operant wi" 3 Md tee ie : pereey o5te Pres a? RA ae f oye, i Rea = z re wits rE Boe Z a Pg we eee w: 5 > be * te & * oy . . eee a2. oo Pees % Gc FS el on ‘ee 40-0" ree Coton o< * bard be . ~* Sk a a . ” i ae we ate 8 nn ae ae a. &' & Cats ha Oat, aia a ay oh) Ph Rng ha can vay Set Ny RRA We aL NA hate Wirt ts SAP TA iy ay “THE JOURNAL OF COMPARATIVE NEUROLOGY AND PSYCHOLOGY EDITORIAL BOARD Henry H. DonaLpson Apo.tF MEYER Wistar Institute of Anatomy Pathological Institute, New York C. Jupson HERRICK OLIveER S. STRONG University of Chicago Columbia University HERBERT S. JENNINGS Joun B. Watson Johns Hopkins University Johns Hopkins University J. B. Jounston Rogpert M. YERKES University of Minnesota Harvard University o VOLUME XxVIII 1908 PHILADELPHIA THE WISTAR INSTITUTE OF ANATOMY AND BIOLOGY The Journal of Comparative Neurology and Psychology CONTENTS OF VOLUME XVIII, 1908 Number 1, January, 1908. An Experimental Study of Imitation in Cats. By Cuartes Scorr Berry. (From the Harvard Psychological Laboratory.) With Two Figures ...........-0.:eseeceeseeeeeee eee Orientation in the White Rat. By Harvey Carr and Joun B. Watson. (From the Bryshie: logical Laboratory of the University of Chicago.) With One Figure..........+-.++-.-++5 Studies on Nerve Cells. I. The Molluscan Nerve Cell, Together with Summaries of Recent Literature on the Cytology of Invertebrate Nerve Cells. By W. M. Smattwoop and Cuartes G. Rocers. (From the Zoélogical Laboratory of Syracuse University.) With Plate Wand’ nbirteensEipures|im they Wextircts -teetactarctater eter ietaleleleloleterelaleveteiefetelevelaterelateletelelersy= Document I of the Report of the President of the Brain Commission (Br.C.). By W. WALDEYER. Neurology at the Physiological Congress, Heidelberg, 1907, and at the Congress for Psvchiatry, Neurology, Psychology and the Nursing of the Insane, Amsterdam, September, 1907. By SHEPHERD Ivory FRANz Cerca ee ee a Books Received «) ajtel ew aie, © 0.8.6 mge lee) e' 6.0) 0 em \e, 6. 0) 0.6 6.6) 6, )e:\s//e! 6] 0/6016) 6 018) © U.S (6, 0)0/18) ONC \e)«) ae eee Number 2, April, 1908. The Architectural Relations of the Afferent Elements Entering into the Formation of the Spinal Nerves. By S. Watter Ranson, (From the Anatomical Laboratory of the University of Chicago.) With One Figure The Nervous System of the American Leopard on Rana pipiens, Compared with that of the European Frogs, Rana esculenta Rana temporia (fusca). By Henry H. Donatpson. (From: theW istar Institute of Anatomy and Biology.) WithSix Figures........-......-.- Preliminary Note on the Size and Condition of the Central Nervous System in Albino Rats Experimentally Stunted. By SuinxisHi Harat. (From the Wistar Institute of Anatomy and TTA) 9 SINE a Se RES Urea aes sen Sumrr Son Toe Toon cd aca cG On the Phylogenetic Differentiation of the Organs of Smell and Taste—By C. Jupson Herrick. (From the Anatomical Laboratory of the University of Chicago). ......4.-00s0eeereeneceee Some Conditions which Determine the Length of the Internodes found on the Nerve Fibers of the Leopard Frog, Rana pipiens. By Karasn1 Taxanasui. (From the Neurological Labor- atory of the University of Chicago.) With Seven Figures............0eeeeeee cere eens i ee OO ee i i eo ace ill 27 45 87 9! 100 Iol 121 151 157 Number 3, June, 1908. The Behavior of the Larval and Adolescent Stages of the American Lobster (Homarus Americanus) By Pur B. Hapiey. (From the Anatomical Laboratory of Brown University.) With ANKE cin, OM MTDiGsn gee goa ddonnpeocosndepooudoobos scddneboosGnGOoaascobocosécss 199 The Reactions to Light of the Decapitated Young Necturus. By A. C. EyctesHymer. (From the Anatomical Laboratory of St. Louis University... 0.20 000ccecee eee e eee s snc cecceees 303 Recent Studies upon the Locomotor Responses of Animals to White Light. By E.D.Concpon... 309 Literary Notices 5c) 45) sie.c 3 ats ee bage sie Rarteare ate low lepere pretenses sakes aiee-saes eae eae 329 Number 4, October, 1908. A Comparison of the Albino Rat with Man in Respect to the Growth of the Brain and of the Spinal Cord. By Hexry H. Donarpson. (From the Wistar Institute of Anatomy.) With Plates and Ti-and OnePipurenuithe Mext yore polrats meets lelelstaloey-te erent ate 345 .The Morphological Subdivision of the Brain. By C. Jupson Herrick. (From the Anatomical Laboratoryiof2neU niversttyioy Ghicag.)srl-cin oe eee iets eee eee eee eee 393 On the Commissura Infima and its Nuclei in the Brains of Fishes. By C. Jupson Herrick. (From the Anatomical Laboratory of the University of Chicago.) With Twelve Figures...... 409 Eversion and Inversion of the Dorso-Lateral Wall in Different Parts of the Brain. By C. U. Ariens Kappers. (Central Institute for Brain Research, Amsterdam.) With Five Figures. 433 : Number 5, November, 1908. The Relations of Comparative Anatomy to Comparative Psychology. Lupwic Epincer. (From the Senckenberg Neurological Institute, Frankfort a /M.) WithsPive Bipuresi/.. eet 437 The Relation of Strength of Stimulus to Rapidity of Habit Formation. By Rosert M. YerKeEs and Joun D. Dopson. (From the Harvard Psychological Laboratory.) With Five Figures 459 Some Reactions of Drosophila, with Special Reference to Convulsive Reflexes. By Frepreric W. Carpenter. (From the Zoélogical Laboratory of the University of Illinois.) With One “BAG UTE S55. chakereiciclares ors ete eieserovevoiertie lel sisinre Gib Sel eseiescisrayarelshnvoms lho n eye operetta 483 Phototaxis in Fiddler Crabs and its Relation to Theories of Orientation. “By S. J. Hotes. (From the Zoélogical Laboratory of the University of Wisconsin) ............ jos ate 493 The Limits of Educability in Paramecium. By Stevenson Situ. (From Hampden-Sidney Col- lege, Virginia.) Wath BoursBipuresei).. ice cic scien aerate a1 eee eee eet 499 French Work in Comparative Psychology for the Past Two Years. By Marcaret Froy WasH- BURN. (From the Departntent of Psythology of Vassar College).........0.0c00eceeeeeeee 511 Literary Notices’ < o'..2 vistors sis sie erouess crete s\gvers7eiclers His Sis Hauale ous Oietevelouetelsagia acc ue olor ceateel tee eye enee eee 521 Number 6, December, 1908. The Cranial Nerves of Amphiuma means. By H.W.Norris. (Jowa College.) With Plates IV, V,, Vi, Villard \ViGDD 3338 cap iiisiecac arti eeer tpt este leita tetera ete eee 527 Additional Notes on the Cranial Nerves of Petromyzonts. By J.B. Jounston. (University of Minnesota.) With) Uhixty-onevEi cures jen sais soc eoeiee «sarees eee erate a eters 569 On the Significance of the Caliber of the Parts of the Neurone in Vertebrates. By J. B. JounsTon. (University, of: Mannesota)) 2) Jerioe a ists «eieramis «nie)elieto 0) ine talsseistel Xisens? || as TIME out | Y our | our First DOOR NOV: AlGiens capoeira fits ole 2 | 2 | 2 INOVcgNG) iojey-a)soe colens spsieyotetoll: | I hf IN OVE Obie aia-trbostte ee mien I Of. INOViRLOM. pte treeeten tierraerar 2 2 2 INOV iL 7iste.crsia cio sel usisiere ste 2 2 2 INGV2iL 72 icine oie 2 Seleieie stele I 2/ INOWecl 7 aceite ee eeree 3 3 3 NOVA 2h Sate einaiocn hither I 10’ NOVA 2n eras oie neice I i! INOVe22e oe oes teen riys I it? INGVRZ Ze eee oeons hate: I 1730” IN OVE 22 sere rie thers I 15” Totalsicicesee oe isin 9 | 9 7 2) 8 Each time X followed Y out she was fed and then put back alone for five minutes. If she did not get out during that time Y was put in with her again. However, the first two times X opened the door Y was in the box with her. Y first turned the button then X pulled the loop. TABLE V. M imitating Y. Date Y GETS ouT M sEEs LAP See LESS 2 UR TIME OUT | ALONE Noy. 16 6 3 6 | Nov. 19 7 7 Zi | Nov. 20 if 7 7 | INOS A Eapone GOOF 6 6 6 | INGA 22rd orate 7 7 7 | (Gta samen 33 30 33 | M did not watch Y very closely until he had opened the door several times, then she began to pay close attention, especially when he went to the button. In all the tests she had with Y she did not once attempt to turn the button. Generally she was inactive when in the box alone. During the first trial on Nov. 28 she scratched at the loop after X had turned the button. ‘The Berry, J mutation in Cats. 9 TABLE VI. M imitating X. M vrottows X| M Gers out OUT ALONE Date X GETS OUT M sees TIME IN OvA2 2 er eee f NOV: 28ieeees aes 4 | 4 4 INOW 2 Bee eceteine INOVA2 Shares IN OWES Ae Gaia aes) | Nove 2 Sicuenate se | IN OVA Shee ere INOVA Sheree nN nN wat Se > eal aotalseae ae 9 9 9 6 second time she was put back after following X out, she turned the button and scratched at the loop; but it was not until X had opened the door four times that she pulled the loop hard enough to open the door. She always pulled the loop with her claws, whereas X generally used her teeth. Experiment 4. Getting Food by Turning Button. Method.—A hole three-fourths of an inch in diameter was bored in the middle of Box I. ‘This hole was covered both on the inside and outside of the box by wooden buttons. Meat was placed in the hole from the outside. To get the meat the cat had to turn the inside button (see Fig 1). Results.—X when put into the box turned the button in less than five minutes. TABLE VIL. M imitating X. Date | X GETS MEAT M sEeEs M Gets MEAT TIME Nee ee | 7 | 7 | INOVWa2 OES scott ao ete 7 | 7 | INONE)2 Feats cist Peer I | I INOVos2 Fisec ce seeeetnene sete | I ie IN Dyce eee eerantee ere ders. | I 1 INOW292 Pere ste cts mcrores I ph IN OVD x her ttstye con Seo eee I 1 INGV 2 7ireeneetrie ieee | I 30” INOVAKZ Sie. eon eee Seoul I 2/ | alo Gallsemerteretrey aise © 15 15 6 10 Journal of Comparative Neurology and Psychology. Each day M was put into the box alone for ten minutes before X was put in with her. After X had turned the button and eaten the meat she was taken out and M was left alone in the box for five minutes. She got no meat unless she turned the button. Occasionally she smelled of the button but she made no effort to turn it until the end of the fifteenth trial. Experiment 5. Raising Small Trap-door. Method.—A door (7 x 9 cm.) was made in the bottom of Box II. A narrow opening was left in the front end of the door. By insert- ing the claws in this opening the cat could easily raise the door and get the meat placed under it. The doorway was closed on the under side so that the cat could not get out of the box. Results.—X learned unaided to open the door in less thantwenty minutes and Z learned almost as soon. Y was left in the boxalone: INOW? O.toae Pec phioree emcee eer. 20/ LN Ke) or ORABRAREDUACH CAG OROOGSEO doca0 46 go’ Nov. 2 Did DGGy To cioars assis ois Prana etc ee re 30° INO. Oe Sadar Gaon eo oMaomce tata Lec 20/ Although he worked at the door more or less, he did not once succeed in getting it open, as he almost invariably scratched in the wrong place. TABLE VIII. Y imitating X and Z. X OPENS THE Y OPENS THE Date Y srEes TIME DOOR DOOR is {9") a Q _ (e) 4 WwW PW YuNXnnany7 RMN PW nunrwn Qn = Nn o o i) -_ as = a a fe) =) + bn ce oe ee oe oe ef Berry, [mutation in Cats. 1 In the tests of imitation which were now made Z instead of X was used part of the time to open the door. The behavior of Y was just the same whichever cat was used. ‘he general method was to take X out after she had opened the door once, and let Y try the door alone for five minutes. If he did not get it open X was then put in with him again. However, on the last day of the experiment X was allowed to open the door six times in succession before she was taken out of the box. During the first part of the experiment Y imitated X very closely. When X was taken out he frequently tried the trap-door; but dur- ing the latter part of the experiment he only looked on while X opened the door and ate the meat. During the first series of six trials on the last day Y merely looked on, during the second series he smelled of the door each time X opened it, and during the third series he reached through the door after X had taken out the meat. After X had been taken out of the box upon the conclusion of the third series of trials Y went to the door and opened it at once. After that he opened the door as fast as I could putin the meat and close it. Experiment 6. Rolling Ball into Hole. Method.—In Box I a hole large enough to admit a tennis ball was made in the middle of the bottom of the box, 12 cm. from one end. In the middle of the end of the box next to the hole and 25 cm. above the floor a small door (6 x 6 cm.) was placed. This door, which opened inward, was held shut by a wooden crossbar. The mechanical devise was of such a nature that when the ball rolled through the hole and fell into a box below, the pressure on the box raised the crossbar and permitted the door to fly open. ‘The opening of the door exposed to view a small piece of meat which the cat easily could reach. In order to make it easier for the cat to roll the ball into the hole a wooden triangle (44 x 44 x 29 cm.) was fastened to the bottom of the box with the hole at its apex (Gee Pies): Results —Below are given the periods during which the cats were given an opportunity to discover that meat could be obtained by rolling the ball into the hole. Two or three times the ball was knocked into the hole accident- ally while the kittens were playing together. Strange as it may seem, X was the only one of the kittens that showed any dispo- sition to play with the ball. It is true that occasionally one of the 12 Fournal of Comparative Neurology and Psychology. TABLE IX. DatTE NE Z M, Z MESSY DOGS Wikies mate a teis crates = 30/ ID tees hi datet coat tie otc 50! DGG7 ecco s as 30’ DIkt Sscocopsopncdd soon 30° | Wecaton.: 30° | Dec. 11.. 30 | Decragee 20 1D eR 7 Bea desis pCO cree me 30° IDI Oc cboacsnce he otout 45’ evepiigseate de potas oc os 60° | [eae 945 - 60’ Janie. 60’ [nein acho aoeeoc aaah 50’ [EEL Basqococabbacgostnd 60 Do tales as te Messe 4 hr. 24 hr. | I hr. | 6;'5 hr. kittens struck it, but never twice in succession. In one week [ taught X to roll the ball into the hole from any part of the triangle. After X had rolled the ball into the hole two or three times in succession in the presence of Y, she was taken out and Y was left mn the box alone for five minutes, then X was put in with him again. [his was continued until Y learned to roll the ball into the hole. Y got no meat when X rolled the ball into the hole unless he got to the door first (see Table X). During the first few trials Y merely looked on, but gradually he reached a point where he occasionally struck at the ball when X was rolling it. ‘The next step was to strike at it when he was in the box alone. When X got the ball almost to the hole Y gave the closest attention, and when the ball went in he dashed to the door and tried to get the meat first. Not infrequently when X got the ball almost to the hole Y knocked it in. Soon after he had reached this stage he rolled the ball into the hole when he was in the box alone. In the case of Z the method was the same as that employed with Y, except that Z was generally fed when X rolled the ball into the hole. Only twice in the forty-one trials of Table XI did Z touch the ball. As far as I could see the only thing Z learned was to associate the opening of the door with the hole, but not with the rolling of the ball. When in the box alone she devoted most of her time to the hole. Y, on the contrary, first formed the associa- tion between the rolling of the ball and the opening of the door. BERRY, Imitation in Cats. I3 TABLE X. Y imitating X. X ROLLS BALL IN HOLE Y sEES Y ROLLS BALL IN HOLE TIME Jan. Jan. Jan. Jan. Jan. Jan. Jan. Jan. Jan. Jan. Jan. Jan. Jan. Jan. Jan. Jan. Jan. Jan. Jan. Jan. Jan. Jan. Jan. Jan. Ete WORN ANWO DAH tw itl bed) md Ddbw OM OD Wo Wd N ee ee ee ee | wo IR ZAG S Aneca eon oats 7O TABLE XI. Z imitating X. X ROLLS PALL IN HOLE Z SEES Z ROLLS BALL IN HOLE TIME Dec. Dec. Dec. Dec. Jan. Jan. Jan. Jan. Jan. Jan. RAR AK AWPwW WV ~ NYO BON 4 WY PLD ERotalsigs seine csere ones 41 ws) a 3)2 | | | | | My next method was to roll the ball into the hole four times in succession myself, and then place it in the farthest corner of the triangle, and leave Z alone with it for five minutes. Z was given a small piece of meat each time the ball went into the hole. During 14 Ffournal of Comparative Neurology and Psychology. the first ten or fifteen trials Z merely looked on. It was not long, however, before she began to strike the ball when it was rolling. Her interest gradually increased until finally she rolled the ball into the hole of her own accord. TABLE Xl. Z imitating Me. IT ROLL BALL Z ROLLS BALL Date Z SEES asia TIME IN HOLE IN HOLE [Bits 278 conde bo assecdocc | 25 23 {fie Oe Goosdceosbuoboae | 25 24 2 Bier Ni pein ak fone Sia dareoecots 20 18 ie DRIES eeateen tute ee | I ie |[2ids Bosesnsvsscdagcqnsc | I 4 Elis Adaaanootcosamessae I 30” [Gis Bcconodousdocacps | I 45” [JEW asahooomandacecns I isi ES A cocatvole das one aoe | I 25” | EROS Cane ciaanane ator o I | au Pins oanioes ao mman AGue I 15” JEU sonanuecddedvacae | I | vil MIG tals eyyaate tetova 70 65 | 9 | For M the ean was ie same as that used with Z except that I rolled the ball into the hole five times in succession instead of four. During the latter part of the experiment the method was varied somewhat by giving M a chance at the ball each time after TABLE XIII. M imitating Me. | I RoLi BALL M ROLLS BALL Date Z M sees ; TIME | IN HOLE IN HOLE JEN neGdo gegeesbaccnes 15 14 EMO Seunucosmoonon se 30 26 we Oye Se a oe ees eee | 25 23 AN AZOR Sen epee ee ee 25 23 IAW Ose res grsvees sist vets 25 25 | RSC Wie et om canoe F 25 23 RED Mi canner ae eee 25 21 Web 4s cade sas arcttueet siete 25 24 Feb. Dio sueifeiaiiejs: vis ejeta aete)s,'e = 26 2 1 aso Atk he A oe ae I 14 Heb NGanactieee ee eee: 7p 22 IGN Eeoei toto Gaocuoe 9 9 HED Faces piss ees ee oy BPebi7int ns. co8 ca toscbstayne 6 6 ols Gioia ween Meco ce en 6 Heb ySi eas, woetrparctenioniele 20 8/30” Totalsx.cwas.sh sneer 258 240 28 Berry, /mitation in Cats. Ts I had rolled it into the hole. The second day she struck at it several times as it was rolling toward the hole. ‘There seemed to be no method in her attempts, for several times she knocked the ball away from the hole when otherwise it would have gone in. On January 31 for the first time she struck the ball when it was not in motion. From this time on it was an easy matter to get her to strike it by tapping on the floor beside it. When she was left alone occasionally she smelled of the ball, but she spent most of her time watching me and washing herself. It was not until the last two days of the experiment that she deliberately rolled the ball into the hole. Experiment 7. Learning to Catch Mice. Method.—A cage 112 cm. long, 83 cm. wide, and 190 cm. high was inclosed on three sides with wire netting. A mouse put into this cage could neither escape nor conceal itself. Results —January 2. A large black mouse was placed in the cage with Z. At first Z very cautiously smelled of it. “Then when the mouse ran she ran after it, striking it with her paw. Although she became rougher in her play during the last half hour, she did not once growl or strike the mouse with her claws. At the end of one hour the mouse was taken out of the cage uninjured. January 3. Y was put into the cage with the same mouse for one hour. When the mouse ran he ran after it, but at first he did not touch it. After a few minutes, however, he began to strike it. When it climbed up the side of the cage he sat and watched it until it came down again. Unlike Z, he used his claws and switched his tail. During the last few minutes of the hour he did not seem to be much interested in his companion. January 4. X was put into the cage with the same mouse for one hour. At first, like the other cats, she merely smelled of the mouse and followed it about the cage, but soon she began to strike it with her paws. A few times she seized it in her mouth. As far as I could see she never used her claws. She played with it much as she played with the tennis ball in Experiment 6. Her interest abated somewhat during the latter part of the hour. ‘The mouse when taken out of the cage apparently was uninjured, and began to wash itself. However, two days later it was found dead in its cage, possibly from injuries received in the experiment. 16 Journal of Comparative Neurology and Psychology. February 14. Y was in the cage with a gray mouse for fifteen minutes. She followed it about striking it gently with her paws. When it ran up the side of the cage she ran up after it and brought it down in her mouth, but she did not injure it. February 15. The same gray mouse was put into the cage with Z for twenty minutes. The mouse climbed up to the top of the cage. Z went up and smelled of it four times before she knocked it down with her paw. She did not pay very much attention to it during the last five minutes. February 15. Y was put in with the mouse for twenty minutes. He soon discovered it up at the top of the cage. After he had gone up and smelled of it three times he seized it with his teeth and threw it down. He switched his tail and his claws rattled on the floor as he ran after it, but he never growled. In all of these trials the cats had not been fed meat for at least twenty-four hours. February 16. A white mouse was put in with X. The cat played with it as usual. After a few minutes M (the mother cat) was put into the cage with X. She killed and ate the mouse while X looked on. X did not dare to approach as M growled very ominously whenever X moved. After M had finished eating the mouse I took her out and put another mouse in with X. She played with it just as she had played with the other one. I could not see that her behavior was influenced in the least by the tragedy she had just witnessed. When Z was put into the cage with her X seized the mouse in her mouth whenever Z approached, but as long as Z did not move she played with it as usual. When the mouse was given to Z she would not let X have it. After a few minutes Z was taken out and M was put in with X._ M killed the mouse at once and began to play with it. She let X have it, but the latter would not eat it, until M had exposed the raw flesh; then she ate it at once. M was now removed and another mouse put in with X. She played with it as usual, but made no attempt to kill it. February 19. A white mouse was put into the cage with X for ten minutes. She was no rougher with it than usual. But when Y was put in with her she seized the mouse and began to growl. When the mouse ran toward Y he did not attempt to seize it even when it was nearer to him than it was to. X._ After removing Y, I fed M a little meat in sight of X. She at once left the mouse, Berry, [mutation in Cats. iN went to the side of the cage next to M and began to mew. Appar- ently she did not realize that she had fresh meat at her disposal. A mouse was now given to M, who killed and ate it while X looked on. X was allowed to smell of the blood on the floor; then another mouse was given toher. She played with it as usual. Apparently she had not profited in the least by M’s experience. Next Y was tested with the same mouse. He was not as rough as usual in his play. I now put M in with him. She killed the mouse and began to eat it. After she exposed the raw flesh I gave it to Y who ate it at once. After he had finished eating ro | gave him another mouse, but he did not attempt to injure it. Five minutes later Z and X were put in with Y. Growling fiercely, he seized the mouse. In fifteen minutes he had killed and eaten it. February 20. A white mouse was put into the cage with Z. As the mouse tried to bite her she picked it up and tossed it about as if it were a rag ball. She did not seem to be angry in the least. When X was put in with her she growled and seized the mouse, but after a few minutes she let X have it. After they had played with it turn about for a few minutes, Y was put in with them. He killed and ate the mouse while they looked on. He was now taken out and a brown mouse was put in with X and Z. X seized it and killed it almost instantly. In less than five minutes she had eaten it. X was now removed and a brown mouse was put in with Z. She played with it but did not attempt to kill it. February 21. Z played more gently with the mouse than usual. X was now allowed to kill and eat the mouse while Z looked on; then Z was given another mouse. She played with it a little while, then refused to take further notice of it. I put M, X and Y on the outside of the cage but they did not arouse Z in the least. She simply ignored the mouse. March 6. Z played very gently with a mouse, until I put X in with her, then she seized it; but X soon succeeded in getting it away from her. After X had almost killed it, I gave it to Z again. She seized it savagely and held on to it, growling almost continuously. In less than a minute the mouse was dead and Z had begun to eat it. March 7. A big brown mouse was given to Z. She played with it but did not attempt to injure it. Fifteen minutes later X was allowed to kill the mouse while Z looked on. After she had half eaten it I gave it to Z who soon finished it. 18 Fournal of Comparative Neurology and Psychology. March 8. Z played with a mouse but made no attempt to kill it. But as soon as she saw X and M, who were now placed on the outside of the cage, she seized the mouse and began to growl fiercely. In seven minutes she had killed and eaten it. March 13. Z was put into the cage alone with a mouse. In fifteen minutes she had killed and eaten it. Experiment 8. Getting Meat out of Bottle. Method.—In the opening occupied by the small trap-door in Box II a pint milk bottle was firmly fastened. It was partly filled with cloth so that the cat could easily reach meat which was placed on top of the filling. Results.—M got the meat in four minutes. Y was successful in ten minutes, but Z failed completely, although she worked hard for twenty minutes. Her method was to stick her nose into the bottle and then reach for the meat with her paws on the outside. She also tried to get her nose and paw into the bottle at the same time. X tried the same tactics as Z, except that she balanced herself with her nose in the bottle, and then reached for the meat simul- taneously with both paws. The next day Z again failed to get the meat in a trial of twenty minutes. After she had ceased trying X was put in with her. Although she went to work very energetically at the bottle she did not succeed in getting the meat, but her efforts did arouse Z to renewed efforts with the result that this time she was success- ful. She was now removed and X was left in the box alone for thirty-five minutes. She did not get the meat. On the following three days X was tested alone for the following periods: [Eins a Sin nmneta gMid.o De an,oaan tics Guana or atypia 60’ Ea?» an OS Ibarniiach> aebchouie nirare oe nica Pickeh ys eres ate 20’ de SOL Boialtacict aw fin Bi BN agt ory TO ODE h voy race 40’ She did not once succeed in getting the meat. After X had been in the box alone for forty minutes dunking the trial of January 23 I put Y in with her. She watched Y very closely as he reached into the bottle and took out the six pieces of meat. After Y was removed X went to the bottle and got the meat in less than two minutes. At first she used her old method, but finding that did not work she went at it as Y had done. In further trials she got the meat as skillfully as did X and Y. yey Berry, /mitation in Cats. 1g Experiment g. Getting down from T op of Cage. Method.—The kittens frequently climbed up on top of the cage which was used in Experiment 7, but they could not get down with- out help. | arranged a broad board (170 cm. long) in such a way that by jumping 40 cm. to this board, walking down it to the lower end, and then jumping 60 em. they could reach the floor. Results.—All three cats were placed on top of the cage, then meat was thrown on the floor in front of it. “They were greatly excited. X got down by the way of the board in three minutes; Y doubled up to follow X, but his courage failed. Z who did not see X get down now jumped down as X did. Y looked on, and again doubled up to jump, but his courage was insufficient. After seeing X get down two more times he followed her down. III. DISCUSSION OF RESULTS. In the discussion of imitation it 1s essential that the term be defined objectively if it is to have much value for the comparative psychologist. ‘That is, it must be so defined that the imitation is always from the standpoint of the observer. I think that Mor- GAN’S use of the term is satisfactory in this respect, for he says, “in the case of an imitative action the stimulus is afforded by the performance by another of an action similar in character to that which constitutes the response.’”* The acts of organisms are generally classified as instinctive, voluntary, and habitual. For each class there is a corresponding type of imitation. As an illustration of instinctive imitation MorGan cites the case of a hen pecking on the ground, and the chick imitating her action. It is the pecking of the mother hen thatacts as a stimu- lus for the instinctive act of the chick. Automatic or habitual imitation I use to designate those cases where the imitative act is simply an involuntary performance of an acquired, as opposed to an instinctive act. An example of this is the involuntary whistling of a tune that one hears another whist- ling. Here the act is involuntary, but not instinctive. On the subjective side voluntary imitation is conscious purposive imitation. The act of another is imitated with a definite end in view. The test for this kind of imitation is refusal to imitate until 3Morcan, C. L. Habit and Instinct, p. 168. London. 1896. 20 Journal of Comparative Neurology and Psychology. the benefits that would come from imitating have been perceived or experienced. For example, suppose two cats are put into a box together. One cat opens a door by turning a button, while the other cat merely looks on. Both pass out and are fed. If now, when the second cat is put back it goes to the button and turns it, thus opening the door, this would be an instance of vol- untary imitation. In the nine experiments with cats which have been described I have found instances of imitation. So the question is not, “do cats learn by imitation?” but instead, “what is the nature and extent of their imitation /” In the first place, what evidence is there for voluntary imitation ? In E xperiment 4, M refused to turn the button until she had seen X turn it several times and get meat. Her failure was not due to lack of hunger, for after she turned the button once she continued to turn it as fast as I could put the meat in and close the hole. I consider this a fair example of voluntary imitation, for M refused to turn the button until she had seen X repeatedly get meat by turning it. If it were merely instinctive imitation we should have expected M to scratch at the button while X was turn- ing it, but this she did not do. She merely watched X, and when X was taken out of the box she went to the button and turned it. Of course it may be said that the act was purely accidental, but her manner seemed to indicate that such was not the case. In Experiment 6, Y refused to roll the ball into the hole until he had experienced the results that came from performing the act. It was then, and not until then, that he began to roll the ball and watch the door. In Experiment 7, it was not until X had seen several mice killed and had eaten two that she seized and killed a mouse when it was put into the cage with her. It seems to me the fairest way of interpreting these cases is to admit that they are instances of voluntary 1 imitation of a low order. I say of a low order, because the imitation did not occur until the required act had been performed many times by the trained animal. In many cases I think it is not so much the association of the trained-animal-performing-the-act with the-getting-of-food, as it is an association of the-act-being-performed with the-getting-of- food. For example, in Experiment 6, Y, I think, first formed the association of X-rolling-ball with ae ponents food, but as the act was repeated by X ‘the ball seemed more and more to attract Berry, / mutation in Cats. 21 the attention of Y until the association changed to rolling-of-ball with getting-of-food. The facility with which an animal imitates will depend, in large measure, upon how closely it attends to what the trained animal is doing. If it does not watch closely what is being done, the association is almost sure to be the-trained-cat with the-getting-of-food. And if this association. is once stamped in, it is doubtful whether imitation can occur. In voluntary imitation the act is performed not merely from impulse, but for the food or freedom that may result from its per- formance. In instinctive imitation, the performance of the act by the imitatee is sufficient stimulus to call out a similar response on the part of the imitator. In other words, the animal sees and then finds itself performing the act. The subject of instinctive imitation has been passed over very hurriedly by most students of animal behavior. ‘They seem to conclude that if a high type of voluntary imitation does not exist among the lower animals, imitation is of but little importance. Now I am convinced from my work with rats and cats that instinc- tive imitation is a factor of very great importance in the mental development of these animals. In nearly all my experiments instances of instinctive imitation were common. For example, in Experiment 2, Z seeing X pull at the knot, went to it, seized it and pulled hard enough to open the door. After they were fed and put back into the box, Z pulled the knot first, X then tried it, and after she had stopped, Y seized it and pulled hard enough to open the door. It was through instinctive.imitation that the cats learned to get out of the box. X was the first cat to find the knot, yet it was Z imitating X who opened the door. ‘The next time Y opened the door after Z had pulled the knot. When they were put back for the third time Z went directly to the knot and opened the door. Z, being the most intelligent of the three cats, was the first to acquire the association between the pulling of the knot and the opening of the door. ‘The other two cats subsequently learned to get out by imitating Z. I think this experiment well illustrates the importance of instinctive imitation. Experiment 3 is also very illuminating in respect to instinctive imitation. After Z had been thoroughly tested without succeed- ing in getting out, X was put in with her. ‘They got out four times in less than fifteen minutes. The first two times X turned the 22 Fournal of Comparative Neurology and Psychology. button and Z pulled the loop. ‘The last two times Z both turned the button and pulled the loop. Here Z learned to get out of the box by imitating X, the less intelligent of the two. Y learned from Z, and X learned from Y. Let us consider the nature of the associations formed in a case of instinctive imitation. X knows how to get out of the box. Y has been tested but has not succeeded in learning to get out. Y sees X pulling at the knot and he instinctively scratches at it a little, until X succeeds in pulling it hard enough to open the door. Both pass out and are fed. A few more times X opens the door, assisted in part by Y. Now if Y is put into the box alone and he opens the door by pulling the knot what associations have been formed? ‘The first time he imitated X in scratching at the knot, the act was an instance of instinctive imitation, for he had no knowledge of an end to be attained beyond the mere performance of the act. But when simultaneously with Y’s scratching, X opens the door, and they both secure food, the condition has been provided for the formation of an association between the scratch- ing at that spot and the opening of the door. If upon being put back Y should scratch and thus open the door, the association formed would be quite independent of X, for the first time X opened the door Y did not associate it with the pulling of the knot by X, but with his own scratching at or near the knot. The first time Y scratched at the spot the stimulus was X scratching at that spot; the second time the stimulus was food to be obtained. Not only is instinctive imitation of great importance in itself, but it is also important in that it leads up to voluntary imitation. It seldom happens that a cat learns by going through the act with the trained cat only once; generally i it must see and help the imi- tatee perform the act many times before it is able to perform it alone. Now in all these trials, after the first one, the imitator either looks on or participates in the act with a knowledge of the end to be attained. Here we have to some extent voluntary imitation, for the imitator is influenced not only by his own movements, but by seeing the other cat perform similar movements. The next step in the learning process is to form the association by observing the other cat perform the act and by sharing with him its benefits. Let me point out more clearly the different steps involved in learning by imitation. Berry, [mutation in Cats. 22 1. Through instinctive imitation the cat performs the act once. As far as performing the act the second time is concerned the cat now is on the same basis as the animal that has accidentally per- formed the act once. But if the trained cat continues to perform the act, then the imitator has in addition to its first experience the experience of the trained cat to help in stamping in the association. Here it is that the transition to voluntary imitation occurs. 2: Voluntary 1 imitation, where the imitator gets food each time the imitatee performs the required act (Experiment 2))) 3. Voluntary imitation, where the imitator is not fed when the imitatee performs the required act, but is free to imitate (Experi- ment 4). 4. Voluntary imitation, where the imitator observes from another compartment the imitatee perform the required act. For reasons already stated' I do not think that imitation of this kind 1s to be found in rats and cats. In the course of these experiments there were many instances of automatic imitation. In Experiment 6, Z formed the habit of looking into the hole in the bottom of the box. If another cat looked into the hole, she would almost invariably take a look. Again, when I changed the nature of the mechanism, yet used the same box, the trained cat went to the place where the string had been and scratched there. After doing this a few times she made no further efforts, but if later another cat went to that same spot and scratched the first went and did likewise. Evidently automatic imitation enables an animal to retain what otherwise would soon be forgotten. Unlike human beings, they are very dependent upon external stimuli to enable them to utilize their past experience. For this reason automatic imitation plays an important part in enabling them to retain and utilize their past. If four or five kittens are taught to perform an act that results in the securing of food, the chances are that such an act will be performed by the individual members of that group much longer if they are kept together than it would if they were separated. For when one performs the act, the others automatically or voluntarily imitate him. In this way acts that have once been learned may be retained and made the basis of the performance of more com- plex acts. 4 The Imitative Tendency of White Rats. ournal of Comparative Neurology and Psychology, vol. 16, p. 360. 1906. 24 Fournal of Comparative Neurology and Psychology. It frequently happened during these experiments that the imita- tion was not exact. For example, in Experiment 3 M learned to pull the loop from imitating X, yet M always pulled the loop with her claws whereas X generally used her teeth. “THORNDIKE would not call this a case of imitation, for in commenting on the résults of his experiments with cats he says: ‘‘Good evidence that he did not imitate is the fact that, whereas 1 (whom he saw) pulled the loop with his teeth, 7 pulled it with his paw.”” To say that this is not a case of imitation 1s as absurd as to say that the small boy does not imitate his father because his father uses his right hand to drive a nail, whereas he, the small boy, being left-handed, uses his left hand. Just as the stimulus for the small boy was his “father driving a nail,” not his “father driving a nail with his right hand,” so in this experiment the stimulus for M was ae pulling the loop,”’ not ‘‘X pulling the loop with her teeth.” In Experiment 6, Z and M learned to roll the ball into the hole from watching me do it. From the way they acted I have reason to think the association formed was, ball-rolling-into-hole with getting-of-meat. Here the attention was centered on the most striking element of the complex, the rolling of the ball. Their attention was focused, not so much upon what I was doing as upon what the ball was doing. As soon as the ball began to roll they lost all interest in me and watched it. ‘This was especially noticeable after I had performed the act sev eral times. This simply shows that certain elements of a given complex are likely to be singled out, and these enter into hee association to the exclu- sion, in large measure, of other elements. I am also led to believe that cats are credited with more instincts than they really possess. It is commonly reported that they have an instinctive liking for mice, and that mice have an instinctive feat of cats. « It is supposed that the odor of a mouse will arouse a cat, and that the odor of a cat will frighten a mouse. My experi- ments tend to show that this belief is not in harmony with the facts. When cats over five months old were taken into the room where mice were kept they did not show the least sign of excite- ment. A cat would even allow a mouse to perch upon its back, without attempting to injure it. Nor did the mice show any fear of the cats. I have seen a mouse smell of the nose of a cat with- out showing any sign of fear. 5 THornpike. Animal Intelligence. Psychol. Review, Monograph Supp., vol. 2, no. 4, p.58. 1898. Berry, Imitation in Cats. 25 It was not until the mouse began to run that the interest of the cat was aroused. The cat then ran after it, playfully striking it with her paw, becoming rougher the longer she played with it. The instinct seems to be for dhe cat io im afer thee winehouse from it. | think it is evident from Experiment 7 that it is through imitation that the average cat learns to kill and eat mice. If this is true, it shows the extreme importance of imitation in the mental development of the cat. Furthermore it indicates that much that has commonly been attributed to instinct is, in reality, due to imitation. However, a potent factor in this learning to kill mice is the mere presence of another cat. As a rule, when one of the cats was left with a mouse it merely played with it without showing any signs of anger; but the moment another cat approached its attitude changed at once. It now seized the mouse and began to growl. In this way one kitten may happen to kill a mouse in trying to keep another kitten from getting it. My experiments have demonstrated furthermore, the fact that important individual differences appear in cats of the same litter. One individual has more intelligence than another, and there are marked variations in the learning ability of the same individual 1 in different experiments. To sum up, I think my experiments have shown: (1) that voluntary imitation of a certain type exists in cats; (2) that cats, to some extent, imitate human beings; (3) that instinctive imita-_ tion in cats is more important than students of animal behavior have supposed; and (4) that cats do not instinctively kill and eat mice, but learn to do so by imitation. ORIENTATION IN OTHE WHERE RAT, BY HARVEY CARR AND JOHN B. WATSON (From the Psychological Laboratory of the University of Chicago.) With One Ficure. In a previous paper’ the present writers advanced the conclu- sion that kinesthetic and organic data play the fundamental role in the reactions of the white rat to the maze. ‘This conclusion was reached by eliminating the other senses singly or in groups. It was not denied that the rat may occasionally use the data from these other senses or that it could use them if the occasion de- manded. ‘The present experiments attempt to supplement this conclusion. In them, conditions were imposed upon the rat which would tend to bring the kinzsthetic factor into strong relief if, as assumed, it does possess fundamental importance in the deter- mination of conduct within the maze. ‘wo experiments were made: (1) After learning the maze, starting always from O, the rats were placed in the positions’ marked x,, x, 3, n the true path- way headed in either the right or the wrong direction and their method of obtaining orientation under these novel conditions was observed. ‘The conclusion mentioned above was then theoret- ically discussed in the light of the new facts thus obtained, to see if difficulties and contradictions appear. (2) After the reactions to the maze became automatic, certain of the runways were either shortened or lengthened. ‘The disturbing effect of these altera- tions upon the rats’ conduct and their methods of learning to adjust themselves to the new conditions were observed. ‘The two experi- ments will be discussed in order. EXPERIMENT I. DES EPEECE OR STARTING THE RAT Al DIPPEREND POSiMIONS. When the trained rat is put down in the maze at unfamiliar starting points, several possibilities of conduct are open to it: 1 Watson, J. B., Psychological Review, Monograph Supplement, vol. 8, no. 2, 1907. 2 See cut of maze, p.28. A similar but unsatisfactory test was reported in the previous paper. See p. 81, Joc. cit. 28 Fournal of Comparative Neurology and Psychology. (1) the animal may not have profited in the least by its previous experience in the maze; the situation may offer a problem de novo; (2) the rat may orient itself immediately as does a human 6IC. = Jp ple SF we ES ee = = OUR. Silas as antan ea = | QUFL . 5" ee LAF x { l ; z ¢ = gi 1 ! | | Ft | 5 art | i= = | el 13 StF 3) ae 7 aie mean |i | 2 selena 3 34Et. a ‘Liz We f= uz | Biioeeele being, when, in a partially strange situation, he suddenly finds some thoroughly familiar landmark; (3) immediate orientation may notoccur, and yet the situation may not be entirely new to the rat; it may exhibit some random movements before starting CARR AND Watson, Orientation in the White Rat. 29 properly; but its conduct might be wholly different from an animal which had not previously learned the maze; (4) if the last con- dition obtains, can the rat learn in time to orient itself immediately when put down at random at any one of two, three or four such starting places? On the basis of results obtained from our work during the past summer, which is presented in detail on page 33, Camimined rack the previous work of Watson? and of Carr,‘ we are ready to give more or less satisfactory data bearing upon the above questions. (1) The situation does not present a problem de novo. (2) Nor does immediate orientation occur. (3) There isa period of ran- dom effort; the rat may wander about, turn around in the alleys several times or run up and down the pathway for a variable distance, acting as though lost or in a new situation. In con- scious terms, its behavior suggests uncertainty, perplexity, and lack of confidence. Finally, a change of behavior is observable. The suggestion of perplexity and uncertainty is gone, the rat starts off with a sudden burst of increased speed and every move- ment thereafter is characterized by the precision and regularity which mark the functioning of an automatic habit. [he remain- ing part of the maze is run in the normal and habitual manner. This change of conduct has been termed “getting the cue. The “cue” may come suddenly while the animal is running back- ward in the maze with irregular speed; the rat may suddenly stop, turn quickly and start off at full speed toward the food- box. The change often comes gradually, especially when the animal starts off running in the right direction. After the cue has apparently been obtained, it may be lost for a time and again found after a short interval; however the cue once obtained is rarely lost. Fur- thermore, once the animal attains orientation, it traverses the rest of the maze without error. This change from random to controlled activity is striking and characteristic, but extremely dificult of description except in anthropomorphic terms. (4) The rat can learn with a sufficient number of trials to orient itself immediately, starting at random from any one, two, or three definite positions in the maze. The number of trials necessary to accomplish this feat has not been determined accurately. One set of rats learned to start from any one of six cul-de-sacs on the 3 Ibid., pp. 82 and 83. 4 Heretofore unpublished. 