. Professor Edw. 
D. Jones. 

Evolution Not the Origin of Species. O. F. 
Cook. 

Some Historical Aspects of Vegetarianism. 
Professor Lafayette B. Mendel. 

Tokyo Toikoka Dragaku (The Imperial! Uni- 
versity of Tokyo). Nachide Yatsu. 


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The Journal of Comparative 
Neurology and Psycholog 
PUBLISHER'S ANNOUNCEMENT. 


Complete sets and separate volumes of back numbers of THE 
JOURNAL OF COMPARATIVE NEUROLOGY (volumes I to XIIJ) are for 
sale at this office at the rate of $3.50 (net) per volume unbound, ear- 
riage pre-paid. Volume XIV, beginning the new series, may be pur- 
chased for $4. (net). The leading articles in the last two issues of THE 
JOURNAL OF COMPARATIVE NEUROLOGY are as follows: 

Volume XIII, Number 4, December, 1903. 

The Rate of the Nervous Impulse in the Ventral Nerve-Cord of Certain 
Worms. By O. P. JENKINS and A. J. CARLSON. Fourteen figures. 

Notes on the Technique of Weigert’s Method of Staining Medullated Nerve 
Fibers. By OLIVER S. STRONG. 

The Doctrine of Nerve Components and Some of its Applications. By C. 
JUDSON HERRICK. 

Columella Auris and Nervus Facialis in the Urodela. By B. F. KInGs- 
BURY. Seven figures. 

Volume XIII, Number 3, October, 1903. 

The Neurofibrillar Structures in the Ganglia of the Leech and Crayfish, 
with special reference to the Neurone Theory. By C. W. PRENTIss. ‘Two 
plates. 

On the Increase in the Number of Medullated Nerve Fibers in the Ventral 
Roots of the Spinal Nerves of the Growing White Rat. By SHINKISHI HATAT. 

On the Medullated Nerve Fibers Crossing the Site of Lesions in the Brain 
of the White Rat. By S. WALTER Ranson. One plate. 

On the Density of the Cutaneous Innervation in Man. By CHARLES E. 


INGBERT. 
Ona Law Determining the Number of Medullated Nerve Fibers Innervating 


the Thigh, Shank and Foot of the Frog. By Henry H. DONALDSON, 


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The Behavior of Paramecium. Additional Features and Gen- 
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of Zoology in the University of Pennsylvania. With 17 


figures in the text... : : : ; ; AAT 
Editorial. E 5 ; : ; : : : eae 
Clarence Luther Herrick. By H. Heato Bawpen. 3 eo 
Bibliography of C. L. Herrick. . : : ; : - 529 


THE JOURNAL OF COMPARATIVE NEUROLOGY AND PSY- 
CHOLOGY is published bi-monthly. ‘The annual volume of six numbers 
comprises about 500 pages, with plates and text-figures. The subscription price 
is $4.00 a year, strictly net (foreign subscription, $4.30, 18s., M. 18, 22 fr., 
L. 22), postage prepaid. 

Authors receive 50 reprints of their papers gratis and additional copies 
are supplied at cost. All MSS. and matter for review relating to the Structure 
of the Nervous System and all business correspondence should be addressed 
to the Manacinc EpiTror aT DENISON UNIVERSITY, GRANVILLE, OHIO. 
Editorial Matter relating to Comparative Psychology and the Physiology of the 
Nervous System should be sent directly to Dk. RoBERT M. YERKES, PsycHo- 
LOGICAL LABORATORY, HARVARD UNIVERSITY, CAMBRIDGE, Mass, 


Entered as second-class matter in the Postoffice at Granville, O. 


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