'ehbot. eh whee ee peiag ss eineeneo-ey wes Thee ida D Se, Fe tm - 3 ; fe ne = ee apa, nad Red teen Ze str Reo Oe ss a ; pee i roe re =Se WS LO ew ee ae ar i : A +h : a ‘ aig: 1S ati RN po e THY rt Maes YAN Ki ,-) i 0, ‘ afte ¢ ie aie i Pade: oh te: pa 4 4 es == — —— a = se =~ EME aoe a So ee : : aS z : ‘ - : et SESH he eer ; * 3 ee — = ” Se $ eat ret 7 vit a ee rs S— 4 a 4 pei! : BBE ae ~ 2e aaa rom Uae ’ = —_ Z EROS ish. SNM if ye obs) » ive Paina te EY esau Ra Ye le SB al SSeS Nr Dwar ae aint ‘Eh : Hea yeas Nea : Dry) ; pa ead SN a oa ee 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. tee: a 7 ae oe [> eat 7 oh | = ~~ ie ON a —e + eet SA ase: He ee => Journal of Comparative Neurology and Psychology. Vol. XIV. Pilate sere eas ae ce te AE igak ts eae 2 Fig. 8. Fig. 9 LH‘ Wilder. de/. = ‘ ey: HELIOTYPE 0O,. BOSTON, gy 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. ‘ ay a8 <3 < ® 7 = > Pc" » ‘ ah * i oa y a “nt , e ‘ 7 > : i £ 5 ’ . ~ + aa — s 1 Ke = f *% } 4 ne Pay, oF uf =| aa ae ig » & Plate IV. Journal of Comparative Neurology and Psychology, Vol. XIV. I Ss > 4 i ~ ~ Dine a3 ee ee i ers * mS : Se | ‘ % 4m i Ea 2% "ae ee is TR, 1 N 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. ) “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. Literature. Apathy, S. 797. Das leitende Element des Nervensystems und seine topograpischen Beziehungen zu den Zellen. Aith. d. zoolog. Station zu Neapel, Bd. 12, D-.495-748;, wal. 23-32. Bardeen, C. R. :03. The Growth and Histogenesis of the Cerebrospinal Nerves in Mammals. Amer. Journ. Anat., Vol. 2, p. 231-257, 15 figs. 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 fluviatilis. Asat. Anz., Bd. 12, p. 31-34. :03. Allgemeine Anatomie und Physiologie des Nervensystems. Lezp- sig. p. viit487, 95 Abdg. u. 2 Taf. Cavalié, M. :02. Terminaisons nerveuses dans le testicule chez le Lapin et chez le Poulet et dans l’epididyme chez le Lapin C. &. Soc. Biol., Paris, T. 54, Pp. 298-360. Dogiel, H. S. 793. Die Nervendigungen in der Haut der dusseren Genitalorgane des Menschen. Arch. f. mikrosk. Anat., Bd. 41, p. 585-612, Taf. 32-33. 798. Die sensiblen Nervenendigungen im Herzen und in den Blutgefas- sen der Séiugethiere. Arch. f. mtkrosk. Anat., Bd. 52, p. 44-69, Taf. 4-6. : Eimer Th. 79. Die Medusen physiologisch und morphologisch auf ihr Nervensys- tem untersucht. TZiidimgen, p. 1-277, 31 figg., 13 Taf. Hertwig, O. and R. ’78. Das Nervensystem und die Sinnesorgane der Medusen monograph- isch dargestellt. Lezps¢g, p. x +78, 10 Taf. Hesse, R. 95. Ueber das Nervensystem und die Sinnesorgane von Rhizostoma cuvieri, .Zettschr. f. wiss. Zoolog., Bd. 60, p. 411-456, Taf. 20-25. Prentiss, Pertpheral Networks. EL Hofmann, F. B. :02. Das intracardiale-Nervensystem des Frosches. Arch. f. Anat. u. Physiol., Anat. Abth., p. 54-114, Taf. 3-6. Holmgren, E. 795. Studier 6fver Hudens och de Kortelartade Hudorganens Morfologi hos Skandinaviska Makrolepidopteralarver. Kg/. Svenska. Venten- skaps- Akademiens Handlinger, Bd. 27, p. 1-84, 9 Taf. 798. Zum Aufsatze W. Schreiber’s ‘‘Noch ein Wort ilber das peripher- ische sensible Nervensystem bei den Crustaceen.”’ Anat. Anz,, Bd. 14, p- 409. : Leontowitch, A. :01. Die Innervation der Menschlichen Haut. Jnternat. Monatschr. f. Anat. u. Physiol., Bd. 18, p. 142-310, Taf. 6-11. Ménckeberg, G., and Bethe, A. 799. Die Degeneration der markhaltigen Nervenfasern der Wirbel- thiere unter hauptsachlicher Beriichsichtigung der VerhAltnisses der Primitivfibrillen. Arch. f. mikr. Anat. Bd. 54, p. 135-198, Taf. 8-9. Nusbaum, S. and Schreiber, W. 797. Beitrage zur Kentniss des peripherischen Nervensystems bei den Crustaceen. Szvl. Centralbl., Bd. 17, p. 625-640, 8 Figg. Ruffini, A. :01. Le fibrille nervose ultraterminali nelle terminazioni nervose di senso, et la teoria del neurone. Revésta di patologia nervosa e mentale, Firenzi. Vol. 6, p. 70-82. Sfameni, P. 3 :02. Sul modo di terminare dei nervi nei genitalia esterni della femina con speciale riguardo al significato anatomico e funzionale dei cor- pusculi nervosi terminali. Monzt. Zoolg. [tal., Anno 13, p. 288-297. Smidt, H. :02. Die intraepithelialen freien Nervenendigung bei Helix und ihre Beziehungen zu Sinneszellen und Driisen. Anat. Anz. Bad, 20, P- 495-506, 8 Abdg. 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. — — 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: % \ , { ; > £ os ess Daze \ BRARY | =, (a BS>t3 Dy ay a ? “sy r ae * Sy ® “a c~ “ A & ‘I ‘ ey ” gf ee 00 Journal of Comparative Neurology and Psychology. &y ‘ Zt 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. ) 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.) ye 7 a ’ \ 1A He ; = % i me 8p ek YY > An = a % : oe fe Me 2 : Pea i Pie 4 i e | 4 j 16 e aa ax 7 wes “ae ') taper wis eo, . . a | e — : ‘ = Ps - 7 ' a - ie ee i ‘ od yal ED exh! '< ; a. Cat, ’ : : r+ 7 ae Pe ya 6 "y nn wf are ay i PS 7 mena ae ce as 4 akc ime we weber: 2a i, ac = : = _ a =~ i, 7 =i } 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. 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. 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.’’ 15 ce Tome III, (En cours de publication) . . 2. . 2. . © 2 we 1555 Aux nouveaux souscripteurs du tome III, les tomes Ier et II sont laissés 4 leur ancien prix, soit 12 fr. chaque (frais de port compris). The 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. Dona.pson, University of Chicago; C. LADD FRANKLIN, Baltimore; G. S. FULLERTON, University of Pennsylvania; H. N. GARDINER, Smith College, Northampton, Mass.; G. H. Howson, University of California; JOSEPH JAsTRow, University of Wisconsin; ADoLF MEYER, N. Y. Pathol. 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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. 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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. 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Reports of numerous cases are cited in our Scientific treatise on Hzmatherapy. It is yours for the asking. The Bovinine Company 75 West Houston Street, NEW YORK Leitz’s Microscopes Are the Standard of Excellence. Sliding and Rotary Microtomes Of Latest Improved Form. Bacteriological Apparatus Laboratory Supplies Duty free prices to Educational Institutions. Catalogues sent on application. New York e iaeor lee rm 411 W. 59t fi ] ft ar. e Cl Ls Lake St. Street. 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 2 ene Pe et, vale eT hi hag ‘ j ‘ies if be is eee Wane :% Volume XIV SEPTEMBER, 1904 Number 5 The Journal of Comparative ee ar PEs Pat sont © x = ol Sep 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. 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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. ates eee ee . : PS 7 Ses sere ee . pe rere re ero ms Ss44 4224", ee te es : des ade rags athe wares pop ele rary faite “t zy erveseees, eso, wa rem ee ttre y ere Seren ee bre Saleig! eels a Roe ee bee ag te tee Sen ry - AAs em, _ ag ag SMa OE Beg + apie ul ean ae ne, ~ ela eS etch. Neletet Ey reheat eal pinto tata’ ‘ Ym ren Te :