30 Fournal of Comparative Neurology and Psychology. basis of an average of eighteen trials for each animal. This would imply that under these conditions, three trials per rat were required by it in order to learn to start at random from any one of six cul-de-sacs. A greater number of trials, however, is neces- sary when the animal is forced to start at random from six such positions in the true pathway. In the latter case, orientation at these positions does not become immediate in less than five or six trials.? With these facts bearing upon the behavior during the establish- ment of orientation Melee us, we may now well ask the question: how does the rat attain orientation? Can he do it in terms of kinzesthetic data alone? From our previous work upon the behav- ior of normal, blind, and anosmic rats in tests of this kind in the Hampton Court maze, it appeared, since no difference in conduct between the normal and defective animals could be found with respect to their ability to attain orientation when put down in the maze at unfamiliar starting points, that visual and olfactory data are at least not largely employed by them as a means of controlling their movements. ‘This conclusion is based upon the assumption that the processes employed as control by the defective rats are the same as those which would have been employed by them had they been normal. Let us suppose, for example, that a normal rat does use visual data, or the data from some other “distance”’ sense, for controlling his movements when the automatic (kin- zsthetic-motor) character of the act is interfered with, as is the case at first when the animal is started in the maze at some point other than the customary one. What would be the nature of the orienting process? Evidently the animal would have to move at random until distinctive familiar visual or other extraorganic stimulation appeared, at which time the automatic series would be restored and the animal might thereafter have no further need for distance sense data during the remainder of the trip around the maze. If, however, we deny to the rat the possibility (or better, the probability) of its using distance sense data in the way described above, it becomes necessary for us to answer the question: how can a kineesthetic-motor series, which has been thrown out of gear become readjusted without control data from some other sense avenue Summarized from Carr’s unpublished results. Carr AND Watson, Orientation in the White Rat. 31 ‘6 If we assume that each separate “unit” (possibly a runway) of the maze affords some characteristic set of kinesthetic impulses which can be utilized as a stimulus to secure the proper: adjust- ment to the succeeding unit, we might have a situation where a distinctive set of kinzesthetic impulses would serve the animal for control exactly like a set of distinctive visual cues, for example. There are four ways in which distinctive kinesthetic groups of impulses might arise. (a) Two runways may be of unequal length. (b) They may be of equal length, but occur in different positions in the total series, 7. ¢., they are preceded by different conditions. (c) They may be alike in every respect with the exception that ne one is entered by a turn to the right, while the other is entered by a turn to the left. In rounding a corner at a high rate of speed, the body sways over to the aaa the weight is thrown on one side, while the feet on the outer side are braced in order to maintain equilibrium. Such differences are so gross and fundamental that it is idle to deny that they possess fimenanel influence upon subsequent behavior. (d) The alleys may be of the same length and be entered by the same direction of turn, but present possible differences in their stimulating effect because they extend in different directions. It is difficult to conceive why and how this can be so, and the possibility is suggested only because of certain observed facts. The successful functioning of an auto- matic habit depends upon the rat’s orientation in felecon to car- dinal positions. Change the direction of the path and the auto- matic act is disturbed to some extent. “The same act accom- plished in two different directions is thus different in some way to the animal. ‘Yhus, it is theoretically possible for the rat to adapt its behavior successfully to a series of objective conditions wholly in terms of the differences in kinzsthetic stimulation, which it offers, without relying to any extent upon data contributed through any of the distance senses. We have no intention of maintaining that the rat discriminates these possible differences in kinzsthetic values in any overtly conscious or intellectual manner, viz., that they know “right” and “left” or cardinal directions, or that they consciously evaluate in any kind of terms the length of the alleys. If, as we have assumed, the automatic behavior of the rat in the maze is governed by distinctions lying within the kinzsthetic impulses themselves, we are in a position to understand the situa- a2 Fournal of Comparative Neurology and Psychology. tion presented to the rat when it is introduced into the maze at some one of these positions. ‘The animal must perforce run up and down the alleys until it experiences some one or several of these characteristic motor situations which would give rise to the necessary stimulations to release the old automatic movement. The rat may run the length of the alleys, around corners, or tra- verse several alleys before getting the cue. Moreover, on this basis, one can conceive why at times the cue should be gradually attained. At such times, a summation of stimuli would be re- quired. On the other hand, it may with justice be argued, as we our- selves above suggested, that if the cue is received through data from some distance sense, the animal must still run about at random until it receives some one or several such characteristic stimuli. [his argument cannot be met wholly, but if our own behavior under similar circumstances can by analogy be made to apply to the case of the rat, we should be allowed to assume, when our elimination experiments are considered, that this period of random activity would be much shorter when distance sense data are employed than when kinesthetic are used. It must be frankly admitted that the purpose of our work was to see whether the facts of orientation offered insuperable difficulties to our theory rather than to attempt to rule out all possibility of the rats’ recetv- ing aid from extraorganic sense data. This assumption granted us, our argument may now be stated as follows. If the animals orient themselves in the maze in the majority of cases by running at least the full length of one alley, by rounding corners into a second alley, or by running through several alleys before picking up the cue, the facts will be explicable in terms of the kinzsthetic hypothesis, and consequently there will be no theoretical difficulty in supposing that the rat’s auto- matic movements in the maze as a whole are controlled by kin- esthetic impulses alone. If, on the other hand, the rats orient themselves in the majority of cases with a minimum of random movement, the facts will not be so easily explicable in terms of our hypothesis, as in terms of some other which would admit that control is inaugurated by data from some distance sense and con- sequently, that automatic behavior in the maze may be guided and controlled effectually as occasion demands by such means. In order to make a careful test of the facts of orientation, sev- Carr AND Watson, Orientation in the White Rat. 33 eral conditions must be observed in the experiment: (1) The alleys of the maze into which the rats are introduced should be relatively long and should differ markedly in their length. (2) When placed in the maze, the animals naturally tend to spring from the hand on the run, and go for a short distance before attempting to adjust themselves to the situation. ‘This tendency should be minimized as much as possible by holding them in posi- tion for a short time, or by allowing them to nibble a crumb of bread when released. (3) Since, with successive attempts, the rats will gradually learn to make immediate orientation, only a few trials for each position should be given. ‘The series of tests, the results of which are given in the paper previously referred to, are faulty in the first and third respects. We have repeated the experiment in order to eliminate these possible sources of error. In order to meet the conditions required under (1), a new maze was constructed the plan and dimensions of which are represented in the cut. The alleys are six inches wide and six inches deep. Finished lumber was used, the cracks in the floor were filled with putty, and the whole maze was given three coats of white paint. ‘The maze was constructed so that it could be sawed across at the dotted lines and divided into three sections for the purpose of the second experiment. The maze was not so divided until the first experiment was completed. ‘The cut represents the maze as used, with the exception that the opening into the cul-de-sac B was closed. The experiment was conducted out of doors in an enclosed yard. The rats were introduced into the maze at the positions x,, x., and x,. Two of these alleys are seven and one-half feet long, while the third is two feet shorter. “This allows the animals to run a distance of two and one-half to three and one- half feet in either direction from the starting place before a turn is possible or necessary. [he experiment was started with twelve rats, but four became sickly and unreliable in conduct and were discarded. The group consisted of three normal males, two blind males and three normal females. After the rats had been thoroughly trained, the experiment was started each day by giving them a preliminary run through the maze and then introducing each rat separately at x, with wrong orientation, at x, with correct orientation, and at x, withwrongorientation. By “wrong” orientation, we mean that the rats were headed back towards lie starting box, O. This procedure was followed the second day 34. Fournal of Comparative Neurology and Psychology. with the exception that the orientation for each position was re- versed. ‘Thus three trials were given each rat per day, and the Same orientation for any one position was repeated every other day. Not more than a total of twelve trials was given to any one rat. ‘These varied conditions were designed to eliminate the possibility of /earning to react immediately to a given position. An accurate account of the behavior of each rat was taken, includ- ing the changes in direction of movement, the distance traversed, the turnings inside the alleys, partial returns and the position where the rat seemed to pick up its cue. “The conduct was noted by two, and sometimes by three observers. In all, 84 tests were made and the results were tabulated in statistical form. No noticeable tendency for the rats to start in the direction in which they have been oriented was observed. ‘They are just as likely to turn around immediately and start off in the opposite direction. Neither do they tend to start either toward the food- box, W, or back toward the original entrance, O. In other words, the direction of starting is apparently a matter of chance entirely, This fact of itself argues the lack of any immediate orientation. The situation in manich they have been placed thus does not influence nor determine their conduct at the beginning of the test. ‘The movements in the latter part of the period of exploration are determined to some extent: The rats tend to migrate back toward the starting box, O. In 75 per cent of the trials, the cue was picked up somewhere between the position where they were released and the box O. ‘The rats often explore on both sides of the position at which they are released, but 85 per cent of the distance traversed in the period of exploration is on the side toward O. ‘This general fact may be difficult of explanation, but that some determining influence is at work is too evident to admit of doubt. The following explanation may be suggested as a possibility. In learning the maze originally, the rats explore for a distance from O and retrace their steps. “This performance is repeated on successive trials with more extensive excursions. When the rats become lost or confused during any trial, although the maze is partially learned, they always run back toward O. It seems that the maze is learned in sections, as it were, and in case the rats become lost at any time, they are able to retrace their steps to more familiar surroundings. When the rat 1s now intro- duced at the position x, and begins to explore, the situation becomes CarRR AND Watson, Orientation in the White Rat. 25 familiar to some extent, and the rat acts as it has been accus- -tomed to in order to get started correctly, 7. ¢., drifts back toward O. Such a conception, however, leaves much to be explained. The general statement that the situation is not entirely novel during the period of exploration and that the behavior of the rats is influenced as a result, is also supported by the fact that few errors are made, 7. e., errors in the sense of running into cul-de- sacs during the period of exploration. Of the 84 ‘trials, errors occurred in but eight. Four of these errors were made by one rat. Such a percentage of errors is possible in running the maze normally. In four cases, the error occurred after the orientation had apparently been secured. But two chances for error were offered in those parts of the maze traversed during the period of exploration. In 55 of the trials, the rats passed by one of these openings leading into a cul-de-sac before securing orientation; and they often passed by the same opening sell times in the same trial. Yet out of these numerous possibilities, only four cases of error of this kind occurred. ‘The exploring movements are thus confined almost exclusively to the true pathway. On the average, the rats turned around 2.5 corners in each trial before being able to pick up the cue; in other words, they explored fully or in part three alleys per trial before becoming oriented. Their explorations averaged a distance of 12.6 feet per trial. Inside the alleys, they changed the direction of explora- tion 1.3 times per trial. In only ten trials out of the 84 was the exploration confined to the alley in which they were placed and in these cases the distance traversed averaged 2.8 feet per trial, while the direction of movement was changed at least once. In 57 cases out of the 84, they went outside of the alley into which they were introduced before becoming oriented. Immediate orientation apparently occurred in seventeen trials. [tis extremely doubtful whether several of these are legitimate cases of immediate orientation. A rat may by chance run forward toward the food- box, W, and become oriented gradually. In four of these cases, the rat went forward to the food-box, but ran hesitantly, made stops, or entered some of the cul-de-sacs. It was our policy to record under the heading of immediate orientation every case that could possibly be interpreted in that manner. As may be seen, these four trials are exceedingly questionable. In four other _ cases the rats turned around several times in the alley before 36 Journal of Comparative Neurology and Psychology. starting off. Nine trials were clear-cut, legitimate cases of imme- diate orientation. However, eight of the total number of imme- diate orientations were made by two rats, and the influence of the learning factor is evident in spite of the small number of trials allowed to each animal. No immediate orientations were made during the first day. Only three cases occurred during the first half of the trials, while the remaining fourteen cases were made during the last half of the tests. iverc was a tendency for the rats to pick up the cue at dis- tinctive points in the maze. In the 67 trials in which there was a period of exploration, the cue was picked up 13 times at O, II times at or near the corner M, 15 times at the turn N, 11 times at the corner P, 7 times at the corner R, 3 times at S and once at T. In only sixtrials was the orientation clearly effected near the middle of one of the alleys, to which number must be added the number of trials in which immediate orientation occurred. This fact, that the cue is picked up at distinctive positions, cannot be explained on the hypothesis that each rat would finally learn to orient itself at some one of these positions and hence that all of the 15 orientations at NV, for example, belong to that one rat, as might very well be the case, if such a point offered a distinctive visual or olfactory cue. As a matter of fact, the greatest number of orienta- tions per rat at any position was four out of a total of twelve trials. The 67 trials give an average of 8.37 per rat, and on the average, these 8.3 37 orientations occurred at 4.75 positions—less than two orientations per position. For any one rat, the greatest average number of orientations per position was 2.2. as general fact that orientation is secured at such distinctive positions as the turns supports our general contention. The statistical results show no differences between the blind and the normal rats in any respect. The females have better records than the males. Their period of exploration is shorter, fewer turns are made inside the alleys, fewer corners are turned, and the percentage of immediate orientations is much higher. Whether this difference is a matter of chance, or whether the results represent individual or sex differences, it is impossible to say. These various results of the experiment speak for themselves. They can be easily interpreted in terms of our theory. We do not mean to assert that they furnish conclusive and indubitable prock CarR AND Watson, Orientation in the White Rat. 37 of our contention, but we do maintain that they can be more readily explained on the basis of our conception® than in terms of a theory which assumes that orientation is secured mainly through some distance sense. EXPERIMENT II. THE EFFECT OF SHORTENING AND LENGTHENING CERTAIN ALLEYS IN THE MAZE. tr. The Effect of Shortening the Maze.—For the second experi- ment, the maze was divided into three sections by sawing it across at the dotted lines. By removing or replacing the middle sec- tion, the maze could be shortened or brought back to its original length. This change merely alters the length of four alleys with- out altering the relation of the turns leading to or from them. The maze was cut very carefully so that the two end sections would fit quite snugly together after the middle section had been removed. For reasons presently made known the cul-de-sac, 6, remained open during Experiment II. The trained rats formerly used were employed in this experi- ment with the exception of the second blind one. ‘This animal became somewhat feeble and refused to work consistently from day to day. After the maze had been sawed through but before the middle section was removed, the animals were allowed to run the maze for seven days. Four trials per day were given each rat. All disturbances of their old habits due to the new smell factors introduced by sectioning of the maze, to the opening of cul-de-sac B, and to the tests described above were thus eliminated. After their reactions became thoroughly automatic, the maze was shortened and the behavior of the rats in the new situation was noted. Each rat was given four trials per day for five days. As above outlined, our theory assumes that the rats make the correct turns in the maze in response to some internal (kinzs- thetic) impulse. Ifthe assumption 1s not true, the rounding of the corners must be in response to some extraorganic scmimlaton received there. ‘That is, the wall at the end of the runways and the opening into the next alley must contribute data through some distance sense. ‘The experiment is designed to test the relative ® With the exception of the cases of immediate orientation. Since two out of eight animals made eight of ‘the nine unquestioned immediate orientations we are willing to admit the possibility of the use of distance sense data in their cases. 38 fournal of Comparative Neurology and Psychology. efhciency of these two possible modes of stimulation in determin- ing the rats’ behavior at the turns. If the animals run at full speed against the ends of the shortened alleys at /, JJ, JV and /, evidently the assumption that they receive extraorganic stimu- lation there of functional value to them is most improbable. If the rats succeed in making the turns as correctly as usual, we must conclude that such conduct is determined wholly by extra- organic stimulations and is not influenced effectively by kinzs- thetic ones. The experiment is decisive in estimating the relative efficiency of the two possible modes of stimulation, because it brings them into functional opposition. The results obtained from this experiment justify our assump- tion that the turns are made in response to differences lying in the kinzsthetic impulses themselves. Marked disturbances of conduct were noticed in every rat. On the average sixteen trials per rat were necessary wholly to eliminate these disturbances, 7. e., to secure accurate, automatic adjustment to the shortened maze. Rats can often learn a maze of this complexity de novo in this number of trials. This fact is evidence of the profound disturb- ances effected by the change. The time for running ne maze was increased despite the short- ened length. The increase of time was hardly proportionate to the degree of disturbance as reflected in the nature of their be- havior. ‘Table I gives the avera'ge time in fractions of a minute. The normal time for running the maze in its shortened form was secured by averaging many individual records of trips made after the reactions of the animals had become thoroughly automatic. The records of the seven animals made after the maze was short- ened were averaged for each trial. The time increases for the first trials, and then gradually decreases toward the norm. The disturbances consisted of (1) running squarely into the ends of the alleys at J, J, [JJ, IV and V; (2) errors, suchas par- tial returns or entering into some of the cul-de-sacs; (3) slow, hesitant and careful movements; (4) stopping here and there and “nosing”? around the sides of the alleys, and (5) compensatory adjustments. By the last phrase, we refer to the fact that, after running into the end of an alley for several trials, the rats often attempted to make that turn too soon and would come in contact with the inner corner of the turn. This tendency was most evi- dent at /V. The alley JV in the shortened maze occupies the CaRR AND WatTSON, Orientation in the White Rat. 39 position of cul-de-sac Gin the lengthened maze. After “bump- ing” into the wall at /V several times, the rats tended to turn too soon and consequently failed to round the turn. As a consequence they formed the habit of running into cul-de-sac /. ‘This error was very characteristic and was difficult to eradicate. TABLE I. Average time for successive trials in running the shortened maze. (Based upon records of 7 rats). Normal .21 min. (5) .33 min. (10) .25 min. CDE e CO) aoe ea (11) .25 “ (2) -45 “ Gry 333) (12) .30 “ (3) 7-45. (Cee ae (13) .22 “ G)-shoe (9) .25 “ (14) .22 “ The following record of Female III, which may be considered typical of the series, furnishes the best description of their be- havior. Sept. 6. (1) Ran into J with all her strength. Was badly staggered and did not recover normal conduct until she had gone g ft. Ran against JV hard and then touched V lightly with nose. (2) Ran into J and ‘‘nosed” IV. (3) Hesitated at J and JV but did not touch walls with nose. (4) Perfect. Sept. 7. (5) Ran into J with sufficient force to land her whole body against the wall. Did not recover normal behavior until after passing JV. Stopped at IV. (6) Ran very slowly and hesitantly. Did not gather any momentum. Hesitation at the four crucial corners. (7) Hugged inner wall atZ. Stopped at IV. (8) Perfect. Sept. 8. (9) Slowed up and hesitated at J and hugged inner wall at IV. (10) Stopped and ‘“‘nosed” at J, IV and V. (11) Perfect. (12) Perfect. Sept. 9. (13) Perfect. Ran rapidly. (14) Perfect. (15) Entered cul-de-sac F. (16) Perfect. Sept. 10. All four trials were correct. One result was obtained which is rather peculiar and is difh- cult of explanation. ‘The six normal rats found little difficulty with the turn at JJ. ‘Three of these animals effected this turn accurately in every trial. One rat touched the wall lightly on the first trial but made the turn accurately thereafter. The fifth rat struck the wall lightly on the ninth trial, but made the turn per- fectly thereafter. The sixth rat hesitated at the turn on the fifth and sixth trials. Out of a total of 120 trials, the rats touched this wall lightly twice, and hesitated momentarily three times. In the remaining 115 cases, the turn was made accurately and unhes- itatingly. On the other hand, the blind rat found as much difh- 40 fournal of Comparative Neurology and Psychology. culty with this corner as with any of the others. He ran into the wall quite hard the first trial, touched it lightly on the second trial and hesitated there the third trial. On the second day, he ran into the wall twice and made the turn correctly thereafter. It may be supposed that this difference between the conduct of the blind rat and that of the normal rats indicates that the latter effected this turn with the aid of visual data. ‘This assumption is hardly legitimate, inasmuch as the normal animals failed to use vision effectively at the other three corners. Neither can one assume that the turn at JV presented visual distinctions not pos- sessed by the other corners, because, if such visual differences exist, they are too minute for the human eye to detect, and, in case the rat possesses a visual acuity superior to that of human beings, it ought to be able to detect a solid wall sufficiently well to refrain from running headlong into it time after time. Again, one may suppose that the normal rats were accustomed to see the opening B before reaching the turn at //, and made the correct adjust- ment in response to this visual cue. On this basis, the normal animals should have had no trouble at the turn V because the opening 7 bears the same relation to the turn V as does B to the turn //. However, this assumption may be supported by the fact that the cul-de-sac H has been open during the previous experiment, while B has been open only some eight days. One may argue that the normal rats had neglected the opening Has a visual cue in the course of the long series of trials which was given them in the learning maze from the first, while the recent opening of B had attracted their “visual attention” and they had learned to utilize it as a visual cue. Such a conception is possible, but the argument is based upon a rather precarious foundation. If the rats can see the opening B so as to react to it, it seems that they ought to be able to see the opening into any alley at the turn and utilize it as a visual cue, inasmuch as there is no reason why they should neglect this cue throughout the course of the long series of tests. When the fact was noticed that the normal ani- mals turned the corner // correctly, it was suggested that the shortened alley leading up to //, which 1s five feet long, possessed the same kinesthetic characteristics as some alley in the lengthened maze. Asa matter of fact, the alley leading from the box O, four and one-half feet long, 1 Is very similar to alley i enceat could be argued that, since the alleys possess the same motor peculiari- Carr AND Watson, Orientation in the White Rat. 41 ties, the turns would be made in a similar manner. ‘The con- ception is ingenious, and it would support our thesis, but on this basis, the blind rat should have had no trouble at //. Conse- quently, we are forced to admit that the phenomenon remains inexplicable so far as the present experiment is concerned. With the exception noted above, no difference between the behavior of the blind and the normal rats could be detected. 2. The Effect of Lengthening the Maze.—After the above series of tests had been completed, the rats were forced to con- tinue running the shortened maze for a period of three weeks, at the end of which time their reactions to 1t had become thor- oughly automatic. The maze was then lengthened by replacing the middle section, and the behavior of the animals under these conditions was observed. In the previous experiment, this middle section had been thoroughly explored by the animals and it should now have presented a minimum of possible sensory dis- turbance.’ The conditions are again such that they bring into func- tional opposition the influences of kinaesthetic cues and any pos- sible distance sense cues which might be involved in rounding the corners of the alleys. If the rats turn in response to kinzs- thetic cues, they should now attempt to turn in the extended alleys at the positions corresponding to the length of the alleys in the shortened form. In the first alley, this position is at Q’. In the remaining alleys, the cul-de-sacs B, G and H now occupy these crucial positions. For example, the distance S-6 in the extended maze equals the distance S-B’ in the shortened maze. According to our theory, the rats should now run into the wall at Q/ and into the cul-de-sacs B, G and H. The results again support our contention. Marked disturb- ances in conduct occurred for twelve trials (three days). After this time, the disturbances occurred occasionally, though they may be regarded as practically eliminated at the end of this period. ‘The time for running the maze was noticeably increased in the first trials, but it was gradually decreased thereafter (Table II). 7 The blind rat whose behavior had become erratic was not used in the shortened form of the maze. We utilized this animal, however, by allowing him each day to run several times through the lengthened form of the maze. In this way, we kept the middle section constantly in use during the experiments in the shortened maze. By this means, the original smell values of this middle section were retained unaltered, for the males at least, since this blind rat was a male, and was kept in the same living cage with all the other males used in the experiment. 42 Fournal of Comparative Neurology and Psychology. These times, as before, are expressed in fractions of a minute. The normal time was secured. by averaging a number of trial records taken immediately before Experiment I was made. TABLE II. Average time for running the lengthened form of maze after becoming habituated to shortened form. g g & { g é (Based upon 7 animals.) Normal .28 min. (3) 52 min. (6) .34 min. (1) 592% Cae Ns G35) (2) .65 “ (5) +49 ° (8) 34‘ As the best description of their behavior, we give as typical the record of Male I for eight successive trials. Oct. 2. (1) Came to a full stop at Q’ and ‘‘nosed” along the wall. Ran into and traversed the full length of alleys B, Gand H. (2) Slowed up at Q’. Entered B its full length. On coming out of B, ran back into 4, started from 4 in the right direction, slowed up at Q’ and partly entered B, G and H. (3) Turned into the wall at Q’ and became badly confused. Ran back and forth between Q/ and A three times. On coming to Q/ the third time, reared upon the wall and ‘‘nosed” about. A slight error was made at B. Ran the full length of Gand made a slight error at H. (4) Ran rapidly to Q’ and then went slowly until turning the corner. Ran past B but hesitated at G and H. Oct. 2. (5) ‘‘Nosed” along the wall at Q’ until turning the corner. Slowed up at B, ran with full speed against the end of G and partially entered H. (6) Ran past Q’ correctly, and went into B its full length. On coming out of B, went back to 4, started from 4 in the right direction, and ‘‘nosed” around the wall at Q’, went back again to 4, turned and came to Q’ and ‘‘nosed” about; continued but hesitated at B, G and H but did not enter them. (7) Slight hesitancy at B and H. (8) Merely slowed up at Q’, B and H. All the animals ran into the wall at Q/ and into all of the crucial cul-de-sacs. ‘These errors had been eliminated to a great extent by the end of the first four trials (first day’s experience), but were again prominent during the first trials of the second and third days. On entering the crucial cul-de-sacs, the rats frequently ran full speed into the end of the alley. “Vhis is evidence that the cul-de- sacs were mistaken for the true pathway. After a few trials, the cul-de-sacs were entered only part way, and finally the disturbance manifested at these positions consisted of hesitations or of a swerve in the direction of the openings without any decrease in speed. At first, the rats actually attempted to turn through the wall at Q’ at the definite position at which they would have had to turn in the shortened maze. Striking the wall at an angle, the rat would slide along it for eight to ten inches and would then go on until it stumbled upon the opening at the end of the alley. This turn occurred relatively accurately (7. e., with respect to old habit) during the first five trials on the average. After this number had CarR AND Watson, Orientation in the White Rat. 43 been given, the animal often struck the wall at a point slightly further on between Q/ and the corner Q. It seemed that the attempted turn was a resultant of two impulses, one to turn at Q/ and the other to go on to Q at the end of the extended alley. Failure to find the opening at Q/ often caused the rat to stop and go back in the maze for a new start, or to go ahead slowly until it stumbled upon the opening. In later trials, the animals ran rapidly past Q’ without stopping or hesitating, but a deflection of an inch or two toward Q’ could be noted; the same behavior was noted as the animals passed the crucial cul-de-sacs. In spite of these various disturbances, 7. e., hesitations, entering the cul-de-sacs, running into the wall and partial returns over the true pathway, it is a noteworthy fact that very rarely was the con- fusion so great that the animals ran into any cul-de-sac other than the three crucial ones. No differences between the behavior of the normal animals and that of the blind rat could be detected. The results of these two experiments, combined with those reported in the previous paper, form rather conclusive proof of the contention as to the fundamental importance of the kinesthetic factor in the rat’s adjustment to the maze. CONCLUSION. In concluding this paper, it may be well to reformulate our contention even at the expense of repetition, by contrasting the habits of the rats in the maze with the habits of human beings in a similar environment. Human beings can form habits of the type we have been dis- cussing (kinzsthetic-motor) which may become absolutely auto- matic. When this latter stage has been reached the “movement to come”’ is. released at the proper time by the afferent (kinzs- thetic) impulses aroused by the movement which has just been made. So far, these statements apply alike to the behavior of rat and man. When an automatic series of movements in man is disturbed, the ‘movement to come” can no longer be released by the afferent impulses arising from the movement just effected. Visual, audi- tory or tactual impulses (cues) are then utilized, 7. ¢., the adjust- ment becomes, e. g., momentarily visual-motor. A few move- . ‘ 44 Fournal of Comparative Neurology and Psychology. ments made in response to these distance sense cues may suffice to restore the kinzesthetic-motor character of all the ensuing adjust- ments. Likewise, when an automatic series of acts in the rat is disturbed, the “movement to come”’ can no longer be released by impulses arising from the movement just preceding. But at this point the analogy between the behavior of rat and man breaks down. The former apparently has no well developed distance sense cues, consequently he must utilize some method other than the one above described to reéstablish the automatic character of his acts. Our hypothesis provides the rat with such a method. According to it, the rat has the possibility of receiving kinzesthetic cues which function for “control” exactly as do visual cues in man. These kinesthetic cues are ordinarily not needed by the rat for controlling his movements any more than visual cues are needed by man for controlling his. But the moment a break occurs in the series of the acts of the rat a cue 1s needed which will lead to the reéstab- lishment of the automatic character of the movement. ‘The rat receives this cue by traversing at random any “unit” of the maze. The group of afferent impulses (kinzesthetic) which are aroused by traversing this unit releases the proper adjustment (z. ¢., the old movement which has been synergized on many past occasions with this particular group of impulses) and the automatic char- acter of the movements is again restored. On this supposition, man’s kinzesthetic-motor habits would differ from the rat’s mainly in this, that whereas the former util- izes distance sense cues for reéstablishing automatic adyjust- ments, the latter utilizes kinesthetic cues. SEUDIES*ON NERVE CELLS: Li THE SMOLLUSGAN: NERVE “CELL; TOGETHER WITH. SUM- MARTES OF RECENT LITERATURE ON THE CY POLOGY OF INVERTEBRATE NERVE (CELLS: BY W. M. SMALLWOOD AND CHARLES G. ROGERS.! Wir Pirate I anp THIRTEEN FIGURES IN THE TEXT. 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INomWay)scice:-es otros foe oe AGULDBERG ice meiceisrsk ohn aie eh eee Christiania. Pf Tis es EEX NER ects, gar deisccte atte ae pehioe ees Vienna. Austria-Hungary......... 2.) (\OBERSTEINER.. nals aan a te eee ee Vienna QB) Vr LEN HOSSE Reve eee ct cee eee Budapest. RAGS HipE s Aa ton doacanien | TemBECHPEREW ani yte sso ao) fica er ere ratte St. Petersburg. 2st PAG ND) O GIT erin cicharteeeeyrerenroit te raleea ess St. Petersburg. Sweden: se eonar eae 1a) JELENSCHEN GA fyrieh cee citat eeeeeee eare Stockholm. 2s 2G URETZUS es osa-ho oe aber teas Stockholm. Switzerland !ss2 (ee fia ior eit WAN LONA ROW Serb iccucscis oe ee Noise oceania Ziirich. Spainss sete exter ok BO sLVAMON A CATAT OS mite iri hrs Situs ai raters Madrid. (irae PO MATLS arenes item tees Baltimore, Md. WS Of North Americat.t4/206 1 Ga) So) MIN Osteen sac aoe eee ee Boston, Mass. 22) HSH DONA@DS ON ani cay rae cir ae Philadelphia, Pa. Thirty-one members in all. At the suggestion of the members assembled in Vienna, the undersigned will put himself in communication with Australia, with the purpose of selecting a member of the Commission to be elected from that country. (A letter has been sent to Dr. Wi1son in Sydney). The large number of members, and their selection from different countries and nations will serve only to advance the Gates MBesidecniist large membership is necessary in order that at the triennial meeting of the Brain Commission, the desired number of members may be present. It may be remarked that only 8 of the 18 members were able to be present at the last meeting. “The same conditions may be looked for in the future. Suggestions as to further elections, particulariy from countries not yet represented, will be gladly received. “These may be forwarded to the present President. The proposals, especially those concerning the Executive Committee, made by the P esident in the previously mentioned Document (A), were accepted. The Executive Committee is composed for the present of the following gent’e- men: W. Wa peyer, Berlin, President of the Br. C. H. OsersTerneEr, Vienna, Vice-President. E. Exxers, P. FLEcuHs1G, \ Members. H. Munx, WPe po WALDEYER, Brain Commission. 89 The reason why the members of the Executive Committee have been chosen thus far solely from Germany and Austria, is merely to facilitate communication with the present President whose home is in Berlin, but this arrangement must not be regarded as establish:ng a precedent. Owing to vacancies caused by death, certain changes became necessary in the special commissions established in London in 1904 for the several departments of brain research. ‘These changes were made at the meeting in Vienna in May, 1906, and are as follows: Rerzius was made President of the Commission on Embryology, and Dona.p- SON was named on this commission in the place of SCHAPER, deceased. On the Commission on the Pathology of the Brain, MinGazzini was named in place of WEIGERT, deceased. At present the seven special commissions are constituted as follows: I. Commission on descriptive Anatomy. WaLpEYER (President), CUNNING- HAM, Matt, ManouvriER, ZUCKERKANDL. II. Commission on comparative Anatomy. EH Lers (President), EDINGER, GIARD, GULDBERG, ELLIoT SMITH. III. Commission on histological Anatomy. Gotcr (President), Ramén y CajaL, DoGIEL, vAN GEHUCHTEN, LUGARO. IV. Commission on Embryology. ReErztus (President), BECHTEREW, DoNALD- SON, Vv. LENHOssEK, C. S. Minot. V. Commission on Physiology. H.Muwnx (President), V. Horstey, Luctant, Mosso, SHERRINGTON. VI. Commission on pathological Anatomy and Physiology. OBERSTEINER (President), DEJERINE, v. Monakow, LANGLEY, MINGazzinI. VII. Commission on clinical Neurology. FLEcHsic (President), HENSCHEN, FERRIER, LANNALONGUE, RAYMOND. The following were recognized as interacademic Institutes for brain study. 1. The Neurological Institute of the Madrid University conducted by Ramén y .Cajar. 2. ‘The Neurological Institute of the Leipzig University conducted by P. FLECHSIG. : 3. The Neurological Institute of the Vienna University, conducted by H. OBERSTEINER. 4. The Neurological Institute of the Ziirich University, conducted by v. Mona- KOw. 5. The neurological department of the The Wistar Institute, Phila., U. S. A., conducted by H. H. Donatpson; M. J. GReENMAN, Director of the Institute. 6. The Neurological Institute in Frankfort a/ M., conducted by Eprncer. In addition to the Institutes already recognized, The Wistar Institute in its neuro- logical department was accepted as a Central Institute for brain study, and conse- quently will be regarded by the Brain Commission as the Central Institute for brain study in the United States of North America. The Messrs. v. Monakow and OBERSTEINER proposed that the Central Com- mission should request the proper authorities in the countries mentioned below, to recognize the Neurological Institute at Ziirich, as the Central Institute for Switzer- land, and the Neurological Institute at Vienna, as the Central Institute for Austria. This request will be made at an early date. go fournal of Comparative Neurology and Psychology. In addition, reports were made on the Neurobiological Institute of the Berlin University, under the direction of O. Vocr, and on the condition of affairs in Norway, Sweden, Holland, England, Italy aad Hungary. In Sweden, Professor LENMALM i is ready to undertake work of this sort. In Norway, Professor GULDBERG is prepared to utilize his Institute for the same purpose. In Holland, Professor WINKLER has taken steps to organize there an Institute for brain study. Assent has also come from Italy and Hungary. The Imperial Academy at St. Petersburg has also reported to the undersigned that the proposition for the establishment of an Institute for brain study will be favorably considered there. Finally, Messrs. BEcHTEREW and A. Doctex in St. Petersburg, and Messrs. DAaRKSCHEWITSCH in Kasan, and Rotu in Moscow, have announced their willingness to place their laboratories or clinics at the service of this cause. The question whether or not a Central Imperial Institute should be organized in Germany, was considered at the session of the Associated Academies in Gottingen in October, 1906. For various reasons such a Central Institute for the united German Empire was rejected by the authorities, who much preferred to leave the organization of the Institutes for brain study to the individual states. ‘I his, however, does not prevent the larger states from establishing Central Institutes as well as local Institutes. As previously stated, the Institutes under the direction of FLECH- sic and of Eprncer, have been already recognized as Interacademic Institutes for brain study. The Institute in Berlin, directed by O. Vocr, has not yet become connected with the Brain Commission. As regards the recognition as Interacademic Institutes for brain study, see section xvil of the constitution. In regard to the Central Institutes and their recognition and arrangement, see section xxi. It is not to be expected that immediately upon their inception the proposed organizations shall at once exhibit a complete activity, but by degrees, a closer union of the separate Institutes will develop, and through experience, that form of organi- zation will be found which will make possible effective codperation. In accordance with Professor LANGLEY’s proposal, made at the meeting of the Central Commission, one of the first steps taken will be towards the further revision of the nomenclature, with the purpose of obtaining international uniformity. Moreover, we beg the Academies still to lend their powerful support to this undertaking which has developed through their initiative, for without such support we shall find it hardly possible to induce the several governments, in view of the many demands made upon them, to grant with the desired promptness, the means necessary for the establishment of specially planned and suitably arranged Institutes for brain study. Finally, we beg the above mentioned Institutes, in accordance with the constitu- tion, to furnish the Central Commission with the necessary reports as to their con- dition and activities, and at the same time, to assist one another through an inter- change of material and publications. By this means, in the course of time, the Institutes may hope to attain the desired completeness in the matter of collections and reference libraries. (Signed) WALDEYER, President of the Brain Commission. NEUROLOGY AT THE PHYSIOLOGICAL CONGRESS, HEIDELBERG, 1907, AND AT THE CONGRESS FOR PSYCHIATRY, NEUROLOGY, PSYCHOLOGY AND THE NURSING OF THE INSANE, AMSTER- DAM, SEPTEMBER, 1907. At both of the congresses named above considerable attention was paid to. topics that are of special neurologica interest. Owing to the difference in the membership, the character of the papers differed in the two congresses, the papers at the Physiological Congress being largely of a purely scientific character, while those at the Amsterdam Congress treated more especially matters in connection with human diseases. In the later congress more attention was devoted to the anatomy of the nervous system than in Heidelberg, although at both the functional study was very prominent. At Heidelberg about half of the sessions of one section were occupied with papers concerned with the central nervous system and the special senses, and at Amsterdam half of the time of the section of neurology and psychiatry and some of the time of the section of psychology and psychophysics were so devoted. Many of the most prominent physiological neurologists were present at the Physiological Congress and few attended the Congress at Amsterdam, although the representation of the clinical neurologists at Amsterdam was large and most important. In addition to those whose papers are abstracted below may be mentioned: BeTHE, EDINGER, ExNER, Gotcu, HErinc, Luctani1, Munk, NAGEL, Nisst, RicHet, SCHAFER, v, TSCHERMAK, Vv. UEXKULL, and VERWoRN at the Physiological Congress; and v. BECHTEREW, CaJAL, V. GEHUCHTEN, V. JELGERSMA, LanGELAAN, Mott, OBERSTEINER, OPPENHEIM, WINKLER, and WESTPHAL at the Congress of Neurology and Psychiatry. Among so many papers it is almost impossible to select those that are of most importance to the readers of the Fournal, but the following abstracts give a fair idea of the diversity of subjects and of the character of the work presented at the two meetings." Professor GAsKELL (Cambridge), 4, gave a general account of his views on the evolution of the vertebrate nervous system, which are already known to some of the readers of the fournal. He considers the vertebrate central nervous system to be developed phylogenetically from the ccelenterate type of oral nervous ring. Onto- genetically there are two types of tissues in the body, the master tissues, connected with nervous system, and the free cells of the body which arose as modifications of the germ cells. The central nervous system has been developed from the combination of the nervous and the alimentary systems; the infundibulum is the relic of the development from the early cesophagus, the crura represent cesophageal commissures, the spinal cord is the ventral chain of ganglia, and so on. All the principal parts of the vertebrate type of nervous system were compared with parts 1 In the report of each paper will be found after the name of the man presenting the paper a letter indicating the congress at which the communication was read: A, for Amsterdam; H, for Heidelberg. Q2 Fournal of Comparative Neurology and Psychology. of the nervous system in the arthropod types. The reason why ontogeny has not so far revealed this form of evolution 1s said to be because all the energies of the embryologists have been bent to the study of the matter from the standpoint of the germ layer theory. A new embryology is, therefore, necessary, according to GasKELL. Numerous charts and diagrams illustrated the paper, but in so limited time it was not possible to go into the matter in sufficient detail that the reader could point out the relation of the hypothesis to conditions of disease, but the main points were well shown. “The salts of nerve, their importance to its function” was discussed by Prof, J.S. MacponaLp (Sheffield), H, ‘The paper gave an account of experiments to deter- mine the changes in the chemical composition of nerves, especially when injured. MacponaL.p found that when a nerve is injured there resales a precipitation of some of the colloid substance of the intramyelin material, ‘he precipitation being accom- panied by the appearance of potassium salts capable of reacting with cobalt nitrate, and of chlorides capable of reacting with silver nitrate. “This change in composition is taken to indicate the explanation of the current of “injury” which is found in injured tissues, and the inference was drawn that the nerve current is about the same sort of change in the composition of the nerve, though in the normal uninjured nerve the salts do not leave the nerve, but change their position. “The potassium salts are normally deposited about the nodes of RANvrER, which act as cathodes by which the electrical current leaves the fiber. ‘There is also a deposition of the chloride salts at these points. Further experiments to indicate the chemical character of the nerve-muscle activity were reported by LANGLEY (Cambridge), H. He gave the results of work to indicate that the effect produced by a motor nerve depends upon the nature of some receptive substance or substances formed by the cell in the region of the nerve ending. In sucha muscle as the sartorius of the frog it can be seen that after the application of a dilute solution of nicotine the muscle contracts, but that the greatest thickening 1 is in the regions where nerve endings are most numerous. When the nicotine is applied to points the response is found only from the parts where the nerve endings are. Other experiments with nicotine, curari, sodium chloride, and adrenalin show that there are in the muscle probably two substances, radicles, one causing the slow the other the brief quick contraction. ‘These substances are believed by Lanctey to be radicles of the contracting molecule in the neighborhood of the nerve ending. ‘The functions that have been attributed to the nerve endings are in reality, according to the author, functions of the muscle plasm, and the ““motor nerve endings are not organs with specific properties.” It is difficult to understand the last statement in a literal manner, for the motor nerve endings must have some relation to the production of the contraction of the muscle, if it be only, and the writer believes this to be Professor LANGLEY’s opinion also, that of starting the chemical change in the muscle protoplasm which we call “contrac ion.” Curari, according to the work already finished, may no longer be considered to act on the nerve endings, but is active on the “receptive radicles” of the muscle sub- stance, and is partly antagonistic to the action of nicotine. Dr. R. Hoser (Ziirich), H, read a paper “ Der Erregungsvorgang als Kolloid- prozess”’ in which he brought forth strongly the chemical view of nerve and muscle activity. The alterations in the excitability which are produced in mu cles and nerves by the application of various salts were formerly attributed by HOBeEr to the . Franz, Two International Congresses. 93 effect of the salts on the colloid protoplasm. Later experiments of the effects of salts on albumen and lecithin have shown that there is a close relation between the effects on colloid and on the excitability. The excitability alterations pro- duced by salts resemble corresponnding (i. e., reversible) electromotor phenom- ena, and a connection can be shown between the alterations of excitability and the condition of the colloid protoplasm. The conclusion that the reader further drew from the results of his experiments is that normal production of excitation by the usual electrical means is accompanied by alterations in the condition (composition) of the colloid. This it will be noted is the same conclusion that was reached by Macponatp in the paper mentioned above. ‘This view of the nature of excitation is corroborated by the fact that the current of rest produced by the action of salts is, like the action current, retarded by various narcotics. According to the view of excitation and the action of various narcotics the nature of narcosis must be or must depend upon some sort of retardation of the colloid process nor- mally accompanying excitation. Dr. N. A. Barsrert (Paris), H, denied that there is any regeneration in nerve fibers, after they have been sectioned. His paper contained statements not in accord with the experience of the return of function in man and other animals, and it was difficult to get the author’s point of view. ‘The abstract of his paper, Pre d’evolution des nerfs sectionnes”’ gives the following conclusions: There exists no autoregeneration of nerves. In strictly physiological evolution the peripheral end of a sectioned nerve remains inexcitable and alw ays degenerates; the central end does not regenerate, but remains excitable and its structure remains normal. If suppuration exists the central end of the nerve also undergoes retrograde degenera- tion. If there be no regeneration of a divided nerve it 1s difficult, or perhaps impossible, to explain how the animal recovers the motor and sensory functions after an interval of time. ‘The experimental evidence adduced by Barsieri in support of his conclusions is not of the best, I believe, for he waited only three months for the regeneration of the vagus nerve. Had he extended his experiments over a longer period of time he would doubtless have been compelled to conclude that regeneration is the rule in respect to the peripheral nerves. Certain nerves and parts of nerves have been long known to have an inhibitory function. Examples of this are the vagus and the so-called vasodilator nerves. The inhibitory function for the muscular nerves was shown by Professor Nico.- arpEs (Athens), 7, by demonstrations on the frog. ‘The nerve fibers supplying the gastrocnemius muscle of the frog are from two bundles of the lumbar plexus. When the upper one of the bundles was stimulated with a tetanizing current the gastrocnemius contracted, but if immediately after the application of the current to the upper bundle the lower bundle was stimulated with feeble currents the con- traction gave way to a relaxation. When strong currents were used for the stimu- lation of the lower bundle at the time the upper was being stimulated, the relaxation did not take place, but the original rise was accentuated. ‘These findings can be explained only on the supposition that there are in the muscular nerves of the vertebrates inhibitory as well as excitor fibers. “This conclusion, as has been hinted at above, is in accord with results from other parts of the nervous system. Against the views of BETHE, Professor F. B. Hormann (Innsbruck), H, con- sidered some evidence regarding the nerve endings in his paper, “Zur Frage der peripheren Nervennetze.”” The histological studies of the nerves going to the 94. Fournal of Comparative Neurology and Psychology. heart and the smooth muscles of the vertebrates as well as to the muscles in molluscs show that in these muscle systems the nerves end not in free fibrils but in end nets. Each nerve can form a closed net for itself or there may be a continuous net formed by an anastomosis between the various nerve filaments. ‘These nets are limited to the final branches of the nerves and are, according to HoFrMANN, entirely inde- pendent of the presence of ganglion cells. “The appearance of the nerve nets with nuclei is an artifact. Physiologically the innervation of the smooth muscles in vertebrates and molluscs, in so far as there are no ganglion cells present, is a local- ized one, and there is no general radiation of the excitation aroused in the central nervous system. Certain conclusions that would follow from this view of the matter were referred to by the speaker, and the paper was discussed by BETHE and LANGLEY. In spinal animals, Professor SHERRINGTON (Liverpool), H, demonstrated the effect of “removal of stimulus from the stepping reflex of the spinal dog” and the “influence of strychnine on the reflex inhibition of skeletal muscles.” A cat was shown in which all the nerves of the four feet were severed, but the animal was able to walk well and accurately. In this animal burning the feet did not produce a reflex withdrawal and there could have been no nerve conduction to the spinal cord. This suggested that an important source of stimuli for the reflexes of walking or stepping is in the proximal part of the limbs. To confirm this supposition SHER- RINGTON divided the spinal cord in a dog at the tenth thoracic vertebra (the animal shown at the congress had the operation performed almost three years ago), and when the limbs of the dog were held from the ground they executed the stepping reflex. When one thigh was gently lifted the reflex immediately ceased in both legs. On allowing the thigh to hang again the reflex began immediately with the same activity as before. ‘The reflex stepping was inhibited by pinching the tail, but on releasing the tail it began with ncreased activity, quicker and with greater amplitude. ‘The antagonistic action of strychnine on the reflex inhibition of skeletal muscles was shown by SHERRINGTON in the following manner: In a decere- brized or spinal cat the vasto-crureus muscle was prepared for examination. All the other muscles of the leg were paralyzed by severing their nerves or their attach- ments. After this was done it was found that stimulation of the internal saphenous nerve below the knee always caused reflex relaxation of the vasto-crureus, which in normal action produces an extension of the leg. After the inhibition was obtained strychnine was injected and then stimulation of the internal saphenous nerve was followed by reflex contraction of the vasto-crureus. In some way the strychnine acted on the spinal cells to change the central inhibition into excitation. Dr. M. Puriirpson (Brussels), 7, demonstrated the movements of a spinal dog and considered the subject, “Sur les réflexes croisés chez le chien.”” The dog had been shown to the congress in 1904 after a complete section of the spinal cord in the dorsal region, and at that time it showed the following: Numerous direct and crossed reflexes, principally of direct extension, direct flexion, and crossed exten- sion; when the animal was suspended vertically the feet of the animal were moved thythmically; when hung horizontally the feet moved faster and the movements were seen to be those of walking, trotting, and galloping; when placed on the ground the feet moved to bring about the propulsion of the animal, and the feet movements were correct in point of view of coérdination but strongly ataxic. In the same animal the dorsal columns of the cord in the lumbar region were extirpated to deter- Franz, Two International Congresses. 95 mine the part played by each of the types of reflexes, the direct and the crossed. After the second operation when the dog was suspended vertically rhythmic moyve- ments were not produced, nor were they when the animal was suspended horizon- tally. The left leg was moved when it was stimulated, the nght not. The right leg did not contribute to locomotion. It can be said, therefore, that the direct and the crossed reflexes may be preserved independently; that the direct reflex is neces- sary for the foot to be kept in a normal position, but that for the rhythmic move- ments, especially those of locomotion, the crossed reflexes are indispensable. A general study of the ontogenetic course of some human reflexes was reported by BycHowsk1 (Warsaw), 4, and from this some phylogenetic conclusions were drawn. ‘The reflexes studied in detail were the knee kick, the tendo Achillis, and the abdominal in new-born children and during the first few months of life He found that the knee kick was constantly present from birth, and that this reflex is more lively than in adults, which is to be explained by the lack of cerebral control. In the first month the Achillis reflex is seldom obtained. From the middle of the first year until the second year it comes more often until it is a constant occurrence. Similarly with the abdominal reflex, althought it is not so constant as the Achillis reflex. These facts are taken to indicate that the Achillis and the abdominal reflexes are later phylogenetically than the knee kick; that the knee kick is purely spinal in origin; that the Achillis reflex is controlled by the midbrain, and that the abdominal reflex is under the control of the cerebrum. Dr. Novoa Santos (Santiago, Spain), 4, reported results-and conclusioris of a study to determine reflex and conscious time. The time taken up by the purely mental part of a reaction has been calculated by the author from a formulathat he has manufactured for the purpose, and he concludes that the mental time varies for the different senses, as follows: touch .or second; vision, .027 second; hearing, .013 second, and soon. From the abstract and the paper it is impossible to properly criticise the work, but it is most interesting that we should find a thoroughgoing interaction hypothesis at the basis of the work. A paper of some anatomical interest is that of Dr. S. J. pe LancE (Amsterdam), A, “Sur l’anatomie du faisceau longitudinal postérieur.”” The author gave the results of his studies on this bundle, made on rabbits, cats, and guinea pigs. Lesions were made in different parts of the medulla oblongata, in the posterior longitudinal bundle, in the nuclei of Derrers and DarkewitscH. Most of the material was examined twenty days after the operation by the Marcu method, and a few speci- mens after three or four days by the Nissi method for nerve cells. In addition to personal material the author had access to material showing the effects of lesions of the cochlear nerve, the vestibular, and the trigeminal, and embryological series of the cat and rabbit. The results of the examination of this material are that the principal fibers of the posterior longitudinal bundle are descending fibers, hay- ing their origin in the nucleus of DarKEwitscH. ‘There are some ascending fibers at the most distal portion of the bundle, with cell bodies in the medulla oblongata, which go to the nuclei of cranial nerves. Some fibers of the vestibular nerve go by way of the bundle to motor nuclei, but there are more crossed fibers than homo- lateral ones. ‘There are also some fibers from the cochlear nerve, but none of the trigeminal fibers go by way of the posterior longitudinal bundle. Professor WINKLER (Amsterdam), 4, reported on “Labyrinthtonus.” Immedi- ately after the extirpation of the labyrinth on one side or after section of the eighth 96 “fournal of Comparative Neurology and Psychology. nerve in rabbits there is found: the eye on the same side is turned down and inward as though the internal and inferior rectus functioned with the other muscles weakened. ‘The contralateral eye is fixed outward and upward as if the abducens muscle were paralyzed. ‘There is a fixation of the head toward the operated side and at times the neck is so much turned that the cheek or the head touches the floor. There i> a decided atony of the extremities. After a time all the phenomena decrease in severity even after complete destruction of the labyrinth. Incomplete extirpation of the labyrinth as well as the extirpation of the cochlea produce the main symptoms noted above, but less completely. Bilateral extirpation of the labyrinths or the eighth nerves produces a strong atony in nearly all muscles; protrusion of the eyes which are level, but with nystagmus; the head is erect but wobbles and is often thrown back in paroxysms; the ears hang down; the back is sunk in; the legs can no longer bear the weight of the body; the animal crawls rather than walks, with the legs apart and the extremities extended. ‘There is, therefore, a normal tonus control by the labyrinth. ‘The removal of the influence produces inexactitude in movement, not paralysis. An interesting report of work on the anatomical relations of the cerebellum was that of Dr. L. J. J. Muskens (Amsterdam), 4, on cerebellar connections. Animals that had part of the cerebellum injured or destroyed were examined by the Marcut method and the results were given in the paper. In the rabbit the flocculus cere- belli (lobulus petrosus cerebelli) contains cortical matter, but also a part of the dentate nucleus; after this whole lobe had been removed no degeneration was found in the restiform body or in the spinal cord, but there was a coarse degeneration of the middle third of the superior crus cerebelli. This peduncle, therefore, is not connected with the spinal cord, but is made up of strands of fibers similar to the fibers in the internal capsule. The ventrothalamic bundle of Propst was also found degenerated in all cases. In the squirrel the flocculus contains only cortical matter and fibers, but no part of the dentate nucleus. In this animal after destruc- tion of the flocculus the degeneration stops in the dentate nucleus. In the cat the superior crus cerebelli was found to be the seat of degenerations, but there were none in the inferior crus or in the cord. In cats, after section of the superior peduncle in front of its decussation caudal to the red nucleus, no degeneration was found in the reticular nucleus and the predorsal region, but in one animal after lesion of the tegmentum (the instrument passing through the middle peduncle) there was some degeneration of transverse fibers, which ran through the substantia reticularis, sweeping dorsally across the raphé Ei ascending to the red nucleus on the other side. Dr. Muskens concluded that the majority of the fibers of the ven- tral cerebello-thalamic bundle may be considered as a part of the decussation of the superior crus; the only difference is that they cross the raphé far more distally in the pons, and in the rabbit at least a number of the fibers appear to run in the crus cerebelli ad pontem. On the physiology of the cerebellum, van RyNBERK (Rome), H, reported some experiments. ‘This was a continuation of the work upon which he had formerly been engaged, but instead of dogs the author used sheep. The cerebellum of the sheep, it will be remembered, differs from that of the dog in that the posterior median lobule of the dog is inconsiderable, and the ansiform lobule is large, while in the sheep there is a large posterior lobule and a small ansiform lobule. Localized results followed different lesions of these parts of the cerebellum, especially those Franz, Two International Congresses. Q7 concerned with movements of progression. When the ansiform lobule was extir- pated on one side there was no observable effect. When this sort of lesion was combined with the destruction of the posterior median lobule there was ambulatory dysmetria in the homolateral forefoot (Hahnetritt of Lucian). After simple extirpation of the posterior median lobule there was always an inability to move, which was transient but for a time complete. After extirpation of the paramedian lobule there was a turning of the animal about the long axis. Dr. W. A. Jorty (Edinburgh), H, read an account of “the effects of lesions of the ascending parietal convolution in monkeys.” He told of experiments that he had performed in which lesions of the ascending parietal convolution were made by the cautery, which were followed by distinct degenerations in the posterior limb of the internal capsule. When the lesion embraced all of the convolution the animals exhibited a preference for the use of the limb on the homolateral side, indicating in general that there was not so good control of the limb innervated or supplied by the nerves going to the ascending parietal (nerves for muscle sensa- tion, probably). There was, however, no definite ataxia noted, but this is not surprising in view of the experiments of SHERRINGTON that are resorded above and other experiments by the same investigator. It is interesting that the ability to salute at the word of command remained unimpaired after the whole ascending parietal region on the opposite side had been destroyed, but the reader gave no indication of how long before the operation the habit had been formed. The paper of LEwenpowski (Berlin), 4, was one of the most interesting at either congress, if he has excluded all other explanations for the condition he reported. The title of his paper is ““Abspaltung des Farbensinnes durch Herder- krankung des Gehirns.”” In this he gave an account of a patient who had hemi- plegia and hemianopia, but in the field of vision still remaining colored stimuli evidently did not mean color, for he could not name a color that was shown to him, or state the color of an object that was given, or select a color when the name was spoken, or match colors. According to other tests there was no definite color blindness, but there was no connection between the colors and the names of colors. On account of the recent disputes regarding aphasia, which have been due to the investigations and writings of Marte, the discussion of the subject by Professor von Monaxkow (Zurich), A. Pick (Prague), LiepMANN (Berlin) and HarTMANN (Graz) was most welcome (4). Pick in discussing ‘““Asymbolie und Apraxie,’ dealt in a very general way with the problems, but referred especially to the mean- ings of the terms used to designate the different forms of disturbance in the appre- ciation of sensations dealing with social intercourse, that is, in the naming, under- standing and in general the appreciation of the things used by all for the conveyance ofideas. He noted the three ways, all different, in which the term asymboly has been used, and urged that the term should be employed in its original sense and should be used to imply what FINKELBERG had first used it to mean, disturbances of the means of expression. If it be used in this sense it would include many of the forms of so-called aphasia, but not all. Agnosia, in WERNICKE’S sense, and apraxia would not be included but considered separate subjects. Von Monaxkow entitled his communication “Aphasie und Apraxie.” Aphasia, apraxia and asymboly, he said, are names for groups of conditions accompanyiny disturbances in a motor or sensory sphere. ‘The conditions are large and can only be roughly outlined but they fall into two main groups: (1) in which especially the use and understanding 98 fournal of Comparative Neuralogy and Psychology. of the signs of language have been lost, and (2) in which orientation in space and time, recognition (by each sense for itself), is included, 1. e., sensory asymboly and agnosia; or in which there is lost the ability to alive gofine ef movements directed to an end, 1. €., motor asymboly and apraxia. Both these groups VON Monakow would join under the general term asemia. He showed diagrams of fifty-two published cases of different forms of aphasia, with lesions in but not limited to Broca’s convolution, of which eight were permanent without improve- ment, two were permanent eae improvement, thirteen temporary with com- plete recovery, ten acute, and five with pure subcortical aphasia, while fourteen cases were negative as regards speech defects. His summary of the results is that aphasia, apraxia and asymboly are usually produced by lesions, more or less indefinitely localized, in the left hemisphere, but that sometimes, though seldom, the lesions are sharply defined. Some of these left residual conditions, while others showed the phenomena only temporarily and the disorder disappeared after a greater or less length of time. ‘The latter type of cases fall into two groups: (1) in which the localized symptoms disappear nearly simultaneously with the general phenomena, and (2) in which the symptoms disappear after some weeks or months, perhaps years, although the form of the lesion remains unaltered. ‘The disappear- ance may be gradual or all the symptoms may disappear at the same time. Some remain as permanent defects. ‘This view of the conditions in aphasia is of special interest as compared with the views of Marre who, to give the situation in brief, believes that all aphasic disorders are of the nature of mental defects, more or less permanent, and who does not believe that the aphasias are caused by well defined lesions in the cerebrum. Von Monakow believes that the sharply defined clinical forms of aphasia and apraxia are due less to the injury as such, 1. e., disturbance of any number or quality of neurones, than to what he calls ee "and that the better the differentiation of the symptoms the more does the principle of diachesis come in. Dhiachesis, it should be noted, is the term used by von Monakow to indicate the lack of aero of certain centers by impulses from other centers, which normally act by their impulses as stimuli to the others. In other words, it is the condition of inability of a secondary center to function because of the destruc- tion or paralysis of the primary center connected with the given secondary center. This is placing the blame one step further back than has usually been done. Dr. HarTMANN took up the subject of what problems are to be solved for a proper understanding of the various speech defects. In regard to aphasia it may be taken as settled that the pathological conditions of asymboly and apraxia appear when both sides of the cerebrum are diseased or when one side is affected with complica- tions of the fiber system of the corpus callosum. It is at present impossible to refer the different forms of aphasia and apraxia to definite lesions in the brain, but careful study of the residual symptoms and of those that are temporary, with minute consideration of the related and general symptoms will help toward a better understanding of the relation of the different parts of the cerebrum to the speech functions. At present we know little regarding the normal physiology of the nerve processes as compared with our anatomical knowledge and we must have more information on the functional side of the associational processes before we shall have an understanding of the complex associations which may be called aphasia, ‘or asemia, asymboly, apraxia, etc. From both the scientific and the social sides the two congresses were very FRaANz, Two International Congresses. 99 valuable. At both congresses special bronze medals were given to each member, at Heidelberg one from the Grand Duke of Baden with the portrait of HELMHOLTZ, and at Amsterdam one with the portrait of the Queen. ‘The social part of both congresses was well conducted, and the short résumés of papers that are given above can do no more than indicate the diversity and interest of the full programs in both series of meetings. In Heidelberg many of the papers were chemical in character and not of special interest to comparative or human neurologists. In Amsterdam there were some few psychological papers and discussions, and one section was devoted to the consideration of questions dealing with the care of the insane. It is expected that the proceedings of the congress of psychiatry, neurology, psychology and the care of the insane will be published, but there will be no official report of the proceedings of the congress of physiologists. SHEPHERD IVORY FRANZ. BOOKS AND PAMPHLETS RECEIVED. Sterzi, G. II sistema nervoso centrale dei vertebrati, vol. i. Ciclostomi. A. Draghi, Publisher, Padua. 1907. Kappers, C. U. Ariens. Untersuchungen iiber das Gehirn der Ganoiden Amia calva und Lepidos- teus osseus. Reprinted from Abhand/. Senkenbergischen Naturforschenden Gesellschaft, vol. 30, DO. 3. 1907. Kohnstamm, O. and Wolfstein, J. Versuch einer physiologischen Anatomie der Vagusurspriinge und des Kopfsympathicus. Reprinted from Fournal fiir Psychologie und Neurologie, vol. 8. 1907. Cole, F. J. Noteson Myxine. Reprinted from Anatomischer Anzeiger, vol. 27, nOs. 12 and 13. 1905. Cole, F. J. and Dakin, W. J. Further observations on the cranial nerves of Chimera. Reprinted from Anatomischer Anzeiger, vol. 28, no. 23. 1906. Cole, F. J. A monograph on the general morphology of the myxinoid fishes, based on a study Myxine. PartI. The anatomy of theskeleton. Transactions of the Royal Society of Edin- burgh, vol. 51, part 3,no.30. 1905. Part IJ. The anatomy of the muscles. Jbd., vol. 55, part 3, no. 26. 1907. Santee, Harris E. Anatomy of the brain and spinal cord, with special reference to mechanism and function. 4th ed. Revised. Philadelphia, P. Blakiston’s Son © Co. pp. xxxvi + 453. 1907. Edinger, L. and Wallenberg, A. Anatomie des Centralnervensystems. 1905 and 1906. Leipzig, Verlag von S. Hirzel. 1907. Waldeyer, W. Ueber Gehirne menschlicher Zwillings- und Drillings-fruchte verscheidenen Geschlechtes. Reprinted from Sitzungsberichte der Kéniglich Preussischen Akademie der Wissenschaften. vi. 1907. Fragnito, O. Le fibrille e la sostanza fibrillogena nelle cellule ganglionari dei vertebrati. Reprinted from Annali di Nevrologia, anno 25, fasc. 3. 1907. Ikegami, K. and Yagita, K. Ueberden Ursprung des Lungenvagus. Reprinted from Okayama- Igakkwai-Zasshi (Contributions from the Medical Society of Okayama), no. 206. 1907. Bender, Otto. Die Schleimhautnerven des Facialis, Glossopharyngeus und Vagus. Studien zur Morphologie des Mittelohres und der benachbarten Kopfregign der Wirbelthiere. Reprinted from Semon’s Forschungsreisen in Australien u.s.w. 10 pp.,g pl. Jena, 1906. Winkler, C. The central course of the nervus octavus and its influence on motility. Reprinted from Verh. Kon. Akad. van Wettenschappen, Amsterdam (2 sec.), Deel 14, no. 1, 202 pp., 24 pl. 1907. Holmes, S. J. Regeneration as functional adjustment. Reprinted from Fournal of Experimental Zoélogy, vol. 4, no. 3. 1907. Holmes, S. J. The behavior of Loxophyllum and its relation to regeneration. Reprinted from Journal of Experimental Zodélogy, vol. 4, no. 3. 1907. Holmes, S. J. Observations on the young of Ranatra quadridentata Stal. Reprinted from Biological Bulletin, vol. 12, no. 3. 1907. Williams, S.R. Habits and structure of Scutigerella immaculata (Newport). Reprinted from Proc. Boston Society of Natural History, vol. 33, no. 9, pp. 461-485. 1907. Dodge, Raymond. An experimental study of visual fixation. Studies from the Psychological Lab- oratory of Wesleyan University, vol.1,no.1. Psychological Review, Monograph Supplements, vol. 8, no. 4. 1907. Sumner, Francis B. Further studies of the physical and chemical relations between fishes and their surrounding medium. Reprinted from 4m. Fournal of Physiology, vol. 19, 10.1. 1907. Kellogg, Vernon L. Darwinism today. New York, Henry Holt G Co. 1907. Bovard, J. F. The structure and movements of Condylostoma patens. Publications Univ. of Cali- fornia, vol. 3, no. 14, pp. 343-368. 1907. Krafft-Ebing and Obersteiner. Die progressive allgemeine Paralyse. Wien und Leipzig, A. Halder. 1907. Frankl-Hochwart, L.v. Die Tetanie der Erwachsen. 2d ed. Wien und Leipzig, A. Hilder, 141 eye vey [a The Journal of Comparative Neurology and Psychology VotumE XVIII APRIL, 1908 NuMBER 2 THE ARCHITECTURAL: RELATIONS OF THE AFFER- ENT ELEMENTS ENTERING INTO THE FORMA- TION OF THE SPINAL NERVES. BY S. WALTER RANSON, -PH.D., M.D. From the Anatomical Laboratory of the University of Chicago. d y & With One Ficure. INTRODUCTION. Some rather surprising observations are recorded in a paper recently published on “Retrograde degeneration in the spinal nerves” (RANSON ’06). It was found that after the division of a nerve, containing 1500 medullated afferent fibers, there occurred a complete degeneration of 4500 spinal ganglion cells and that this was accompanied by little or no degeneration of the dorsal roots. It was at once appar- ent that these results would be very difficult to explain on the basis of the usual conception of the spinal ganglion, Accord- ingly, the literature dealing with the architecture of the spinal nerves and of their dorsal root ganglia has been carefully reviewed in the hope of finding some observations that would be of assist- ance in interpreting these facts. Another reason for presenting the normal relation of the sensory elements of the spinal nerves is the fact that in order to obtain a norm for the second cervical nerve of the white rat (the nerve studied in this series of experiments) it was necessary to make a study of the numerical relations in that nerve and these obser- vations have some value from the anatomical point of view. 102 fournal of Comparative Neurology and Psychology. This work was begun under the direction of Dr. H. H. Don- ALDSON, to whom the writer is indebted for many suggestions. THE SPINAL GANGLION. I. The distinction between the large and the small cells and the functional significance of the two forms.—It has long been known that there exist in the spinal ganglion two well marked types of cells, which differ from each other both in size and staining reaction. As early as 1886 v. LENHossEK made a careful study of the small cells and expressed an opinion concerning their functional sig- Fic. 1. The drawing represents a section 5/4 thick from a spinal ganglion of a white rat, prepared by a modification of Donaccio’s Method VII, Zeiss, ocular 4, Objective ;'5. nificance. According to his description, which relates in this instance to the spinal ganglion of the frog, these cells are very small, sometimes not more than 5 in diameter; they are often angular and possess a relatively small amount of cytoplasm sur- rounding a large nucleus. In 1895 he adds to the previous descrip- tion that the small cells are characterized not only by their size RANSON, es Nerves. 103 but also by the fact that they stain more intensely with the diffuse protoplasmic dyes. Among those who have confirmed these observations of v. LENHOSSEK may be mentioned FLEMMING (95) and Cox (’98). These small cells correspond to LuGaArRo’s Type Ill and Haratr’s Type II. In connection with another investigation the writer has obtained preparations of the spinal ganglion by a slight modification of Donacaio’s Method VII! (Donaccio ’o4) which demonstrate in a very striking manner a difference, probably chemical but possibly structural, between the large and the small cells. Since no other method presents so marked a contrast between the two cell types it is worth while to note the peculiarities of these preparations (see Fig. 1). The large cells present an absolutely colorless cytoplasm, throughout which there is a network of deep blue threads. These are largely absent from the nucleus. The small cells, on the contrary, present a cytoplasm of a deep violet which is almost entirely free from the blue threads, while the nucleus contains them in abundance. ‘These same threads are seen in the axis cylinders. After a careful study of the literature it has not been possible to identify these threads with any known structure; but since the granular reticulum of CajaL, the Nrsst- bodies, the Gotat-intracellular-net, the canals of HoLMGREN, the neurofibrils of BeTHeE and the still different fibrils of DoNAGGIo and Cajat together with the remaining protoplasm and the nu- cleus must occupy nearly all the space in one small cell, it does not seem probable that the threads just described are new structures. There can be no question however concerning the clear distinc- tion which these preparations show between the large and the small cells, since the difference is a constant one and the picture is always the same. ‘The distinction so strongly emphasized in these preparations is probably a chemical one and has its counter- part in the functional differences about to be mentioned. It should be noticed that there is a certain number of transitional cells which partake of the qualities of both large and small cells and are usually of medium size. Several are represented in the 1 Donaccio’s Method VII (modified).—Pieces 2 to 3 mm. in thickness are fixed for 24 hours in a saturated solution of mercuric chloride in ro per cent formalin to which has been added 1 per cent of glacial acetic acid; iodine-water 24 hours; distilled water 2 hours; pyridine 48 hours (change once); distilled water 24 hours; ammonium molybdate 24 hours; distilled water 1 hour; pyridine 48 hours (change once); an aqueous solution of thionin T5000 prepared at least two weeks previously (change once and stain for 48 hours); dehydrate and embed in paraffine; cut sections 5 to 7/ thick. 104. ‘fournal of Comparative Neurology and Psychology. drawing; they correspond to Harat’s Type III. These inter- mediate cells represent the stages through which the small cells pass while developing into the larger ones, a process which, as we shall see, is constantly going on in the growing animal. Rawirtz (80), in studying the spinal ganglia of various animals, had his attention drawn to these small deeply staining cells and came to the conclusion that they were young developing ganglion cells, the immediate result of a supposed—but confessedly un- demonstrated—cell division. As proof he advances his observations that they are seldom found in the grown animal, but, on the con- trary, are relatively frequent in the young. voN LENHOSSEK (86) does not agree with these statements of Rawirz, for, while he admits that these cells are found more abundantly in young than in adult animals, he has also found them in large numbers in the full grown frogs. “I believe,” says v. LENHOsSEK, “that one may account for the presence of these little cells through the following consistent explanation: while, in the course of embryo- logical development, the majority of ganglion cells become very much enlarged, a part of them as well as their associated nerve fibers stop at lower stages of development; such undeveloped nerve cells represent the little cells under discussion. According to this conception the cells in question would not be young and capable of further development, but represent ganglion cells remaining permanently at primitive stages of evolution.” In 1895 v. LENHOsSEK returned to the subject of the significance of the small cells. “It is not superfluous to insist that the smaller cells, even indeed the smallest cells, are not to be regarded as func- tionless rudimentary structures, but as elements which just as truly as the large cells are functional parts of the nervous mech- anism: we find them associated just like the large cells with a process which divides in the typical way”’ into a central and a peripheral fiber. “‘Still less is it justifiable to look upon them as young elements still undergoing development. We are dealing here therefore not with cells which will further divide or other- wise develop . . . . . but with cells which are formed small once forall.” Evidence, to be presented in a succeeding paragraph, sup- ports v. LENHOSSEK in his contention that the small cells are not young in the sense of Rawirz; but that all, large and small alike, being derived from a cell division at an early embryonic period, Ranson, Spinal Nerves. 105 may be designated as old. It would seem, however, that the oint concerning their incapacity for further development is not so well taken. We will return to these points in another para- eraph, and will now consider BUHLER’s conception of the raison d’étre of the small cells. BUHLER (’98) noticed that under physiological conditions in the toad, the frog and the rabbit there occurred a degeneration of a few isolated large ganglion cells, which were however not described. ‘The degeneration is, to all appearances, not very rapid; in a spinal ganglion of a frog about 20 or 25 at a time, in rabbits relatively much fewer. He assumes that these disappear- ing ganglion cells are recruited from the ranks of the small cells, which develop into large cells as they are needed. “Since after the earliest stages a proliferation of ganglion cells no longer occurs, in order to remain capable of functioning throughout the period of life, the spinal ganglion must receive for its portion in the anlage sufficient reserve material in the form of undeveloped cells.” Hatat (’02) has. argued against this assumption on the ground that the number of spinal ganglion cells is approximately constant throughout the life of the individual. However the recent obser- vations of Kosrer on the spinal ganglia of cats, dogs and _ rabbits give some support to BUHLER’S statement (KéstER’ 03, p. 1098). “One recognizes, in every section of a normal ganglion, cells with all possible. appearances of degeneration. One can see cells with eccentric swollen or fragmented nuclei, coarse and fine chromato- lysis, and all the changes which one may look upon as the reac- tional manifestations of the cells to the physiological degeneration found by Stcmunp Mayer in the peripheral nerves. We can, therefore, speak of a physiological degeneration of nerve cells.”’ From these observations it would seem not impossible that a cer- tain very slight amount of degeneration is going on constantly in the normal ganglion; and the question, whether or no the small cells are, as BUHLER assumes, capable of replacing the cells lost in this way, is a question worthy of some consideration. Hatat (’oo) has given some attention to the significance of the small darkly staining elements, which with their scanty cyto- plasm and large nuclei present many of the characters of embry- onic cells, and concludes that they are “in a growing state or in a more or less permanently immature condition.”’ In order to test this assumption he (’02) counted the number of large and 106 = ‘fournal of Comparative Neurology and Psychology. small cells in the spinal ganglia of the VI C., IV T., and II L. nerves of four white rats, ranging in weight from ten to one hun- dred sixty-seven grams, and found that, while the total number of cells in each ganglion remained approximately constant, there was a constant increase in the number of large cells and a corre- sponding decrease in the number of the small cells. “This can only mean that the small cells are developing into large ones, and that therefore a considerable number of the former retain their capacity for development at least during the growing period. It is of interest to note in this connection the observations made by Honce (’89) that after electrical stimulation of nerves it 1s chiefly the large cells in the associated spinal ganglia that show the effect of fatigue. Considering all the cells large which have one diameter 50s or over and those small which have not, a count gives the following results: TABLE I. Effect of Stimulating Ganglion Cells (Hopce). In 100 Larce Ceirs, Nuctei In 100 SMALL Cexts, Nucier SHRUNKEN. NormMat. SHRUNKEN. Norma. 5 95 Resting fo) 100 94 6 Stimulated 8 gz Hopce did not attempt an explanation of these interesting results; but in the light of the preceding discussion there seems to be little room for doubt that these small unworked elements are the immature cells of Harat. In summing up this discussion concerning the functional sig- nificance of the small cells of the spinal ganglion, it may be said that the absence of mitosis in the spinal ganglia during extra- uterine life excludes the possibility of their being young cells in the sense of Rawirz. No more acceptable is the view of v. LEN- HOSSEK that they are elements, the development of which has been permanently arrested; we must rather agree with Hatat that they retain for a long time their capacity for development, that, faces some of them are always in the process of transformation through- out the growing period of the animal. During the time that they are still undeveloped they do not show fatigue when the nerve is stimulated electrically. It is not yet satisfactorily determined whether they may serve as reserve cells capable of replacing the mature neurones destroyed by trauma or disease. Ranson, Spinal Nerves. 107 2. Classification of the spinal ganglion cells according to the number and character of their processes.—Since in this paper we are not directly concerned with the form of the spinal ganglion cells, we need only mention the most important points under this heading. ‘That the cells of the spinal ganglion were all associated with a single T-shaped process was the accepted view until 1896, when Doctet published his important work on the form of the elements in the spinal ganglion. To Docret belongs the credit of having first clearly differentiated the following cells in the spinal ganglia of mammals. A. Unipolar cells. Type I. ‘The well known unipolar cells, both large and small, with the .typical T-shaped processes of RANVIER. Type II. A new form first seen by Doctet, the single process of which breaks up into numerous fine branches that end in peri- cellular baskets within the ganglion itself. B. Bipolar cells—very few, only one or two in each ganglion. C. Multipolar cells with two nerve processes, one centrally, the other peripherally directed, and many dendritic processes arising from the angles of the irregularly shaped cell body. These dendrites penetrate the capsule and end among the cells of the ganglion. The observations of DocirL were made upon preparations stained ‘by his modification of the methylene blue technique. More recently (’05) Caja has published a preliminary account of his studies on the spinal ganglion with his new silver method. One of his cell-types is distinctly new and may be described here since it serves to emphasize the wealth of connections within the ganglion. ‘This is an unipolar cell, possessed of very fine den- drites which take origin, sometimes from the surface of the cell itself, sometimes from the origin of the axis cylinder. These dendrites gradually enlarge and terminate in spheres, encircled by an entire system of concentric capsules. “These dendrites sometimes bifurcate and give rise to a pair or more of terminal globes. He distinguishes two varieties among these cells: in one the terminal spheres are found beneath the capsule of the cell of origin and are in relation with the pericellular “nests” of Cayat and Doctet, in the other the terminal globes are lodged in the intercellular spaces sometimes far distant from their point of origin. 108 fournal of Comparative Neurology and Psychology. We return now to a point more directly in keeping with the gen- eral purpose of this paper, namely, to the form of the small cells. Hata (’o1), apparently quoting from DocieE1, says that “the number of these cells from which no axon can be traced is large.” Harpesty (05) agrees that “a larger portion of these extra cells belong probably to the anaxonic type of neurone, latent cells which have not yet developed processes.”’ Both Harari and Harpesty had in mind only the fact that the small cells were not connected with medullated fibers in the dorsal root or peripheral nerve—a fact which stands uncontested—but the conclusion that these cells are necessarily anaxonic is unnecessary and mis- leading. I[ have not been able to verify the citation from DociIE1, and there seems every reason to believe that instead of being nu- merous such apolar cells do not occur at all in the spinal ganglion. In his extremely careful study of these structures, which lead him to insist on the presence of bipolar and multipolar cells, although never more than two or three such were found in one ganglion, DocieEL does not mention the presence of these “anaxonic neu- rones.”’ On the other hand, he describes in detail the single process of the small cell as being a typical T-shaped process with two branches, one directed toward the spinal cord, the other toward the periphery. ‘These processes are usually destitute of myelin, but a few are medullated for a part of their course. He was able to trace these non-medullated processes of the small cells into the dorsal roots and into the peripheral nerves as far as the junction of the afferent and efferent fibers. The absence of apolar cells is again the implication of v. LEN- HOSSEK in the quotation already given. “We find them (the small cells) just as truly as the large cells associated with a pro- cess which divides in a typical way.”’ But v. LENHossEK does not leave the question in this obscure way, but says, in another place (Bau des Nervensystems, p. 268), “If we study thespinal ganglion of one of the more highly developed vertebrates or even the frog with suitable isolation, teasing or staining methods, we find in it, in addition to the interstitial connective tissue, blood vessels and nerve fibers, also numerous nerve cells of varying size of which the typical form is unipolar. There are no apolar cells.” We have also to note the negative findings of HopcE (’89), who, having obtained physiological results that lead him to expect large numbers of apolar cells in the spinal ganglia of frogs, under- Ranson, Spinal Nerves. 109 took to demonstrate their presence in teased preparations but came to the conclusion that “Apolar cells do not occur in the spinal ganglia of frogs in any considerable numbers, none having been found.” 3. Interrelations among the spinal ganglion cells.—The spinal ganglion is not to be regarded as an aggregation of more or less spherical cells each independent of the others and connected only with its central and peripheral processes; but is in reality a com- plicated mass containing the ramifications of dendrites and axis cylinders, forming exceedingly intricate intercellular meshworks and pericellular baskets, the cells in this way being brought into close functional relations with each other. Moreover there are sympathetic fibers which enter the ganglion via the ramus com- municans to join in the formation ae ree baskets. ARONSON (’86) was the first to describe the pericellular baskets in the spinal ganglion and his observations were confirmed by Caja | (go). The latter investigator regarded them as ramifica- tions of fibers from the sympathetic system. It was DoGIEL however who first cleared up our notions on this point by describ- ing a variety of cell (“Type II”) which has for its sole function the establishment of intraganglionic connections. SPIRLAS (’95) called attention to the existence of collaterals arising from the processes of the embryonic spinal ganglion cells. The observations were confirmed upon adult material by Docrer in 1896: “from the processes of many large and small ganglion cells, before their division into two fibers, one, two or three col- laterals of varying thickness are given off which at a greater or less distance from their cells break up into fine threads.”’ Levi (05) has followed the embryological formation of these collaterals. In 1896 Huser described a variety of spinal ganglion cell from the axon of which recurrent collaterals are given off. These run back and end in disks upon the cell from which the axon arose. Sull another means of intercommunication between the spinal ganglion cells is found in the dendritic processes of the multipolar cells and the more numerous unipolar cells of CaJAL, possessing fine dendritic branches with spherical endings which may either be in connection with the immediate pericellular basket or may run for considerable distances in the intercellular spaces to make connections in other parts of the ganglion. Expressed in other words, the relations are as follows. Sym- 110 = fournal of Comparative Neurology and Psychology. pathetic fibers enter the ganglion and break up about the cells, especially those of Docrex’s Type II. The single processes of these cells of DocieL break up within the ganglion into a multi- tude of little twigs which form baskets about still other cells, while the stem process of many of the latter, 1. e., the ordinary spinal ganglion cells, gives off delicate collaterals, which also take part in the formation of the fiber complex of the ganglion. All this wealth of axonic ramifications, together with the dendritic branches of some of the cells, forms a basis of intercommuni- cation which argues for a close functional relationship among the individual spinal ganglion cells. THE DORSAL ROOTS. 1. The relation of the fibers of the dorsal roots to the cells in the substantia grisea of the spinal cord. Examination of Nissu’s view that they are axons of such cells.—A very peculiar observation noted in a paper recently published on “Retrograde Degeneration” (RANSON ’06), namely, that after half of the spinal ganglion cells have disappeared as the result of section of the associated nerve, there are to be found in the dorsal root very nearly if not quite the normal number of fibers—and all this according to careful counts made on a considerable number of animals—has led to a careful consideration of Niss’s (’03) recently published conception of the dorsal roots, as a possible though improbable explanation of these results. Had the idea that the dorsal root fibers are independent of the spinal ganglion cells been advocated by any lesser author- ity we might indeed pass it by as unthinkable; but we cannot so lightly treat a statement by Franz Nissi. According to him (03, p. 334), “° The posterior root fibers are united with the cells of the spinal cord and especially with the cells of the substantia gelatinosa and only pass through the ganglion; and... . the cells of the spinal ganglion also send fibers toward the periphery.” The facts on which he bases this remarkable assertion are that after section of the posterior roots the cells of the spinal ganglia do not show change, while certain cells in the spinal cord, especially the cells of the substantia gelatinosa, undergo chromatolysis and even complete degeneration. It may be said however that, while true axonal reaction does not occur after section of the root, yet very considerable changes are induced in the ganglion cells Ranson, Spinal Nerves. 1g (Kierst and Koster); and there are plenty of cases of degenera- tion in neurone chains similar to the disappearance of the cells of the substantia gelatinosa—e. g., the degeneration of the motor cells with their peripheral motor fibers after section of the dorsal roots (BRAEUNIG ’03). He also cites, as bearing on this point, the anomalous trigeminus found by v. GUDDEN in a calf, which showed no sensory root fibers. ‘The ganglion itself was normal, as were also the fibers of the peripheral nerve arising from it, although these peripheral fibers were greatly decreased in num- ber. According to Nissi’s view the fibers whose cells were located within the brain had failed to develop, while those whose cells were located in the Gasserian ganglion had developed nor- mally. It would seem that these are rather insufficient grounds for revising our conception of the dorsal root, based as it is on such a large number of careful investigations; and it should be remem- bered, in this connection that those who have worked with the histology of the spinal ganglion, whether in teased preparations or Gotci-material, have considered the dorsal root fibers identi- cal with the central branches of RANviER’s T-fibers. Of the existence of some fibers in the dorsal root whose cells lie in the cord, there can be no doubt, at least so far as certain of the lower forms are concerned (CajAL ’90; v. LENHOSSEK ’90; and VAN GEHUCHTEN ’93). According to the experiments of JOSEPH (’87) on the second cervical nerve of the cat, these fibers are also found in mammals. After section of the dorsal root, he has observed that some fibers in the central portion remain normal and in the nerve a small number degenerate. At first opposed by StncER and MUNzER (go), these results of Jos—EpH have been confirmed bythese same authors in a later paper (’95) and anticipated by the earlier work of KAHLER (’84). KopczyNski (’06) has been unable to verify these observations. It is to be borne in mind that, while these direct observations show the presence of fibers of passage in the spinal ganglion, they also indicate that only a few fibers are of this category and that these are efferent; and by no means do they support the view of Nissv that all the fibers of the dorsal root arise from cells situated in the spinal cord. And, as we shall see, the condition described in the paper on retrograde degeneration, namely, the presence of 112 ‘Fournal of Comparative Neurology and Psychology. a normal dorsal root associated with a ganglion which has lost one- half of its cells, is susceptible of another explanation than that suggested by Nissx’s theory. All in all, then, while the evidence requires that we should be open-minded on this question, it 1s not sufficient to overthrow the belief that the dorsal roots are pre- dominately composed of the central branches of Ranvrer’s T- processes. The evidence from the silver preparations, that one branch of the stem process of the spinal ganglion cell runs through the dorsal root, is very convincing. ‘This evidence has been well summarized by vAN GEHUCHTEN (’92). 2. Numerical relations between the spinal ganglion cells and the medullated fibers of the dorsal roots —FREUD (’78), working on Petromyzon, found a considerable excess of fibers in the dorsal roots over the cells in the spinal ganglion, due to the fact that the cell bodies of many of the afferent neurones are located in the spinal cord. Hopce (89) counted the dorsal root fibers and the cells in the associated ganglion in the frog, and found about three cells for each fiber. BUHLER (’98) has shown that the number of cells in the spinal ganglia increases as the test- -animal is higher in the zodlogical series; ieast for fish, it is greatest in mammals. He also found that in the frog there were about five ganglion cells for each dorsal root fiber. GAuLE and Lewin ('96) touted in the rabbit a ratio between cells and fibers of 6 tor. Harpesty (’05) found in the frog a ratio varying from 2.7 to 3.6 cells per fiber. FArAT (02), working on the white rat, obtained the following results for the adult specimen of 167 grms. body weight. TABLE II. Ratio of Spinal Ganglion Cells to Dorsal Root Fibers (Hatat). NERVE. Numeper or Cetts. Numsper or Fizers. Ratio. WEES Galore rissa oa a cictste Scan aye wise tensia ra ensiavcters Wy Sy aNore es lepeteever {2,200 4,227 Mes ee 1 DY’ feed DUR Se Nese OR en ae UI ON iy nin Alene Py ee AE) are ie 4,406 1,522 1:4.8* TTT Sees Bh ce stcnaaentnarty sicny Ate eatte tobales Potene eT Sey Manas Aes Sota 9,442 1,644 Wh G7] * The figures 2.7 and 4.3 given in the original are obviously misprints. The writer, in studying the normal relations in the second cerv- ical nerve of the white rat, has obtained results confirmatory of those of the authors already mentioned. In the three cases in which the dorsal root fibers and spinal ganglion cells were enu- Ranson, Spinal Nerves. ig merated in the same individual nerve, a rather constant ratio of approximately 1 fiber to 3.2 cells was obtained. The first two specimens were 72 days old and weighed about 11o grams, the third was six months old and weighed 188 grams. TABLE III. Ratio of Spinal Ganglion Cells to Dorsal Root Fibers (RANsoN). SPECIMEN. Numeper or Certs. NumperorFipers. CELLs PER FIBER. TONGA SS. Sats aixi= sis icye lowe nierer Raieteie ee ts 7,721 2,472 Ban FELSES SEE Ao doc Sion COs 8,116 25394 ah3 Gimonthh Sa. pict epee ernie 8,624 2,689 Bh The number of cells in a given spinal ganglion exceeds the number of medullated fibers in the corresponding root; this excess holds alike for frogs and mammals, although the actual percentage of the excess varies greatly. Hartat and Harpesty ascribe to the anaxonic cells the responsibility for this condition; but, since we know that these cells do not exist in any appreciable number, we are thrown back upon the non-medullated fibers of the small cells as the chief source of the discrepancy. While it is possible that the majority of these non-medullated fibers ‘do not push out into the dorsal root, it seems probable that the number of cells in the spinal ganglion does not exceed the number of axis cylinders in the dorsal root by so large a number as it does the number of mye- lin sheaths. A count of the dorsal root fibers obtained by a dif- ferential axis cylinder stain is the logical method of answering this question. 3. The increase in the number of medullated fibers in the grow- ing animal.—HarpeEsTy (’05) has shown that, when his frogs were arranged in a series of increasing body weight, there was a general, though not very regular, increase in the number of fibers in the ventral and dorsal roots as well as in the peripheral nerves. The white rat however in the hands of Harat (’03) has given uniform results, showing a regular increase in the number of med- ullated fibers both in the ventral and dorsal roots. The II C. nerve of the white rat shows more variability; in a general way however the number of fibers is increasing. athe increase is, however, by no means as rapid, nor is there such a large number of fibers added as in the nerves studied by Hartat. These observations are recorded in the accompanying table. 114 ‘fournal of Comparative Neurology and Psychology. TABLE IV. Rate of Medullation in the Second Cervical Nerve of the White Rat (RaNson). MepDvuLtaTteD FIBERS IN THE MeEDULLATED FIBERS IN THE AGE. Dorsat Root. VentTRAL Root. TROY SE: step ere ode -o.2) = cys ra Pa ae een Tat 1608 TACOMA YS haere isles arckeksyetaie ee ciate ae eTaNe eee 1521 Mays (AVELAPC). whale sano erac 1564.5 [oi Skaly RU AOS ARNO DS nidlon Gacnigins hp at soe 2472 689 TROY Scie: Sette is toe Steep eect er eR 2394 660 7 PLE Ke tnaeOa ec TS Gril co aes Se 1059 590 TOMA S oe aces toeeeeten taste keira heer cere 2217 591 72. days\(aVverare) yaa etsalars aerate 2261 —— 63245 G Months. eens eo Re ee ee eee 2891 773 Grmonthsee netics cat Chee ata 2689 723 6hmonthsi(averape) 2.0) eke ieer 2790 aR OMG THES NERVE: 1. The proportion of sensory and motor fibers.—All investi- gators have found a larger number of fibers in the dorsal than in the ventral root. According to INGBERT (’04) the ratio of all the motor and sensory fibers arising from the left side of the human spinal cord is I : 3.2, and from the second cervical segment alone 1:6. Harat (’03) working with the C. VI, T. IV, and L. II nerves of the white .rat finds an average ratio of 1 :2.3. The normal relations in the C. II nerve of the white rat are expressed in the following table, representing the writer’s enumeration of the ventral and dorsal root fibers for that nerve. TABLE W: Number of Ventral and.Dorsal Root Fibers in the II C. Nerve of the White Rat (Ranson). AGE. VeNTRAL Root. Dorsat Root. Ratio. a days\ MLOrPEMS.)! conser ee cere 689 2,472 TeeigeiG a2 days” (UOPEINS: ees Ieee eek eke ewe 660 2,394 13/906 72h GAYS | CIO SPEMIS 2) ony pnieectalstata =o bictoytieysactes stares a cheek 590 1,959 I 33.3 FI ay Si LTO! PUMS:) aincrs ca Racacheae TATE = meets oreiledoak 591 2,217 27 This table shows that the ventral root fibers are about 28 per cent as numerous as the dorsal root fibers. 2. The distal excess.—As has been said, considerably more sensory than motor fibers enter into the formation of the peripheral nerve. But, when we compare the sum of the fibers in the ventral and dorsal roots with the total number present on the distal side of the ganglion, we find a distinct excess on the distal side. ‘The earlier investigators who undertook to compare the number of fibers on the two sides of the ganglion, either found them equal or Ranson, Spinal Nerves. 115 else the peripheral count so little in excess that they regarded it merely as a matter of technical error and attached no significance to it. Later, Brrce (’82) found an excess of fibers on the periph- eral side of the II C. ganglion of the frog amounting to 16 per cent; and BUHLER (’98), also working on the frog, found in one nerve an excess of 25 per cent. Harpesty (’99, ’00, ’05) has spoken of these extra fibers as the “distal excess’’ and found that it varied in the frog from 5 per cent to 61 per cent. GAULE and LEwIN (’96) found a distal excess in three of the sacral nerves of a rabbit of 19 per cent, II per cent, and 15 per cent, respec- tively. My observations on the II C. nerve of the white rat are confirmatory of these previous results. Here we have to do with a distal excess of 8 or 10 per cent. ‘This is of interest since DALE (00) found in coccygeal nerves of cats an average distal excess of only 0.63 per cent. TABLE VI. Showing the Distal Excess in the II C. Nerve of the Adult White Rat (RANsoNn). | | | VENTRAL | Dorsat | SuM oF | DistTat 2 2E Sum or | Ventrat| Dorsat WEIGHT. | | ogee AGE | Roor. Roor. | Roots. | Excess. Rami. | Ramus. | Ramus. | | | oF D.E | | a S | | 302 grms..... 646 2386 AS | AGT 8 3289 | 887 2402 161 grms..... wes 2090 2762 276 10 3098 | 708 2390 Harpesty has made a careful study of the possible explana- tions of this distal excess. It is much too complicated a question for us to enter upon here. It can only be said in passing that there is evidence for the presence of medullated fibers of sympathetic origin which pass through the nerve to end in the ganglion and, hence, would not be found in either of the roots. There is also evidence that both sensory and motor fibers may bifurcate at the level of the ganglion. But after a careful consideration of all the possibilities, HARDESTY does not think any one cause sufficient to explain the facts and believes that several factors must operate together in the production of the distal excess. The idea of NissL, discussed in a previous section, that the dorsal root fibers pass through the ganglion without making any connections and are there joined by others arising in the ganglion, would, if it should be found correct, offer an adequate explanation of the dis- tal excess, especially of those cases where the excess is large and 116 “fournal of Comparative Neurology and Psychology. amounts to more than 60 per cent, as in one case (HARDESTY ’coO) where 337 fibers on the proximal side were associated with 544 on the distal side of the ganglion. In those cases however, where the excess is not more than 5 per cent (2422 proximal to 2543 distal fibers, HarpEsty ’05), the hypothesis of Nissx would require that very few fibers originate in the ganglion. 3. The presence of non-medullated fibers inthe nerve.—It has already been said that DocrieL was able to trace the non- medullated fibers as far as the junction of the afferent and efferent roots. So important is this work of Docret’s that a full quotation may be given. Ausser der Grosse besteht der einzige Unterschied zwischen den in Rede stehenden Zellen und den grossen Ganglienzellen darin, dass von einer jeden solchen Zelle immer nur ein einziger dusserst diinner und wahrend seines ganzen Verlaufs myelinlos bleibender Fortsatz abgeht. Von der Zelle gewohnlich in der Form eines kleinen Konus beginnend, bekommt der Hauptfortsatz das Aussehen eines dusserst diinnen, nicht selten varicésen Fadens, welcher noch unter der Zellkapsel, oder sofort nach dem Austritt aus ihr, 2-3 bogenférmige Biegungen macht, worauf er mehr oder weniger gradlinig oft eine sehr lange Strecke zuriicklegt und sich endlich V- oder T-férmig in zwei diinne varicése Faserchen teilt. Soviel ich weiss, hat Retzius zuerst die Aufmerksamkeit auf das Vorkommen kleiner Ganglienzellen in den Spinalganglien der Sdiugetiere (Kaninchen) gelenkt, indem er sich tiber dieselben folgender- maasen ausdriickt: ‘Im Gegenteil geht, besonders bei kleineren Ganglienzellen, oft von einer schwach abgeschniirten Stelle der Zelle ein blasser Auslaufer aus, welcher zuweilen sich auf weite Strecken verfolgen lasst und dabei die marklose Beschaffenheit behilt; langlich-ovale Kerne treten in gewissen Entfernungen an ihm auf, und er wird allem Anscheine nach zu einer gewohnlichen myelinfreien Nerven- faser; wie sich diese im spateren Verlaufe verhalt, konnten wir nicht ergriinden. Einmal sahen wir indessen diesen blassen Auslaufer sich dichtomisch teilen.”? Es is mir gelungen diese Liicke in den Beobachtungen von Retzius auszufiillen und nachzuweisen, dass die Hauptfortsatze der kleinen Zellen und die aus ihrer Teilung hervorgehenden Fasern, soweit sie in den Ganglien und sogar in den hinteren Wurzeln und an deren Zusammentrittsstelle mit den vorderen Wurzeln zu verfolgen sind, iiberall den Charakter markloser Fasern bewahren, oder aber nur an einer gewissen Strecke von einer dusserst diinnen, friihner oder spater wieder verschwindenden Markhiille umgeben werden. It is important to note in this connection that WEIGNER has recently shown that there is a considerable number of non- medullated fibers in the nervus intermedius; and this should lead to an examination of other cranial and spinal nerves to determine if non-medullated nerve fibers had not been overlooked in them. It will be shown in my next paper that the small cells of the spinal ganglion, which DociIEt says possess non-medullated fibers show typical axonal reaction after section of the peripheral nerve and that it is these small cells that degenerate and disappear, facts which can be explained only on the assumption that these non- medullated fibers extend into the peripheral nerve. ‘The existence of these fibers and the degeneration of the small cells offers a satis- factory explanation of the results presented in the former paper on Retrograde Degeneration in the Spinal Nerves. Ranson, Spinal Nerves. 117 BIBLIOGRAPHY. ARONSON. Beitrage zur Kenntnis der centralen und peripheren Nervenendigungen. Inaugural-Diss. Berlin. 1886. (Cited after Docrer.) Berue, A. Allgemeine Anatomie und Physiologie des Nervensystems. Leipzig. 1903. Bircge, E. A. Die Zahl der Nervenfasern und der motorischen Ganglienzellen im Riickenmark des Frosches. Arch. f. | Anat. u.] Physiol. p. 435. 1882. BraeEuniG, Kart. Ueber Chromatolyse in den Vorderhornzellen des Riickenmarkes. Arch. f. [Anat. u.| Phys., P- 251. 1903. Ueber Degenerations-vorginge im motorischen Teleneuron nach Durchschneidung der hinteren Riickenmarkswurzeln. Arch. f. [Anat. u.| Phys., p. 481. 1903. Bunter, A. Untersuchungen iider den Bau der Nervenzellen. Verhandlungen der Physik.-med. Gesellschaft zu Wii-xburg, N. F. Bd. 31. 1898. Bum, A. Die experimentelle Durchtrennung die vordern und hintern Wurzel des zweiten Halsnerven bei der Katzte und ihre Atrophiewirkung auf das zweite spinale Halsganglion. Sitz. Ber. Ges. Morph. Physiol. Miinchau, p- 18. 1903. Cayat, S. RaMOn y. Sobre la existencia de terminationes nerviosas pericelulares en los ganglios nerviosos raquidi- anos. Pequenas comunicaciones anatomicas. Barcelona. 1890. (Cited after Doctrt.) : Types cellulaires dans les ganglions rachidiens de homme et des mammiféres. C. R. Soc. Biol., Paris, T. 58, p. 452-453. 1905. Cassirer, R. Ueber Veranderungen der Spinalganglienzellen und ihrer centralen Fortsitze nach Durch- schneidung der zugehérigen peripheren Nerven. Deutsche Zeitschr. f. Nervenheilk. Bd. 14, S. 150. 1898. Cox, W. H. Der feinere Bau der Spinal Ganglienzellen des Kaninchens. Anat. Hefte, Adth. 1, Bd. to. 1898. Beitrage zur pathologischen Histologie und Physiologie des Ganglienzellen. Internat. Monats- schrift fiir Anat. und Phys., Bd. 15, p. 240. 1898. Date, H. H. On some numerical comparisons of the centripetal and centrifugal medullated nerve fibers arising in the spinal ganglia of themammal. Fourn. of Physiol.,vol.25, p.196. 1900. Doaiet, A. S. Der Bau der Spinalganglien bei den Sadugetieren. Anat. Anzeiger, Bd. 12, S. 140. 1896. Zur Frage iiber den Bau der Spinalganglien beim Menschen und bei den Saugetieren. Internat. Monatsschr. fiir Anat. u. Physiol., Bd. 15, p. 343. 1898. Zur Frage iiber den feineren Bau der Spinalganglien und deren Zellen bei Sdugetieren. Internat. Monatsschr. fiir Anat. u. Physiol., Bd. 14, p. 73- 1897. Donaaaro, A. The action of pyridin upon the nervous tissues. Annali di Nevrologia. vol. 22. 1904. Ref. Rev. Neurol. and Psy., vol. 2, p. 635. FLemMMinG, WALTHER. Vom Bau der Spinalganglienzellen. Beitrage zur Anatomie und Embryologie als Festgabe fiir F. Henle von seinen Schiilern, S. 12. 1882. Ueber den Bau der Sipnalganglienzellen bei Saugetiere, und Bemerkungen iiber den der centralen Zellen. Arch. fiir Mikrosk. Anat., Bd. 46, S. 379. 1895. FLEMMING, F. Die Structur der Spinalganglienzellen bei Saugetieren. Arch. fiir Psych. u. Nervenkrank- heiten, Bd. 29, S. 969. 1897. Freup, S. Ueber Spinalganglien und Riickenmark des Petromyzon. Sitzungs-berichte der k. Akad. d. Wissench., Bd. 78, Abth. 3. 1878. 118 fournal of Comparative Neurology and Psychology. Gap. Anatomie und Physiologie der Spinalganglien. Archiv f. [Anat. und] Phys., p. 570. 1887. Gap AND JOSEPH. Ueber die Beziehungen der Nervenfasern zu den Nervenzellen in den Spinalganglien. Archiv f. [Anat. und] Phys., p. 199. 1889. GauLe anp Lewin. Ueber die zahlen den Nervenfasern u. Ganglienzellen des Kaninchens. Centrabl. f. Physiol., H. 15 u. 16. 1896. Harpesty, IrvING. : Further observations on the conditions determining the number and arrangement of the fibers forming the spinal nerves of the frog (Rana virescens). ‘fourn. Comp. Neurol., vol. 10, p. 323. Igoo. On the number and relations of the ganglion cells and medullated nerve fibers in the spinal nerves of frogs of different ages. four. Comp. Neurol. and Psy.,vol.15§,p.17- 1905. The number and arrangement of the fibers forming the spinal nerves of the frog (Rana vires- cens). Journ. Comp. Neurol., vol. 9, p. 64. 1899. Hata, SHINKISHI. Number and size of the spinal ganglion cells and dorsal root fibers in the white rat at different ages. ‘fourn. Comp. Neurol. vol. 12, p. 107. 1902. On the increase of the medullated nerve fibers in the ventral roots of the spinal nerves of the growing white rat. Fourn. of Comp. Neurol. vol. 13, p. 177. 1903. The finer structure of the spinal ganglion cells in the white rat. Journ. Comp. Neurol., vol. IT, ips 0.) L900: Hoper, C. F. Some.effects of electrically stimulating ganglion cells. Am. Fourn. Psychol., vol. 2, p. 375. 1889. Hott. Ueber den Bau der Spinalganglien. Sztzungsb. d. k. Akad. im Wien. Bd. 70, Abth. 2. 1875. (Cited after Harar.) Horton-Smity, R., Jr. On efferent fibers in the posterior roots of the frog. ‘fourn. Physiol. (Foster). 1897. Huser, G.C. : The spinal ganglia of Amphibia. Anat. Anz., Bd. 12, S. 417. 1896. Incsert, C. E. An enumeration of the medullated nerve fibers in the ventral roots of the spinal nerves of man. Fourn. of Comp. Neurol. and Psych, vol. 14, p. 209. 1904. Josrru, Max. Zur Physiologie der Spinalganglien. Arch. f. [Anat. u.] Phys., S. 296. 1887. Kaiser, O. Die Functionen der Ganglienzellen des Halsmarkes. Haag. 1891. Kreist, Kar. Experimental-anatom. Untersuchungen iiber die Beziehungen der hinteren Riichenmarks- wurzelen zu den Spinalganglien. Arch. f. path. Anat. u. Phys., Bd. 175, p. 381. 1904. Korczynsx1, S. Experimental Untersuchungen aus dem Gebiete des Anatomie und Physiologie der hinteren Spinalwurzeln. Neurol. Centralbl., p. 297. 1906. Koster, G. Ueber die verschiedene biologische Werthigkeit der hinteren Wurzel und des sensiblen peri- pheren Nerven. Neurol. Centralbl., vol. 22, p. 1093. 1903. Zur Physiologie der Spinalganglien u. der tropischen Nerven sowie zur Pathogenese der Tabes dorsalis. Lerpzig. 1904. v. Lenuosskéxk, M. Beobachtung an den Spinalganglien und dem Riickenmark von Pristiurusembryonen. Anat. Anz., Bd. 7, p. 528. 1892. Centrosom und Sphire in den Spinal Ganglienzellen des Frosches. Arch. f. Mikr. Anat. und Entwicklungsgeschichte, Bd. 46. 1895. Der feinere Bau des Nervensystems. Berlin. 1895. Ueber den Bau der Spinalganglienzellen des Menschen. Arch. f. Psych. u. Nervenkrank- heiten. Bd. 29, S. 345. 1897. Ranson, Spinal Nerves. 2119 v. LENHOsSEK. Ueber Nervenfasern in den hinteren Wiirzeln welche aus den Vorderhorn entspringen. Anat. Anz., Bd. 5, p. 613. 1890. Untersuchungen iiber die Spinalganglien des Frosches. Archiv f. mikroskop. Anat., Bd. 26, p. 370. 1886. Lucaro, E. Sulla patologia della cellule dei gangli sensitivi. Rzvista Patol. nerv. e ment., vol. 5, nos. 4, 6, 9; vol. 6, no. 10; vol. 7, no. 3; vol. 8, no. 11. Levi, G, ; Beitrag zur Kenntnis der Structur des Spinalgangliens. Anat. Auzerger, Vol. 27, p. 158- 1905. Lewin AND Cae : Ueber die Zahlen der Nervenfasern und Ganglienzellen in den Spinalganglien des Kaninchens. Centrabl. f. Physiologie, Bd. 10, p. 437. 1897. MariNEsco. Essai de localisations dans les ganglions spinaux. Revue Neurol., vol. 16. 1904. Nissz, F. Die Neuronenlehre und ihre Anhanger, p. 282, 333. ‘fena. 1903. Ranson, S. W. Retrograde degeneration in the spinal nerves. Journ. of Comp. Neur. and Psy., vol. 16. 1906. Rawirz, B. } Ueber den Bau der Spinalganglien. Archiv f. mikr. Anatomie, Bd. 18, S. 283. 1880. Rerzius, G. Weiteres zur Frage von den freiers Nervenendigungen und anderen Structurverhiltnissen in den Spinalganglien. Biol. Untersuchungen von Prof. Dr. G. Retzius. ‘fena. 1900. SHERRINGTON, C. S. Regeneration of the afferent root fibers. Schafer’s Text-book of Physiology, vol. 2, p. 804. 1900. SINGER AND Minzer. - Beitrige zur Anatomie des Centralnervensystems. Denkschr. der Kais Akad, d. Wiss. zu Wien, Bd. 57. 1895. (Cited after van GeHUCHTEN.) Stemacnu, E. Ueber die motorische Innervation des Darmtractus durch die hinteren Spinalnervenwurzeln. Lotos, N. F. Bd. 14. 1893. Van GEHUCHTEN, A. Les éléments moteurs des racines postérieures. Anat. Anz., Bd. 8, p. 215. 1893. Nouvelles recherches sur les ganglions cérébro-spinaux. La Cellule, T. 8, p. 255. 1892. Watter, A. Sur la reproduction des nerfs et sur la structure et les fonctions des ganglion spinaux. Miiller’s Archiv, p. 392. 1852. Warrincton, W. B. Further observations on the structural alterations in the cells of the spinal cord following various nerve lesions. fourn. of Physiol., vol. 25, p. 462. 1900. Warrincton, W. B., and Grirrity, F. On the cells of the spinal ganglia and on the relationship of their histological structure to the axonal distribution. Brain, vol. 28, p. 297. 1904. Wercner, K. Ueber den Verlauf des Nervus intermedius. Anat. Hefte. Bd. 29, p. 97- 1905. THE NERVOUS SYSTEM OF THE AMERICAN LEOP- ARD FROG, ~RANA_ PIPIENS, COMPARED -WITH THAT OF THE EUROPEAN FROGS, RANA. ESCU- LENTA AND RANA TEMPORARIA (FUSCA). BY HENRY H. DONALDSON. (Professor of Neurology at the Wistar Institute.) (From the Wistar Institute of Anatomy and Biology, Philadelphia.) Wirn Srx Ficures. With the advances which are being made in the correlation of function and structure, the need is felt on many sides for a more detailed, accurate and quantitative determination of the anatomical, physiological and chemical differences between closely related species, as well as between the same species from different local- ities. The general notion of a physiological and chemical criterion for species has been discussed by DE VarRicny (’gg) and, although this is not the place to review the literature touching this topic, it is nevertheless appropriate to name CaMERANO’S paper (00) on the variation of the toad, which, among his many important contributions in this general field, is the one most closely related to the following investigation. Moreover, KELLIcoTT’s recent study of correlation and variation in internal and external charac- ters in the common toad (’07) emphasizes relations which have a direct bearing on the interpretation of my own results. In 1898 I made a study of the weight of the brain and of the spinal cord in the bull-frog R. catesbiana (DoNaLpson ’98). Two years later, in collaboration with Dr. D. M. ScHoEMaAKER, 122 “fournal of Comparative Neurology and Psychology. a similar series of observations on the leopard frog, R. pipiens,? was published (DoNnaLDsoN and SCHOEMAKER ’00). In 1902, utilizing the data in both of these investigations, [| was able to show that the weight of the central nervous system in both of these species could be calculated by a formula based on the body weight and on the total length of the frog (DONALDSON 102) For comparison with these results the observations of FuBINI (81) on the European frogs were alone available. An examination of Fusint’s tables, which are discussed in part in my paper of 1898, referred to above, showed that his findings were so irregular and so different from my own, that it was fair to conclude that he had not worked with sufficient care. In order to test this conclusion, I obtained in the spring of 1898, through the courtesy of the Zoological Institute at Zurich, Switzer- land, a series both of R. esculenta and R. temporaria (fusca), all the specimens having been fixed in formalin by a uniform method. A comparison of these specimens with the fresh R. pipiens on the one hand, and on the other with R. pipiens fixed by the same method, indicated that the central nervous system in R. pipiens was heavier than in the European species, and at the same time did not support any of the peculiar findings of FuBINI, such as the relatively great weight of the spinal cord. Neverthe- less, limitations in the range in size of the Zurich series and the possibility that the European and American species were differ- ently affected by the fixation treatment, led me to delay publica- tion on this point until fresh material could be examined. ‘The opportunity to do this came in the summer of 1904. In July of that year, through the courtesy of Professor SHERRINGTON, I was able to examine a series of R. temporaria (fusca) in the physio- logical laboratory of University College at Liverpool, England; and in August, through the courtesy of Professor GAULE, a cor- responding series of R. esculenta was examined in the Physio- logical Institute of the University at Zurich, Switzerland. In order to eliminate as far as possible, the influence of season on this comparison, Dr. Hatat examined for me, also in August, a series of R. pipiens in the Neurological laboratory of the Uni- 1In previous papers on the leopard frog, published from my laboratory, this species has been designated as Rana virescens brachycephala, Cope. It now appears that this name is not correct, and that the species in question should be designated Rana pipiens (Schreber) as given above (Donatpson, Science, vol. 26, p. 655, 1907.) Dona.pson, American and European Frogs. 123 versity of Chicago. It is the results of these three series of obser- vations which are now to be compared. As the foregoing shows, this investigation was undertaken primarily to test the correctness of Fusini’s observations. It has resulted however in bringing to light several differences be- tween the nervous systems of the species compared, and these differences seem worth recording. At the same time, FuBINI’s observations have been found untrustworthy. ‘This, however, is a matter of smallimportance, and the brief discussion of FuBINI’s work will be deferred to an appendix. Before presenting the data on the nervous system, it will be desirable to record some of the characters in which these three species of frogs closely resemble one another. ‘The resemblances important for our present purpose are enumerated below: (1) In external appearance and shape; color markings excepted. (2) In the range in body weight (the heaviest specimens are always females). (3) In the ratio obtained by dividing the body weight by the total length, that is, the average amount of body weight for each running millimeter of total length. It will be necessary to interrupt the enumeration for a. moment in order to elaborate this point (3). In the full tables are given the body weight and the total length of each individual examined. In the condensed ‘Table 10, these same data are arranged to give the averages for groups of three. Thus for each species in the latter table there are four entries, and in each entry both the average body weight and the average total length are given. If the former be divided by the latter Body weight Total length we obtain a number which represents the average amount of weight for each running millimeter. Since the increase in bod weight is more rapid than the increase in total length, this value of course changes with the absolute weight of the frog, increasing as the frog becomes absolutely heavier. ‘The values thus obtained are given in Table tr. These values are better understood when thrown into a curve, as in Chart I. It appears from the chart that the curves are nearly parallel, 124 ‘fournal of Comparative Neurology and Psychology. TABLESr: Bopy WeicurT Boru oe PER Mi L.iMe- IN GRAMS. TER IN GRAMS. Es. PUPILS $28 cc tage tae Fak cpoel MTC ee ee 14.9 . 102 seh) Bigs 30.8 .168 43-2 218 Re esculenta: stiri seniae tec eters ory ca eos ee Te Ee 15.9 114 22.0 134 35.0 -199 40.2 -208 Re temporaria’ acer ste ts ciate eh Oe ee Cn SE A 15.9 .107 23.1 - 137 28.0 .162 4153 077, 220° Gms. for each Millimeter -200 160 160 140 120 100 Bo dy weight—¢ms. 10 15 20 en 30 30 40 45 CHART 1. Showing the average amount of body weight for each running millimeter of total length. R. p. = Rana pipiens. R. e. = Rana esculenta. R.t. = Rana temporaria. DonaLpson, American and European Frogs. 125 and that on the average, the lower figures differ only 4.1 per cent (R. pipiens) and 2.3 per cent (R. temporaria) respectively, from the highest figures, given by R. esculenta. The relation of body weight to total length is therefore nearly the same in all three species. (4) In the fraction of the total length represented by the com- bined lengths of the leg bones. Table 2 gives these figures in their final form. TABLE 2. Percentage of the total length represented by the combined lengths of the leg bones. No. or SPECIMENS. ii oBa quae pee smbAdo onc ny ldo deo oooh ueduonbuassocUedocooUodo aeons 12 68.7% Reresculentalct ic wt onion bite ois aieterote ces ORDO REC OST Raat etc acer 5 70.7% iY iG OeIP oes s Fondo ajo adhoe oasbauE sco dp cosddousctouoooomousUbanded degen 6 69.4% The percentages in the foregoing tables were obtained as fol- lows: ‘That for R. pipiens from an average of twelve records on individuals ranging from 14. 85 to 42.54 grams in body weight (DoNALDSON and SCHOEMAKER, ’ oo, Table VID); that for R. escu- lenta from five specimens of the Zurich series of 1898, having a body weight of 12.3-20.4 grams; and that for R. temporaria (fusca) from six specimens of the same series ranging in body weight from 17.9-34.7 grams. Table 2 serves to show that in this character the three species are nearly alike. (5) In the proportional lengths of the several leg bones. TABLE 3. Naas Foor S : Femur. Trsia. (Tarsus AND | SPECIMENS. | Pes). IREBPUPLEM Sess -elesetaley-Perckeltokatotets\ole< efeleta| 2% 12 25.5% 29.3% 45.2% IR@wescnlentatess wreccrtesgeter stots che 'orsie's\reke 5 262395 1) 12822.% 45-5% ING (EEO INE SE RAS Ae cigde Odde On OO So RORE 6 26.1% 28.7% 5.2% The figures in Table 3 are based on the same data as were used for Table 2. For comparison in the case of R. esculenta how- ever, we have in addition, the measurements from BOULENGER (97). These are taken both from his tables and from measure- ments made on the bones as represented in his plates. 126 ‘fournal of Comparative Neurology and Psychology. The data from BouLENGER give the following: TABLE 4. rs ig eae || | | Foor R. ESCULENTA. S i | Femur. | Trem. (Tarsus AND PECIMENS. | | Prs) Dat JA Sea ae oo: se Bet, ane : Mariety,rabibinda.so%t..G t-ciessie oak as 1M.+1F. | 26.7% | 29.2% | 44.1% Warietysrabibundace sr seri claiecil lr LBS | 277% Yt ab % 43-47% Weir Gis slay men Caocostoooedbooddsunbea: 1 M.-F. | 26.8% 27.3% 45-9% Wena lnssre sch ocobeabsonboocdsonae 1M.+1F.| 25.9% 26:59" =| 47.6% * Measured from Boulenger’s Fig. 101, p. 280. In my Zurich series the individual measurements correspond to those for the varieties rabibunda and typica as determined by BouLencer. The average for these from the above table (4) 1s: AVERAGE VALUES FOR VARIETIES RABIBUNDA AND TYPICA. 1 i hg 4 Oe Sa Ta aRiQ A Hom ar eicer An abc So mace Oto Sound Chin Oia e.codt Osc ose 27.0 UME Ril Soe ene an ot GL GEE ree ero She CSOs Loe FOC Lod ba da he dec 28.3 Iie 0 (an eee NSE Baio Chior er ac ce aap DE Un Rime Gata s a sa oae aie cor 44.7 And these values are close to those given for R. esculenta in Pa: For comparison in the case of R. temporaria, an average of two determinations, one male, one female, by BoULENGER 1s avail- able. ‘These give DST) dex Ree a a oe eee Se Se eee SOM Orr Sole ci OU oc Cnc 25.6% HI Sh Ee ee er | Wa On eins A tt nr tee ay oh OR RSPEI OCI Oe OCU AD OGD ob Gadaab os 28.4% 1 hoya Se eecan SO ECR Dona Gn okie Sere Dom Otooad.che dot so0necmoanoa: 46.0% which is in fair agreement with the values giyen in Table 3. (6) In the relative length of the entire central nervous system (that is, the length of the brain plus the length of spinal cord), in relation to the total length of the frog. This relation is of course not a constant one, because the total length of the frog increases more rapidly than the length of the entire nervous system. “To make the comparisons, therefore, the percentages must be recorded in relation to the total length found for each individual or group. ‘The data used in this deter- mination were the following: Ten (10) specimens of R. pipiens ranging in total length from 124 mm. to 185 mm. inclusive. The data being taken from the DonaLpson, American and European Frogs. 127 research of DoNALDSON and SCHOEMAKER (’00). ‘These cases are averaged in groups of five. Twelve (12) specimens of R. pipiens, these being the same as are given in Table 7 and averaged in groups of four (observations by Dr. Harar). Both of the foregoing series of measurements were made on the fresh specimens. Ten specimens of R. pipiens, after fixation in formalin, aver- aged in groups of five, and ranging in total length from 128-174 mm. ‘This was the series used to control the measurements on the European frogs received from Zurich in 1898. From the Zurich series of 1898, there were taken one group of five esculenta, ranging in total length, after fixation, from 128-170 mm., and also a series of fifteen R. temporaria, averaged in groups of Bie: and ranging in total length, after fixation, fain I5I to 179 mm. It seems fairest to tabulate the fresh, separately from the fixed material, so the first lot, entirely R. pipiens, is given in Table 5. TABLE s. R. pipiens. Percentage values of length of the entire central nervous system, the total length of the frog being taken as the standard. Measurements on fresh specimens. PeER CENT VALUE OF THE LENGTH oF Torart LENGTH ENTIRE CENTRAL AVERAGES OF MM. Nervous System, Beebe Carat ereraiere catshoxe Senet ereiare relies ce cncis wlohe Tow aeets wear hee 150 17-2 Bs dobcsegoqodonaen da droondd Spd guRdaooUs Sop ar ao SORES 153° 17.8 Got poBee dgdanoudaen Sn obadand on CASE EMeaee ic ome aan to c 175 172 RBG R So bn b Ue Cote OG ROO OE Lot CAC DEER BS doe Toe 177 16.2 11S wale alee eo eD BA eee DIRE Een COORDS Com eae oe SEC 196 16.3 TABLE 6. Showing the same relation as Table 5. All measurements on material fixed in formalin. acer ater poset PER es VALUE OF Rae AVERAGE | 7 ory THE LENGTH OF THE OF ENTIRE CENTRAL Nervous System. 1 CE Ol SAEs (a ra ee Sha a 5 133 18.2 eS CULE Nba Pere nce See adnuaiske beeen 5 h so 14S | 17.9 NenteMPOharials varpndteilge cia cine aecuiels som ae os ecissnises8r6 | 5 158 16.9 (Restemporattae/ssr creck locas Mereci ode ait cca s ek 5 166 | 16.2 IER eH TAE SGM G aM A GATS © olin Ree oie che ener Ee SS ree 5 167 16.4 Rep tem POkAKiar rs aciy nesters cee gees ciara eels es 5 173 16.0 128 fournal of Comparative Neurology and Psychology. Table 5 shows that the value in question ranges in the fresh speci- mens from 17.8 per cent to 16.2 per cent, and also tends to diminish as the total length of the frog increases. ‘The same relations are shown in Table 6, in which all three species are represented, and these form as satisfactory a series as is given in Table 5. We therefore conclude that in this character—the relative length of the entire central nervous system—the three species resemble one another closely. It should be pointed out here that it follows from this that the smaller weight of nervous system which we find in the European forms (see below) must be associated with a diminution of one or both the transverse diameters, since the foregoing shows that it is not associated with variations in total length. (9) In the arrangement of the main branches of the crural and sciatic nerves (DUNN ’oo and ’o2). In the papers to which ref- erence 1s here made, this point is fully discussed. In view of the fact that the several species are similar in the foregoing characters, we might expect a high degree of similarity in the weight and structural relations of the central nervous sys- tem. Such however is not the case, and we turn therefore to a statement of the differences which have been observed. The technique of weighing, measuring and dissecting, was uni- form for the three species. This has already been described (Donatpson, ’98, DoNaLDsoN and SCHOEMAKER, ’00). It may, however, be well to repeat here that the body weight was taken in a closed box; the weight of the contained ova being deducted from the body weight of the unopened specimen, in the case of the females. Also in both sexes correction was made for the stomach contents. In taking the total length, the frog was suspended by the lower ‘jaw, and the distance between the tip of the nose and the longest toe, the legs being fully extended, was measured with vernier calipers. ‘The central nervous system was removed immediately after death, and the brain separated from the spinal cord by a "section at the level of the tip of the calamus scriptorius. Both brain and cord were separated from their nerves by severing the latter at the points of their attachments to the central structures. To obtain the percentage of water, the material was dried for several days until it maintained a constant weight. For this a water bath ranging from 85° to 95° C. was used. | Donatpson, American and European Frogs. 129 Although this is probably not the best method, it was uniformly applied in the case of all three series, so that the results are at least comparable, though the absolute values for the percentage of water may be open to question, until it has been shown that this material dried in vacuo, gives similar results. Material examined.—The specimens of R. pipiens were 12 in number (10 males and 2 females) ranging in body weight from 11.6-47 grams. ‘They were taken in the neighborhood of Chicago in the month of August, and examined between the twenty-third and thirty-first of August. For the data which are presented in Table 7 I am indebted to Dr. S. Harat. TABLE 7. Data on R. pipiens. Bopy Torar WEIGHT IN GRAMS OF B Ee Pep SUN To Weicut | Sex. |LeNGcrTH IN Hans WEieHe WeEEs: SS —————— TO eh a Canes Brain. Sp. C, |Corp Weicur.| Brain. | gp ¢, 11.6 M. 130 0918 .0666 0252 2.64 Satan || Mergal 16.0 M. 150 .1148 .0796 0352 2.26 igaedae hye teleyat 17.0 F. 159 . 1054 .O714 .0340 2.10 84.0 80.6 20.8 M. 170 312325) | .0844 0388 Deady 85.2 81.6 22.5 M. 162 116) | .0807 0358 2.25 84.5 80.4 26.4 M. 180 1372 .0946 0426 222 84.4 78.4 27.6 F. 179 -1416 .1014 | .0402 2.52 84.8 80.1 30.6 M. 180 -1454 | .0998 | .0456 2.18 84.6 79.8 34.2 M. 190 ais) 1056 0462 - 2.28 85.6 81.6 41.8 M. 197 1652 -1146 | .0506 2.26 86.9 82.2 43-9 M. 200 1708 1210 | .0498 2.42 85.8 80.7 47.0 M. 198 1664 - 1140 0524 erty) 84.4 80.5 The specimens of R. esculenta were eleven in number (3 males and (8 females) ranging in body weight from 12.4-45.03 grams. They were taken near Zurich on July 31, and were examined between August 1 and 5. [he data are given in Table 8. The specimens of Rana temporaria (fusca) were twelve in num- ber (8 males and 4 females) ranging in body weights from 14.05— 32.81 grams. ‘They were taken near Liverpool shortly before July 11, and were examined July 11 and 12. ‘The data are given in Table 9. In all the foregoing series there is considerable individual varia- tion in the characters observed, and so for the purposes of com- parison, the complete tables have been condensed by taking the . 130 ©= ‘fournal of Comparative Neurology and Psychology. averages for each three successive individuals, thus giving four entries in each of the condensed tables. The only exception to this statement is in the case of R. escu- lenta, with but 11 records, and there the third entry in the con- TABLE 8. Data on R. esculenta. Bopy | Torar | WEIGHT IN GRAMS OF suena eeu eee °° ies Brain WEIGHT | WaTER Weicur | Sex | LeNGrH 1N| PVN MSE ae am 7 oe [sahecyae Se So AOR enon anton Gob oo a cocoon 63 65.8 EMSS Ye SH6 0.0 op oud edd LOMO OO RuaR DOB MOaG Geo sno nO aN cl 40 lcs) * This measurement was not made by Mr. Taxanasut, but has been calculated from other data in his tables. In accordance with Boycort’s results, we should expect in this series of R. pipiens, with an average sciatic length of 57.3 mm. to find longer internodes than in the series of R. temporaria, with an average sciatic length of only 48.2 mm., but on the contrary, the internodes in R. pipiens are much shorter. “To make the com- parison fair however it is necessary to reduce the measurements on R. pipiens to the measurements of the R. temporaria series, 3 Mr. Taxanasui kindly allows me to use the data from his forthcoming paper on the internodes in R. pipiens. 146 Fournal of Comparative Neurology and Psychology. which is taken as the standard. ‘Todo this, we divide the observed values for the R. pipiens series by 1.188, since 57.3 mm., the average length of the sciatic in the series of R. pipiens iSuPLoss per cent of 48.2 mm., the average length of the sciatic in the series of R. temporaria. The observations thus reduced to the same standard are given in the following table. TABLE 19. Giving the lengths of the internodal segments in ¢ on the medullated fibers of the sciatic nerve, for frogs with a sciatic length of 48.2 mm., arranged according to the Wee of the fibers. R. TEMPORARIA | R. PIPIENS | ‘ | i RELATIVE VALUE NuMBER OF (Boycorr) DiaMeTeR oF | (TaxanasH1) | NuMBER oF | | or LENGTHS IN OpsERVATION | LENGTH OF Fizers. | Lenoru or | Osservartions | : R. PIPIENS. INTERNODES INTERNODES. In all adout 767 5-5 -9f4 | 500 159 | 65% 1050 #1186 6-6.9/4 586 107 | 49% 1102 7-7 -Oft 705 92 64% 1159 8-8.92 | 826 16 | 71% | 1288 9-9-9 917 4 | 71% 1399 10-10. 9/4 929 47 | 66% | 1416 II-I1. g/t | 942 14 | 66% | 1536 12-12 .9f 1027 5 66% * As will be seen, Boycorr’s value for the length of the internodes in fibers 6-6.9/ in diameter, is plainly aberrant, and therefore the percentage value for the internodes of fibers having this diameter in R. pipiens, is excluded from the general average. The foregoing table shows that when grouped according to diameters, the internodal lengths in R. pipiens range between 64 per cent and 71 per cent of that in R. temporaria, the average being 67 per cent. It follows from this that R. pipiens has three sheathing cells ona fiber, where R. temporaria has only two, and therefore more cells in the length of the sciatic. Consequently R. pipiens has the finer and more complete con- struction, although it is not possible to say what physiological advantage goes with this difference in structure. ‘There are no observations on R. esculenta to compare with those just given. Conc.usions. From the observations presented, we conclude that the three species studied are similar in general form and proportions, but that R. pipiens has: 1. A heavier central nervous system. Dona.pson, American and European Frogs. 147 2. A heavier brain and spinal cord. 3. A heavier brain in proportion to the weight of the spinal cord. 4. A greater percentage of water in both the brain and spinal cord. 5. A larger number of both sensory and motor medullated fibers in the spinal nerves (when compared with R. esculenta). 6. A slightly greater proportion of sensory fibers in the spinal nerves (when compared with R. esculenta). 7. Shorter internodes, and therefore a greater number of sheath- ing cells (when compared with R. temporaria). With the possible exception of the percentage of water, the interpretation of which is not yet clear, all these characters may be counted to the credit of R. pipiens as indicating a higher devel- opment of its nervous system, and if we may make these charac- ters a basis for physiological predictions, we should expect the American leopard frog, R. pipiens, when compared with the Euro: pean, R. esculenta and R. temporaria, to give (1) more perfect general reactions associated with (2) less perfect reflex ones, and also to be both (3) stronger and (4) more sensitive. APPENDIX. T he observations of Fubint,’8r. In 1881 Fusini published, under the title “Gewicht des Cen- tralen Nervensystems im Vergleich zu dem Korpergewicht der Thiere be1 Rana esculenta und Rana temporaria,” a study of the weight of the brain and spinal cord in the two European species commonly used for experiment. His data are comprised in eight tables, each sex being represented by four tables, and the records on twelve specimens entered in each table. His main object in this study was to show that in the female frog, the weight of the central nervous system was less than in the male. As I have elsewhere explained (DoNnaLDsoN and SCHOEMAKER, ’00), he does not show this, having fallen into error by reason of his failure to appreciate that the relative weight of the central nervous system diminishes with the increasing body weight of the frog. Despite this failure in the interpretation of his records, it was desirable to examine further his original tables in order to deter- 148 “fournal of Comparative Neurology and Psychology. mine what he had recorded concerning the weight of the brain and spinal cord. The weight of the brain and of the entire central nervous sys- tem is given in all the tables. “The weight of the spinal cord can be obtained therefore by subtracting the former from the latter. Having the weight of the brain and spinal cord, we can find the ratio between them. ‘There are moreover two tables, one for each species, in which we have the body weights of males to compare with the weight of the central nervous system. In the other six tables, the body weights for the males (two tables) are given “after evisceration”’ and for the females (four tables) without correction for ova. In these cases the body weights can only be estimated. These data have been carefully worked over, with a view to determining how they compare with my own. In the first instance, FuBINI’s observations on the brain weights in unopened males of R. temporaria, are closely similar to mine. He obtains, however, weights for the spinal cord nearly double mine; thus his brain cord ratio is abnormally low. ‘This is shown in the following table. TABLE 20. Showing the ratios of brain weight to the cord weight as determined by FuBINI, and by me. Rana temporaria DoNALDSON Das | REPETITION OF TABLE I2. Ratio. paces Ratio. Bopy WEIGHT. | Bopy WeiGuT. 15.9 Deis | 23.1 (male observed) | 1.26 29n 1.86 | 25.0 (male estimated) 1.70 28.0 1.87 31.0 (female estimated) 1.14 Bing 1.87 35.0 (female estimated) 1397/9) Rana esculenta. DoNALDSON Rose REPETITION OF TABLE I2. Ratio. Ratio. Bopy WEIGHT. Bopy WEIGHT. 15.9 2.29 20.0 (male estimated) 1.76 22.0 ey} 28.2 (male observed) 1.25 35-0 2.09 30.0 (female estimated) 1.80 40.2 2.05 35.0 (female estimated) 1.62 Donatpson, American and European Frogs. 149 In the same way his observations on the weight of the brain in R. esculenta run only 10 to 15 per cent below mine, but the weights for the cords are much higher than mine, and the ratios as seen in the above table, are quite impossible and hopelessly irregular. In view of these relations of brain to cord, I conclude that Fust- NI’s results are in general not trustworthy, and therefore do not require further discussion. BIBLIOGRAPHY. Bircg, E. A. 1882. Die Zahl der Nervenfasern und der motorischen Ganglienzellen im Riickenmark des Frosches. Archiv f. Anat. u. Physiol., Part 5 and 6, p. 435-570. Bou encEr, G. A. 1897. The tailless Batrachians of Europe. Published by the Ray Society. London. Boycott, A. E. 1904. On the number of nodes of Ranvier in different stages of the growth of nerve fibers in the frog. Ff. of Physiol, vol. 30, p. 370-380. ‘CAMERANO, L. 1900. Richerche intorno alla Variazione del “‘Bufo Vulgaris” Laur. Mem. d.r. Accad. d. sc. di Torino, S. 2, vol. 50, p. 81-153. Donatpson, H. H. 1898. Observations on the weight and length of the central nervous system and of the legs, in bull-frogs of different sizes. Ff. of Comp. Neurol., vol. 8, no. 4, p. 314-335: 1902. Weight of the central nervous system of the frog. Decennial Publications, University of Chicago, vol. 10, p. 3-15. Donatpson, H. H., and ScHormaxker, D. M. 1g0o. Observations on the weight and length of the central nervous system and of the legs in frogs of different sizes (Rana virescens brachycephala, Corr). 7. of Comp. Neurol., vol. 10, no. I, p. 109-132. 1902. Observations on the post-mortem absorption of water by the spinal cord of the frog (Rana virescens). 7. of Comp. Neurol., vol. 12, no. 2, p. 183-198. Dunn, E. H. 1900. The number and size of the nerve fibers innervating the skin and muscles of the thigh in the frog (Rana virescens brachycephala, Corr). 7. of Comp. Neurol., vol. 10, no. 2, p. 218-242. 1go2. On the number and on the relation between diameter and distribution of the nerve fibers innervating the leg of the frog (Rana virescens brachycephala, Corr) . of Comp. Neurol., vol. 12, no. 4, p. 297-328. Fup, S. , 1881. Gewicht des centralen Nervensystems im Vergleich zu dem K6rpergewicht der Thiere, bei Rana esculenta und Rana temporaria. Motrscuorr’s Untersuchungen zur Naturlehre des Menschen und der Thiere, Bd. 12. Harpesty, I. 1899. The number and arrangement of the fibers forming the spinal nerves of the frog (Rana virescens.) F. of Comp. Neurol., vol. 9, p. 64-112. Ketuicott, W. E. 1g07. Correlation and variation in internal and external characters in the common toad (Bufo. lentiginosus americanus, Le. C.) #. Exper. Zodl., vol. 4, p. 575-614. pe Varicny, H. ’99. Sur la notion physiologico-chimique de l’espéce. Volume jubileum de la Soc. de Biol de Paris, p. 598. aus oY se us us : wis , Se ay ~ iay 4 Dito 7 PRELIMINARY NOTE ON THE SIZE] AND CONDE TION OF Whit CENTRAL, NERVOUS, SYSTEM IN ALBINO} RATS. EXPERIMENTALLY )STUNTED. BY SHINKISHI HATAIT, Ph.D. (Associate, The Wistar Institute of Anatomy and Biology.) For these observations five litters of rats were so divided into two groups that the average body weight was nearly the same in both and one group was given the full laboratory ration, while to the other was fed the minimal amount of bread, corns and cereals. The normally fed group constitutes the “first controls,” and the underfed rats, the “stunted group.” For further comparison, young rats with the approximately same body weight as the “stunted group,” bit much younger, were taken for the “second controls. ”’ Beginning at the age of thirty days, the underfeeding consider- ably retarded the growth of the stunted group so that when they were, on the average, 170 days old they weighed 91.5 grams, whereas the “first controls” —of the same average age—weighed 146.5 grams. ‘The younger rats from 80 to 100 days old which formed the “second controls,’’ weighed on the average 86.3 grams. It must be remembered that during the time the behavior experi- ments were carried on (for nearly thirty days), the experimented rats were fed with normal diet and as a consequence these rats gained somewhat rapidly in body weight. ‘Therefore the pos- sibility of obtaining permanently stunted rats by means of under- feeding is still undetermined. All the rats were killed and weighed immediately after the behavior experiments were ended. The main results obtained from the present experiments are exhibited in the following table. External characters—The most conspicuous external differ- ences between normal and stunted rats as shown by the stunted rats are in the length of the body and of the tail, both of which 152. fournal of Comparative Neurology and Psychology. were considerably reduced with respect to the body weight.t This peculiar difference, as is seen from the table, holds true in every case. Further, the ratio between the length of the body and TABLE I. < ss | sae ee ae : em Ee & ol = | ey Eee Toes! & | | Sh 5 | t | Zz 5 =e: = | een ee me a cree Ree es ea ba 5g Bot AB 9) 26° | 2a teh Were be ce ae so s/he ae a a Zz Me = Seeleers 5 ats Oe | Pace ae | = 4 és a aoa ical | ee Ae pee % " ~ ral =) | 48 i Age Ze, = oS z 5 a = nl Wc et edb cic aces RE 2! WN n x ea | @ eS | & a) Q A | A a days grams mm mm | 1 aes ars. | 186-2 | 489.5) “158° | 1.8996, 5597 78.365) 70.573) 1st control 1 Meiers [a2 ||) LOO. 2a) samc 112 |1 6325] -4030 78.623) 72.641 stunted Bessie 8o-100| 105.7 155 | 131 | (1.6313, 4049 78.900 72.925 2d control Mis | 182 186.7 190 | 154 1.6578, .4862 78.447) 70.547 Ist control Minas | 182 | 113-7 E55) 5) Too). | |1.5678 3756 78.772| 73-003 stunted Mie 80-100) 99.7 157) i) wen |1.7029 -4059 78.971) 73-121 2d control | | | | 1 EE Ae 164 | 119.1 167 130 1.6671 1.4524 78.315 71-353 Ist control IND ee 164 FOL LS 7a LOS! 1.5884 |.3573 78-374, 71-760\stunted Meer 80-100) 87.4 | 154 | 119 |1.7156 | 3579. 78.870 72.981 2d control | | } | | | : 1c 164 | 126.9) |||) 170 | 139 ‘1.6859 4941 78.118, 71.623 Ist control F.......) 164 | 89.3 | 140 | 113 | ‘1.6053 |-3730,78.477| 72-193 stunted lieege ee 80-100] 61.7 | 128 113 |1.4880 +2975 78 .568 *71 .092 2d control | | | | | | | | | | IG Jee LQ ae Ati 312) oe GO) sain eitaicne | |1.7698) |.4459 78.675) 72.303 Ist control ae esas 127 ee TORO Mal Laz 105 1.7394 -3404 78.836) 73.413 stunted Ici Se 80-100) iste NO AER ae |) Bis 1.5110) +3359, 79-139) 73-861 2d control | | | Averages. lyse M | 170 | 146.4 175 | 143 1 Het Sea eels ge |.4877/78.384| 71.280 1st control LSE iigfeies\| Cha Ts 144. | 108 1:0.7501.6267 1.646 |.3699,78.616, 72.602 stunted | | | | | F+™M Soares 86.3 147 120 a : 0.816 1.6098 1.629 |.3604/78.889 72.796 2d control | | | | | | | * Thisisthe only exceptional case, where percentage of waterin the second controlis less than that of the stunted. that of the tail is considerably less in the stunted rats than in the control rats. The ratio just mentioned is found to be on the average I :0.82 in both “first”? and “second controls” while 1 The measurement taken from the tip of the nose to the anus is designated as “body length” while that from the anus to the tip of the tail is designated ‘‘tail length.” Hatal, Nervous System of Albino Rats. 153 in the stunted rats the ratio is 1 :0.75. Underfeeding therefore produces short tailed individuals. ‘The nature of this result has still to be investigated. Central nervous system.—Yhe weight of the brain and spinal cord and the percentage of water in both were separately deter- mined according to the usual procedure. The weight of the encephalon was found to be normal to the body weight in both the controls and stunted rats, the brain weight of the first controls is heaviest and that of the “stunted” and ‘“‘second controls”’ follow in the order named. The relation between body and brain weights was tested by the formula, Brain weight = 0.554 + 0.569 log (body weight — 8.7). This formula has been developed through the study of our [abor- atory records and gives us the theoretical weight of the brain for any body weight. ‘The former was found to be normal even in the stunted group. As seen from the table, the difference between calculated and observed brain weights on the average was about 1.5 per cent, indicating a normal relation of the brain weight to the given body weight. Thus we conclude that the normal relation between the body and brain weights was not dis- turbed by stunting. We have as yet no satisfactory method for determining the normal weight of the spinal cord in respect to either body weight or any other characters. Nevertheless the proportional weight of the spinal cord in the experimented and in the second control rats with respect to the brain and body weights suggests that it also has grown normally (see Table 1). Therefore we conclude that the weight of the spinal cord and brain are similarly related to the body weight. Consequently so far as the weight of the central nervous system is concerned, the normal relation to the body weight is still maintained by the stunted rats. It is interesting to note in this connection that the definite rela- tion between the body and. brain weights is not disturbed even when the growth of the body has been considerably accelerated by means of the lecithin? or when the rats have been once starved and then returned to normal diet so that the final body weights ? The effect of lecithin on the growth of the white rat. American Fournal of Physiology, vol. 10, no. I. 1905. 154. ‘fournal of Comparative Neurology and Psychology. become normal to the given age. Whether or not this definite relation between the brain and body weights can still be maintained even when we modify the conditions in other ways will be the subject of further investigations. Percentage of water in the central nervous system.—The per- centage of water in the central nervous system was always higher in the stunted rats than in the first controls, despite the fact that ages of the two groups were the same. On the other hand, this value in the stunted rats—though slightly less—was very close to that of the second controls which were much younger. It has been established in the laboratory that among rats of the same age, those with heavier brains have a smaller percentage of water than those with lighter brains. ‘Therefore the higher percentage of water in the stunted rats as compared with the first controls indicates “‘a usual”’ rather than ‘‘an unusual” condition, since we should expect to find a somewhat higher percentage of water in the rats with less heavy brain at a given age. We conclude therefore that the percentage of water in the central nervous system in both the controls and stunted rats is normal, in the latter of course having due regard for age and body weight, as well as weights of the brain and spinal cord. Since the percentage of water and that of the extract are in- versely related we may infer that somewhat greater percentage of water found in the central nervous system in the stunted rat indicates with highest probability relatively smaller development of the medullated nerve fibers in that organ when compared with that of the first controls. ‘This statement is correct at least for the peripheral system, as a recent investigation’ by Mrs. J. W. Hayes shows that the number of medullated fibers in the second spinal nerve in heavier albino rats is greater than that in the less heavy rats of the same age. A further discussion of this general point is however reserved for a future publication. Conclusions.—Our final conclusions are, then, that aside from the shorter length in the body and tail, which is not only absolute but relative also, the stunted rats differ from the normal rats only in the absolute magnitude of the measured characters, while, on the other hand, when differences in the central nervous system 3 Effect of partial starvation followed by a return to normal diet on the growth of the body and central nervous system of albino rats. American fournal of Physiology, vol. 17, nO. 5. 1907. * As yet unpublished. Hatal, Nervous System of Albino Rats. 155 are compared with the growth of the entire body the growth of the stunted rats may be considered just as normal as that of the controls. The stunted rats were made the subject of tests, by Mr. Joun W. Hayes, fellow of psychology in the University of Chicago, to determine whether their behavior was modified by their arrested growth, and the results will be published by him later. ON THE PHYLOGENETIC. DIFFERENTIATION OF THE ORGANS OF SMELL AND TASTE. BY C. JUDSON HERRICK. (From the Anatomical Laboratory of the University of Chicago.) There are in vertebrates two systems of sense organs adapted to respond directly to peripheral chemical excitation, the organs of smell and taste. In this respect they are in contrast with the other sense organs of the body; but when we come to compare the two chemical senses with one another we find it difficult to discover any objective difference between their stimuli or any explana- tion for the development of two chemical senses in the primitive aquatic vertebrates. And yet the very lowest vertebrates exhibit important morphological differences between the peripheral organs of smell and taste, a complete separateness in the nervous path- ways to the brain and still more important differences in the central reflex connections within the brain. In view of the simi- larity in the nature of the stimuli to which the peripheral organs respond, these fundamental central differences have thus far baflled explanation. Let us first consider briefly the criteria by which in the case of human beings the modalities of sense may be distinguished. (1) Doubtless he most important criterion for us is direct introspec- tive experience, the psychological criterion. (2) The adequate stimuli of the various senses exhibit characteristic physical or chemical differences, the physical criterion. (3) The data of anatomy and physiology may differentiate structurally the recep- tive organs and conduction paths of the several types of sensation, the anatomical criterion. (4) The type of response varies in a characteristic way for the different senses, the physiological criterion. It is impossible in the present state of our knowledge to frame adequate definitions of Al of the senses in terms of any one of these criteria alone. Thus, we are not able introspectively to dis- 158 ‘fournal of Comparative Neurology and Psychology. criminate between olfactory and gustatory sensations, but rather elaborate physiological experimentation is necessary to enable us to effect the analysis of these two sets of stimuli. Again, the anatomical and physiological bases of several of the senses are still very imperfectly known and in still other cases we are almost wholly ignorant of the distinctive chemico-physical qualities of the stimuli which call forth diverse sense modalities. ‘The latter point is notably true for the senses of smell and taste. “The com- mon statement that we smell substances only in the gaseous state and taste liquids (solutions) 1s only approximately true, if at all, in the mammals, and certainly cannot hold for the lowly aquatic vertebrates where the differentiation of these two sense organs in practically their definitive form first occurred. Attention has been drawn to the fact that, while tastes can be classified under the four subjective qualities, sweet, sour, bitter and salty, the innumerable odors are apparently quite incapable of any such classification. ‘To this it may be added, on the one hand, that ZWAARDEMAKER claims to be able to classify the known odors into some nine groups which he compares with the four classes of taste, and, on the other hand, that some recent studies on the chemical physiology of taste* go to show that it is a reaction between the receiving organ and the ions of the sapid substances and that the ions belonging to a given group, such as those giving “‘salty’’ tastes, do not all produce the same sensation quality. In other words, the four groups of taste qualities, like the nine groups of smell qualities, are more or less ill defined both from the standpoints of their psychological and their physico-chemical criteria. It is to be expected that future research will shed additional light on the physical and psycho- logical criteria of smell and taste, but it will not eliminate their strong similarity. These considerations suggest that smell and taste have origi- nated phylogenetically from a common undifferentiated chemical sense, a conclusion which is supported by the morphological rela- tions of their cerebral centers. The details of this anatomical evidence are far too complex to be summarized here and the reader 17... KAHLENBERG: The action of solutions on the sense of taste. Bul. Univ. Wisconsin, Science Series, vol. 2, pp. 1-31. 1898. T. W. Ricuarps: The relation of the taste of acids to their degree of dissociation. Am. Chemical Fournal. 1898. HERRICK, Organs of Smell and T aste. 159 is referred to the exposition and discussion of the cerebral centers for smell and taste given by JOHNSTON and HERRICK.? But despite these fundamental similarities, it still remains true that the organs of smell and taste are topographically widely sep- arated and structurally very different both peripherally and cen- trally. Their central neural pathways and connections are in fact as different as are those for hearing and vision,. two senses whose psychological and physical criteria are most clearly defined. The anatomical relations of the gustatory system are known in lower vertebrates and those of the olfactory system are well under- stood and are tolerably uniform throughout the vertebrate series. It is possible to determine by experiment to which one of the peripheral sense organs an animal responds when given a chemical stimulus. “The anatomical criteria of smell and taste are therefore clearly defined. As far as vertebrates are concerned, we may define taste in accordance with the anatomical criterion as the reaction or sen- sation arising from the appropriate chemical stimulation of the organs newness back (wherever found in the body), and smell as the reaction or sensation arising from the appropriate chemical stimulation of the termini of the olfactory nerve. (See the Addendun, p. 165.) These definitions cannot be extended to the invertebrates unless homologous organs can be discovered among them. It may well be that there are no such organs in the invertebrates, a single chemical sense alone serving their needs; or two or more chemical senses may be present among the invertebrates which are wholly unlike either of the vertebrate senses. In this discussion it will be observed that I take a somewhat different standpoint from that of NAGEL,’ who defined taste and smell in terms of the state of physical aggregation of the stimulus. Smell, he says, is the faculty of perceiving vaporous (damp fformige) substances and taste is the faculty of perceiving liquid substances. It follows from this, he argues, that it is not proper to attribute to aquatic animals a sense of smell in addition to a sense of taste, but both functions fuse into a single one. 2 J. B. Jounsron: The nervous system of vertebrates. Philadelphia, 1906, chap. 10. C. Jupson Herrick: The central gustatory paths in the brains of bony fishes. Journ. Comp. Neurol. and Psych., vol. 15, 1905, pp. 450-454. 3W. A. Nacet: Vergleichend physiologische und anatomische Untersuchungen tiber den Geruchs- und Geschmackssinn und ihre Organe, mit einleitenden Betrachtungen aus der allgemeinen vergleich- enden Sinnesphysiologie. Buibliotheca Zoologica, Stuttgart, Heft 18. 1894. 160 Ffournal of Comparative Neurology and Psychology. His argument for the absence of smell in all aquatic animals is based upon the definition of smell as the perception of gaseous or vaporous stimuli. He adduces evidence that when air is dis- solved in water it 1s incapable of absorbing the vapors given off by volatile substances unless these vapors are soluble in the water itself, stating that they cannot be dissolved in the air contained in the water. They affect the organs, therefore, as true solutions, not as gases dissolved in water. He says (p. 60), “All substances which pass over into water from an object lying in the water, say a decomposing organic body, diffuse themselves in the water in accordance with ihe laws of the diffusion of liquids, not those of gases and vapors, even though the object in question when brought into the air may have vaporous emanations. Tt is unnecessary to summarize here his elaborate argument for the absence of smell in fishes based upon anatomical differences in the receptive olfactory organs between fishes and air breathing vertebrates; for when examined closely in the light of our present knowledge these differences are seen to be trifling when com- pared with the broad resemblances of both peripheral and central organs of smell throughout the whole vertebrate phylum. NaGEL’s conclusion is expressed on p. 62: “We can with the greatest probability assume that the end-buds of the glossopharyn- geus in the mouth of fishes and amphibians serve the chemical sense, Viz: taste, and thus function in eating. We can with some probability assume that the sense organs of fishes and aquatic amphibia supplied by the N. fecivens likewise serve the chem- ical sense; but this 1s certainly no olfactory organ in the sense of that term in the land animals. What the occasion of its chem- ical excitation may be is quite unknown. ‘The method by which it is excited is with highest probability similar to the excitation of the taste buds in the mouth, 1. e., the excitation follows through substances dissolved in water.”’ This conclusion, to my mind, simply illustrates the fact that it is impossible in the present state of our knowledge to interpret these two senses in terms of the physical stimuli. It is not meant to imply that there is no difference between the physical stimuli of smell and taste; for I think it probable that further research will bring such differences to light. But these differences are appar- ently very small in aquatic animals, whereas the structural differ- ences between the nervous apparatus involved are very great indeed, even in the lowest fishes. Herrick, Organs of Smell and Taste. 1601 Our argument thus far leads to an apparent impasse. The physical and psychological criteria of smell and taste seem inade- quate to account for the definite and fundamentally different anatomical peculiarities of the organs in question. But we have not yet considered the fourth line of evidence mentioned at the beginning, that which we called the physiological criterion; viz: the characteristic responses normally following the stimulation of these organs of sense. A suggestion made by Professor SHERRINGTON in his recent Lectures on the Integrative Function of the Nervous System seems to me to put the matter in a perfectly clear light. Asis well known, SHERRINGTON classifies the sense organs (receptors) into (1) extero- ceptors, adapted for response to stimuli arising from without the body; (2) proprioceptors, sense organs lying within the body adapted to report to the central nervous system the physiological state of the organs of somatic response themselves (typified by muscle spindles, neuro-tendon organs, etc.); (3) interoceptors, organs set to to guard the receptive surfaces of the body—-enteron, lungs, etc. Exteroceptors which are excited by stimuli arising at a distance from the body are termed by SHERRINGTON distance receptors. The physiological analysis here outlined is full of helpful sug- gestion in the morphology of the nervous system. Putting SHER- RINGTON’S analysis into correlation with that of the new school of functional morphologists, we recognize his first two types of recep- tors as falling’within the somatic sensory group, for the chief organs of response (effectors) 1n both cases are the somatic or skeletal muscles. SHERRINGTON’S third type is the visceral sensory system, calling forth reflexes in the visceral musculature (including the specialized striated visceral muscles of the branchial arches and their derivatives 1n the higher vertebrates). The taste buds lying within the mouth of vertebrates are typical interoceptors, and they with their nerves and cerebral centers are classified as specialized visceral sensory organs. ‘They are in gnathostome vertebrates usually stimulated by food contained within the mouth and the effectors with which they are most directly connected are the visceral muscles of the jaws, gills, cesophagus, etc. In the protochordate vertebrate ancestry it is probable that there was but one chemical sense, and that feebly developed; for these animals probably did not masticate their 162 “fournal of Comparative Neurology and Psychology. food, and the undifferentiated primordial chemical sense may have been as important in determining the chemical character of the environing water as of the food eaten. Be that as it may, with the appearance of teeth which pierce or crush the food, the organs of chemical sense within the mouth and pharynx assumed an important function as guardians of the en- trance to the cesophagus, an interoceptive function which they per- form in all gnathostome vertebrates—the organs of taste. Parallel with this differentiation within the mouth, the organs of chemical sense lying outside the mouth at the rostral end of the body would assume more and more importance as organs for detection of chemical differences in the surrounding water, differences result- ing usually from the presence of sources of chemical alterations of the water lying outside the body of the fish. ‘These external organs of chemical sensation in the leading segments of the body were finally aggregated as the organ of smell. The differences in the character of the stimulus applied to these two organs may have been very slight at the beginning (and indeed may be so still); but in the case of any organism possessing the power of free locomotory movement the physiological significance of the stimulation of the two sense organs may be very different indeed. The object which acts as a stimulus to taste buds is already within the mouth. The appropriate reaction is typic- ally a contraction of the visceral musculature of the mouth and pharynx adapted either to masticate and swallow or to eject the object, as the case may require. The somatic musculature is not necessarily brought into play. The olfactory organ, on the other hand, has become a distance receptor and the appro- priate reaction is a movement, usually locomotor in type, of the somatic muscles, taking the animal toward or away from the source of the stimulus. Even though the stimuli in the two cases were identical, it is evident that the difference in the character of the response would bring into play a very different central reflex apparatus for the distance reaction from that for the mastication or swallowing reflex. This difference between the characteristic reaction of the intero- ceptor and the distance receptor is in my opinion the sufhcient explanation for the most important structural differences between the olfactory and gustatory systems of vertebrates. [his same feature involves, it is true, a certain degree of difference between Herrick, Organs of Smell and Taste. 163 the physical stimuli and the psychical qualities of odors and savors, especially in the higher vertebrates; but these are in all animals quite subordinate to the type of reaction involved. A critical examination of the central conduction paths for smell and taste supports this view of the case. The central olfactory apparatus is very constant throughout the vertebrate phylum. The organ of smell, as befits a distance receptor, 1s located in the leading segments and its central connections are with the extreme tip of the neural tube; indeed in all of the true vertebrates it has grown out rostrad beyond the primary neural tube, the entire rhinencephalon lying in the telencephalon, or ultra-terminal brain. The path extends from the olfactory bulb to the tuberculum olfac- torium and other structures in the base of the forebrain, thence directly back to the olfactory centers in the thalamus or else first to the olfactory cerebral cortex (hippocampal formation, etc. ) and then to the thalamus. ‘The two principal olfactory centers in the thalamus lie in the epithalamus and hypothalamus respectively. Each of these thalamic centers receives in higher vertebrates olfac- tory tracts from both the basal and cortical olfactory centers of the forebrain; and each sends a strong tract to reach the motor centers. These tracts are the tr. habenulo-peduncularis (fasc. retroflexus or bundle of Mrynert) and the fasciculus pedunculo- mammillaris (tr. mammillo-bulbaris). In lower vertebrates both of these tracts can be traced far downward into the medulla oblon- gata, where they come into relation directly with the motor nuclei of the cranial nerves and the evidence is that either directly or indirectly they pass still farther into the spinal cord for the somatic motor reflexes characteristic of olfactory reactions. The central gustatory path is well known only in fishes. Here there are much more direct reflex connections with the visceral motor nuclei of the cranial nerves than the olfactory system shows, and in most fishes no important connections with somatic motor nuclei save by way of the hypothalamus and tractus mammillo-bul- baris. There are certain fishes, however, in which taste buds have been developed secondarily in the outer skin of the general body surface. Here they have been shown to function as exteroceptors! and in these cases the central connections of the cutaneous taste 4C, Jupson Herrick: The organ and sense of taste in fishes. Bul. U. S. Fish Commisssion for 1902+ Washington, 1904. he central gustatory path in the brains of bony fishes. ‘fourn. Comp. Neurol. and Psych., vol. 15, no. 5. 1905. 164 Fournal of Comparative Neurology and Psychology. buds are very different from those of the phylogenetically older taste buds within the mouth. In the catfish and carp, the primary cerebral center for all of the cutaneous taste buds is the facial lobe, from which secondary gustatory tracts of the typical sort pass out to the visceral motor centers, and in addition a direct secondary path to the funicular nuclei where these gustatory impulses are codrdinated with tactile 1 impressions from the same areas of skin.» A single path leaves the funicular nuclei for the somatic motor centers, thus serving as a common reflex path for both tactile and gustatory impulses from the skin. In the cod® the cutaneous taste buds effect somatic motor connections in an entirely different way, passing directly from the equivalent of the facial lobe into the fasciculus longitudinalis medialis and thence to the somatic motor nuclei, indicating that the cenogen- etic connection of the taste buds which act as exteroceptors with somatic motor centers has been acquired independently in the gadoids and the Ostariophysi. The interesting point in this connection 1s that within the group of teleosts taste buds, which typically in fishes act as interoceptors, have secondarily acquired exteroceptive functions, and parallel with this change a new central reflex path has been established between the primary centers of cutaneous (exteroceptive) taste and the somatic motor centers. It is probable that at a much more ancient period in the phylogeny of vertebrates an analogous dif- ferentiation took place in the primordial unspecialized chemical sensory apparatus, one part becoming a typical interoceptor (gus- tatory apparatus) and establishing its most direct central reflex connections with the visceral muscles of mastication, deglutition, etc., and another part becoming a typical exteroceptor (olfactory apparatus) and early establishing direct central reflex connec- tions with somatic muscles of iene? eye movements, etc., in addition to the visceral motor reflexes characteristic of a visceral system. It should be expressly stated that the claim is not made that all anatomical differences between the organs of smell and taste are explained by this principle, but only that in this way the direction 5 C. Jupson Herrick: On the centers for taste and touch in the medulla oblongata of fishes. ‘fourn. Comp. Neurol. and Psychol., vol. 16, no. 6. 1906. ®C. Jupson Herricx: A study of the vagal lobes and funicular nuclei of the brain of the codfish. Fourn. Comp. Neuro!. and Psych., vol. 17, nO. 1. 1907. HERRICK, Organs of Smell and Taste. 165 of the original phylogenetic differentiation was determ:ned and that this is still the dominant feature of the two systems in ques- tion. The conclusion is that the agencies which acted to produce the differentiation from each other of the senses of smell and taste are not to be sought primarily in the stimuli calling forth the reflexes, but rather in the character of the response evoked by the stimulus. ADDENDUM. As these pages pass through the press an abstract of the very interesting experiments of PARKER appears in the Pro- ceedings of the American Society of ZoGlogists (Sczence, n. s., vol. 27, no. 690, March 20, 1908, p. 453). PARKER has previously determined that the skin of the body of the frog and of various other aquatic animals is sensitive to chemical stimuli. Quite in accord with those results, he now finds that the same is true for the common fresh water catfish, Ameiurus. ‘This fish possesses taste buds innervated by the nervus facialis scattered in the skin over practically the whole body surface. If the nerves supplying these taste buds on the trunk are cut, the fish no longer reacts to a bait in the normal way (by turning to snap at the bait) when it is presented to the flank of the body. Nevertheless such operated fishes are sensitive to sour, saline and alkaline solutions when applied to the skin of the trunk. These results, together with the control experiments described, demonstrate that the spinal nerves of this teleost, like those of the frog, are sensitive to certain external chemical stimuli. The important question at once arises, are these responses to chemical stimulation of the spinal nerves transmitted by the same nerve fibers which transmit the tactile stimuli, or by some other compo- nent of the spinal nerves? We know from abundant physiological and clinical experience that the cutaneous rami of the spinal nerves of man transmit impulses which are perceived introspec- tively as very diverse sensation qualities (touch, temperature, etc.). There is evidence that some at least of the different functions of the sensory spinal nerves are served by anatomically different neurone systems; but whether the ability to respond to direct peripheral chemical stimulation is limited to one or more of these systems or common to all of them, further experiment alone can determine. 166 fournal of Comparative Neurology and Psychology. Chemical irritability may prove to be more far-reaching and fundamental in nervous excitation than is commonly recognized. However this may be, two special reflex mechanisms have been very elaborately differentiated in vertebrates along quite diverse lines for precise and rapid response to special external chemical stimuli, the organs of smell and taste; and the explanation offered in the preceding pages for the phylogenetic differentiation of these two functional systems is not directly dependent upon any theory regarding the ultimate nature of the primordial undifferentiated sensory type from which they have sprung. Professor PARKER concludes the note to which we have referred with the remark, “From these experiments it is to be concluded that the sense of taste in horn-pouts is complex and involves not only the seventh nerve, but also the spinal nerves.” Assent to this proposition will be readily granted only if we define the sense of taste in accordance with the “physical criterion” (see p. 157) as NacEL does. In the opinion of the writer neither this criterion nor the “anatomical criterion” (as I have used it on p. 159) alone is adequate in the present state of our knowledge to serve as the basis for generally acceptable definitions of all of the so-called senses. Pending the extension of our knowledge in these fields, fruitless controversy may be avoided by a clear recognition of the fact that harmonious conclusions can be expected only on the basis of an explicit understanding regarding the standpoint chosen in every discussion. SOME CONDIAIONS: WHICH DETERMINE -THE LENGTH OF fHE INTERNODES FOUND ON. DHE NERVE FIBERS OF THE LEOPARD FROG, RANA PIPIENS. BY KATASHI TAKAHASHI, Rigakushi. (From the Neurological Laboratory of the University of Chicago.) Witu SEveEN Ficures. INTRODUCTION. In the winter of 1903-04, the following study of the growth of the internodes on the nerve fibers of the leopard frog, was begun, in order to determine whether on a lengthening nerve fiber the number of internodes increased or remained constant. While this study was in progress, the interesting paper by Boycotr ’o4, “On the number of nodes of Ranvier in different stages of the growth of nerve fibers in the frog,’’ was published. The species of frog used by Boycott was the common Rana temporaria (fusca) of England. After briefly referring to the scanty literature on the subject of the internodes (see KOLLIKER ’96), which shows that they have different lengths in different species of animals, are longer in old than in young animals, and longer in fibers of great than in fibers of small diameter, Boycorr presents evidence which demonstrates beyond reasonable doubt, that in the growing sciatic nerve, at the point where it divides into the nervus tibialis and nervus peroneus, the average length of the internodes increases very nearly as does the length of the nerve itself. It would seem from this to follow that the number of internodes should remain constant. ‘The cal- culations show however a very slight but regular increase in the estimated number of the internodes as the frogs become larger. This result, noted but not explained by Boycort, and touched on later in this paper is, I believe, susceptible of an explanation, which at the same time leaves Boycort’s main conclusion intact. 168 Fournal of Comparative Neurology and Psychology. The second important point brought out by Boycott, although not especially commented on by him, is illustrated in the accom- panying Table 1, which is copied from Boycort’s paper, with a slight change made by putting the “sciatic length”’ in the col- umn where the body lengths are given by him. TABLE 1. Average internodal lengths (#2) corresponding to each diameter. Rana temporaria (fusca). Copied from Boycott, fournal of Physiology (FosTER), vol. 30, p. 373, 1904. Diameter eee e2 nase | 4L | 5 | 64 | 74 | 8e | on | 10m | rim | 12 | 13h | 14/t | 15/4 Sates | | | | . me | | | ¢ | gf | P| Psa Be | = a7, 0 aw ali mm. | ne | Bee I 18.2 | 205 | 339] 450] 524] 535] au 657| 660; 667) 797| | II 2h ak 428] 525) 592] 659] or) 772) 742| 789] 846] 865] 890) | JOD Sy eyes | 770 819 770| 878} 968) 1007) 1069] 1043) 1177) ThVi) 462608) 579 1000, 766 1186, 1102) 1106 1243) 1358) 1361) a a 1576) 1766 rae | | It is here seen that on fibers of a given diameter from small (young) frogs, the internodes are shorter than on fibers of the same diameter, taken from large (old) frogs, the size being indi- cated by the sciatic length. If we apply the notion of growth to the interpretation of this table, and remember that a fiber of a given diameter in the small frog, becomes a fiber of greater dia- meter in the large frog, then it is found that the average of the measurements in Group I of fibers from 2» to 11 in diameter, which is 546, compared with the average of the measurements for fibers from 6p to 15! in diameter, in Group IV, which is 1370/5 gives an increase in the length of the internodes amounting to 2.51, and this corresponds very nearly to the increase in the length of the sciatic nerve, from 18.2 to 46.6 mm., which is 2.56. As will be observed, the average difference in gone in the two series compared is 4p. This method of comparison is admittedly crude, but under the conditions, furnishes a satisfactory confirmation of BoycorTtT’s general conclusion that the number of internodes is not increased during growth, but that their average length increases as does that of the nerve in which they are found. | TakaHASHIl, Internodes on Nerve Fibers. 169 In view of the results obtained by Boycott, it was thought best in the present study to examine especially some points which he has left untouched. These will be presented under the following heads: 1. The average length of the internodes at different levels along the nerves to the leg. 2. The length of the internodes at different levels on fibers of like diameter. 3. The length of the internodes on fibers in the roots of the spinal nerves. 4. The number of medullated aheee at different levels in the legs of tadpoles of increasing size. 5. A comparison of the length of the internodes in the Amer- ican frog, Rana pipiens, with their length in the English frog, Rana temporaria (fusca). Before proceeding to the discussion of the special topics, I desire to state that this study was made under the direction of Prof. H. H. Dona.pson, to whom | am indebted also for the revision of my manuscript. Moreover, I wish to thank both Dr. EK. H. Dunn and Dr. S. Harat for their aid and suggestions given to me dur- ing the conduct of this investigation. MATERIAL AND TECHNIQUE. For this study, the common leopard frog, Rana pipiens (SCHRE- BER) was used, the specimens having been obtained from a local dealer and probably collected in the country about Chicago. The frogs were killed with chloroform; the body weight, corrected for ova in the case of the females, was taken in a closed box, and the total length, i. e., the length from the tip of the nose to the up of the longest toe, as well as the body length, i. e., from the tip of the nose to the tip of the urostyle, were both recorded. In some cases also, the length of both the dorsal and ventral roots of the III and IX nerves (Gaupp’s numbering) was determined. ‘The data thus collected are given in Table 2. In preparing the material, the following methods were employed: A short piece of the fresh nerve was cut out and laid on a wedge- shaped strip of cardboard, the piece of nerve being extended to its normal length. ‘This was fixed, and at the same time macerated, by being placed for twenty-four hours in the following solution (A): 170 ©‘fournal of Comparative Neurology and Psychology. Osmicracid 5 fer..)crs ote ied ox atone oNerenciettsre tehs, wtaerahe wl vote Ac aeet ante aaa Rater I .00 per cent, 5 parts Chromic acid iia cacissp sates ae wtldis oe sais sss tees. seme alemabotee ©.25 per cent, 3 parts iy diochloriciacidls 2: )a)s sciscpice Hla tiac s¥'eis = aieje tes i's loon tias = okie evel tiets O.10 per cent, 2 parts After washing for twenty-four hours in running water, the speci- men was transferred for twenty-four hours to the following solu- tion (B): Gili CONTE Feats a apo choc nsefeie. ate Sage’ sis oss Srasnrs edema egeretrsis staievosy aio) speurotabe ave tae Renters 10 parts Koupericenttyal colo lsytercestselaretacatare shee veka ole eiestsceterssae ee) aleye teks atezas AAA see 20 parts Hydrochloric decid! | bos. se aclele stove ss 4 sien re cloimoninie svetenelelcls muoe peters eet aera eays 0.09 parts After this treatment, the specimens are preserved in solution (€): (CIM ca git) = hae Aan aonb AC peer ccna Ar olla ALU RAT erring anos ospswoaade 10 parts Rel posi@olecleol Wasa seiburaas sears Conon AbOnan £odaas IOC CURAEDONS hdc Sonas* 20 parts This last solution (C) should be renewed once or twice at inter- vals of twenty-four hours. ‘Thick nerves were slit longitudinally with a razor, after they had been in solution (A) for two or three hours. ‘This was done to assist the penetration of the fluid. The specimens were teased in solution (C). TABLE 2. Data on the specimens of Rana pipiens used in this investigation. Entries arranged in the order of increasing body length. V, ventral; D, dorsal. Tora. | Lenoru eae Rs Bose Date oF No. | Sex. |BopyWeIGHT L >. | OF III Sprnat | or TX Sprnar ENGTH. or Bopy. | pes 3 | Ragan’ KILune. vt ae el aCe J grms. mm. | mm. mm. mm. I M. 55 104 | 39 | V «85 2.6 | D .64 2.1 Aug. 29,’05 2 M. 23.5 169 | 71 | V2.6 7.0 | Des 6.5 | Jan. 04 3 10 26.0 166 72 Jan. 29, ’06 4 LBs 22 | 180 78 V2.4 | a he! | | D2.4 7.1 Mar. ’o4 5 M. BIRO. 1's} 192 80 | | (Dec. 03 6 M. 37-0 204 | 80 | Nov. 703 7 M. 61.1 226 89 | V9.5 D 9.0 July 16,’04 8 M. | 63.0 222 89.4 V2.0 | 5-9 | | D1.6 | 5-4 Aug. 3, 705 The technique just given, fails however to yield satisfactory results when applied to the nerve roots of the III or [X nerve as the fibers become brittle and distorted. Moreover, the roots TakaHasHl, Internodes on Nerve Fibers. 171 of the III nerve do not yield to the technique which proved fairly satisfactory in the case of the roots of the IX nerve, so that the technical problem is complicated. In the case of the IX nerve, I used in the first instance solution (D): OsmicacideveceR ee eer Torre eereree icles coe eseisiorsiare oitya/eceretar ©. 10 per cent, 4 parts Chromicaeid aac ity ioeis oneinie oie cies cite ioe sie! Ae Sleeha see e)site ©.02 per cent, I part The specimen was left in this solution for twenty-four hours, then washed in running water for twenty-four hours, and finally preserved and teased in solution (E). 50 per cent glycerine. This should be renewed several times. Later, in place of solution (D), I used solution (F): (ORMIEE a lecio SSA Ooo Rinne See ee Uc SoUtod cboenigans omasadcc cou ep osd ©.100 per cent, 5 parts CITI Or et Gta Sie teCs mEIO eS Os ce tony Oca ae soa aod ©.025 per cent, I part PACE teraGidiaseyasa hes irtysiass eos lie aw aly ci ema sree rs wyoual main eetree ©.100. per cent, I part This gave somewhat better results than solution (D) but none of these solutions acted upon the roots of the III nerve sufficiently well to justify an extended study of its fibers, hence only one III nerve was examined. It is fundamental to the following argument, that the treat- ment of the nerves should not materially alter the length or the diameter of the fibers which are to be measured. It was neces- sary therefore to examine the effect of the solutions here employed, and this was done by measuring samples of the nerve as they were passing through the solutions. Sixteen samples from different levels along the nerves to the leg were first measured, after having been for two or three hours in solution (A) and then finally measured after treatment in solution (C) when they were ready to be teased. “The measurement showed an average loss in length of 3.6 per cent and an average loss in diameter of 12.8 per cent. In the case of eight other specimens (four from the III nerve, and four from the [X nerve) examined in the same way, the loss in length was I per cent, and in diameter, 8.6 per cent. The loss in length is trifling; that in diameter however seems large. It is probable nevertheless that it is to be mainly credited rather to a diminution in the connective tissue sheath, and to the 172 ‘fournal of Comparative Neurology and Psychology. compacting of the fibers, than to a diminution in their individual diameters, and it is therefore not thought that the normal diameters of the fibers are as much modified as the above measurements would indicate. The samples of nerve were teased with fine needles under a dis- secting microscope, and measured directly with a compound micro- scope, using lenses and eyepieces (with micrometer scales), suited to the determination of length on the one hand and diameter on the other. The full series of individual measurements will not be printed here, but the original records remain in my posession, and a com- plete copy of them has been put on file at the Wistar Institute of Anatomy and Biology in Philadelphia, where it may be examined at any time. In the case of the condensed tables which follow, it should be stated here, once for all, that the averages used are always “weighted for the number of cases,” while in those instances where it seemed important, there is printed in parentheses along with the average value, the number of measurements on which it is based. ‘The value for the internodes is always given in thou- sandths of a millimeter (). I. THE AVERAGE LENGTH OF THE INTERNODES AT DIFFERENT LEVELS ALONG THE NERVES TO THE LEG. As has already been stated, Boycorr ’o4, limited his observa- tions to the average length of “55 internodes taken from one local- ity, the distal end of che’ sciatic nerve. ‘The attempt was therefore made to determine the average length of the internodes at various localities along the nerves supplying the leg. Fig. 1 gives the arrangement of the nerves to the leg, based on a dissection made by Dr. DuNnN ’02. The levels from which sam- ples of the nerve were taken are indicated by interruptions in the drawing, and designated by letters, S,; Pope eras Booey Bettas ene The first four are from the nerve in the thigh, the fifth and sixth from the nerve in the shank, and the seventh from the nerve in the foot. In each instance a bit of the nerve was prepared according to the method already described, teased as completely as possible, and fifty or more measurements made on the internodes of the fibers, always preferring the larger to the smaller fibers in each instance. TaKkaHasul, Internodes on Nerve Fibers. ie Table 3 gives the results of this sampling; the average at each level being based on the fifty largest fbers which were found. The method used is sufficiently accurate to justify the state- ment that on passing peripherally along the nerves to the leg, the fibers of larger diameter become less frequent, and the average N.VIII---- ING IK oe es pee: <== belies S as pe ar nee | pePl Crurotarsal Fic. 1. Giving the main trunks in the nerve to the right leg of the Leopard Frog, as seen from the dorsal aspect. The levels of the several joints are indicated, and also the localities from which pieces of the nerve were taken. These latter are indicated by interruptions, and designated by the letters used in the text. Based on Fig. 1, Dunn ’oz. Pi, n. peroneus lateralis. T1, n. tibialis r. superficialis. P2,n. peroneus medialis. Tz, n. tibialis r. profundus. length of the internodes diminishes correspondingly. With the exception of the level S,, in which, owing possibly to the large number of fibers present, the sampling is less representative than at the lower levels, the internodes show a steadily diminishing length as indicated in the last column of Table 3. The relations of the diameter and the length of the internodes at the several levels are shown in Fig. 2. The levels are indicated 174. ‘fournal of Comparative Neurology and Psychology. in the figure in their relative positions, and the locations of the hip, knee and crurotarsal joints are shown. It would follow from this, of course, that if we attempted to determine, as Boycott did, the number of internodes character- istic of the nerve between its origin and any distal point, we should find this number to increase as the sample of the nerve was taken nearer and nearer to the foot. ‘This is exactly what we should TABLE 3. Showing the average diameters of the fibers and the lengths of the internodes at the several levels in the nerves to the leg of Frog 6. Body weight, 37 grams; total length, 204 mm. For the identification of the levels, refer to Fig. 1. The number of measurements is given in parentheses above the length of the internodes to which it applies. | | | | | | | | | GENERAL | | | | | AVERAGES. Average | | | | ENE Diame- | | Di | Inter- ter. | | | | | cae | nodes in in ft 5.0 6.6 8.7 | 10.2 |12/0/12.5|12.8] 13.0 |15.0|16.2) a eaatee Range | (6.2—)}| | (10.0-) | | (13.0—)| | —— (7-5) | a2 a ea bp et | | Levels | | | Sy | (13) | a5)) (5) | Gz) | @)| @ | 987 |1240 1020 | 1225 |1200174c] 12.1 | 1154 Se (6) | (3) | (9) | (2) | | youl | IIIr 1438) 1520 | 10.4 | 1175 5s |G) |@} | | | | 1043 |1283| | 10.4 1072 Ts @) | Ge) |G) | Cr) @) | 938 | 1044 1120 | 1051 1160 10.5 1052 qT (20) | (30) le | HStG™ 793 | | | QuOw) |e soz T2 |(27) | (2) | @) | | | | 684 858 | 1110 | | | | 5.8 | 747 Ts | (34) | (46) | | 588 731 | 5-5 632 expect, as Dr. DUNN ’o2 has shown that the fibers of larger diame- ter run the shorter courses. The foregoing result however does not inform us whether the fibers of a given diameter in the same animal have internodes of like length throughout their course. To determine this it is necessary to measure series of fibers of like diameter at different levels, and compare the results with one another. In Frog 6, which furnished the material for Table 3 there is not a sufficient TakaHAsHl, Internodes on Nerve Fibers. L725 number of measurements of small fibers at the upper levels to make possible such a comparison. It was therefore necessary to examine other specimens. Level a oF as T TT ae al tt 1200 1000 800 600 400 Crurotarsal 200 mm°O lo20 40 60 80 100 120 150. Fic. 2. Showing the average length of the internodes at the several levels in Frog. 6. The values for the diameters have been multiplied by 100, and as this frog is in the growth phase in which the length of the internodes is about 100 times the diameter of the fibers, the two curves run close together. The positions of the hip, knee and crurotarsal joints are also shown. 2. LHE, LENGTH OF THE INTERNODES AT DIFFERENT LEVELS, ON FIBERS OF LIKE DIAMETER. For the determination of the length of the internodes at different levels, on fibers of like diameter, Frog 5, weighing 31 grams and having a total length of 192 mm., was used. At each of the seven levels, over 100 internodes on fibers from 5 to 7.54 in diameter were measured. For presentation, the fibers have been divided ~ into three classes, having an average diameter of approximately 5-34, 6.3 and 7.3”, respectively. The results thus condensed are given in the accompanying Table 4. 176 Fournal of Comparative Neurology and Psychology. TABLE 4. Showing the average length of the internodes on fibers of like diameter at the several levels in the nerves to the leg of Frog 5. Body weight, 31 grams; total length, 192 mm. At each level the measurements are grouped in three classes accord- ing to diameter. ‘The number in parentheses indicates the number of measure- ments. LEVEL. | INTERNODES. | INTERNODES, INTERNODES. S; Diametensneeiaer looks 6.4/4 7-3 (27) 611 (47) 623 (34) 805 So |) Diameter<.)- <1. -- | 5.4/4 6.344 7 -4it (42) 645 (38) 706 (40) 889 S3 Diameters ses cee | 5-3H 6.344 7-2 (79) 769 (36) go2 (17) 1000 T Diameter nse cc 5.2 6.344 7 3 | G8) 646 (30) 787 (50) 836 T; Diameters errs: 5-24 6.44 7-4U (58) 636 (31) 870 (26) goo Te Diameter. i... or 5-1 6.34 7 -3U (74) 608 (32) 787 (18) 744 T3 Diameters.) sens. | 5 -2f 6.34 7.1 (72) 818 (25) 917 (9) 1011 When the data in this table are read horizontally, we observe that in all but one instance out of the twenty-one (TJ ,, 6.3 and 7.3/4) the fibers with greater diameter have the longer internodes. When the measurements are read vertically however the length of the internodes on a fiber of a given diameter varies irregularly from level to level.- Fig. 3 illustrates these relations. In order to plot these internodal lengths fairly, the diameters of the classes at each level must be made exactly equal, hence they are all reduced for the purposes of this figure to precisely 5.3,, 6.34 and 7.34. The reduction is made by the method of simple proportion. By reason of this reduction, the internodal values are in some cases slightly different in the figures from those in the tables but at most these differences are slight however and hardly detectable on figures of the size here used. As it will be necessary for comparison with Tables 6 and 7, to have the measurements from Frog 5 for the levels S,, J and 7, brought together, we now present the data in the accompanying Table 5. It is to be noted Bee in the case of all three diameter classes, that the fibers at T,, the level of the foot, give higher values than TAKAHASHI, I[nternodes on Nerve Fibers. 177 Revel S24 Ses 5 SE By T, 1 tu Crurofarsal |, 1000 ws sa : ie Nt nee 7 Hip Baim AK N 5 eae e | eed Y Fe eS Wie 600} ~~ y ere ee 600 400 200 O mm 01020 40 60 680 100 [20 150 Fic. 3. Showing the average lengths of the internodes at the seven levels in Frog 5. The data for each of the classes has been reduced to the diameters 5.3/4, 6.344 and 7.3/4. The diameters multiplied by 100 are indicated on the verticals. Level 5S, iQ de At Crurotarsal| _ 1000 Boa a mm °0 10 20. 40 60 60 100 120 1D0 Fic. 4. Showing the average length of the internodes at the levels S, 7, and T, on the fibers 5.3/1, 6.34 and 7.3/4from Frog 5. The data are the same as those used in Fig. 3. The diameters multiplied by 100 are indicated on the verticals. 178 ‘fournal of Comparative Neurology and Psychology. appear at S,; that in the mid-position J and T, give intermediate values. ‘This can also be seen by an examination of Fig. 3. TABLE s. Showing the average length of the internodes on fibers of like diameter at the levels S,, T and T; in the nerves to the leg of Frog 5. Otherwise, this table is similar to Table 4. LEVEL. INTERNODES. INTERNODES. INTERNODES. Si Diameter cer 5-2 6.44 | 7-3 . (27) 611 (47) 623 (34) 805 ily Diametermen eek 5.2u 6.344 he gist? (38) 646 (30) 787 | (50) 836 T3 rameters clot 5.2 6.344 7-1 (72) 818 (5) 917 (9) rot In view of this result, it was thought necessary to determine this same relation in other specimens. Before commenting on the foregoing results, therefore, the additional observations on this point will be presented. A large specimen, Frog 8, body weight 63 grams, total length 222 mm., was examined. ‘Three localities on the nerves to the leg, namely S,, J and J, were selected, and more than 100 inter- nodes measured at each level. “he measurements were made on fibers from 5 to 7.54 in diameter. ‘These have been arranged as before, in three classes, approximately 5.3, 6.34 and 7.3 in diameter, and the data thus condensed, are given in Table 6. TABLE 6. Showing the average length of the internodes at the several levels in the nerves to the leg of Frog 8. Body weight, 63 grams; total length, 222 mm. At each level, the measurements are grouped in three classes according to diameter. ‘The numbers in parentheses indicate the number of measurements. LEVEL. INTERNODES. INTERNODES. INTERNODES. S; | Diameter ar scar | 5.3h | 6.34 7-5 | | (45) 711 (31) 828 (44) 909 T iametencsree ier 51h 6.4/ 7-4/ (61) 589 (33) 723 (44) 923 Ts Diametenee set ser 5. 1b | 6.34 | 74h | | (79) 806 | (56) 963 | (48) 1015 TaKkanasul, Internodes on Nerve Fibers. 179 When read horizontally, the records in Table 6 show that the length of the internodes increases with the increasing diameter of the fibers. When read vertically however it appears that while at J, the internodes are always longer than at S,, yet the internodes for fibers with the diameters 5.3 and 6.3” at the level J are shorter than those either above or below this level. Comment on this result will be made later. Fig. 5 also represents these relations, the measurements at all three levels having been reduced to exactly the same diameter, namely, 5.34, 6.34 and 7.3. Level 5, a de O mmo0O10ece0 40 60 80 100 120 150 Fic. 5. Showing the lengths of the internodes at the levels S,, T, and T3, on fibers 5.3/4, 6.344 and 7.3/4 in diameter from Frog 8. The diameters multiplied by 100 are indicated on the limiting verticals, In addition to Frog 8, still another specimen, Frog 3, body weight 26 grams, total length 166 mm., was examined in the same way. More than 100 internodes on fibers ranging in diameter from 3.754 to 6.3” were measured at each of the three levels 8, Pia tee. The measurements are treated as before, and are presented in Table 7 The table reads regularly, both horizontally and vertically, and thus shows a steady increase in the length of the internodes, as 180 Fournal of Comparative Neurology and Psychology. the fibers increase in diameter, and also along a given fiber from S, towards the foot T,. TABLE 7. Showing the average length of the internodes at the several levels in the nerves to the leg of Frog 3. Body weight, 26 grams; total length, 166 mm. At each level the measurements are grouped in three classes according to diameter. ‘Lhe numbers in parentheses indicate the number of measurements. LEVEL. | INTERNODES. INTERNODES. | INTERNODES. | S; Diameter.......-. 3.91 5.2 | 6.3) (12) 416 (72) 520 | (25) 578 4 | Diameter. cle ea | 4.0ft 5.24 |. 6.34 rat) 435 (64) Gor |= (23) 692 T3 WeIDScUMe LET tetetarsye ucts = 4-0}t 5.24 | 6.34 ; | (24) 578 (53) 7or 3 s\ (Oy) 805 Fig. 6 exhibits these relations in the form of curves. Level 95, EP T; jl | 800 Ra: sek oi 6.5 600 al ee e=---—s Crurotarsal So aN eae + .O 400 2 l “0. Oe 10 20 40.060 2O0n.100 420 . asa ' Fic. 6. Showing the average length of the internodes at the several levels, S,, T and T3, on fibers 4/4 5.34 and 6.3/4 in diameter, from Frog 3. The other indications as in Fig. 5. As the foregoing represents all the data collected in connection with this question, we return to a discussion of the fundamental point, namely, the length of the internodes on fibers of a given diameter through their entire extent from 5S, towards the foot The, An examination of Tables 5, 6 and 7 shows: TAKAHASHI, Internodes on Nerve Fibers. ISI First, that on fibers of a given diameter, the internodes are not of the same lengths at the several levels; Second, that in general, the internodes become longer as we pass toward the periphery; Third, that they are markedly elongated at T7,, the level of the foot. In attempting to explain these relations, we naturally call to mind the fact that in Rana pipiens, the average proportional lengths of the leg bones are ROTI a Soa Greases reer eea ros ROM ors eRe aio oat a uals Trete hoe Tele- eae otcuandcee oe 26.1 CD ori Tatra a cite Sci Gecko Recreate eT era ia aorta inG iG Sen ecretd OE Beate ae eee 29.6 PRaTSusiamd Pegi sev everctovcate vive ei eet es el oy sta hetero) ELE eRe Na reid e Sayer Nee 44.3 These figures are the averages from Table XI in Donatpson and SCHOEMAKER ’00. As these relative values remain practically unchanged during the growth of the leg in length, it follows that the increments in length must be in the same proportion, and therefore a lengthen- ing of 100 units in the femur, is accompanied by a lengthening of 113.4 units in the tibia, and 169.7 units in the tarsus and pes. If, for the moment, we assume that the portion of the nerve in each segment of the limb 1s so linked with that segment that it lengthens at the same rate, then we should expect a corresponding relation in the length of the internodes; provided, of course, they were of equal length when first laid down. It appears worth while to put this conclusion to the test, so far as the data in hand will per- mit. Before this can be done however several adjustments and cor- rections must be made in the raw values. In the first place, as the intermediate level J is within the limits of the thigh, and hence associated with the femur, the measurements, at Ticare excluded from the following comparisons, and we contrast only the length of the interriodes at S, with that found at T,, to deter- mine whether these lengths stand in the same relation as the incre- ments of growth in these segments of the limb, namely, as 100 : 169.7. In order to do this, it is necessary to compare the inter- nodal lengths belonging to classes of fibers having exactly the same diameters. We choose as the standards for the diameter classes, AM, 5.34, 6.34 and 7.3, since the observed values can be reduced to these standards by alterations which never amount to more than DTD 182 Fournal of Comparative Neurology and Psychology. In doing this, we assume that the reduction can be made by simple proportion. ‘The results based on the reduced values are given in the following Table 8. TABLE 8. Showing the relative length of the internodes at J; compared with those at S, as a standard, in the case of the several diameter classes in all three frogs (Frog 3, Frog 5 and Frog 8). We eee es peas Retative VALUE RELATIVE VALUE IN ft AT T3 FOR EAcH fees T3. AVERAGE | ee ean DiaMeTER Crass. | FoR Eacu Froc. 13 ya Ee Al 4.0 425 578 | 136.0 5-3 530 714 134-7 6.3 578 8c5 139.2 | | 136.6 Bropurycceworos: isa) 623 834 133-8 6.3 645 917 140.9 | | Te 805 1039 | 129.1 | 134.6 Brog:8.. sce .| ier) 711 837 1 yA] | 6.3 828 963 116.3 73 885 1001 Wigs 115.7 A study of Table 8 reveals several points of interest. First, the internodes at J, are always considerably longer than at S,. Second, the relative value at J, ranging from 136.6 to 115.7, is always much less than the relative growth of the foot, namely, 169.7. Third, it appears that this proportional excess of the internodes in the foot tends to diminish in the larger frogs. Frog 8, the largest, showing a value of 115.7, whereas Frog 3, the smallest frog, shows 136.6, and Frog 5, intermediate in weight and length, gives an intermediate value. We conclude from these relations, that while the length of the internode along the fiber is probably influenced by the elongation of the segment in which it is found the effect of the local elongation is more or less distributed over the entire length of the nerve fiber. If we wish therefore to discover what is really taking place as regards the lengthening of the internodes, we must study the changes over the entire extent of the fiber. TAKAHASHI, JInternodes on Nerve Fibers. 183 For this purpose it is necessary to determine the average length- ening of the internodes during the period of growth on the nerve fibers taken from Frog 3, Frog 5, and Frog 8. ‘To do this fairly, the diameter classes must be made exactly similar. In addition, due account must be taken of the fact that not only do the inter- nodes increase in length, but the fibers to which they belong, increase at the same time in diameter, and therefore a diameter class of given size in the smaller frog must always be compared with a class of greater diameter in the larger frog. “To make this, comparison it 1s necessary to obtain some notion of the amount of change in diameter which may be expected to occur in the cases we are examining. Finally, for comparison, it is necessary to determine in the sev- eral frogs compared the proportional lengthening of the nerves to which these fibers belong. In the absence of direct observations, we assume that the length- ening of the fibers which pass from the intervertebral foramina to the foot, 1s proportional to the lengthening of the leg itself. To determine what this is, we proceed as follows: Since in the case of the frogs in question, the length of the legs is always a constant fraction of the total length of the frog, it follows that the increase in the length of the legs will be in pro- portion to the increase in the total length of the frog. Treating the data in this way, we obtain the results shown in Table 9. TABLE 9. Showing the relative length of the legs in Frog 3, Frog 5, and Frog 8, based on a comparison of the total lengths of these same frogs. Group (A). Frog 3taken as the standard. Group (B). Frog 5 taken as the standard. Froe. | Torat Lenoru. | Ratio For THE LEGs. mm Graupy [ica cisc a ke yer ee en 166 100.0 CAN eye eo eae Pa at aR 192 115.6 Sirah ih aaa eaey aap rsbenat. 3) 222 Magra Group [ick pate ere nse ote ot oli 192 100.0 (G23) SMES Beso hae de, Aon os eater aaa 222 115.6 From Table g it appears that when Frog 31s taken as the stand- ard in Group (A) the length of the leg in Frog 5, is 15.6 per cent greater, and in Frog 8, 33.7 per cent greater, while in the second 184 fournal of Comparative Neurology and Psychology. instance, Group (B) where Frog 5 is taken as the standard, the leg in Frog 8 is 15.6 per cent greater. Our next step is to make an approximate determination of the increase in the diameter of the growing fibers in the frogs in which the nerves to the leg increase 15.6 per cent over the standard. To determine the increase in diameter which probably occurs when the nerve increases 15.6 per cent in length, we proceeded as follows: By comparing the sum of the internodal lengths of the 4, 54 and 6 fibers in Group I of Boycort’s table (reprinted as Table 1 on p. 168) with the corresponding sum of the 54, 6” and 7» fibers in Group II and these in turn with the sum of the 6y, 7” and 84 fibers in Group III, it was found that for an increase of 1y1n diame- ter, there was an average increase in internodal length of 25.9 per cent. Since we assume in the case of our own frogs that the inter- nodal length will increase in proportion to the increase in the length of the nerve, and since the latter amounts to 15.6 per cent, it follows that if an increase of 25.9 per cent in internodal length, calls for an increase of 1m in the diameter of the fiber, then 15.6 per cent increase in internodal length, will call for approximately 0.6 increase in the diameter of the fiber. This result is based of course on Boycort’s measurements made on R. temporaria. It seems justifiable to apply it to R. pipiens however because, although DonaLpson ’o8 has shown that the internodes in R. pipiens are shorter than in R. temporaria, he has also shown that the proportional differences in length are nearly the same for the several diameter classes, and hence any given change in the diameter, is associated with the same relative change in length of internode in both species. Accepting therefore this determination of the diameter increase, the next step is to compare the internodes on the fibers of a given diameter of one specimen of R. pipiens, with the internodes in another specimen, on fibers which are 0.6m greater in diame- ter. To do this, we select from the foregoing Tables 5, 6 and 7, the internodal lengths on fibers for the diameter classes 5.3, 6.3 and 7.3 from all three levels. This permits us to make nine comparisons. Thus in each of these comparisons, as for instance in the first one, in Table 1o the average internodal length in the diameter class 5.3 at S, in Frog 3, is compared with the average internodal TakaHasul, Internodes on Nerve Fibers. 185 length on fibers 5.9 in diameter at S, in Frog 5, and the same procedure is followed in each of the other eight comparisons. The foregoing tables, 5, 6 and 7, however, show the internodal values only for the diameter classes 6.3” and 7.3, while for our present purpose, it is necessary to use those for 5.gu and 6.gp. The desired values are obtained by the simple proportional reduc- tion of the internodal length of the 6.3 class to that for 5.94, and of the 7.34 class to that for 6.9. In view of all conditions, the values thus determined, are prob- ably nearly correct, although the method is open to some theoret- ical objections. The comparisons which are thus made possible are given in [Table Io. TABLE to. Showing the growth of the internodes on the fibers 5.3/4 and 6.3 in diameter, in nerves which increase 15.6 per cent in length. Internodes from Frog 3, com- pared with those from Frog 5, and from Frog 5 compared with those from Frog 8. AVERAGE PERCENT- PERCENTAGE LeveEt. Froc. | Diameter in /t. | INTERNODES. I -f AGE INCREASE FOR | Pet Eacu LeveL. | | | Ss; 3 5-3 530 | 5 5-9 596 12.4 Rasta eae es Ge aie 023 8 5+9 773 24.1 cia | 6.3 635 8 6.9 834 31.0 225 IB 3 ise 601 5 5-9 738 22.7 5 5-3 646 8 5-9 667 3.2 5 6.3 787 8 6.9 863 9.6 11.8 T; 3 5-3 714 465 5.9 856 20.0 5 53 834 8 5-9 903 8.2 5 6.3 917 8 6.9 945 3-0 10.4 186 ‘fournal of Comparative Neurology and Psychology. As Table 10 shows, the average growth of the internodes at S, is 22.5 per cent, which is greater chen that at J, 11.8 per cent, or at T 5, 10.4 per cent. Also the percentage increase at the level S, is greater in the larger than in the smaller frogs. ‘These results accord with those previously noted in the examination of the internodal lengths on fibers from the same frogs, in which the length of the internodes in the foot becomes proportionally. less as the frog becomes larger (see Table 8). To determine the average growth of the internodes on individual fibers, it 1s necessary to measure the fibers of a given diameter class taken from the same frog, at all three levels, and Table 11, based on the data in Table 10, gives the values found. TABLE 11. Showing the percentage increase in the average length of the internodes on fibers of a given diameter, when all three levels from the same frog are included. The averages used are those given in Table to. FRoG 3 Froc § Froc § | WMiametenancttettecmcx yyy ciel 5.3 ee 5-3 6.34 Sie Sa DER Cit ee katie ey 12.4 24.1 31.0 {RE Sea teens ae Stare PING) ane 9.6 Dig ees ic a ethcd tehin on ete 20.0 8.2 3.0 Averages foreachfrog..... 18.4 11.8 14.5 Grand average........... 14.9 per cent increase. It is seen from the foregoing, that the average increase in the length of the internodes in Frog 3, fibers 5.3 in diameter, is 18.4 per cent, Frog 5, fibers 5.31n Hiameee 11.8 per cent, and Frog 5, fibers 6.3 in : diameter, 14.5 per cent; the grand average for the three frogs being 14.9 per cent. The nerves to which these fibers belong have lengthened in each case 15.6 per cent, so that the accordance is fair in each instance, except in the case of the 5.3/4 group in Frog 5. It should be recalled however that in the 6.3, group in Frog 8, at the level JT, a very low value was obtained (Table 6). Becaice this value is less than that at S,, it may be considered aberrant, and it is the presence of this value which causes the low percentage, 3.2 per cent, in Frog 5, at the level Ts If this observation is excluded, the value for the 5.3” group in TaKkaHasHl, Internodes on Nerve Fibers. 187 Frog 5 becomes 16.1 per cent or nearly that for the lengthening of the nerve, and the grand average becomes 16.4 per cent, or a little greater than 15.6 per cent, which represents the lengthening of the nerve. It seems allowable therefore to conclude that the internodes in the 5.3” and 6.3” diameter classes, grow, on the average, at approximately the same rate as does the nerve in which they are found. Nevertheless on passing distally along the nerve, the length of the internodes in a given diameter class, tends to increase in such a way as to suggest that it is influenced by the growth of the segment of the limb to which the internodes belong, although this influence becomes less marked as the frog becomes larger. 3 THE LENGTH OF THE INTERNODES ON FIBERS IN THE ROOTS OF THE SPINAL NERVES. Touching this point we have observations on the roots of the IX nerve in five frogs of different sizes. In his plate VI, Har- DESTY (’g9) has given some excellent drawings of the nerve roots in this frog. he species used by Harpresty was designated Rana virescens but is the same as that here designated, Rana pipiens (see DONALDSON ’07). The present data are brought together in Table 12. Each speci- men is given the number which it bears in Table 2 but the series is arranged in the order of the increasing length of the nerve roots. Table 12 shows that as the nerve roots increase in length, the internodes on the fibers in these roots also increase in length. The average length of the internodes is somewhat less in the dorsal roots than in the ventral, and this, in each instance, goes along with a smaller average diameter of the fibers measured. Fig. 7 shows these relations also. Using the data in Table 12, we may form the supplementary Table 13 in which are compared the values for the length of the ventral or dorsal root, with the corresponding values for the inter- nodes on fibers in this root. ‘The series of ratios given in Table 13 indicate that the internodes‘on fibers of both roots lengthen in about the same proportions as the roots in which they appear. It is interesting to observe that this lengthening of the roots is quite independent of the increase either in the total length, or in 188 Fournal of Comparative Neurology and Psychology. the body length, of the frogs concerned. It appears from this, that the internodes on the roots of the [X nerve grow as do the internodes in the nerve to the leg. Concerning the limits of the stretch of nerve which we have to examine, we may feel very sure that in the case of the dorsal root they have been correctly deter- mined. This stretch lies between the spinal ganglion and the point of union of the root with the cord. In the case of the ventral root however the corresponding stretch appears to be between the cord as one limit and the junction of the ventral with the dorsal root as the other, although further observations are necessary to establish the latter limit beyond dispute. TABLE 12. Showing the length of the nerve roots of the IX nerve, and the average length of the internodes on the fibers in them. ‘The averages were obtained from random sampling and are based .on the measurement of 50 fibers in each case. m 2 & ; : 2 = 5 E saat Re eee: Piss ke ieee g eis ze | Qe 8] 588 8/588 2 as | a ae ace Re fete en eit Peay --h e w- 3% | ~ a HZ < Kaa | MERE? i Tieiez uns Bae = SE > <> O pw wma et Ond gm Oo On Gens us KA Zbd> & Sie q i, & Sts | “ed Zu Poot RS Soa ela ha eRe rile fk Se) yin Z ee hes RS | er Rs et hee es s a) grms mm, mm. lt Lt I M 5-5 10.4 Ges 8.6 389 | 6.4 303 3-9 eat | 8 M 63.0 (eng V5.9 T2059 ile LOS 10.2 | 961 | 89.4 D5.4 | | | | 2 M 23.5 | 169.0 VFO ike Weegee ute Qin Hee csaeh Oh Ate A ale Sse | 4-4. | 3 955 ee ESS D6.5 | | | 4 F 27.2 180.0 WG (87) 13.6 132 ga pale al 1116 M 6 ie a | | 7 1.1 226.0 | 9-5 14.7 1339 10 Ga(oyweal\fie an tidlse! 89.0 | Dg.o | | In the relations between the diameter of the fibers and the length of the internodes in the dorsal and ventral roots, there are cer- tainly no striking differences, since in the ventral roots the inter- nodal length is on the average 84 times the diameter, while in the dorsal roots it is 87 times. If we compare the length of the inter- nodes on fibers of a given diameter in the ventral and dorsal root and also in the sciatic nerve at the level S, in Frog 8—the only specimen in which the comparison can be made—it appears that TakaHasnl, Internodes on Nerve Fibers. 189 Lu 1400 Internodes 1200 1000 io 800 6 600 6 400 4 200 2 O Prog No. 1 8 e +4 C Fic. 7. To show the length of the dorsal (D.R.) and ventral (V.R.) roots respectively, in the IX nerve of the five frogs examined, and the corresponding lengths of the internodes on fibers from these roots, the measurements for the roots are given in millimeters on the vertical to the right, and for the internodes in /4, on the vertical to the left. TABLE 13. Based on data in Table 12 and comparing the relative increase in the length of the nerve roots with the relative increase in the length of the internodes as shown by a series of ratios. Paes = | VENTRAL Roots. Dorsat Roots. | | SEBEL Ratios or LENGTH ear or Lenctu Ratios or Lencru Ratios or LENGTH or Roots. | or INTERNODES. | or Roots. or INTERNODES. | | | | | | | LaNGay oe) CORE bere he a er he | 1.00 1.00 | 1.00 1.00 Average of Frogs 8 and 2 2.48 | 2.80 | 2.83 3.16 Average of Frogs 4 and 7... Anat 3-42 | 3 83 3-74 1gO “fournal of Comparative Neurology and Psychology. the internodal lengths are greater in the sciatic than in the spinal roots. ‘These values are given in Table 14. TABLE 14 Showing in Frog 8 the lengths of the internodes on fibers 10, 11.25 and 12.5 in diameter from the ventral and dorsal roots of the IX nerve, and from the sciatic at the level §,. The numbers in parentheses indicate the number of measure- ments made in each case, and apply to the internodal value above which they are placed. INTERNODAL LENGTHS. IX NERVE DIAMETERS IN /4 = ie IX Nerve Sciatic NERVE | VENTRAL Root. Dorsat Root. LeveL 8}. | (28) (16) (46) 10.00 1064 1037 | 1147 (24) (12) | (11) Tiles 1018 gio 1238 | (24) (10) (51) 12.50 18 8 Co) 1015 1316 | Just what interpretation is to be given to the difference in the internodal lengths, from these several localities, must await the collection of a much larger number of observations. We turn next to the comparison of the length of the internodes in the III, with those in the IX spinal nerve. Owing to the tech- nical difficulties already mentioned, p. 171, we have only a limited number of observations on the ventral root of the III nerve of Frog 2, to be compared with those on the fibers in the ventral root of the LX nerve from the same frog. If we select the fibers 1oy to 15 in diameter, inclusive, and tabulate the average values of the inter- nodes for each diameter class, we get the results presented in Table I5- TABLE 1s. Giving the length of the internodes on fibers Iop to 15/4 in diameter, in the ven- tral roots of both the III nerve and IX nerve of Frog 2. The numbers in parentheses indicate the number of observations. DiaMETERS IN /!...- oe ies Mp lir.6 | aly | ouighagies rigfagis) fp vie Nout 15 IMME MR ees obosuade (12) (8) (17) (2) Tee): g6o 1052 1050 1210 1440 TX eRe ie Mate € (2) | (1) (8) (1) (9) (2) (26) 980 | 940 985 1000 1220 1130 1147 ‘TAKAHASHI, Internodes on Nerve Fibers. IQI An examination of Table 15 shows that for fibers of the same diameter, the internodal lengths are nearly alike in the two nerves. If we make a general average, we find the relations given in Table 16. TABLE 16. Giving the average diameters and average length of internodes on the fibers from Ios to 154 in diameter, found in the ventral roots of the III and IX nerves of Frog 2. DIAMETER IN /. INTERNODAL LENGTH. NerverElie s2 niin hott alent ey cee s TF 1051 Nerve DXi ivan ocaie caeoran erent ai 14.0 1117 In view of the small number of observations, we may look upon these values as similar, but the fact that they are similar, is the surprising result, since in this particular case (see Table 12) the length of the ventral root of the III nerve is 2.6 mm., while that of the [X nerve 1s 7.0 mm., giving aratio of 1: 2.7. _If we assume that these roots had the same length when medullation began, it would appear that since the [X nerve had become 2.7 timesas long as the III, the internodes should stand in a like relation. The measurements show that such is not the case. Unfortu- nately, at the moment, it 1s not possible to explain this result. The discrepancy possibly arises through taking as the distal limit of the ventral roots the point of junction of the ventral with the dorsal root, and yet the assumption of this limit fitted perfectly with what has already been found in the case of the [X nerve. There are of course many suggestions which might be made, but it seems best to leave the question in abeyance, until a larger number of observations, especially on the dorsal root of the III nerve, has been made. 4 THE NUMBER OF MEDULLATED FIBERS AT DIFFERENT LEVELS | IN THE LEGS OF TADPOLES OF INCREASING SIZE. To fill out our information as to the way the medullary sheaths of the nerve fibers are acquired in the frog, the number of the med- ullated fibers at the level of the knee was counted, and compared with the number at the entrance to the foot, in the legs of tadpoles of increasing size. Io prepare this material, the legs, or so much 192 ‘fournal of Comparative Neurology and Psychology. of them as was needed, were fixed in I per cent osmic acid, and then embedded and sectioned in the usual manner. ‘The sec- tions were made 12, 1n thickness, and at the knee, the number of medullated fibers in the trunks of the nervus tibialis and nervus peroneous was counted. ‘This number was contrasted with that found in the four trunks entering the foot, namely: the ramus superfcialis and ramus profundus of the nervus tibialis, and the nervus peroneus lateralis and medialis. At both levels the number of fibers 1n several successive sections was counted, and the average taken. ‘The results of this exam- ination are presented in Table 17. TABLE 17 Showing the number of medullated fibers at the level of the knee and ankle in the leg of the tadpole. ‘Tadpoles of Rana pipiens. | NuMBER OF FiBers IN ACROSS | Ratios or NuM- NuMBER OF SPE- LENGTH OF LENGTH OF SECTION AT THE LEVEL oF BER AT KNEE CIMEN. SHANK | Foor. ; = ar; —— | To NUMBER AT KNEE. ANKLE. | ANKLE. mm. mm, I 1.18 0.68 23 4 Sasa Il 1.29 0.80 25 6 4.16-1 UI 1.50 0.96 30 8 Besa IV 1.88 1.36 85 25 3.40-1 V 3-68 27 286 118 2.42-I It appears from this that both the absolute and relative number of medullated fibers entering the foot, increases as the leg of the tadpole becomes longer, rising from 1 :5.75 to 1:2.42. Ina large mature frog, Dr. DuNN (’o2) has shown that the ratio is 1 : 1.66, an increase of 34 fold over the ratio in the smallest tad- pole. At the moment however we have no data by which to determine when the ratio found in the largest tadpole’s leg here examined passes over to that in the mature frog. It is assumed that the medullated fibers which are counted at he level of the knee, represent fibers already medullated through- out their entire length, as well as fibers incompletely medullated, but having a sheath extending as far as the level of the section. The same assumption is made for the fibers at the level of the foot. TakaHashHl, Internodes on Nerve Fibers. 193 It is shown then that the medullation of fibers going to the shank, the more proximal segment of the limb, is more nearly complete than that of those passing to the foot, the more distal segment, and probably the greater part of this difference depends upon the fact that many of the fibers destined for the foot are not medullated at all. This result, taken in conjunction with those of HarpEsty (’99) on the nerve roots of the frog, and Harat (’o1, ’02), on the nerve roots of the rat, indicates very clearly that new medullated fibers are continually being added to the nerves during the period of growth. 5 A COMPARISON OF THE LENGTH OF THE INTERNODES IN THE AMERICAN LEOPARD FROG, RANA PIPIENS, WITH THEIR LENGTH IN THE ENGLISH FROG, RANA TEMPORARIA (FUSCA). In his study, entitled “The nervous system of the American leopard frog, Rana pipiens, compared with that of the Ol ae frogs, Rana esculenta and Rana temporaria (fusca),’’ Dr. Don- ALDSON (’08) compared the measurements of the ee made by me on Rana pipiens, with those made by Boycorr on Rana temporaria. ‘Taking the same locality in both cases, and reduc- ing the measurements on R. pipiens so that they apply to frogs of the same total length as those measured by Boycott, a series of values was obtained for seven diameter groups. It appeared from a comparison of the results (see DonaLpson ’08, p. 146, Table 19), that the internodal lengths in Rana pipiens, ranged between 64 and 71 per cent of those found in Rana temporaria, the average being 67 per cent. The comparison appears to be a fair one, and if this is granted, it 1s evident that Rana pipiens has on its fibers three sheathing cells, where Rana temporaria has two. ‘This result further draws attention to the fact that the character in question is subject to considerable variation, and that this appears not only in forms widely separated zoologically, but also within the genus Rana, at least in the case of the two closely related species here compared. 194 ‘fournal of Comparative Neurology and Psychology. CONCLUSIONS. In the leopard frog, Rana pipiens, we have found: 1. The average length of the internodes on the fibers in the nerves to the leg diminishes towards the periphery. ‘This diminu- tion is accompanied by a corresponding diminution in the average diameter. 2. Inthe same frog, the length of the internodes at different levels on fibers of like diameter in the nerves to the leg, increases toward the periphery. This increase appears to be associated with the more rapid growth of the distal segments of the leg, but the influence of the segment on the portion of the nerve within it, is less marked as the frogs become larger. 3. When the average length of the internodes on fibers of a viven diameter is compared with the average length on the fibers which represent them in a larger frog, it 1s found that the lengthen- ing of the internodes corresponds with that of the nerve to which they belong, thus supporting BoycorT’s (04) general conclusion. 4. Inthe roots of the IX spinal nerve, the internodes lengthen in proportion to the lengthening of the nerve, but at the same time, the lengthening of these roots is only loosely correlated with the increase either in the total length or in the body length of the frog to which they belong. 5. When, in the same frog, the ventral root of the III nerve is compared with the ventral root of the IX nerve, it is found in both of them, that the fibers of the same diameter have internodes of the same length. In the case chosen, the ventral root of the IX nerve had become 2.7 times the length of the III nerve and we should therefore expect to find the internodes on the fibers of the IX nerve much longer than those on the corresponding fibers in the nerve III. The explanation of this result awaits further observa- tions. 6. A determination of the number of medullated nerve fibers at the level of the knee and of the ankle in a series of tadpoles’ legs of increasing length, shows that the relative number of medullated fibers at the ankle, increases as the leg becomes longer, thus prov- ing that the fibers to the more distal divisions of the limb are medullated later. 7. It follows from the foregoing result that so long as the nerve receives new (young) fibers, there will always be internodes which TakxanasHl, Internodes on Nerve Fibers. 195 are relatively short, since they belong to fibers which have been subjected to the lengthening process for only a short time. The presence of these fibers reduces the average length of the inter- nodes, and hence accounts in part at least, for Boycorr’s observa- tion that on the average the lengthening of the internodes in the sciatic nerve is slightly less than that of the nerve itself. It also accounts, in part at least, for the wide range in the length of the internodes found on fibers of the same diameter. 8. In the leopard frog, Rana pipiens, the length of the inter- nodes at the distal end of the sciatic nerve, is on the average, only about two-thirds that of the corresponding internodes in Rana temporaria (fusca) as measured by Boycorr (’04). SUMMARY. The foregoing conclusions may be made more vivid perhaps if, in the light of our present knowledge, we attempt to picture the growth changes which affect the internodes on the nerve fibers of the leopard frog. From the observations of Hrs (’86) Harrison (or, ’04—06), BARDEEN (’02—03), and others, we know that the axone grows out from the cell body into the peripheral nerve, accompanied by its sheathing cells. “There are no observations to show whether before the formation of the myelin the sheathing cells cover approximately the same length of fiber in all fibers, or at all periods of growth, but our observations as they stand, would favor such a view. In the leg of the tadpole, the formation of myelin occurs first in the fibers which run the shorter course, and interpreting the find- ings of Harpesty (’99) and Haratr (’03) showing a diminishing number of medullated fibers in the spinal roots as we pass away from the cells of origin, it appears that the development of the myelin progresses from the cell of origin toward the end of the axone. When the axone has made its distal connection, and the myelin is formed, then the lengthening begins, and continues so long as the nerve to which the fiber belongs, continues to grow. In the nerves to the leg however this process is modified by the fact that the internodes have a tendency to lengthen at the same rate as the segment of the leg to which they belong; although this process is more marked in the younger than in the older frogs. Despite this 196 Ffournal of Comparative Neurology and Psychology. however the average length of the internodes on fibers of a given diameter increases as does the nerve in which they occur. The interpretation of the internodes, as we find them in a sam- ple taken from any nerve, is complicated by the fact that for a long time during growth, new medullated fibers are appearing. As these new fibers start with very short internodes, and are late in appearing, they. have been affected by the lengthening process for a shorter time than those fibers which were completely medul- lated at an earlier date. They must consequently exhibit inter- nodal lengths shorter than would be expected, and since their absolute number increases as the frog becomes larger, and their presence lowers the average length of the internodes at any level, it will necessarily follow, as shown by Boycorr (’04), that the aver- age length of the internodes increases a little less rapidly than that of the nerve to which they belong. This is our explanation of Boy- coTT’s result. While this change in the length of the internodes is taking place, there is also’a change in the diameter of the fibers. In general, the increase in diameter is in advance of the increase in inter- nodal length, so that, as Boycotr has shown, fibers of a given diameter have longer internodes in larger frogs. The exact relation of these two processes has still to be worked out, but this relation, depending as it does on the medullation of the fibers at different dates, and on the fact that all fibers of small diameter are not destined to become fibers of large diameter (BoucHTon ’06), but may remain permanently small, seems to account for the great variation in the length of the internodes on fibers of the same diameter, quite aside from the fact that consecu- tive internodes on the same fiber may have very different lengths. While the foregoing description is based on the study of the nerve to the frog’s leg, we find that it applies also to the growth changes in the roots of the [X spinal nerve, when we take as the limits of the dorsal root, the spinal ganglion on one side, and the spinal cord on the other, and in the case of the ventral root, the spinal cord on one side, and the junction point of the ventral and dorsal roots on the other. When however we compare the internodal lengths in the IX ventral root with those in the III ventral root of the same frog, taking the same limits, we get the surprising result that the inter- nodal lengths are similar, although the lengthening of the IX nerve TakauasHl, Internodes on Nerve Fibers. 197 has been 2.7 times thatof the III. Thisresult still awaits an expla- nation. BIBLIOGRAPHY. BarpeEeEN, C. R. 0203. The growth and histogenesis of the cerebrospinal nerves in mammals. Amer. Fourn. Anat., vol. 2, pp. 231-257. Boucuton, T. H. 06. The increase in the number and size of the medullated fibers in the oculomotor nerve of the white rat and of the cat at different ages. ‘fourn. Comp. Neurol. and Psychol., vol. 16, pp. 153-165. Boycort, A. E. 204. On the number of nodes of Ranvier in different stages of the growth of nerve fibers in the frog. Fourn. Physiol. (Foster), vol. 30, pp. 370-380. Donatpson, H. H., and ScHormaker, D. M. 00. Observations on the weight and length of the central nervous system and of the legs in frogs of different sizes (Rana virescens brachycephala—Corr). ‘fourn. Comp. Neurol., vol. 10, pp. 109-132. Dona.pson, H. H. 07. Rana pipiens. Scrence, n. s., vol. 26, no. 655, p. 78. ’08. The nervous system of the American leopard frog, Rana pipiens, compared with that of the European frogs, Rana esculenta and Rana temporaria (fusca). ‘fourn. Comp. Neurol. and Psychol., vol. 18, pp. 121-149. Dunn, E. H. ’oz. On the number and on the relation between diameter and distribution of the nerve fibers innervating the leg of the frog (Rana virescens brachycephala, Corr). ‘Fourn. Neurol., vol. 12, pp. 297-328. Harpesty, I. ’99. The number and arrangement of the fibers forming the spinal nerves of the frog (Rana virescens). ‘fourn. Comp. Neurol., vol. 9, pp. 64-112. Harrison, R. G. ’o1. Ueber die Histogenese des peripheren Nervensystems bei Salmo salar. Arch. f. mtkr . Anat., vol. 57. ‘04. Neue Versuche und Beobachtung iiber die Entwicklung der peripheren Nerven der Wirbelthiere. Sitz.-Ber. niederrhein. Ges. Nat. Heilk., Bonn, pp. 55-62. 06. Further experiments on the development of peripheral nerves. Amer. ‘fourn. Anat., vol. 5, Pp. 121-131. > Hara, S. ’03. On the increase in the number of medullated nerve fibers in the ventral roots of the spinal nerves of the growing white rat. ‘fourn. Comp. Neurol., vol. 13, pp. 177-183. His, W. 86. Zur Geschichte des menschlichen Riickenmarkes und der Nervenwurzeln. Red. Orange. Green. Blue. I 45 minutes 8 ° ° 2 2 | g minutes 8 | ° ° 2 3 14 minutes 8 I ° I 4 | 18 minutes 9 ° I ° cotals Wace eerie screenees 33 I I 5 Case 3—In this instance the red and orange glass plates were removed and black paper substituted. The photopathic reaction was found to be definitely positive, the young larve grouping in the blue area. Now, as before, the window at the end of the box corresponding to that overlying the black paper was opened to the subdued light of the room, while brilliant daylight entered the blue end of the box. As will be observed, the conditions of this experiment are similar to those of Experiment 11, save that, in this instance, a greater difference between the intensity of light at opposite ends of the box existed. Between tests the light from both sources was cut off and the larve were allowed to scatter. The results, which may receive the same interpretation as those of Experiment 11, are tabulated below (the arrow indicates the direction of light entering the end window of the box): DIsTRIBUTION OF LARVAE. Test. AFTER | | —> Black. Green. Blue. I 5 minutes | 10 ° 2 7 minutes | 7 3 fo) 3 10 minutes 10 ° ° | RO false eee bee ico oiecieysbarcioton eine | 27 3 ° 220 Fournal of Comparative Neurology and Psychology. Conclusions from Experiments 11 and 12: In the results of the foregoing experiments, we have further evidence to support the conclusions drawn from Experiment 3. In Experiment 12 the larve passed from a region of greater (blue) to one of lesser (the red, or in Case 3, the black) light-intensity in moving toward the source of light in the direction of the incident rays. It must be assumed that in Case 3, there was a much greater difference in the intensity of light at the two ends of the box (overlying the blue glass and the black paper respectively) than in Case 2, or in Expert- ment 3. These experiments were performed many times, under several different conditions of light, and with larve of ages vary- ing from a few hours to two days. The same results were obtained in every case, except that in the older first-stage larve the reactions were not so definite (more individual variations) and a stronger light was required to bring about the same responses as were manifested by larve under four hours old. In these cases, as also in Experiment 3, rays of lesser intensity (but in a horizontal plane) which struck the larve in such a way as to cause a body- orientation in which a normal swimming position was still main- tained, were more influential in determining a progressive orienta- tion than were the more intense rays which struck both eyes equally, but which came from below, and had a tendency (as will be shown in detail later) to throw the larve out of their normal swimming position. As the writer has shown elsewhere (1907a), — galvanotactic reactions in the young lobsters occurred only when the tail or the back was turned wholly or partly toward the anode. Although at first sight it appears that the causes for this condition of reaction can have nothing in common with the causes which determine a progressive orientation to the directive influence of light rays only when the swimming position is favorable, it may not be inappropriate to suggest that here also the direction of the impact of light with reference to the axis of the body of the larva, may have some influence on the reaction. Experiment 13. Case 1—Ten larve, twelve days old, were placed in box 4, mounted over the light-shaft. When the glass plates were arranged in the order designated below, the photo- pathic reaction was as follows: Haptey, Behavior of the American Lobster. 221 DIsTRIBUTION OF LARVAE. Test. AFTER Red. Orange. | Green. Blue. I 5 minutes ° I | 2 7 2 Io minutes I I | I 7 3 | 15 minutes I I | 2 6 4 | 20minutes 2 ° ° 8 5 25 minutes ° I ° 9 Motalss..s. jst tee ae to arn 4 4 5 a7) Case 2—When the order of the glass plates was changed to red, blue, orange, green, the following results were obtained: Red, 25 Dilie, 31 Olanee. a. Geen. g. ase 3—After redistribution of the larve had taken place, the small window opening at the green end of the box was uncovered to the diffuse light of the room. ‘The resulting reactions were as follows: DisTRIBUTION OF LARVAE. Gites AFTER - : Red. Blue. | Orange. Green. 4 2 minutes fo) 3 | 3 4 2 4 minutes I 3 3 | 3 3 7 minutes I a | I = sil FG 4 10 minutes I 2 | 3 | 4 WOtalses. ctvisys seeds eae « 3 II | 10 | 16 Case 4—Once more the order of the glass plates was changed to blue, green, orange, red, and the window at the red end was uncov- ered to the light of the room. ‘The results of the three sets of tests were: Blue, 9; green, 5; orange, 3; red, 13. Experiment 14—The following observations deal with cases of larvee suddenly submitted to a light of great intensity, as for instance when they are brought from subdued daylight into full sunlight, or when the brilliant rays from an acetylene lamp fall upon larve which had been for sometime in darkness. Case 1—July 18, 4 p.m. Fifty first-stage larve, about thirty hours old, which had been reacting positively in lights of low or medium intensity, were placed (in a glass jar) in the bright sunlight of the west table. Every larva at once moved to the room side of the jar. Within a few minutes, however, all returned to the window side of the jar. Ten minutes later they were divided 222 ‘fournal of Comparative Neurology and Psychology. about equally on each side. Next they were returned to the dark box and submitted to the weak light from the small window. Here they manifested a definite positive reaction which continued until evening. At 8:30 these fifty larvae were suddenly submitted to the intense rays of an acetylene light. ‘The result was a uni- versal negative reaction. Within two or three minutes, however, a few larve began to return toward the light, and within four minutes all had become positive in their reaction. Case 2—A group of fourth-day first-stage larva in the glass jar was subjected to light of low intensity and found to manifest a positive reaction; when subjected to a much stronger light the same larve were still universally positive. This reaction, once established, endured through the period of gradually diminishing intensity of light accompanying the coming of night. ‘The next morning these (now fifth-day) larvae were found to be negative in reaction. It was feared, however, that the manner of reaction might have been changed because of the long period of confine- ment which they had undergone. For this reason a fresh lot of twenty-five larvae from the same group (fifth-day, of the first and second stages), was secured. It was observed at this time that about a third of the number of those in the hatching bag had moulted into the second stage, and that the others were very near the moulting-period. When these larve were put in the glass jar, placed in the dark box and submitted to subdued light from the small window, six tests showed fifty-five to be negative, and ninety-five positive. When these same larvz (now thirteen first- stage and twelve second-stage), under the conditions of stimula- tion stated above, were subjected to light of still greater intensity by placing the jar nearer the small window of the dark box the results showed that fifty-nine were negative and forty-one were positive. At 3:30 p.m. these same larvae were removed from the dark box and placed (in the glass jar) on the west table, where they were suddenly subjected to the bright afternoon sunlight. Every larva came to the room side of the jar and remained there so long as observed. Case 3—The larve mentioned above were liberated and another lot of twenty-five (of the same group, but all in the second stage) was secured at 8 o’clock in the evening. The intense rays cf the acetylene light were suddenly directed upon one side of the jar. Haptey, Behavior of the American Lobster. 223 This resulted in a sudden and universal positive reaction which, however, soon became indefinite. ‘The larve gradually returned to the darker side of the jar and, as in the case mentioned above, remained there so long as observed. Case 4—When, on the other hand, another group of larvae which was reacting positively to a light of low intensity, was brought by slow degrees into a light of great intensity, there resulted no sud- den, temporary change of reaction such as that observed above. The reaction usually remained unmodifed, but if it was reversed it remained permanently so. The same statement holds for larve which had been reacting negatively to light of low intensity. When they were brought by slow degrees into light of great intensity, seldom did a sudden temporary change in reaction result. Conclusions from Experiment 14: The stimulation brought about by suddenly submitting larvee to intense light may cause at least two kinds of response: first, in the case of early first-stage lobsters (about thirty hours old, and manifesting previously a posi- tive reaction), a definite and universal, though temporary, negative response; second, in the case of early second-stage larvae (about five days old, and giving previously a negative reaction), a definite and universal, though temporary, positive response. From Case 4 it appears that a gradual change of intensity (extending over an equal or even a greater range of "ntensities) may not bring about a similar result, although a permanent reversion in the reaction may sometimes ensue. Larvae which have recently moulted are most susceptible to slight differences in light-intensity; and the reaction of such larve is frequently negative, while the reaction of larve which are approaching the moulting-period is more often indefinite or positive. Experiment 15. Case 1—The following experiment involved the use of the Y-tubes described on p. 207. Ten positively reacting lobsters, five hours old, were placed in the tube at the end designated a (Fig. 5, B). The Y-tube was then placed in position in the dark. Over one arm was laid a red glass, over the other arm an orange glass, and then the screen was drawn from the window to allow the light rays to strike the tube in the direction shown in Fig. B. ‘Tests were made about five minutes apart. After each, the return of the lobsters to the (a) end of the tube was induced merely by reversing the tube so that the end (a) was 224 ‘fournal of Comparative Neurology and Psychology. toward the window; the position of the red and orange glass was also reversed. The distribution at the end of each test was as follows: aiesn. Rep arm. | STEM. | ORANGE ARM. igs Soc § Schaaae Sito bec eres ae ioe eee ° ° | 10 $e Sono co obo © obo O Oo DOU ES eOODOUL Oo I | 9 Dosod sand opauaoopnArgde de ap aobe bone fo) I 9 ESOC Gator dee COBY booms amet a otdios ° 2 8 FRO talStino tec oer eee ee fo) 4 | 36 Case 2—Next, green and blue glass plates were substituted for the red and orange, the method of the experiment otherwise remain- ing the same, and the green and the blue glasses were reversed in position at the end of each test. A series of four tests showed the following results: Green arm, 11; stem, 2; blue arm, 27. | \K B Fic. 5. Showing the Y-tubes as set up for experiment. The arrows indicate the direction of the light rays. The cross-hatched areas represent the glass plates of the darker color laid over the arms of the tubes. The ends designated a, represent the starting point for the negatively reacting (A), or the positively reacting (B), larve. Case 3—One more test of the reaction of this group of positive larvae was made at this time, which was far more delicate than either of the preceding, for the difference in the intensity of the glass plates used was less. In making a selection of glass slides two were chosen which had been purchased for “red glass.”” On close inspection, however, and by test with sensitized paper, it was observed that one slide was somewhat lighter in color tone than Haptey, Behavior of the American Lobster. 225 the other. These glasses were used in the next experiment. The darker of them may be designated as red, the lighter as ruby. The results of four tests were as follows: Ruby arm, 21; stem, 10; red arm, 9. In the last experiment, with this group of larve, it was found that a great intensity of light, striking the red slides, was required to bring about reaction; and that, even then, several larvee would remain in the region designated x (Fig. 5, B), near the junction of light and dark. These experiments were repeated with both black and white backgrounds for the arms of the Y-tube. The results agreed with great uniformity, differing only in the length of time required for the reaction. From these last experi- ments we may conclude that the first-stage lobsters, at the age of five hours or less, are extremely sensitive to slight differences in the intensity of light, more so in fact than older lobsters of the first and later stages; for it was seldom with these older lobsters that the delicate reaction to the ruby and the red glasses observed in’ Experiment 15, Case 3, could be induced. Experiment 16. ‘Twenty first-stage larva, slightly over two days old (for which to light of nearly all intensities reactions on the first and second day had been positive), were put in the glass jar, and this in turn was placed in the dark box. They were sub- mitted to light from a small window one inch wide and two inches high, before which the colored glass plates could be placed so as to illuminate one side of the jar with red, blue, green, or orange rays, as the case might be. The reaction in each of these lights was as follows: Licut. PosiITIveE. NEGATIVE. 1 °o7eya (ey et A RE oe Tee ORIN PERIOD Cook AD 20 ° Oran cen sers eet teers eee ie ee iors cio tol: 20 ° (AAA RO hae oo Bb ouder Mee duce coer eharaed oor 19 I TOUS emeeres ee Haat en mie Fiera: Bin aatercde, Genenantacl Ute cthonce Byers Ibe 18 2; NUE Te re rie ein eee arte erate ated cx spores reneNe, syle YoNercs= 15 5 IDEN pos onan gas Deus Ud Sb Rac O GEG AO DONIC OU ao croc 3 17 * Subdued daylight passing through one or two thicknesses of white paper. Here it is shown that the negative reaction to lights of great intensity, which was first discovered in larve thirty hours old (Ex- periment 14, Case 1), and which, as we shall see, persists for a variable length of time, has become accentuated and remains for the time permanent. The next series of observations were made upon lobster larve on the fourth day after hatching. Many of them 226 ‘fournal of Comparative Neurology and Psychology. were 'earing the moulting-period and preparing to pass into the second stage. Experiment 17—July 17, 8:30 a.m. About one hundred fourth- day, first-stage lobsters (Group A) were taken from one of the hatching bags and placed in the glass jar in the dark box. The majority reacted positively to daylight through the small window. At 1 o’clock, when examined again, about one-half of them were reacting negatively. The jar was then removed and placed in the light of the west window where the intensity was greater. At once every larva became negative in reaction. In order to determine whether this mode of reaction was a nat- ural incident in the life of the larva of this age, or whether the response had been induced as a result of their having been so long subjected to experimentation, twenty-five first-stage larve (Group B) were removed from the same group as that from which the larva mentioned above were taken. When these twenty- five were put in a glass jar and placed in the west window beside the group mentioned above, they gave a positive reaction. After five minutes, half were positive and half negative. At 5:30 the sun was low and the light weak, but all the larve gave a negative reaction, which persisted, as did the negative response in Group A mentioned above, until far into the twilight. It may be further noted in this connection, that five of the laree which reacted negatively in the afternoon were placed in abso- lute darkness for four and a half hours. It was believed that the positive reaction might be renewed; but this was not the case when they were again brought into daylight of several intensities. Experiment 15. Case 1—July 20, 4 p.m. A number of fourth- day, first-stage larvae were removed from the hatching bag and put in the glass jar. This was placed in the dark box and the larve submitted to red light through the three by three inch win- dow. The resulting reaction was positive and remained so even when the intensity was still further diminished by inserting num- erous sheets of paper behind the red glass. Finally, a point was reached where the positive orientation was lost and a homogeneous scattering occurred. When the intensity of the light was again increased, the positive orientation returned; but, with a still greater increase in intensity, this response became again less defi- nite, and finally, 1 in the more intense blue and white light, the neg- ative reaction again appeared. Haptey, Behavior of the American Lobster. a2 Case 2—In the evening, when other observations were made upon the same group under the influence of the acetylene light, burning dimly, the reaction in the glass jar was positive ade: (all the colored glass plates. When the intensity was increased by sub- stituting a lamp which burned more brightly, the group divided, half going to the positive and half to the negative side. When the intensity was increased still further (reinforced by a brilliant oil burner and reflector) a greater number gave a negative reaction. As it afterward transpired, the larvz used in these last tests did not moult to the second stage until on or after the fifth day. Case 3—July 23, 1:20 p.m. Fifty fourth-day, first-stage larva were put in the glass jar and placed in the dark box. In the red light the reaction was definitely positive. The reaction under the different intensities obtained by colored glass plates may be tabulated as follows: Cotor. Positive. NEGATIVE. TRG erate ave sats ahs satay ctoriee cs oe 5 yazan auras areiletapepena she caustisyedeia opel 50 ° LOSE REBT de all cen orn oo conrad haacktbd Ste Sato CHOU fae 47 3 Greenreciiiatyer th oe ee oie cee oie dope shots @ cicere ee 43 7 BIGGS Bat aie ccdecsic 2c ccs s bikers etepshotutet acens hie eis SRS 36 14 WiHIte as aire vets stain ol siete, Soayty Slecaiaveraler crane dis eunye oaeln Sitees, alata 23 27 Case 4—July 31, 10 a.m. ‘Twenty-eight first-stage and second stage larve of the fifth day (all nearly ready to moult to the second stage) were put in the glass jar and placed in the dark box. Under lights of different intensities the results were as follows: Licut. Positive. NEGATIVE. 1£rcfa lagen ts Bree Bi Ae ea SUG, CISION BIG EERIE ORCI Eee 28 ° OGiVPooa0 Se otbooo COMET CoOpDORC ADs ooU rnb Soeo 22 6 Greens ec ore Sieh hate Bites sete ents Sees PRR Miah onan es 18 10 Be See teon eae ental tetera Pana ee Cheese El Re epae ees 12 16 VJ te ratthercra ety neat erereden tou eh ciate oe eben bach c ak oronstrsy sister) are coesos 14 14 Daylioht 725 G-ccctetayee careers Suet Seances chino Soe fo) 28 In this particular case it was observed that under the orange light the negative larve were of the second stage, while those which retained for the longest time the positive reaction (in the case of the blue and white glasses), were the lobsters which were nearest to the moulting-period. When fresh, clean larva, which had moulted into the second stage within a very few hours, were selected and submitted to several different intensities of light, they invariably gave the negative reaction. 228 ‘fournal of Comparative Neurology and Psychology. Case 5—July 23, 1 p.m. Twenty fifth-day, second-stage larve were taken from one of the hatching bags and put in the glass jar. This was placed in the dark box and the larve were submitted to illumination from the red light. ‘There was some random swim- ming, but the general reaction was positive, except in white light, in which three were positive and seventeen negative. Next, the jar was removed from the dark box and placed on the west table in subdued sunlight. Here the reaction was definitely negative. At 4:30 when the jar was returned to the box (at this time in the afternoon the light was much less intense than earlier) a positive reaction was obtained in red, orange and green light. Conclusions from Experiments 16, 17, 18: From the result of the last three experiments the following tentative conclusions may be drawn. ‘The general negative reaction to light of great inten- sity, begins on aibioutt the chard day of the first stage, continues for the most part uninterruptedly until the moulting-period is near; just before the moult the. reaction becomes indefinite or, more often, positive; directly after the moult into the second stage (which occurs on the fourth or fifth day of the first-stage- period), the reaction to lights of nearly all intensities again becomes defi- nitely negative. 2. Second Larval Stage. Experiment 19. Case 1—July 19, 8:30 a.m. Observation of a group of sixth-day, recently moulted second-stage larvae demon- strated that a negative reaction took place when the larve were put in the glass jar and placed in the dark box. ‘This was true for daylight coming through the three by three inch window, and in both blue and green light. In the case of orange and yellow light, however, the reaction was similar to that in either yellow or orange, but perhaps less definite. It may be here recorded that a group of first-stage larva, about one and a half days old, subjected at the same time to these conditions, gave a positive reaction, not only in orange, but also in blue, and even to white light. ‘These reac- tions took place on both black and white backgrounds, but they were more definite on white. But when the stimulus of the orange rays was continued for ten minutes or more, in this case also, the negative reaction began to appear again and many larve came to the room side of the jar. Hapotey, Behavior of the American Lobster. 229 Case 2—July 23, 5 p.m. ‘The larve used in this case were of the seventh-day group of the second stage, having been taken from the hatching bag at 9 a.m. At 5 p.m. under red, orange, green, blue and white lights, entering through the three by three inch window, all were definitely negative. They had also shown a negative reaction in several intensities of light in the morning. At 7 p.m. further observations were made on the same group of larve. The following quotation is from the daily note book. “July 23, 7 pm. One of the best demonstrations of the per- sistency of the negative reaction of these seventh-day larvae was exhibited this evening. Larvz taken from the hatching bags at g a.m. have reacted negatively at every observation during the day. At 7p.m. it was observed that this group, which still re- mained in the glass jar near the west window, continued to pre- sent a definite negative reaction. This negative response continued until 7:55 p.-m., when the light became too faint to determine either a body or a progressive orientation. Here it is to be observed that the negative reaction on the part of these second-stage larve was continued through a long series of gradually diminishing inten- sities of light. After all signs of body-orientation or progressive orientation had vanished in the case of the group of larvae men- tioned above, the intense light from the acetylene lantern was suddenly thrown open one side of the glass jar. A most definite negative reaction resulted. ‘This response, it will be observed, 1s different from that recorded in Experiment 14, Case 3, for in the latter case the sudden illumination determined a definite positive reaction.” Experiment 20. Case 1—July 24, 9 a.m. Thirty eight-day, second-stage larvze were taken from one of the large bags and put in the glass jar in the dark box. The time of moulting into the third stage was near at hand, and many of the individuals were already ‘‘fuzzy”’ and sluggish in their movements. Illumination through the three by three inch window, by the colored lights, gave these reactions: Couor. Positive. NEGATIVE. 1 Ree Rp Mtoe cr et eneteo a eR fee PP Ni is OR EL 30 ° (Osi. hoe k oes See cona soo a narebauenanbaboesunorcass 27 a Greent enue ee ee toe ate S.o Se OO EEE EA OE. 17 13 13] DORA BOR ste Bice crs aie atrocity a aa ones HERA een eae 13 17 IDEN Papo rootos accackno 6 Omcnie Hao Ome nm ooMOucn neo: 13 17 230 fournal of Comparative Neurology and Psychology. Before we state the next case, one consideration must be noted. In the previous pages, use has been made of such terms as “ third- day,” “‘seventh-day,” and “eighth-day” larva, to distinguish the age, and roughly the stage, of certain groups of lobsters. Because of the use of these terms, it must not be supposed that there 1s always a constant relation between the age and the stage of the larve. Among the larvze of a single group which have been hatched and have developed under ale conditions, a fairly constant relation between the age and stage is invariably main- tained. But for different groups of larvz, this correlation does not necessarily exist, for it is entirely possible, and indeed it very frequently happens, that a group of seventh-day larve may be in the third stage, while a lot of eight-day individuals are in the sec- ond stage. ‘The differences in rate of development are due to such factors as water density, temperature, food-supply, and con- ditions of light and darkness, which, as the writer has shown (Haptey ‘o6b), may act either directly upon the body processes, or indirectly by favoring or preventing the growth of various body parasites such as diatoms, protozoa, and algz that naturally develop in profusion on the bodies of the young larve. This explanation will perhaps make clear why, in the following case, we apparently retrace our steps to consider the case of seventh- day larve. In point of fact, these larva were, at the time of experi- mentation, somewhat further developed than were the eighth-day larve mentioned in Case I. Case 2—July 20, 9 a.m. Twenty seventh-day larve (eight second-stage, twelve third-stage) were removed from the hatch- ing bag, put in the glass jar, placed in the dark box and illumi- nated by the light through the three by one inch window. After a half hour, observation showed that the larve were equally divided between the window side and the room side of the Jar. After five minutes’ exposure to red light, thirteen larvae were posi- tive and seven were negative. When, however, the amount of light was increased by opening the large three by three inch win- dow, only three larvee remained positive while seventeen became negative. ‘This proportionate reaction endured for several hours, or until observation ceased. Case 3—July 20, 8 p.m. Twenty seventh-day, early third- stage larvae were taken from one of the hatching bags, placed in the glass jar, and illuminated by an acetylene light. A more or Hapbtey, Behavior of the American Lobster. 225 less scattering negative reaction at first resulted. When the amount of light was increased by supplementing the acetylene with a bril- liant oil burner the response was more definitely negative. Case 4—July 21, 9 a.m. Twenty-two eighth-day, early third- stage larvae were taken from one of the hatching bags and put in the glass jar in the dark box. When subjected to subdued day- light through the three by one inch window, sixteen out of twenty- two gave the negative reaction. In orange light the reaction was seventeen negative, five positive; in red light eighteen negative, four positive. Here attention may be called to the fact that these third-stage larve gave a negative reaction to practically the same intensity of light as determined a positive response for larve in the late second stage. Case 5—August 3, 2 p.m. Twenty eighth-day, early third- stage larvae were taken from the hatching bags and put in the glass jar in the dark box. They were submitted to the colored lights, with results as follows: Cotor. Positive. NEGaTIVE. FRG Stars aaa yeaa eget Mae te a sae saa toca ee ae 8 12 OEE: Sass An ai Are ee, ee Re aie a FN 6 14 Greentnca Wi ver erty Ne Aste eae y he ele oe 3 17 eR arise pe tenia a eat eth pane hey i) Ne 2 18 Botta Tica eta as ea ee ae pe Oa ee iN 9 6 14 IDR febog sort het. Sao e TARE oe. ARMOR LAE ag fo) 20 Conclusions from Experiments 19 and 20: The conclusions which we draw from the two foregoing experiments support fur- ther those formulated for Experiments 16, 17 and 18, on ps 226% In, Expenment 20, Case was observed the definite positive response which was manifested toward the end of the second larval stage when the moulting-period was near. In Case De where a group of larve which included individuals of both the second and third stages was used, it was observed that the reaction was either positive or negative; and that those larvze which gave the negative reaction most definitely or gave it first were usually the larve of the early third stage. In Cases 4 and 5, in which only third-stage larvee were employed, it was observed that, in general, the reactions to lights of nearly all intensities were negative. As in the case of the first-stage larve, it was found that the reaction of second-stage larva, just before the moulting-period, usually changed from negative to positive, and again became negative at the beginning of the third larval state. 232 ‘fournal of Comparative Neurology and Psychology. 3. Third Larval Stage. By the ninth day it is only in exceptional cases that the larve have not entered the third stage; and it frequently happens that they are nearly ready to enter the fourth. ‘The swimming of the third-stage larve is much like that of the earlier stages except that in the third stage there is greater difficulty in using the swimmerets of the thoracic appendages, especially during the last part of the stage. One reason for this is the fact that, as the larve grow older and larger, they more often play the host to multitudes of diatoms, alge and protozoa which gather in such quantities as seriously to interfere with the processes of swimming and eating. In the preparation for the moult from the third to the fourth stage, moreover, occur the most important changes that the young lob- ster undergoes in the course of its life. “These changes appertain not alone to modifications in the external form of the body and to the form and functions of many of the body appendages, but also to points of internal structure. Among the changes during this period of metamorphosis we may enumerate the following as important in connection with our study of behavior: (1) The loss, in the moult from the third stage, of all functional swimming attachments of the thoracic appendages; (2) the great develop- ment of both the first and second pairs of antennz and of the chelipeds; (3) the accession of functioning swimmerets on the under side of the second to sixth abdominal segments; (4) a great change in the form of the body, and a consequent modification of the manner of swimming. In view of these important changes, which are taking place in the anatomy of the lobsters as they pass from the third into the fourth stage, it does not appear unjustifiable to believe that these processes have an influence on the behavior of the larvae even before they emerge in approximately the adult structural type, endowed with a new body form, new functional apparatus and new reac- tions. We shall now undertake a study of the behavior of the third-stage larvz as they approach and finally pass this most crit- ical period of their life history. Experiment 21. Case 1—July 22,9:30a.m. Thirty ninth-day, third-stage larvae were removed from the hatching bag, put in the glass jar and placed in the dark box. Under stimulation by the red rays, although there was no definite positive reaction, most of Hap.ey, Behavior of the American Lobster. 223 the larvae swam about at random on the window side of the jar. When orange glass was substituted for red, half of them came to the room side of the jar. In the case of green glass, a few more reacted negatively, and when blue glass was substituted for green, all but five larvae gave a negative response. ‘These five did not manifest a definite positive reaction, but swam at random on the window side of the jar. When the colored glasses were removed and the larvae were submitted to the influence of diffuse daylight through the small window, all reacted negatively. Case 2—August 4,9 a.m. Twenty ninth-day, third-stage lar- ve were taken from one of the hatching bags and placed in the dark box. Stimulation by the colored light resulted as follows: Cotor. Positive. NEGATIVE. REG ar R ee ROR ee tLe hirer ctedeLoie vaeloeraisinelwtas 6 14 (ONETANG pobire atino > Gob. oc OHIon ne Ecco Baer pea a erte 3 17 GEC eee hore Te eS Ce EIS TUNA Iel HIS wd Sarees 2 18 Do LU TORN Se Ata Bacay uray SAU air Sy Mnech Bee Te eae a ae aL oe oo 2 18 IWihiites’: Reais ae ce aes err mg Sree, cok Leg ves MET Ryewncs Bh ° 20 Warliiah tapssetese cts eee deren rtnncucunynemere nak Ove tial aves ° 20 Case 3—In the present case it was attempted to learn whether the sign of the photopathic reaction in the larve of this stage cor- responds to the sign of their phototactic reaction. To this end, ten ninth-day, third-stage larvz, fresh from the hatching bag, were placed in the glass-bottomed box B, which was set over the light-shaft and mounted upon colored glass plates. After each observation either a period of five minutes was allowed for a uni- form distribution of the larva to take place, or the box itself was reversed, leaving the glass plates in the same order. In other instances the order of the glass plates was changed. During this experiment the water in the box was eighteen to twenty mm. deep. The results are presented below: Rep. ORANGE. GREEN. Biue. 4 ° Dye, 5 I 5 fo) 2 7 Rep. ORANGE. Buiue. GREEN. 2 q 3 4 I I a 4 Rep. Bue. GREEN. ORANGE. I 5 3 I 2 2 3 3 BuueE. Rep. GREEN. ORANGE. 6 ) 3 I 5 I 2 x 234 fournal of Comparative Neurology and Psychology. The larvae which were used as stated above, and which presented a positive photopathic reaction in every instance, were next trans- ferred to the glass jar and placed in the dark box. Here, and in tubes, the assumed phototactic reaction was uniformly and def- nitely negative; and this was true in the case of lights which were both of greater and of lesser intensity than in the tests above men- tioned. Case 4—To confirm the results obtained in Case 3, similar tests were made with another group of ninth-day, third-stage larve, fresh from the hatching bag. Notwithstanding the fact that this series of observations was not started until 5 o’clock in the after- noon when the light was fading, the results were similar to those obtained in Case 3. ‘That is to say, the photopathic reaction was definitely positive, but the phototactic reaction, as shown when the larve were transferred to the glass jar in the dark box, was as definitely negative. Experiment 22—The following experiment and observations concern the tenth-day, third-stage larvae. Most of these lobsters were well along in the third stage, and many were covered with body parasites. Case 1—July 23, 9 a.m. Thirty tenth-day, third-stage larvae were transferred from one of the hatching bags to the ‘elas j jar and placed in the dark box. After having been submitted for one-half hour to light coming through the red glass (three by one inch window), the reaction was uniformly negative. In the case of orange, yellow, green, blue and white light the results were the same. In all of these reactions, however, one fact was noticeable, the body-orientation of these larvae was much less definite than in any previous case of the same or earlier stages. Case 2—July 26,9 a.m. A mixed lot of thirty third-stage larve, most of which were ten days old, although some were older and some younger, were transferred from the hatching bag to the glass jar. When submitted to the colored lights in the dark box, the following results were obtained: Cotor. PosITIve. NEGATIVE. INGAws sobobanao pede OSatotODemOocedHOoo Modo odacd ous 3 27 (QMAIHES oso md Londo on obdasboocsbecOUpH One adIdss0NGC aS 13 17 (Oa I ee Maren ot A AOAC OG ao Eee Oud TAC 8 22 13 LOTR roe Cra ie ON a RRSIOR PATIO RMR Cicer neice Gin Ore Shree c 13 17 Hapb.ey, Behavior of the American Lobster. 235 In consideration of the apparent fluctuations in the sign of reac- tion manifested by the above-mentioned larve, it may be noted that these lobsters represented a group in which some were “early,’’ others “advanced,” third-stage larve. Indeed many were approaching the third moulting-period; the significance of this for the behavior of the larvz we shall consider in the next few cases. Case 3—July 27,2 p.m. Thirty eleventh-day, third-stage lar- ve were transferred to the glass jar and placed in the dark box. Under colored lights, although the general reaction was negative, many were positive. Experiments “made upon the larve in the elass- bottomed box B to determine the photopathic reaction at this time, showed that the larvae gave neither a definitely positive nor a definitely negative reaction. Other tests indicated a definitely positive reaction. When, however, light was admitted to the box through the end window (as well as through the bottom), first from the red end, then from the blue end, of the box, there resulted a definite negative phototactic response. The arrows show the direction in which the light entered the box. — Rep. Buue. ORANGE. GREEN. I 2 I 6 I I ° 9 ° fo) fo) 10 — Rep. ORANGE. GREEN. Buue. ° ° ° 10 ° ° I 9 e Rep. ORANGE. GREEN. Biure. <— 5 I 2 2 6 fo) 2 2 9 I ° ° The foregoing cases demonstrate that these larve manifested a definitely negative phototactic reaction under the conditions of illumination described; and that, by those rays which had a direc- tive influence, they could be driven into a region of either greater or lesser light intensity, as represented by the blue and by the red ends of the box, respectively. It might be argued that, so long as the eyes of the larvae are homolaterally stimulated, variations in intensity can not cause or change the orientation, and that orienta- tion results only from a heterolateral stimulation. But this is by no means true, for it has been noted in the foregoing pages, and it will be further demonstrated, that slight differences in intensity, 236 “fournal of Comparative Neurology and Psychology. when coincident with a homolateral stimulation, may even reverse the index of progressive orientation. Case 4—July 24, 9 a.m. Thirty-five eleventh-day, third-stage larvae were transferred from the hatching bag to the glass jar and placed in the dark box. The reactions to the colored lights were as follows: Cotor. Positive. NEGATIVE. 1 SAGs PA a ae eR eI A i a eR el ee Pe Cat er 15 20 Onan ge sei Soph et Ath aye eine these Milos: Ine Oe AEN Oa REET 16 19 Green. chs 2 See AN; coleih an sittin cat eye Rare ne enter ee ke 8 27 13) Toews ere Py eek ii mira ARON ree aa RCL ONE ME a AB Ace 8 27 Witte hea is ters mer gNeh) teeal et ascii ite betaine at AER EL eT 7 28 Next, the jar was placed in full daylight, on the table before the west window. All larvae came to the room side. In this case there were seven larve which became the special object of obser- vation, since they invariably manifested a positive reaction until they encountered daylight. ‘This group was set aside, and before night four of the seven had moulted into the fourth stage; conse- quently their exceptional behavior was due to the fact that they were in a different physiological condition than the majority of the group used in Case 4. Experiment 23. Case 1—In this experiment is continued the examination of the reactions of other twelfth-day larve which were approaching the third moulting-period. “Twenty-three larve were placed in the glass jar and observed under the influence of the célored lights in the dark box. The results were as follows: Cotor. Positive. NEGATIVE. Reds. See fore, sen itt ailie Orel Ursa ele ate Gore eats | ° ° I 9 fo) 2 | I 7 | I I | 4 4 | I ° 3 5 | | | Motalsess.ctey attest cos 2 3 9 | 25 | | 82 Grand Totalsiee ena 5 7 9 1 21 246 “Fournal of Comparative Neurology and Psychology. Case 2: Photopathic reaction—August 9, 3:30 p-m. Ten fourth-stage lobsters were removed from one of the confinement bags and placed in 16mm. of water in the glass-bottomed box. The glass plates were arranged in the order given below, and tests were made at five-minute intervals. The results, which showed a diminished tendency to remain in the areas of greatest illumina- tion, are represented in the following table: Rep ORANGE. GREEN. Buve. 3 2 I 4 4 ° 3 3 1 2 I 6 2 2 4 2 2 4 2 2) 12 10 ait : 17 When, some hours later, the same lobsters were tested again the results of five trials were as follows: Blue, 13; green, 9; orange, 7; red, 21; apparently in this instance it can not be said that the mid-fourth-stage lobsters were either positively or negatively pho- topathic. Yet the last instance shows a tendency toward a neg- ative reaction. Experiment 26. Reaction of late fourth-stage lobsters. Case 1. Photopathic reaction—August 12, 2 p.m. Ten late fourth-stage | lobsters were transferred from one of the confinement bags (where the majority had already entered the fifth stage) to the glass-bot- tomed box which was placed over the light-shaft in order to test the photopathic reaction. In this case nine consecutive tests were made, three minutes being allowed for each orientation. The results, which are characteristic of all other tests, and which show a tendency on the part of the lobsters to avoid the light, may be recorded as follows: No. Buvue. GREEN. | ORANGE. Rep. Miss Sopa aU Nea eee I 2 I 6 7 OE hi es mre e tbat St toa I ° 3 6 RECO OOBO tapiosws Shr obb ome ee Soe 3 ° 2 5 “Sndo boda oxteaon GAS OCmN en e.O8 te 3 4 I 2 EU Cn oh Opes e ons Stee 2hO Bcaita Groote I 2 | I 6 aes oct SNe Bean CORRS SWS os 3 I | fo) 6 Fl coo RTE MN Re tee OS a oe 5 3 fe) 2 Bie ate Ae Lee aes an he, See I I | I 7 92. 4 2, | 2 2 MOtAlSe hss say eRe ee 22 15 II | 42 Hapbtey, Behavior of the American Lobster. 247 Case 2. Phototactic reaction—August 10, 3:30 p.m. ‘Ten late fourth-stage lobsters were taken from one of the hatching bags and put in box B, which was placed in the dark box so that the end window faced the light, the intensity of light being modified in each case by interposing colored glass plates between the end window and the light. The tests, which were made at three- minute intervals, and which showed a very definite negative reac- tion, were as follows (in the fourth tests of the first and last sets respectively, one lobster was accidently killed, thus making the totals incomplete): CoLor I 2 3 4 I I I 7 ° I 2 7 ° fo) I 9 I fo) 2 6 Oranges acters hoe va eect e ae raise 2 2 6 29 ° I 2 7 I ° I 8 I I 2 6 I I I 7 LATOR cue meds eee ND LAL PE a 3 3 6 i 28 ° ° I 9 ° 2 I 7 I I + 4 I ° 3 5 REG nist ieocrcoun contacts Sle as 2 3 9 25 Motalsvacnmat a eis Peck | 2 8 21 82 Conclusions on the reaction of fourth-stage lobsters—The obser- vations thus far made upon the behavior of fourth-stage lobsters appear to demonstrate the following points: (1) Throughout the entire fourth stage-period (with the exceptions noted under Experiment 24, Cases 5 and 6), the lobsters manifest a negative phototactic reaction, which is accentuated in the latter part of this stage. This behavior is quite different from the positive reac- tion which supersedes the negative in the case of second and third- stage larve just previous to their moult into the third and fourth stages respectively; (2) This type of reaction after the first part of the fourth stage-period, cannot be reversed or modified, as was 248 fournal of Comparative Neurology and Psychology the case in earlier stages, by using different intensities of light (3) The photopathic reaction, which in the early fourth-stage lobsters is definitely positive, changes by the latter part of the stage to negative in the majority of individuals. “Thus it can be observed that, just as the third-stage larvae might at the same time (or suc- cessively) manifest both a negative phototactic and a positive pho- topathic reaction, so may the lobsters of the fourth stage. Other points regarding the behavior of fourth-stage lobsters will receive consideration in connection with the subject of contact-irritability. 5. Fifth Stage. The body-form of the fifth-stage lobster is similar to that in the fourth-stage, and we might therefore expect to find similar types of reaction. It will be seen, however, that there are. many points of difference in behavior which are of such a nature that they can not be attributed, either wholly or in part, to changes in body-form or in the swimming appendages. The changes are doubtless the consequence of modifications which have taken place in the body-processes or in the physiological states of the lobsters themselves, and which have resulted from the cumulative stimula- tion during the earlier life of the lobsters. Generally speaking, it may be said that the reactions of the fifth-stage lobsters are Sho typical for the adult form, and are especially characterized by the light-shunning tendency. This form of behavior could be observed readily by watching the lobsters in their confinement cars; but, for the sake of certainty, the same experiments, to which the larve of earlier stages had been subjected, were repeated with the fifth-stage lobsters. Since the reactions did not appear to undergo any noticeable modification as the lobsters passed through the fifth stage, there is no need for considering the early, mid and late fifth stage-periods separately, as was done for fourth-stage lobsters. The type of reaction presented in the early fifth stage- period differs in no way from the behavior of lobsters in the late hifth stage-period; and both are characteristic of the behavior in alll later | stages. Ex periment 27: Case °F: Photo pathic reactton—In the first instance, ten fifth-stage lobsters were transferred from one of the confinement bags to the glass-bottomed box and this was placed over the light- shaft. alike method used was the same as in pre- Hapey, Behavior of the American Lobster. 249 vious experiments. In the second instance the blue glass was removed, and the space where it had lain was left clear, thus per- mitting the reflected daylight to enter this area of the bottom of the box. The results of both tests show a negative reaction which was more definite in the second instance. Buvue. GREEN. ORANGE. Rep. a I 2 6 2: I 2) 5 3 I I 5 2 3 2 3 8 6 7 19 DayLiGHtT. GREEN. ORANGE. Rep. fo) 2 2 6 ° 2 2 5 I 2 2 5 fo) 2D 2 6 I I 3 5 ° 2 4 + 2 12 15 30 Case 2. Phototactic reaction—Further demonstration of the definitely negative phototactic response of fifth-stage lobsters was given by the experiments on contact-irritability (Exp. 29, p. 256). Here is clearly shown the extreme manifestation of this negative phototactic response, which frequently would have culminated in fatal results by driving the lobsters from deep to shallow water and leaving them stranded where they would certainly have died had they not been returned to the water at the end of the experi- ments. Here, as has been found in the case of many animals, the total behavior is completely dominated by the light influence. It may be said further that in the case of the fifth-stage lobsters light of different intensities does not cause a change of reaction from positive to negative, or from negative to positive, as was the case in the earlier stages; nor do we ever find the individuals “heading” into the light, as may be the case in the fourth-stage larve. For the fifth-stage lobsters any intensity of light which influences their behavior in any degree, determines, under experimental condi- tions, both a negative body-orientation and a negative progressive orientation. In the foregoing pages it has been shown that larvae which were positively photopathic could be made to pass from regions of greater to regions of lesser light intensity by submitting them to 250 ‘fournal of Comparative Neurology and Psychology. the directive influence of light of sufficient strength. In these cases, it was observed that the photopathic reaction was invariably subservient to the phototactic, although the latter was also very dependent upon a certain optimal intensity for bringing about a positive or negative response. In the following instance we shall observe that, although the directive influence of the light rays is capable of modifying the orientations which relative intensities of light have determined, still the directive influence can not quite obliterate the evidence of a photopathic reaction, as was possible in the younger larvae. In other words the tendency of the fifth- stage lobster to “select” the darker regions has become almost as firmly fixed as has the tendency to react negatively to the directive influence of the light rays. In the first larval stages the photo- pathic response invariably gives way to the phototactic. In the fifth the two tendencies clash; and the resulting orientation of the lobster is determined, not by one, but by both of these factors. (4.) Case 3. Photopathy versus phototaxis—Ten fifth-stage lobsters were put in box B. This was mounted upon the colored glass plates over the light-shaft as in previous experiments. The preliminary observation showed that there was a definite tendency for the lobsters to congregate at the red end of the series of glass plates, thus demonstrating a negative photopathic reaction. Now the window at the red end was opened to diffuse light. After a period of ten minutes, observations of the position of the lobsters were begun, and continued at five-minute intervals. The follow- ing results show that, although the negative phototactic response is still manifested, it has been greatly modified by the tendency on the part of the lobsters to avoid the brightly illumined area at the end of the box: DayuiGut. GREEN. ORANGE. Rep. I 4 2 a I 3 3 3 2 3 3 aD I B 4 D I 2 - 3 2 3 3 2 8 18 19 15 In the next case, the end of the glass plate series, which in the previous instance admitted reflected daylight, was covered with a blue glass and the illumination of this area thus rendered less Haptey, Behavior of the American Lobster. 25m intense, while the end window of the box (at the red end) remained open, as in the last experiment. The results, which demonstrate that the phototactic reaction had still further overcome the photo- pathic, were as follows: Buve. GREEN. ORANGE. Rep. 2 2 4 2 I 3 2 4 3 2 3 2 3 2 2 3 4 3 2 I 2 3 2 2 15 15 15 15 In the last two instances it becomes apparent that the fifth- stage lobsters, unlike the early-stage larvae, could not be forced, by the directive influence of the light rays, into an area of greater light-intensity. In other words, the tendency to manifest a nega- tive phototactic reaction was not sufficiently strong to overcome the tendency to give a negative photopathic response. (B.) Experiment25. Phototaxisleading to fatal results—Before bringing to a close this consideration of the reactions to light in lobsters of the fourth and fifth stages, it may be appropriate to introduce the results of some experiments whose aim was to show the extreme nature of some phototactic reactions. In other words, attempt was made to determine whether or not the strong direc- tive influence of the light rays could compel the larvz so to act that they would do injury to themselves as in the familiar case of the moth that flies into the flame, or of Ranatra, mentioned by Hormes (1906). The reactions of the fourth-stage and fifth- stage lobsters will be considered together. Case 1. Fourth-stage lobsters—For this series of experiments box B was set up as represented in Fig. 7, being supported at one end so that the bottom of the box made an angle of about fifteen degrees with the table. The box was filled with water so that when it was slanted, the water-line did not quite reach the angle made by the hatiess ara upper end, B. In this way there was created an inclined plane, slanting eae the window end, J, of the box to the higher end, B. ‘The water consequently diminished in depth as the end, B, was approached. At this end there was an inch or more of the bottom of the box not covered by water. The light from the window, L, was reflected into the box by the mirror, 252 ‘fournal of Comparative Neurology and Psychology. M, for the purpose of discovering whether the larve in presenting their negative phototactic reaction, would allow themselves to be driven into the shallow water. By means of a hole in the bottom of the box, the water could be withdrawn very gradually (a few drops a minute), so that if the larve persisted in remaining in the Fic. 7. Diagram of apparatus as set up to test the extreme phototactic reactions, leading, in the case of fourth and fifth-stage lobsters, to fatal results. L, source of light; M, reflecting mirror; 4, end of box adjacent to ‘‘window;” B, end of box not covered with water, where the lobsters were stranded. In the cover of the box are shown the sliding partitions. shallow area, they would, in the course of a few minutes, be stranded on the dry bottom. ‘Ten fourth-stage lobsters were first used for experiment and the results, ascertained by counts made as in all other cases, were as follows: (The arrow shows the direc- tion of the light coming through the end window of the box, while the numbers at the top of the columns represent the division areas of the box): TEST. = Iie 2: 33 4. NuMBER TIME | STRANDED. (after). I I I | 3 5 4 5 minutes 2 I 2 | I 6 3 IO minutes B ° I I 8 | 6 20 minutes 4 I I | 3 | 5 | 5 5° minutes Motalsaeanr a | 8 | 24 | 18 The results of this experiment and of several others similar to it, show, that out of a total of twenty-four larve which gathered HaDLey, Behavior of the American Lobster. 253 in the area farthest from the light, eighteen allowed themselves to be stranded rather than to retrace their course into deeper water, and in so doing to approach the light.‘ Case 2. Fifth-stage lobsters—When the same experiment in- volved the fifth-stage lobsters, the results were similar. The only difference that could be observed was that the intensity of the reaction was greater for the fifth-stage than for the fourth. The result of twelve tests, each with ten lobsters showed the distribu- tion to be as follows: Area I, nine; area 2, ten; area 3, twenty- one; area 4, eighty, of which seventy were “‘stranded.’’ These last would have perished, had they not been returned to the water at the end of each successive test. (C.) Conclustons concerning the reactions to light of fifth- -stage lobsters—The results of the foregoing experiments on the reactions of fifth-stage lobsters, demonstrate the following points: (1) Like the fourth-stage lobsters, the fifth-stage lobsters are neg gatively pho- totactic from the beginning of the stage to the end of it, and this holds good for all intensities of light “which cause any reaction whatever. (2) Unlike the early fourth-stage but much like the late fourth-stage lobsters, the fifth-stage lobsters are per photopathic from the beginning of the stage to the end. ); Lhis negative photopathic reaction, unlike He photopathic tee of the earlier stages (in which case the photopathic reaction was entirely subservient to the phototactic), has itself become a well grounded tendency, and, although it can be modified, it can not be entirely obliterated (so far as its value in causing a certain orienta- tion 1s concerned) by the tendency to react to the directive influence of the light rays. (4) The intensity and energy with which the late fourth-stage, but especially the fifth-stage, lobsters manifest a negative phototactic reaction may lead to results fatal to the lobsters themselves. (D.) Contact-irritability versus reaction to light—In the preced- ing section the phototactic and the photopathic reactions, together with some points of their inter-relation, have been considered. We shall now examine that response of lobsters to solid portions of their immediate physical environment which may be ascribed to contact-irritability or thigmotaxis. It frequently happens that single types of reaction (phototaxis, chemotaxis, geotaxis, and the like) may be studied to best advan- *Tt should be noted, however, that the water in no case receded more than § to 10mm. as measured horizontally on the bottom of the box. 254 fournal of Comparative Neurology and Psychology. tage only when another stimulus of known effect is present and operative. For instance, if the two conditions of stimulation which respectively bring about a photopathic and a phototactic reaction are so arranged as to oppose one another (1. e., by determining opposite reactions in the larvz), and if the constant effect of one set of conditions is known, then it is possible to form an estimate of the persistency of the reaction determined by the opposed set of conditions. For example, if light rays of low intensity coming through the end of box B, resulted in driving the enclosed larvae, which had just previously given a negative photopathic reaction, to the opposite end of the box, and at the same time forced them from a region of low into a region of high intensity, we should say that the negative photopathic reaction of these larvae was of slight importance as compared with the phototatic. If, on the other hand, it was learned by experiment that the rays entering the end window of box B would not force the negatively photopathic larvae from the dark into the brightly illuminated end of the box, but resulted in their gathering ‘in the middle of the box (for instance, in the green or orange area) then it might be inferred that the neg- ative photopathic reaction had a greater influence in determining the final reaction of the larva, although it was in this case directly and strongly opposed by the tendency to manifest a phototactic reaction. In the following experiments, made to discover the value of contact-irritability in determining the reaction of the larva, the principle mentioned above was made use of, and in this instance a combination was made between experimental conditions which would allow the demonstration of contact-irritability, and those which would insure the manifestation of negative phototaxis if no other modifying conditions (such as contact-irritability) were present. But before going farther with the description of the technique of the experiments, a few observations on the behav- ior of the lobster larvae under natural circumstances may be con- sidered. This may form a better basis for the consideration of experiments dealing with contact-irritability versus reaction to light under the especially devised conditions to be described. It might reasonably be imagined that the loss of the swimming branches (exopodites) of the thoracic appendages, which takes place with the entrance to the fourth stage, would at once deter- mine a very radical change in the habits of lobster larvae. We should surmise that the larve would immediately abandon their Hap ey, Behavior of the American Lobster. 255 pelagic manner of existence and enter upon a more sedentary life among the rocks and weeds of the sea bottom. But this is by no means the case, for never in the life history of the lobster do we find surface swimming more strongly manifested than in the fourth stage, and just after the loss of those accessories without which swimming would have been impossible in any of the earlier stages. The energetic surface-swimming of the fourth-stage lobsters was evident from many observations, made under both natural and experimental conditions. It was observable not only in the large hatching bags but also in the quiet water surrounding the bags and hatching apparatus. One case 1s especially noteworthy. In July a steam launch, of which the captain lost control, rammed one of the floats which suspended six large hatching bags containing lobsters in various stages. As a result many fourth-stage lobsters were suddenly liberated in the water about the hatchery. When order had been restored, an attempt was made to recover the lost lobsters, and over five hundred of the fourth-stage which were swimming actively at the surface of the water were picked up with scrim nets. A far different phenomenon obtains in the behay- ior of fifth-stage lobsters under natural conditions. ‘This is illus- trated by an interesting sequence of changes in the swimming habits. When the majority of the lobsters in the bags were in the fourth-stage, they usually swam near the surface. As the larvee moulted into the fifth stage, fewer lobsters were to be seen. The reason for this was ascertainable if one poked with a stick about the mass of weeds and alge adhering to the sides and bottom of the bag. Here could be found, carefully hidden, a large number of fifth-stage lobsters. By the time all the individuals in the bag had passed to the fifth-stage, scarcely one could be discovered swimming freely. Whenever a number of fifth-stage larve were liberated in the open water, it was an interesting sight to observe them swim for a moment, then turning head down, disappear for good in the deeper water—a great contrast to the behavior of the fourth-stage lobsters under similar conditions. Another set of observations refers to the burrowing instinct of the young animals. When early fourth-stage lobsters were trans- ferred to glass dishes, on the bottom of which was a layer of sand, gravel and a few broken shells, they at first paid no heed to these conditions, but for several days continued to swim as persistently asever. Finally, however (usually within two or three days after 256 ‘fournal of Comparative Neurology and Psychology. having been placed in the dish), the lobsters began to plough through the sand of the bottom, especially near the rim of the con- tainer, and to construct burrows beneath shells, stones or other objects in the sand. Yet, even after these burrows were com- pleted, the fourth-stage lobsters seldom remained in them, but came out and crawled rapidly over the bottom or swam more or less actively near the surface of the water. When, on the other hand, fifth-stage lobsters were introduced into the dishes contain- ing sand, gravel, and shells they commenced burrowing at once and when the burrows were completed they showed a much greater tendency to remain therein than did the late fourth-stage larve. Although the fifth-stage lobsters came out for food, free swimming wasseldom indulged in duringsuch sorties. ‘The question now arises as to what conditions or factors cause the energetic surface-swim- ming of the early fourth-stage lobsters and the bottom-seeking and burrowing habit of the late fourth and the fifth stage. Are these reactions to be explained as phototropic, geotropic, or thig- motropic reactions Or do all three of these, and perhaps still other factors, unite in determining the final result? While we are not yet prepared to venture an answer to these queries, the records of a few simple experiments which were undertaken to _ ascertain the value of the part played by contact-irritability in determining the orientation of the fourth and fifth stage lobsters, under certain known conditions, will be presented. Experiment 29. Fourth-stage lobsters—The technique em- ployed in the present experiment was as follows: One-half of the bottom of box B, was sprinkled with sand to the depth of five mm., the box was filled with salt water to a depthof 3 cm., ten early fourth-stage lobsters were introduced, and the box covered. The aim was to learn whether, in the total absence of light, the larve would “choose” either the sanded or the clear area. The result of a typical test 1s presented below. The readings were taken every five minutes, and after each reading the lobsters were caused to distribute themselves about the box: SANDED AREA. CLEAR AREA. if 2 3 4. 4 3 2 I 2 2 3 3 3 2 2 3 I I 4 4 ie) 8 II II Hapbey, Behavior of the American Lobster. 257 These and other tests were made, but in no case was it apparent that the early fourth-stage lobsters showed any preference for the sanded area. When, in another series of four trials involving ten lobsters each, the window at the sanded end of the box, was opened so as to allow the rays to stream through, every lobster but one was driven to the compartment farthest from the light. When this experiment was tried with late fourth-stage lobsters, it appeared that a greater number remained on the caned area, even in the presence of the light conditions mentioned above. The results of a typical experiment of this sort involving five trials of ten lobsters showed that, while thirty were driven to the clear space, ten remained on the sanded area. Experiment 30. Case r. Fifth- stage lobsters—In this instance ten fifth-stage leeeter: were placed in box B# as arranged for the previous experiment, no light being admitted at the ‘end ob the box. The record of seven trials separated by a period of from five to ten minutes, showed a decided preference for the sanded areas; while forty remained on the sanded region, only twenty gathered on the clear area. Case 2—In the next instance the end window at the sanded end of the box was opened to the light, but with a red glass so inter- posed that the intensity of light in this region was not great. A period of from ten to forty-five minutes was allowed for each orien tation. Although the influence of the light tended to drive the lobsters off the sanded area the results of six trials (ten lobsters each) showed that thirty-seven fifth-stage lobsters remained in contact with the sand, while twenty-three moved to the clear area. Case 3—In the next series of six trials (ten lobsters each) the intensity of light was modified by substituting an orange glass before the end window. The results showed twenty-five on the sanded area, thirty-five on the clear. Case 4—In the last series of six trials (ten lobsters in each) the conditions were still further modified by removing the orange glass and thereby greatly increasing the intensity of the light which entered the end window of the box. This demonstrated that a light of great intensity would drive the fifth-stage lobsters off the sanded area. At the end of the experiment only thirteen lobsters remained on the sanded area, while forty-seven remained in the clear region. Finally, the sand was removed from the box, and the reaction of these lobsters was tested with unobstructed light 258 ‘fournal of Comparative Neurology and Psychology. entering the end window. ‘The resulting reaction was invariably and definitely negative; and this with light of all the intensities used in the previous cases. Conclusions from experiments on contact-irritability versus reac- tion to light—Although these experiments can hardly be called critical, they demonstrate that the presence of the sanded area in the box did modify the reactions of the fifth-stage lobster. That there was manifested a tendency to remain in contact with the sand, to burrow in it, and not to be dislodged by such intensities of light as would normally rout the entire group of lobsters and send them to the end of the box farthest from the light. These facts, more- over, cannot be said to hold true for the fourth-stage lobsters that were used in the foregoing experiments, and which showed no well defined preference for the sanded area, at least in the early part of the stage-period. VI. MECHANICS OF ORIENTATION. The aim of the present section is to report the results of a series of observations which were made in order to answer the following question: By what movements of the lobster larva are the reac- tions to light accomplished ? In our effort to answer this question we shall, for the present, attempt to avoid so far as possible con-— siderations which deal directly with the ultimate causes of orienta- tation; in other words, we shall limit ourselves to the observation of the actual movement of the body, or of certain parts of the body, of individual larve; and attempt to show what relation exists between these movements and the external factors which appear to determine them. First, however, it is necessary to establish some points regarding the natural behavior of the larvae when the influence of external stimuli is at the minimum. I. The normal behavior of the larve—In view of the fact that swimming constitutes the chief activity of the larval lobsters, our question resolves itself into the following: What is the nature of the normal swimming? When one first observes the behavior of individual larvz amidst the thousands contained in the large hatch- ing bags no difference is evident in the swimming of the first three stages. In all instances the back of the larva is, for the most part, uppermost, the abdomen bent under and downward at an angle of about 60° from the longitudinal axis of the cephalo- Hapbtey, Behavior of the American Lobster. 259 thorax, which in turn is inclined about 30° from. the hori- zontal plane. In daylight this position may be maintained with- out modification for several minutes, but the equilibrium is often interrupted by other body-movements which, upon superficial examination, appear to be of a most diverse and ill-ordered nature. There are leanings, turnings, fallings, somersaults, revolutions and rotations which follow each other in no apparently definite sequence, and which disturb the general equilibrium greatly or slightly as the case may be. Whether the balanced equilibrium, the devious rotations or other activities are present, the exopodites or swimming attach- ments of the thoracic appendages beat the water more or less con- stantly with short vibratory strokes, sometimes lifting the larvz high toward the surface, and again allowing them to sink to the bottom, where they frequently lie for some moments almost motion- less, only again to resume their varied activity. Now they swim forward, now backward, now lurch to the side, now to the rear, always maintaining more or less energetically these apparently aimless movements. Such is the nature of the swimming in day- light or other brilliant illumination; but for our purpose it cannot be called the normal swimming of the lobster larvae. It is only under special conditions that the latter may be observed; and, in view of the fact that it is the conditions of light which influence more strongly than any other factors the behavior of the larve, it is only when they are under certain light-conditions that we may expect to find manifested what we may call the characteristic or normal swimming. The twilight or nocturnal swimming of the larval lobsters inva- riably gives us the fairest example of natural behavior. At such times alone (or when the larve are submitted to artificially pro- duced twilight) variations in temperature and the multiplicity of conflicting cross-light influences are eliminated. Frequently when the twilight was so dim that observation was rendered difficult, the swimming was delicate and regular, and the young larve would mount up, bird-like, to the surface of the water, hover many sec- onds in a single position, or swim backward or forward with equal ease. In sucha case, when a lighted match was brought near the side of the jar in which the larvae were confined, the same restless and uncertain swimming, characteristic of the diurnal activities, was again manifested, together with the accompanying leanings and 260 ‘fournal of Comparative Neurology and Psychology. rotations. From these facts it may be assumed that the twilight swimming of the larve probably represents the natural behavior or at least the behavior that arises purely from the internal states themselves; and that the peculiar antics characteristic of the day- light swimming represent a type of behavior chiefly due to the action of external stimuli. The question now naturally arises—Do the various turnings, rotations, leanings, and fallings which constitute the appar- ently haphazard behavior of ‘the larval lobsters when swim- ming in daylight or other brilliant illumination, give any indica- tion of method? Observations have given a suggestion as to the means whereby we may attempt to ascertain the value of certain light-conditions in determining these peculiar forms of behavior.® If larval lobsters of any of the first three stages are subjected to the influence of light which comes from one direction only, as from the side, the first fact observable is that the larve undergo a certain body-orientation; they turn away from the light and place the long axis of the body parallel to the direction of the rays. The second fact which may be noticed is that the larva move in the direction of the light rays either toward or from the source of illumination. A third fact, which is of prime importance and which involves those stated above, is that no matter whether the progressive movement of the larve be toward or away from the source of light, the orientation of the body (head away from the source of light) remains unchanged. ‘To state the matter briefly we may say that, whatever the nature of the progressive orienta- tion of the larva, the body-ortentation 1s at all times, and under all conditions, negative. BOHN (1905, p. 8) has clearly pointed out this fact for the larvae of the European lobster. In this regard he says: “En général, les larves de homard se placent dans le sens négatif; méme, dans les premieres heures aprés |’éclosion, alors qu’elles se groupent vis-a-vis des lamps, leur téte se tourne du cote oppose, et les larves s’approchent de la lumiére en regardant lobscurité, c’est-a-dire en reculant. Ainsi, aprés_ léclosion, orientation a lieu dans le sens négatif, mais le déplacement se fait dans le sens positif. Dans le suite, si le sens de l’orientation 5 Many of the observations which follow were made previous to the writer’s knowledge of the excellent work of GrorGes Boun (1905) along similar lines, upon the larve of the European lobster, Homarus vulgaris. The writer would acknowledge, however, his great indebtedness to this investigator, whose work has proved suggestive in the highest degree, and whose observations on the mechanics of behavior the writer has been able, in the majority of instances, to verify as well as supplement. Haptey, Behavior of the American Lobster. 261 reste le meme, le sens du déplacement peut changer.” Lyon (1906) has recorded a similar observation for several larval stages of Palemon. This condition of affairs is rather at variance with the majority of observations on the phototactic reactions of animals and it 1s contrary to the condition of body-orientation which we find in the fourth stage of the lobster itself, for in this stage (at least in some of the assumed phototactic reactions) the body-orien- tation brings the head toward the source of illumination instead of away from it as is invariably the case in the first three stages. The question has already arisen as to what we may mean by a positive phototactic reaction, for in this case it is clear that we may very frequently have a negative body-orientation coupled with a positive progressive orientation. Until we know more regarding the differences between body-orientation and progressive orienta- tion, it may be considered safe to say that the direction of the pro- gressive movement, with respect to the source of illumination, may be held as the surest criterion of the sign of the phototactic response of animals. On the other hand the point has been made clear by some writers, that in the body-orientation of organisms the definite relation of the body-axis to the lines of active force is the primary consideration for all problems of progressive orientation. How- ever this may be, we have before us at least one instance wherein, although the relation of the body-axis to the lines of force is an important consideration, the body-orientation per se has little or nothing to do with the question of the positive or negative progress- ive orientation of the organism; for as we have already observed, conditions which invariably determine a negative body-orientation may determine either a positive or a negative progressive orienta- tion, as other circumstances demand. We may, therefore, first concern ourselves with the mechanics of progressive orientation and then turn with better understanding to the mechanics of bod y- ortentation, for these two reactions apparently depend upon quite different circumstances. 2. The mechanics of progressive orientation—The only means of locomotion possessed by the larvz of the first three stages are the exopodites of the thoracic appendages and the strong, flexible abdomen with its broad terminal fan (Fig. 1). It is but seldom, however, that the latter is used, and never when it is a question of progressive orientation to light. We are then confronted with the problem: How, by the motion of the thoracic exopodites 262 ‘Fournal of Comparative Neurology and Psychology. alone, is the larval lobster able to execute those movements which determine his progress either toward the source of illumination or away from it? If the larval lobsters in any of the first three stages be put in a glass jar which is surrounded by black paper and placed in sub- dued daylight, the short vibratory strokes of the exopodites can be readily observed. At one time, certain individuals may be seen to swim rapidly backward, and again forward, with no appar- ent change in the position of the body or in the direction of the stroke of the exopodites. If, however, the thoracic appendages themselves be carefully watched, one can observe that, from time to time, these limbs undergo either a forward shifting (extension) as shown in Fig. 8, or a backward shifting (contraction) as shown in Fig. g. ‘his change from the “anterior” position to the “ pos- Fic. 9. Fic. 8 shows a larval lobster with the thoracic appendages in the extended or ‘anterior” position; the resulting movement is forward and upward. P) Fic. 9 represents the appendages in the contracted or “posterior” position; the resulting move- ment is backward and upward. terior” position may occur at short intervals, each position may persist for some seconds, or there may be a successive alteration with periods of longer duration in either one position or the other. It may be observed further, that when the thoracic appendages take the “‘anterior”’ position, the direction of the strokes of the exopodites becomes somewhat forward as well as downward, and the resulting motion of the larve becomes backward and upward. When, on the other hand, the thoracic appendages assume the “posterior” position, the stroke of the exopodites becomes back- ward and downward; and the resulting motion of the larve becomes forward and upward. During a great part of the time, the upward movement of the larve, as a result of the outward and downward stroke of the exopodites, does little more than compensate for the natural tendency to sink toward the bottom. For this reason the Hapbtey, Behavior of the American Lobster. 263 progress of the larvae may often be directly torward or directly backward with but slight deviation from the horizontal plane; while at other times, when the stroke of the exopodites is directly outward and downward (exclusive of either the “forward” or “backward’’ factor), the larvae may mount to the surface in nearly vertical lines. It thus becomes evident that the progression of the larvz, back- ward or forward, upward or downward, is largely determined by the position (state of extension or contraction) of the thoracic appendages. In other words, if for the greater part of the time these appendages are in the “‘anterior”’ position the phototactic reaction of the larva is positive; but on the contrary, if the thoracic appendages are more frequently in the “ posterior ” position, then the consequent reaction of the larva 1s negative. Naturally the next important question which arises 1s: What conditions deter- mine the “anterior” or the “posterior” position of the thoracic appendages? It cannot be questioned that these changes are directly due to certain variations in the 1 intensity of the illumination and are modified by the “physiological state” of the larvae them- selves; and that, furthermore, the state of extension or contraction of the thoracic appendages, and the stroke of the exopodites, are regulated to a great degree through the mediation of the eyes and the nervous system of the larva. But further consideration of this subject must be postponed until later. In the meantime we may turn our attention to the mechanics of body-orientation. 3. The mechanics of body-orientation—Under the present heading we shall consider the nature of those peculiar movements which the lobstet larvae undergo when they are under diverse and changing conditions of stimulation, in order to explain the cause of these actions and to show their relation to certain definite laws which may be said to regulate to a great degree the body-orienta- tion of the larvae. As we have observed, it is the influence of light which is most active in determining the behavior of the larve; furthermore, it is in the absence of such influences as diverse and changing conditions of illumination afford that the most realistic picture of the normal behavior of the larve is obtained. It will then prove the most practical method of approaching this problem, first, to obtain conditions of light which allow natural behavior (normal swimming); and then, by gradually modifying these con- ditions, to observe the effects upon the behavior of the larve. 264 “fournal of Comparative Neurology and Psychology. A. Tue Errects oF Direcr LIGHTING AND SHADING. Tech- nique and Methods of Observation—This section deals more espe- cially with the directive influence of light rays so introduced as to strike the larve from different directions; from before, from behind, from the side, from above, from below, or obliquely to the body- axis. [hese conditions were obtained, for the most part, in two ways. ‘The larve were placed either in a cylindrical glass jar, or in an especially constructed rectangular glass box (similar, per- haps, to the révélateur used by Bonn), three inches wide, six inches long, and two and a half inches deep, all sides and the bot- tom being of glass. Either of these receptacles might be placed in the dark box already described. ‘To regulate the intensity, slides of colored glass were used as in the earlier experiments, Water Zevel Fic. 10. Fic. 11. Fic. 10 represents a dorsal view, Fig. 11 a lateral view, of a larval lobster in the glass container. For description, see Case 1, p. 265. while to change the direction of the rays a series of mirrors was employed. In certain instances, when light from the bottom was required, the receptacle containing the larvae was placed upon a glass plate raised a certain distance above the bottom of the box, and the mirror was placed below. In still other instances the direction or the intensity of the light was modified by the use of light-absorbing (black) or light-scattering (white) backgrounds. These were used more frequently when the observations were made in diffuse daylight, and the subdued light came to the glass con- tainers from several different directions. From the experiments it appears very probable that in determining the orientation of the organisms, the backgrounds were instrumental only in regulat- Hap ey, Behavior of the American Lobster. 265 ing the amount and the general direction of the light which they reflected or absorbed. First, however, we shall consider the effects of suddenly throwing the light from a certain direction upon larvee oriented in various positions. Case 1. Illumination from before—In the first instance the behavior of a single larva was studied (the stage does not matter). It was oriented in the rectangular container, in the dark box with its head toward the three by one inch window, which was closed (Fig. 10), but in such relation to the glass box that its longitudinal axis was parallel to the direction of the rays of light coming from this window when it was opened. While the larva was so oriented, the screen was drawn aside and light from the small window was allowed to strike the larva “head-on.”’ Underthese conditions, one of two reactions resulted. ‘The larva underwent either a forward or a backward somersault, or rotation, which brought the back below with the head directed away from the source of illumination. Whether the rotation was backward or forward made no differ- ence in the resulting orientation and which one occurred depended upon the direction of the rays of light which struck the eyes of the larva. In normal swimming the body of the larva in any of the first three stages is bent about 30° from the horizontal. Now if the rays of light had the direction of 4 or B (Fig. 12) the rotation was usually forward, while if the light came from below, direction C, the rotation often was backward. After this first orientation the larva (position 5’) frequently performed a rotation on its long axis, either to the left or right, which brought the back again uppermost, and it then progressed in the direction of the rays, either toward or away from the source of illumination. Corollary 1—If the rays striking the eyes of the larva had the slightly oblique direction shown in Fig. 13, a or c, but were in direc- tion or plane B (Fig. 12), then the larva pivoted at the middle of its own longitudinal axis and swung to one side or the other, always keeping the back uppermost. If the rays of light took the direction designated a!— a‘ or c'— c*, the result was the same; the larva swung until the longi- tudinal body-axis was parallel with the incident rays, and the head was directed away from the source of illumination. Corollary 2—If the rays striking the eyes of the larva had the oblique direction, at — a‘ or ct — c* (Fig. 13) in plane J of Fig. 12, then the resulting movement was a combination of the forward 266 ‘fournal of Comparative Neurology and Psychology. rotation and the side swing (Cor. 1). In other words, the larva performed a side-somersault, and ended with the back directed below and to the side. Whether it turned to the left or to the right depended upon the direction of the rays in either the a or the c series. At the end of this reaction the larva usually became righted again with the back above and the head away from the light, and continued its progressive orientation in one direction or the other according as the reaction was positive or negative. Corollary 3—If the rays striking the eyes of the larva had the oblique direction at — a‘ or c! — c‘, and were in plane C of Fig. 12, the resulting reaction was a combination of the backward rota- Fic. 12. For description, see Case 1, Cor. 1. Fic. 13. For description see Case 1, Cor. 2. tion and the side swing (Cor. 1). That is to say, the larva per- formed a backward side-somersault, became oriented as in Cor- ollary 1 and 2, again turned the back uppermost, with the eyes directed away from the source of light, and continued its progress- ive orientation, in one sense or the other. Case 2. Larva lying with back downward, head toward light—In these instances, the larva was oriented head toward the (closed) window, and back downward. The rays were introduced from before, as in Case 1. It may be said that this orientation was difficult to obtain. Often it was necessary to wait fifteen minutes Haptey, Behavior of the American Lobster. 267 : or more before it occurred, then at the proper moment the light was admitted and the consequent reaction observed. On the other hand, it was common to find the larve on their backs and oriented obliquely to the rays of light. When the larva was oriented in this manner and the light was admitted, there usually occurred either a forward or a backward rotation (Fig. 14), but the forward rotation was most common. Whichever one occurred, however, the final orientation was the same: the back of the larva was again brought uppermost, and the head was directed away from the source of light. Fic. 14. For description, see Case 2. Fic. 15. For description, see Case 4. Corollary 1—If the larva was oriented with the back below, the head toward the closed window, and the body-axis oblique to the direction of the incident rays, the resulting orientation was a com- bination of the upward and forward rotation and a swing of the body, pivoted on the middle of its long axis, away from the inci- dent rays (this last reaction was similar to Case 1, Cor. 1, except that in the former instance the larva oriented back below). The final orientation was as in Case 2 (Fig. 14, B’). Whether the inci- dent rays were in plane 4, B, or C did not appear to make as much difference in the manner of orientation when the lobster was lying back below. It was observed that rays coming from above (plane 4) more frequently determined the backward rota- 268 ‘fournal of Comparative Neurology and Psychology. tion; and that rays coming from below (plane C)more often deter- mined a forward rotation. Case 3. Larva lying with the side downward; head toward light —In this case, the larva was oriented with one side uppermost and the head turned toward the source of light. The conditions may be represented by Fig. 14, if it be imagined that for the present case the larve are lying i in a horizontal plane rather than in the vertical as originally intended in this figure. The arrows 4, B and C’ represent rays in the same vertical plane, while (a), (b) and (c) represent them in a horizontal plane. When the light was admitted to a larva so oriented, the reaction was similar to that described undér Case 2. In the present instance, however, when the rays had the direction (a), the backward rotation was more likely to occur than when the rays had the direction 4 as in Case 2. Rays in the direction (b) or (c) almost invariably determined a for- - ward rotation, in which, if the larva was fatigued, 1t would merely turn through 180° in the same plane, and become oriented, still lying on the side, but with its head away from the source of light. Th however, the larva was fresh and active at the end of the rotation of 180° in the arc of a circle (4’), it would rotate through go° on its longitudinal axis and come into the normal swimming position with the back uppermost and the head directed away from the source of light. Case 4. Larva oriented with back above; head directed away from the source of light—When the larva was thus oriented and the light was so introduced that the rays streamed in a direction parallel to the longitudinal axis of the larva, no change in the body- orientation took place. The progressive orientation, however, might continue as either positive or negative. In case, however, the light came from the sides a or c (Fig. 15) the larva reacted by swinging (pivoted on the middle or end of its longitudinal axis) to either one side or the other, and it might then undergo positive or negative progressive orientation. If the direction of the rays changed through the seriés, a, b. c, the larva could likewise be made to swing as regularly as a pendulum and for long periods of time, according as the light came from one side or the other. Indeed the animal was quite at the mercy of the influence of light. In case the light came somewhat from above as shown in Fig. 16, A, the larva would incline itself farther forward, the num- ber of degrees of rotation depending upon the degree of the angle Haptey, Behavior of the American Lobster. 269 formed by A with the horizontal. When the angle was slight the forward rotation of the larva was but a few degrees, and it continued to swim in this body-position, and might undergo a positive or negative progressive orientation, as ordinarily. When, however, the angle between 4 and the horizontal was greater, the degree of rotation of the larva was proportionately greater, and in certain cases it might undergo a rotation of 180° and fall to the bottom. When, on the other hand, the incident rays struck the larva in the direction of C (Fig. 16), then the larva underwent a backward rotation whose degree was dependent upon the breadth of the Fic. 16. For description, see Case 4. Fic. 17. For description, see Case 6. angle between C' and the horizontal. If the angle thus formed was slight, the backward rotation of the larva was correspondingly slight, and it would continue to swim in the position designated C (Fig. 16), undergoing positive or negative progressive orienta- tion as other conditions of light might determine. If the angle formed between C’ and the horizontal was great, the degree of backward rotation of the larva was proportionately greater, and a fall to the bottom, tail downward, might result. Corollary 1—When the direction of the rays was determined by compounding the vertical series of light factors (4, B, C, Fig. 12) with the horizontal series (a, b, c, Fig. 15), the resulting reaction was a combination of the two types of behavior described above. 270 ‘fournal of Comparative Neurology and Psychology. Case 5. Larva oriented with back above and longitudinal body- axis at right angles to direction of light rays—When the larva was oriented as above and the rays were introduced at right angles to the longitudinal axis (Fig. 13, a’, c?) the behavior was similar to some phases of Case 1, Cor. 1. The larva swung directly away from the source of light until its longitudinal axis was par- allel to the light rays, with the head directed away from the source of light. Obviously the swing might cover from 1° to go” and either positive or negative progressive orientation might follow. If the larva was lying with the back below, but otherwise oriented as in the previous instance to the directive influence of the rays, the reaction was the same; namely, a swing to one side. This resulted in placing the longitudinal axis parallel to the rays of light. Frequently, in such case, the larva would undergo a rotation on its own axis, so that it assumed a position with the back uppermost and the head directed away from the source of light. Whether or not this “righting reaction” occurred, appeared to depend largely upon the degree of freshness. Individuals which had undergone fatigue more frequently refused to rise from the bottom. It was at no time possible, however, to fatigue the larve to such an extent that they would not give the “swinging-reaction ”’ into line with the light rays. By alternately changing through an arc of 30° the direction of the light which struck the larvee from behind (Fig. 15, a, b, c), they could be made to swing, pivoted on the middle or end of their longitudinal axis, in an arc of equal degree. This pendulum-like activity in answer to the change in direction of the light-stimulus was extremely constant and in no case was it observable that the reaction was diminished by fatigue in spite of long periods of such alternate directive stimulation. It may be added here that prolonged direct stimulation from behind never produced a change in the body-orientation of the larva. The progressive orientation, however, might take place in either the positive or the negative sense. Case 6. Larva oriented with back above; light enters from above —Under the conditions mentioned above, the larva was forced to give one or two reactions, depending upon the degree of intensity and the suddenness of introduction of the light: (1) In some instances (especially when the light had the direc- tion, b, Fig. 17), the larva first rotated through an arc of greater or less curvature and finally assumed a new swimming position Hapbey, Behavior of the American Lobster. 275 with the longitudinal axis of the body bent at a greater angle from the horizontal plane (Fig. 17, B’). This new swimming position was usually maintained so long as the conditions of light fémamed the same, but was sometimes replaced by the second form of reaction, which usually occurred when the light had the direction a, and which was merely an exaggerated form of the first. (2) In this second type of reaction the rotation of the larve was not limited to an arc of a few degrees, but was extended into a forward “somersault.’’ This in turn took place in one of two ways: (a) the larva might accomplish a rotation of 360° and return to its original position with the back above, but since the stimulation from above remained the same, it would not rest in this position, but would continue for a time to perform complete rotations without pause, after which it would come to rest as shown in Fig. 17, B’. “This new swimming position was sometimes maintained as long as the conditions of light remained unchanged, though it might give place to further rotations; (b) the larva might, as a result of the forward rotation, come to rest with the back directed below, but this orientation was only momentary, because the influence of the light from above immediately determined a backward rotation. ‘This last reaction might culminate when the larva had gained the new position shown in Fig. 9 B’, or it might be continued into one or more backward rotations oul 360° and culminate after a greater or less number of such rotations, by coming into the new swimming position mentioned above. This orientation would be maintained as long as the same condi- tions of light were in effect; or it might be interrupted from time to time by rotations in arcs of varying degrees, and in either of the directions mentioned above. Corollary r—If, when the larva was oriented as in Case 6, the light was introduced from both sides and above, the resulting reac- tion was a combination of the forward rotation and the side swing. If the light came from above and behind (Fig. 17, 5, then the direct assumption of the new swimming position B’ more frequently resulted without the variable number of rotations through 180° or 360°. Case 7. Larva oriented with back below; light enters from above —Under the above conditions of orientation (Fig. 18) there was usually one constant form of reaction. The larva would undergo a backward rotation through about 120°, and come into a new 272 ‘fournal of Comparative Neurology and Psychology. swimming position with the axis of the body bent downward several degrees from the normal swimming position (perhaps 45°from the horizontal), the exact amount appearing to be dependent upon the intensity of the light. ‘This new swimming position was usually maintained as long as the conditions of light remained unchanged. It might sometimes be interrupted by backward rotations through 360°. These rotations invariably culminated in the assumption of the new swimming position (Fig. 18, B). In case the direction of the rays was both from the side and from above the resultant reaction was a combination of the reaction described above and the direct side swing. Fig. 18. For description, see Case 7. Fic. 19. For description, see Case 8. Case 8. Larva oriented with back above; light enters from below —Under these conditions of orientation, the nature of the reaction was similar to that described in Case 6. Usually there resulted a direct backward rotation through a few degrees, which produced a new swimming position, Fig.19, B’. This was usually constant while the conditions of light remained the same, but it was some- times interrupted by backward rotations through an arc of greater extent, or even by a variable number of complete backward rota- tions through 360°. At the end of these, however, the new swim- ming position B’ was invariably assumed. Combinations of the Hap ey, Behavior of the American Lobster. 278 directions of the light (as both from the side and from above) produced modification in the reaction, but these could at any time be predicted if the individual constituents of the light were known. Case 9g. Larva oriented with back below, light enters from below —Under the conditions of orientation stated above the resulting reaction was similar to that described under Cases 6 and 8, but reversed. As in these instances, one of two results usually oc- curred: (1) The larva would undergo a forward rotation through a variable number of degrees, and assume directly a new “swimming-position’’ as shown in Fig. 20, 5’. It was readily observed that the head was directed upward and away from the Fic. 20. For description, see Case 9. light, not downward at an angle of about 30° from the _hori- zontal, as in the normal swimming position; (2) it might happen, however, that instead of assuming this orientation the larva would merely come to an orientation with the back below and with the head directed upward as a slight angle as shown in Fig. 20, C’. It might, again, undergo one or more complete rotations forward, through 360° and then assume the new position shown in Fig. 20, B’, which position might be retained as long as the light conditions remained unchanged. ‘The definiteness in these two reactions could be modifed, as a result of changing slightly the direction of the light. 274 ‘fournal of Comparative Neurology and Psychology. In addition to the facts regarding the effect of direct lighting upon body-orientation, which have been presented in the form of these nine cases, several other conditions might be mentioned: 1. Ifthe longitudinal axis of the larva was parallel to the direc- tion of the incident light rays, and the head away from the light, then the introduction of light produced no change in the body- orientation, but it might cause a positive or a negative progressive orientation. 2. In order that the unmodihed forward or backward rotation might occur, it was learned that the light rays must strike both eyes with equal intensity, and consequently in a direction exactly perpendicular to any transverse body-axis of the larva. 3. In case the incident rays came from a direction that was not exactly perpendicular to the transverse axis of the larva, be the angle of difference ever so slight, the perfect backward and forward rotation would not occur, but would be greatly modified by swingings of, and revolutions on, the longitudinal axis of the body. 4. This type of belavior could not be observed unless the con- ditions of light were reduced to a single directive influence, and this factor handled with very great precision. The effect of blocking the illumination—In the previous section we have examined the reactions which were brought about by suddenly introducing rays of light in directions which maintained a certain definite and specified relation to the longitudinal or trans- verse axis of the larval lobsters. In the present instance, however, we are to consider the nature of the reactions which are produced as a result of suddenly excluding or blocking the principal source of hight by which the larvz have just previously been stimulated. The “cut-off”? was made by closing the window through which the light came, and thus leaving the larve in the subdued and diffuse light which entered the dark box from the room. Since the body-orientation of the larvz to the directive influence of the light is always the same, obviously there could not be many differ- ent varieties of orientation caused by the change in the conditions of light. Such as were possible, however, may be described as follows: Case ro. Larva ortented with the back above and the longitudinal body-axis exactly parallel to the incident rays—In case the larva was oriented as described above, when the light was shut off Hap.ey, Behavior of the American Lobster. 2.75 there usually resulted a forward rotation through 180°. ‘This feaction . caused. the larva sto; becoine oriented (often on the bottom) with the back below and the head toward the previously existing source of light. “This position was not maintained, but was succeeded by a “righting reaction,’’ usually a revolution on the longitudinal axis, which brought the back again uppermost. After this response the larva might swim in diverse directions. Case 11. Larva oriented with the back above and the head away from the light, which comes slightly from the side—lf, when the larva was oriented as described above, the light was suddenly cut off, there resulted a swing of the long body-axis so that the larva was brought more or less nearly to face in the opposite direc- tion; i. e., in the direction from which the light had previously come. This orientation, however, was not permanent, but other consequent reactions occurred and the larva might swim in one of several directions. Case 12. Larva oriented as in Fig. 17, B’—If the direction of the light was from above, and the orientation of the larva as in Fig. 17, B’, when the light was cut off, the head of the larvae would swing upward to face the direction from which the rays had pre- viously come. Consequently, however, the orientation became that of the normal swimming position. f Case 13. Larva oriented as in Fig.20, B’—When, as the result of light stimulation from below (as in Case g), the larva was oriented with the head directed upward, and the illumination was sud- denly cut off, the head of the larva would swing downward to face the direction from which the light had previously come; sometimes the larva would perform a rotation in an arc of greater or less extent and fall to the bottom. The body-orientation with head down- ward was not maintained, however, but was at once superseded by the normal swimming position. It thus appears from these cases that there was usually an excess- ive movement to produce the new body-orientation; but that these movements invariably ended in the assumption of the nor- mal swimming position. Résumé of experiments on the effects of direct lighting and shad- ing—(A) The effect of suddenly submitting the larval lobsters to a light which has a directive influence is to cause the larve to orient themselves in such a manner that the longitudinal axis of the body finally assumes a definite relation to the direction of the 276 “fournal of Comparative Neurology and Psychology. light rays. This orientation is a position with the long axis of the body parallel to the light rays, and with the head turned away from the source of light. (B) The effect of suddenly blocking the light to which the larvae are reacting phototactically is to cause a new body-orientation by which the head is usually brought to face the direction from which the light had previously come. In either of the cases mentioned above the body-orientation is brought about by a single motor reflex or by a longer or shorter series of motor reflexes, some of which are “over-produced’’ movements. These movements include the following types: 1. Forward or backward rotations,’ or somersaults—These were rotations in an arc, of a few degrees, which directly determined a new swimming position with the head raised or lowered, depend- ing upon the direction from which the light or shadow had been introduced. In other cases these rotations took the form of a variable number of complete rotations through 360°, either back- ward or forward, in which the body of the larva formed a constant part of the circumference. 2. Revolutions on the longitudinal axis of the body or rollings— The revolutions or rollings took place either to the mght or left, but usually in such direction that the back of the larva became directed more or less toward the light. They might be through a few degrees, or they might exceed go°, in which case the larva fell to the bottom. In the case of larvae one of whose eyes had been injured this revolution took place very rapidly, oftne at the rate of one hundred and fifty per minute, and always in a deter- mined direction, the normal eye over, the injured eye under (Hap- .LEY 1907b). 2 Swingings of the longitudinal axis of the body—These reac- tions were swingings in eich a direction that the head was brought by the shortest path to face the dark, and the tail to point toward the light. ®°Three similar types of movement are described by Boxn (1905, p. 4) as follows: 1° Mouvement de manége—lanimal décrit un cercle de plus-ou moins grand rayon, l’axe du corps, Spice en arc, faisant partie constamment de la circonférence; la rotation se fait tantét dans le sens des aiguilles d’une montre, tantét dans le sens inverse. Parfois, au lieu de décrire un mouvement de manége Bs = animal décrit des courbes de rayon variable qui constituent une sorte de spirale. ° Mouvement de rotation en rayon de roue—l’axe du corps ne dévie pas; il est une des parties d’un nae rayons du cercle décrit, et non une partie de la circumférence du cercle: la téte peut se trouver a la circonférence ou au centre. 3° Mouvement de rotation sur axe, ou roulement: Yanimal tourne autour d’un axe longitudinal qui traverserait le corps dans sa longeur; la rotation commence par une inclinaison de Panimal d’un cote, et le sens de la rotation se trouve ainsi determiné. Le roulement peut s’accompagner d’un mouvement de translation et devient un mouvement en pas de vis. HaDLeEY, Behavior of the American Lobster. 277 4. Rotations in the radit of a circle—In these the longitudinal axis of the larva formed a radius, and with either the head or the tail at the center the animal rotated about a fixed point. ‘These reactions were uncommon and, as yet, unexplained. These four types of movement seldom occurred separately, except under especially devised experimental conditions. Under natural conditions, they were usually combined to form a compos- ite action. ‘To the previously mentioned simple components, how- ever, all the more complex movements of the larval lobsters could be reduced. B. ‘THe Errecr oF SCREENS AND BackGRouNnpDs—lIt 1s prob- able that the reactions which are brought about through the use of backgrounds, are, generally speaking, dependent upon the same factors and conditions of illumination which are effective when light-absorbing or light-scattering screens are used. ‘The term “screening” has been employed by Boun (1905) to designate his method of submitting organisms to the influence of surfaces of light and shade. This i investigator made use of screens of black and white of such size that he could readily bring them close to the sides of the glass containers in which the organisms under observa- tion were placed. He has made a special study of the reactions of Crustacea to the influence of such screens, and in several instances the observations of the writer upon the larve of Homarus ameri- canus merely confirm certain points in Boun’s earlier work. In many instances, however, new facts have been added. T he influence of white screens—The lobster larve were confined in a cylindrical jar, crystallization dishes, or in a rectangular glass container. The latter was used most frequently. The larve were then placed in the dark box and this was illuminated in such a manner that a general twilight was produced and the directive influence of light was ata minimum. While making observations it was even found necessary that the writer should wear a black mask over his face and collar, and, often, darken his hands in order not to modify the uniform light. For white screens pieces of white cardboard were employed, and brought over, under, or beside the receptacle containing the larve, as the case might re- quire. Sometimes the screen was brought gradually toward the container, sometimes abruptly; but in all cases the results were definite and agreed with great uniformity. In order to secure the best results with the white screen, it was found best to reduce the 278 “fournal of Comparative Neurology and Psychology. intensity of light within the dark box below the degree used in the case of the black screens. The results of the series of experi- ments with white screens may be summarized as follows: Case 14—When the larva wasoriented with back above and the screen, held vertically, was so introduced from before that its plane was at right angles to the longitudinal axis, and parallel to any transverse axis of the larva, there resulted a rotation through 180° with, perhaps, a fall to the bottom. After this, and as a result of a revolution on the body-axis, a “righting reaction” usually occurred and the back would again be brought above. Now, with the head directed away from the white screen, the larva might either approach or depart from it, according as the pro- gressive orientation was positive or negative. Sometimes, instead of producing a rotation through an arc of 180°, the larva under- went a series of rotations, its body forming a constant part of the circumference. The final orientation mentioned above would, however, invariably succeed. In case the screen was not held squarely before the larva, but somewhat at an angle to any transverse axis, the consequent reaction was a direct side swing away from the screen in order to place the longitudinal body-axis perpendicular to, and the head away from, the screen. In other cases there resulted a combination of the side swing and the for-. ward rotation, so that the larva performed a sort of “half-somer- sault,’’ and eventually assumed the normal swimming position, with the head directed away from the screen, as pointed out above. Case 15—When the larva was oriented with the back above and the screen, held vertically, was made to approach the posterior end of the larva, no change inthe body-orientation resulted. There might occur, however, either a positive or a negative progressive orientation. Case 16—In this case the larvae were swimming promiscuously about the container. When the screen was made to approach larve which held a position with the back above and one side turned toward the screen, these larve experienced a swing of their longi- tudinal axis so that the head came to be directed away from the screen and the longitudinal body-axis at right angles to the plane of the screen. Case 17—-When the screen, held horizontally, was made to approach, from below, a larva which held the normal swimming position, one of two reactions(which probably represent different Haviey, Behavior of the American Lobster. 279 degrees of the same reaction) resulted: (1) The larva would swing the head upward as shown in Fig. 20, B’, and maintain this swimming position so long as the light Sonne remained un- changed, or (2) it might, on the other hand, experience this same reaction in an exaggerated form, i. e., dies might result a back- ward rotation through 180°, which reaction would cause the larva to fall to the bottom and to assume a position with the back below and with the head directed upward at a slight angle as shown in Fig. 20, C’, Usually, however, this form of orienta- tion resulted only when the light was of greater intensity, such as that secured in cases of direct illumination. Case rS—When the larva was oriented in the normal swimming position and the white screen was made to approach from above, the reaction was similar to that described for Case 6, p. 270. The one difference was that while the direct lighting ahs caused a number of complete rotations through 360° before the final body-orientation was assumed, the white screen, on the other hand, usually acted by changing the swimming position directly to that of Fig.17, B’. This difference in response was probably due to the difference in the intensity of light (direct or reflected) coming from above. The black screen—The method of conducting the experiments with the black screen was almost the same as that for the white screen. ‘There was one point of difference. It was found that, in order that the black screen should determine any reaction of the larvee, it was necessary to have a slightly greater illumination with- in the dark box. The following report of cases shows the result of making the screen to approach, from various directions, the larve diversely oriented. Case 19 —When the larva was in the normal swimming position and the back screen was presented opposite the head, and at right angles to the longitudinal axis, the orientation was not changed, but was retained constantly so long as the screen remained in position. Case 20—When the larva was in the normal swimming position and the screen was made to approach from behind, so that its plane was parallel to a vertical plane passing through both eyes of the larva, there usually resulted a forward rotation of 180° in the arc of a circle. ‘This reaction brought the back of the larva below, and the head toward the black screen. This position was — 4 i ae 280 “fournal of Comparative Neurology and Psychology. at once further modified by a revolution of 160° on the long body-axis, either to the left or right (determined by the nature of the lateral or secondary illumination), and the larva again assumed the normal swimming position, but with the head directed toward the black screen. In case the plane of the screen was not exactly parallel with the vertical plane passing through the eyes of the larva, the reaction was not represented by the simple forward rota- tion, but was modified by side movements. Case 21—When the larva was in the normal swimming position and the black screen approached from the side, several reactions might occur. Most commonly the larva underwent a swing of its longitudinal axis so that the head was brought to face the screen. Another reaction sometimes observed was a rolling, or revolution, on the long body-axis, in such a manner that the back moved away from the screen. At the same time there occurred a swing of the longitudinal axis which caused the head to be directed toward the screen. These two reactions might occur simultaneously, and the resulting reaction be a blending of the two components mentioned above. ‘The rolling on the longitudinal body-axis was seldom over go° from normal (back above), usually less. Yet in cases where the illumination in the dark box was greater, or when the screen was introduced suddenly, the rolling motion might exceed go°, and the larva fall to the bottom of the container. Case 22—In this instance the larva oriented in the normal swim- ming position and the screen was made to approach from above. This combination produced several forms of reaction. In cases where the general illumination in the container was not great, the larva merely experienced a slight change in the direction of the longitudinal body-axis; the head assumed a superior position, so that the long axis of the body was nearly horizontal, or even directed upward at a small angle, rather than bent downward at an angle of 30° from horizontal, as in the normal swimming position. On the other hand, if the illumination was greater, the larva might undergo a rotation on its own longitudinal axis through 180° and fall, back downward, to the bottom. What- ever reaction occurred, it could be explained as an effort of the larva to turn the head toward the black screen, and the degree to which this was attained depended very much upon the intensity of illumination throughout the container. The type of reaction mentioned above was demonstrated to better advantage Hap ey, Behavior of the American Lobster. 281 in the following experiment. A large tube containing a number of larvee was placed in an upright position on the laboratory table, and the upper half covered with a roll of black paper. The larvze gathered in the more brightly illumined end of the tube, which was below. So long as they swam in the lower part of the illuminated area, they assumed the normal swimming position, but whenever they came into the upper regions, and approached the edge of the black paper, the direction of the longitudinal body-axis was changed from 30° below horizontal to 30° or even more above the horizontal plane. Case 23—In the following case the larva was oriented in the normal swimming position and the screen was made to approach from below. As a result the larva usually reacted by a slight for- ward rotation, the head passing through an arc of a few degrees, and producing a still greater angle between the longitudinal axis and the horizontal plane. ‘This new swimming position was sel- dom subject to further modifications so long as the light conditions remained unchanged. Regarding the reactions of the larve of Homarus vulgaris under similar experimental conditions, BoHN (1905, p. 11) remarks: “Si la larve nage le dos dirigé le haut, il y a roulement de go° ou de 180°, la par suite la larve dévie laterale- ment ou tombe.” Such a result as the above was not observed by the writer. On the other hand, it was observed that, whatever the body-orienta- tion of a group of larva might be previous to the approach of the black screen from below, its presence usually determined a rise of the larvae from the bottom of the container to the upper waters, where normal swimming was manifested so long as the screen beneath remained in place. When it was removed, however, or replaced by a white screen, the consequent réaction was, as we have already seen, characterized by rotations and revolutions through go° or 180°" ‘These reactions in turn resulted in bringing the larve again toward the bottom, and in determining a consequent absence of larvz in the regions near the surface of the water. Case 24—In this instance the larve were oriented with back below, and the black screen was made to approach from behind in such a manner that the plane of the screen was parallel with a vertical plane passing through both eyes of the larva. Under these conditions (see Fig. 14, 4’) the reactions were as follows. When the black screen. G. was introduced, the larva, 4’, under- 282 “fournal of Comparative Neurology and Psychology. went a forward rotation through an are of 180°, and assumed the normal swimming position, 5’, with the back uppermost and the head facing the screen. ‘This orientation was maintained with a greater or less degree of constancy so long as the conditions of light remained the same. If, on the other hand, the screen was so placed, or the larva had such a position, that the plane of the screen was not exactly parallel to the vertical plane passing through the two eyes of the larva, a different reaction was expe- rienced, In this instance the first response was a revolution on the longitudinal axis, usually through 180°. This resulted in bringing the back of the larva uppermost, and was usually fol- lowed by a swinging of the longitudinal axis, which brought the head to face the screen. The direction of this side swing (to the left or the right) was determined by the angle which the longitu- dinal axis of the larva made with the screen. For instance in Fig. 15, the larva designated 4’ would swing to the right, while the larva designated C’ would swing to the left, each in the direc- tion indicated by the arrows. In other words we may say that the larva would swing in that direction which brought the head, by the shortest course, to face the screen. But the two reactions men- tioned above might, as in previous cases, be blended to form a composite reaction, which differed from either of its simple com- ponents. Case 25—In the present instance the larva was oriented lying on its back and the screen was introduced from before. Under these conditions, as in Case 19, there was no modification in the body- position. In certain instances the larva underwent a revolution through 180° on its longitudinal axis and assumed a position with back above and head still directed toward the black screen; butin the great number of cases the orientation remained un- changed. Case 26—In case the larva was oriented with the back below and the screen was made to approach from the side the reactions were as follows. ‘The larva experienced a rolling or revolution on its longitudinal axis, in consequence of which the back moved away from the screen through an angle of 90°, occasionally more. At the same time there was a swinging of the longitudinal axis, itself, so that the larva came face to face with the screen, eventually with the back uppermost. During this reaction the larva often departed from the screen. As in Case 21, mentioned Hap ey, Behavior of the American Lobster. 283 above, these two reactions might occur at the same time, and then the resulting reaction was a composite. Case 27— “In the present case the larva was oriented with back below and the black screen was introduced from above. Under these conditions it usually underwent a slight forward rotation with a consequent rise from the bottom, and came into a new swim- ming position with the longitudinal axis directed somewhat upward as shown in Fig. 20, B’. Case 28—In this instance the larva was oriented with back below and the black screen was introduced from beneath. ‘The reac- tions were usually as follows. The larva underwent a revolution of about 180° on its longitudinal axis, and assumed practically the normal swimming position, with the back uppermost and the head bent downward at an angle of about 30°. In other cases, however, this new position was brought about by a different sort of reaction; namely, a backward rotation through an arc of 180°. This resulted in throwing the larva again into the normal swim- ming position. Generally speaking, we may say that, when black or white screens were made to approach larve of any one of the first three stages, diversely oriented, the larva manifested two forms of re- sponse. First, a motor reflex, which tended to place the longitu- dinal axis in a certain relation to the plane of the screen; secondly, and subsequent to the first response, a progressive orientation, toward or away from the screen, as the luminosity of the screen, the physiological state of the larva, and other conditions of the case, determined. Whenthe white screen was used, the larve commonly became oriented with the head directed away from the screen. In the case of black screens, on the contrary, the head was directed toward the screen and the back more or less away. These reactions occurred whether the screens were made to approach from above, below, behind, or the side. After body- orientation had taken place, the larvae might approach or recede from the black or the white screen, according as they were reacting positively or negatively. The mechanics of reaction upon which orientation to the screens was found to depend, agree, for the greater part, with the types of reaction to black screens reported by BoHN (1905), who has made a careful study of the effects of causing a black screen to approach the larve of Homarus vulgaris, diversely oriented. There are, 284 fournal of Comparative Neurology and Psychology. however, certain disagreements. First, it is certainly true that bringing the black screen parallel to the longitudinal axis of the larva frequently determined a rolling of the larva on its own lon- gitudinal axis, whatever the original orientation may have been. But in Case 21, certain orientations of the larva were noted in which these rollings did not occur. It is true, moreover, that the progressive orientation often took place in that direction in which the back was directed. But several instances were observed wherein the orientation to the black screen resulted merely from a swinging of the longitudinal axis of the larva so that the head was directed toward the screen and where consequent progressive orientation was either a movement backward or forward, head foremost or tail foremost, as in positive or negative phototaxis. We have now examined somewhat in detail the effects of sudden illumination and of sudden shading, the effects of white screens and of black. If we now compare the detailed results of these studies, we note that the effects produced by introducing a white screen are comparable with those obtained by suddenly admitting illumination, while the results brought about by black screens are comparable to those determined by suddenly cutting off the light. In other words, the larve appear to respond to the influence of screens of black and white by reactions which are dependent upon the same simple forms of response observed under the con- ditions of direct lighting and shading. In view of this correspondence in the nature of reaction to direct lighting and to screens of black and white, it may be considered probable that the screens and backgrounds are instrumental in determining the behavior of the larve, only in so far as they are themselves the source of (reflected) illumination. Thus, when the black background causes a swing of the larva, as a result of which it comes to face the screen, we cannot say that the primary factor is the blackness of the screen; but rather that the small amount of light reflected from the screen permits rays of light from other directions to become effective, The larva “heads” to the black screen because his eyes encounter no light rays coming from this direction; and he turns away from the white screen because his eyes encounter stronger reflected light from this than from any other direction. The effect of backgrounds—The question of the influence of backgrounds in determining the orientation of crustacean larve Hap ey, Behavior of the American Lobster. 285 has been brought forward by KEEBLE and GaMBLE (1904). Aside from the effects of screening, the more general problem of back- grounds did not receive especial attention in the course of the pres- ent investigation, but, as we shall see, the question of screening which we have discussed in the preceding section is probably only a single phase of the problem of backgrounds. The following experiments which were performed more or less at random in connection with other experiments, but which deal with the ques- tion of backgrounds, may, however, be presented. By the term background, as it is used in the present case, is meant the permanent color-tone of the surrounding walls (as a whole or in part) which confined the young larve. This condi- tion was somewhat different from that determined by the use of screens which were movable and could be placed at any angle with reference to the body-axis of the larve. Backgrounds were employed in several different ways. ‘They were sometimes repre- sented by the black or white lining of the reaction boxes; again, by the ground upon which the glass dishes or tubes rested, and in still other cases by the outer covering of these dishes, or tubes. The subject may be considered under two heads: (1) the effect of backgrounds in connection with the purely photopathic response ; (2) their effect in determining the “choice” of a particular region of light-intensity when phototaxis also is operative. In view of the fact that the investigation of the first phase of this problem was not undertaken in the present work, we may pass directly to the consideration of the second point stated above. T he effects of backgrounds in connection with both the phototactic and the photopathic ‘res ponse—Under this head we may consider those conditions of experiment, which, although they be chiefly productive of reactions to the directive influence of the light, never- theless were modified by response to the intensity of the light. These conditions were secured by the use of Y-tubes. The fol- lowing experiments serve to show why, in the case of the larval lobsters, the tendency to gather in the brighter areas (assumed positive photopathy) is often associated with positive phototaxis; and why a tendency to gather in the darker areas (assumed nega- tive photopathy) may be associated with negative phototaxis. In the diagrams of Fig. 21 are represented the Y-tubes as set up for experiment. ‘Those whose arms are above were arranged for experiment with larva having positive phototactic reaction; those 286 ‘fournal of Comparative Neurology and Psychology. whose arms are at the bottom, for larve having a negative phtoto- tactic reaction. In tubes 4 and B one side of one arm was fitted with a band of black paper which extended half over the circum- ference of the arm and a very short distance down each stem. In tubes C and D the same arrangement existed, save that white instead of black paper was used. In every case the light rays came from the window in the direction of the arrows. In all cases of larvae manifesting a negative reaction, the start was made at the end of the tube (lying horizontally on the table) nearer the window. In the case of positively reacting larva, the start was made from the end of the tube farthest from the window. The end marked a in every instance was the end from which the larve moved, the purpose of the test being to determine in which arm of the tube the larve would eventually gather. A B c D E F Fic. 21. Showing the Y-tubes set up for experiment. In every case the light came from above in the direction of the arrows. The tubes whose arms are above were set up for positively reacting lobsters; those whose stems are above, for negatively reacting lobsters. In tubes 4 and B the cross- hatched areas represent the part covered with black paper. In tubes C and D the clear area was covered with white paper. Tubes E and F are shown equipped with the glass plates placed over the arm. In every instance the larve were started from the end of the tube designated a. For further explanation, see Cases 29-33 inc., pp. 286-289. Case 29—The tube was arranged asin Fig. 21, 4. Ten posi- tively-reacting, first-stage larvae were placed in the Y-tube, and, by certain manipulations of the light and by virtue of their positive reaction, they were made to congregate inthe stem end. Then suddenly, the direction of the light was changed so as to come in the direction of the arrows. Immediately the larve oriented with their heads toward the end a, and passed through the tube toward the light. As soon as they approached the region marked x they came under the influence of the dark background bounding the side of the tube. Immediately, as we have seen to be the case in previous instances, the longitudinal body-axis swung so that the HaDLeEY, Behavior of the American Lobster. 287 head came to face, more or less obliquely, the dark background, B’. The directive influence of the rays, however, continued to draw the larve on, but since they must travel in the direction in which the tail pointed, they entered the arm /, and passing close to the inside continued until further progress was prevented by the end of the arm. Space will not be taken to show the numerical results of this and similar experiments. Sufhce it to state that nearly all of the positively reacting larve, of whatever stage or age, when submitted to these conditions of experiment, feared as has been described above. This experiment was modified by placing the Y-tube so that the uncovered arm of the tube rested upon a piece of black paper. The results were invariably the same; the majority of the larve progressed to the arm of the tube not overlying the black ground. Case 30—In this case the conditions of the experiments were further modified by reversing the Y-tube so that the arms pointed away from the window. In this instance larve which were mani- festing a negative reaction were employed, and were first placed in the: end (a) , nearer the window. When the light was admitted the larvae at once oriented with their heads directed away from the light and began to move away from the window. When they had reached the point designated x, they immediately underwent a swing of the longitudinal axis, as in previous cases, so that the head was directed toward the blacks ground, bounding the outer surface of the arm c. Thus they would continue, passing close to the inner wall of the tube until the majority had gathered in this arm. In this instance, however, the larve would usually rest between x and c, instead of moving to the end of the arm. Case 31—Here the black background bounding the outer side of one arm was exchanged for a white ground of the same size and having the position shown in Fig. 21 C. Third-stage larve giv- ing a positive reaction were employed for the experiment. They were started in the end a. When the light was admitted, the usual body-orientation resulted, and the larve began their progression through the tube toward the window. When they had arrived at x they came under the influence of the white ground and turned their heads away from this side. Progressive orientation then con- tinued and the larve eventually became grouped in arm c. Sim- ilar results were obtained when half of this arm of the tube was laid over a sheet of white paper. 288 “fournal of Comparative Neurology and Psychology. Case 32—The previous experiment was further modified by reversing the Y-tube so that the arms were directed away from the window (Fig. 21, D). Larvae which were giving a negative reaction were employed. ‘They were placed in the end a, and the light was admitted. After the usual body-orientation had taken place, the progression away from the window began. When the larve reached the point x, and had come under the influence of the white ground bounding one side of the tube they would swing their heads toward the right and continue their progress until all were gathered in arm c. This was somewhat unexpected. It eventually trans- pired, however, that the white ground bordering the outer surface of the tube did not act as a reflector or intensifier of the light rays, but as an opaque shield, cutting off the rays which would other- wise have entered the arm c. ‘Thus, as in Case 30, the negatively reacting larva had merely grouped themselves in the arm where the light was least bright. When the Y-tube was so placed that half of arm c rested upon a sheet of white paper the result was differ- ent. The larve congregated in arm J, which was, under these con- ditions, the region of least light intensity. Case 33—The four cases mentioned above were supplemented by other experiments involving the use of colored glass plates. As described in Experiment 15, these plates were so placed over the arms of the Y-tube that a difference in the intensity of light striking one arm was caused by interposing a red, orange or yellow glass plate between that arm and the source of illumination. In these cases the positively reacting larve gathered in the arm where the light- intensity was the greater, while the negatively reacting larve grouped themselves in the arm where the light was least bright. As a rule, the larve of earlier stages seemed to be more susceptible than the others to slight differences in the intensity of light at the entrance to the arms. Thus is explained the tendency for positively reacting larve to gather in regions of greater light-intensity, and on the other hand, the tendency of negatively reacting larvae to congregate in regions of lesser light-intensity. This condition of affairs has, no doubt, given many investigators reason to believe that such reactions are but manifestations of a positive photopathy; and that photopathy and phototaxis are fundamentally the same. We now know, however, that the reaction just described in Case 5 is due to the combined effects of two tendencies; the one to turn the head Hap ey, Behavior of the American Lobster. 289 toward the dark areas (areas of non-stimulation); the other to move in the direction of the longitudinal axis of the body either toward or from the source of light. Were we dependent upon such experiments as these for our belief in the existence of a sep- ‘arate response to light-intensity, regardless of directive influence of light, we might well say that the photopathic and phototactic responses are, in the end, one and the same. But the writer has adduced in the previous section other data which separate more clearly these two types of reaction. VII. ANALYSIS. It has for some time been the custom to state that certain organ- isms are positively phototactic or positively photopathic, and that other organisms are negatively so. The index of reaction for several crustaceans has been so recorded, but the observations are usually incomplete, often uncritical, and sometimes of ques- tionable significance. It is true that, in a very general way, organ- isms react positively or negatively to light. For instance, it may be said that the lobstershuns the light, that Palemonetes is attracted by the light, and that the larve of Limulus avoid the light. The definite statement, however, that the larve of Limulus are negatively heliotropic, or that Palemonetes and larve of Homarus are positively phototactic, is as inadequate as would be a biography written on the basis of a single day’s association with a human ind1- vidual. It may be true that by the time the adult stage is reached, the reactions of many animals have become more or less stereo- typed, so that reactions like those of the moth to the flame, are easily predictable. In the larval and adolescent stages, on the other hand, the reactions are frequently more variable. ‘To say that the lobster of the second larval stage is positively phototac- tic or positively photopathic is, as has been demonstrated, by no means a correct interpretation of the facts of the case, for slight changes in the conditions of stimulation may be sufficient to reverse the index of reaction. This variability doubtless occurs in many arthropods. It thus becomes evident that, although the young lobsters may be regarded as machines upon which many different external forces act and cause certain reactions, still (except for the definite body-orientations which are invariably determined by the directive influence of the light rays) they are 290 “fournal of Comparative Neurology and Psychology. machines the nature of whose operations can seldom be predicted unless the age, the stage, the kind and degree of the stimulus, are accurately own here conditions of reaction indicate the extent to which the behavior of young lobsters is determined by their physiological states; and the foregoing experiments show in what way these physiological states change, not only from one stage-period to another, but even during the same stage-period, through the influences of metabolism, development, and perhaps still other factors. “The extent to which the natural behavior of animals in their natural environment can be explained on the basis of the results of laboratory experiments depends largely upon the animal and the kind of reactions involved. It is quite probable that some of the characteristics of reaction, which have béen de- scribed in the present paper, determine in alarge measure, the daily behavior of the larval and early adolescent lobsters when they are in their natural environment. Unfortunately, however, we know too little regarding the behavior of lobsters under natural condi- tions, to attach great importance to far-reaching explanations of their daily activities on the basis of laboratory experiments. A few points, however, may be noted. The reports of biological surveys make it clear that, at the surface of the ocean or of bays in which lobsters are known to live and breed, the stage most often taken in the tow-nets is the fourth; the larval stages are much less frequently found, the fifth stage seldom, and later stages never. Observations which were made on lobsters of different stages taken from the Wickford hatchery and liberated in the surround- ing waters of Narragansett Bay yield similar evidence regarding the immediate natural distribution. In these cases the lobsters of the larval stages were found to swim for a brief time, then grad- ually disappear from the surface; the fourth stage lobsters swam actively at the surface so long as they were observed; while the fifth and all later stages plunged at once into the deeper water and were immediately (eae to sight. As the writer has already suggested, it is impracticable to attempt to explain the natural behavior of larve of the first three stages, on the basis of the reactions which have been discussed at some length in the present paper. ‘The light (depending upon its intensity “and directive influence; and upon the age, stage, and previous condition of the larva) may determine at one time a posi- tive, at another a negative, response, so that the general reaction Haney, Behavior of the American Lobster. 291 of groups of lobster larve can in no way be readily predicted. One exception to this may be stated. ‘The first-stage larvee, directly after hatching, would be strongly drawn to the surface of the water by virtue of both their photopathic and of their phototactic response. After the first day or two, however, begins that modi- fication and variation in the phototactic action which, for groups of uncertain age and condition, makes any accurate prediction of their movements quite impossible. In the case of the fourth-stage lobsters there 1s a better basis for the correlation of the natural and experimental types of behav- ior. We know that, under experimental conditions, hungry fourth-stage larvae, when submitted to food stimuli, will rise imme- diately to the surface of the water and swim about excitedly for some moments; we know also that the early fourth-stage larvee, under certain experimental conditions will leave a region of low light intensity and remain in regions of greater light intensity. We have learned, moreover, that the same fourth-stage larve, under different experiméntal conditions, will usually shun the light when it has a single directive influence, and travel in the direc- tion of the rays away from their source. Finally, we have observed that the fourth-stage lobsters, except in the latter part of the stage- period, show a definite tendency to remain at the surface of the water. The question now arises: What is the cause of this surface- swimming? Is it a response to the intensity of light, to the direc- tive influence of light, to hunger, or to gravity? Although we know something of the effects of several of these factors when they act separately, it is difficult to ascertain their individual influence when they work in combination. If, however, we can discover any parallel between a certain type of reaction under experimental conditions and a certain mode of behavior under natural conditions, and find that as one is modified or lost the other is also, then, and then only, are we justified in believing that we know the deter- mining cause of the particular type of natural behavior in question. We have such a parallel between the photopathic (and occasionally the phototactic) reactions and the surface-swimming tendency of the fourth-stage lobsters. As the former becomes modified and is eventually replaced by the negative reaction, so the latter is changed and finally gives way to the bottom-seeking tendency as the lobsters pass on through the fourth stage-period. With 292 Fournal of Comparative Neurology and Psychology. such a parallel before us, it cannot be doubted that there exists a certain causal relation between the positive photopathic reaction and the surface-swimming tendency on the one hand, and the negative photopathic reaction and the bottom-seeking tendency on the other. But the photopathic reaction may not alone be respon- sible for the surface-swimming tendency on the part of the fourth- stage lobsters. The presence of food particles in the water excites them strongly, and causes them, when in the glass jars, to swim excitedly at the surface of the water. It therefore appears quite within the bounds of possibility that chemotropism may also play a part in determining the surface-swimming of the fourth-stage lobsters. The explanation of the behavior of the fifth and all later stages, in the light of the foregoing experiments, rests upon a more certain basis. We have observed that the fifth-stage lobsters invariably manifest both a negative phototactic and a negative photopathic reaction. In general this may be said to explain the fact that lobsters in the fifth and all later stages shun the light at all times. Little work was done on the behavior of the older lobsters, and it is hoped that future investigations may continue along this line. In connection with the mechanics of orientation, the writer has shown that the reaction of larval lobsters to light is made up of two components—body-orientation and progressive orientation; and that the former is primary while the latter is secondary. In the earlier pages of this paper it was demonstrated that the progressive orientation is dependent upon a great number of conditions, and that the orientation responses are relatively complex reactions which are dependent in great measure upon the obscure, changing, internal conditions which are embraced under the general term, “physiological states.”’ In later pages, on the other hand, atten- tion has been directed to those conditions of light which deter- mine the body-orientation alone; and the results recorded have made it clear that the movements producing the body-orienta- tions are types of action which simulate more closely pure reflexes, direct, constant, and invariable. As Bown (1905a) has well said, it is impossible to take definite account of the complicated series of phenomena which take place in the nervous system of animals even as low as the arthropods, for these are dependent not alone upon complicated connections between neurons, but also upon their variable states. Yet it 1s Hapbtey, Behavior of the American Lobster. 2.93 apparent that this difficulty applies rather (at least in the reactions of the larval lobsters) to those movements which determine the progressive orientation to light, than to those which determine body-orientation. ven in the latter somewhat less complicated and more easily explained phenomena, however, we are still far from recognizing the underlying causes. It is true that we can understand in a way why the “ posterior position” of the thoracic appendages determines a negative response, while the “anterior position’? determines a positive response. We can, moreover, understand why a more intense illumination of the eye on one side causes a greater activity of the swimmerets on that side, and a consequent swing of the larva away from that side. “This phenomenon was well shown by experi- Fic. 22. Diagram showing the rostrum and one eye of a larval lobster; a, b, c, d represent direction of light striking the eye from behind, below, in front and above; a./.s. represents posterior lateral surface; p./.s. represents anterior lateral surface. For further explanation, see p. 297. ments which the writer performed upon larve with blinded eyes (HapLey 1908). These experiments demonstrated that, when the right eye was blinded, the direction of forward swimming was invariably to the right; in other words, the exopodites beat more vigorously upon that side of the body whose eye was most stimu- lated, and the larva was, in consequence, “pulled around”’ like a boat. These reactions are explainable on the grounds of a heterolateral stimulation and a consequent unequal action of the muscles on the two sides of the body. But we do not understand as clearly how or why the action of the light striking with equal intensity the corresponding areas of the posterior surface of the eyes (Fig. 22), for instance, brings about these “anterior” or “posterior” positions of the thoracic appendages, and the con- 294 “fournal of Comparative Neurology and Psychology. sequent positive or negative reactions. Nor do we understand why, when the larva is in one “ physiological state,’’ a certain inten- sity of light (striking equally the posterior lateral surface of the two eyes) causes a positive reaction, while if the same larva is in another “physiological state,” the same light (striking with the same intensity the same parts of the eye- -surfaces) causes the oppo- site reaction; or again, why when the larva is in the samme “ physio- logical state,” one intensity of light causes a positive reaction, while light of slightly less intensity determines a negative reaction. No more do we know why the illumination of the upper surface of the eyes (Fig. 22,d) causes a forward rotation; or the illumina- tion of the lower surfaces (b), a backward rotation; or the illumi- nation of the anterior surface (c), a forward or a backward rota- tion. These as yet unexplainable conditions of reaction may well convince us that, however simple and mechanical some of these reactions appear to be, many of them are extremely complex, and indicate a very complex relation between the different regions of the eyes and the nervous centers. Yet, as has been stated, to such a degree as any of these reactions can be explained, those which are concerned in the processes of body-orientation are more easily interpretable on the “‘simple-reflex’”’ hypothesis. In view of this fact the writer would differ from the conclusion reached by Boun (loc. cit., p. 41): ‘‘ Tous ces phénoménes (the reactions of larve of Honaris vulgaris) sont en relation avec des états physiologiques particuliers. Sous influence de léclairement, l’état physiologique des larves de homard ne tarde pas a changer, et les tropismes aussi.” The present writer would limit the appli- cation of this theory to those reactions of the larval lobsters which are concerned with progressive orientation, excluding body-orien- tation. Regarding the relation of the type of reaction found in the larval lobsters to the tropism theories, inference has already been made in the preceding paragraphs. First, to what extent does the behavior found in the larval lobsters agree with the local action theory of tropism? The primary demand of this theory is that the body of the organism should become so oriented with respect to the source of illumination that the anterior end is made to point either toward or from the source. Under these condi- tions the index of reaction is said to be positive or negative, accord- ing as the organism moves toward or from the light. “This Hap ey, Behavior of the American Lobster. 295 orientation is produced, according to this tropism theory, by the direct action of the stimulating agent on the motor organs of that side of the body on which it impinges. A stimulus striking one side of the body causes the motor organs of that side to contract or extend or to move more or less ‘strongly. This, of course, turns the body till the stimulus affects both sides equally; then there is no occasion for further turning and the animal is oriented” (JENNINGS 1906a, p 206). This is also brought out by Hott and LEE (1901, p. oe “The light operates, naturally, on the part of the animal which it reaches.”” Thus, this tropism theory requires that, in order to determine the direction of movement, the stimulus must act more strongly on one side of the body than on the other. It is needless to say also that in the majority of cases the same conditions of stimulus which cause an animal to direct the head away from the source of the stimulus, also determine a movement in the same direction. ‘Therefore, if we separate, as has been done in this paper, body-orrentation from progressive orientation, We can say that, in most organisms, the index of body- orientation agrees with that of progressive orientation; the con- ditions of stimulation which cause the one likewise determine the other. Let us now see to what extent the behavior of the larval lobsters agrees with these requirements of the local action theory of the tropisms. In order to treat the matter concretely we must consider it under two heads. First, body-orientation; then, progressive orientation. It has been shown in the previous pages that, whatever the sign of progressive orientation may be, the body- -orientation 1s invari- ably negative; and that this body-position is produced as a result of diverse reactions which are attributable to the relative inten- sities of light which strikes the eyes of the larve. This body- orientation, moreover, 1s consta t; it is not dependent upon the age, stage, previous st mulation, hunger, “physiological state,” or upon any modifications of the external stimulus, such as changes in intensity, duration of stimulation, etc. The orienting reaction always comes about in the same way, so that we here have a case where the “same-stimulus-same-reaction” principle invariably holds. In other words, the reactions by which the larval lobsters secure the characteristic body-orientation are typical and invari- able motor-reflexes. Beyond producing the body-orientation, the direct motor-reflex 296 “fournal of Comparative Neurology and Psychology. ceases to influence the behavior of the larval lobsters. From this moment on, a multitude of conditions appear to be brought to bear to determine the consequent progressive orientation of the young animals in one sense or the other. No longer can we say, “same stimulus, same reaction’? (SPAULDING 1904), for there is now no constant form of reaction even to the same stimulus. The reactions appear to be no longer so dependent upon the nature of the external stimulus, but are more largely regulated by the “phys- iological states.’”’ ‘This we might consider as the cumulative result of a long series of previously acting stimuli, to which others are constantly being added with two effects; first, of bringing about a definite reaction determined by the nature of the stimulus and by the present physiological state; second, of further modifying the physiological state itself, so that even the reapplication of the same stimulus might provoke a quite different reaction. It can not be doubted that the series of changes, which occur in the behav- ior of the lobster larva as they pass through the successive stages, is largely due to this gradual modification of the physiological condition—the cumulative effect of a long series of antecedent stimull. We may sum up the preceding paragraphs by saying; (1) The reactions by which the body-orientation of larval lobsters is produced are invariable motor reflexes, and the method of such orientation 1S, therefore, quite in accord with the requirements of the local action theory of tropisms. (2) The reactions by which the progressive orientation is produced, although appearing to be simple reflexes, are not invariable but are dependent upon many conditions of stimulation, and especially upon the physiological states. In view of these facts, it appears that, while the body-orientation of the larval lobsters is not of primary importance in determining the index of the progressive response to the directive influence of the light rays (since the body-orientation and the progressive orientation are dependent upon quite different factors), still it is of primary importance in determining the general line along which the movement shall take place, either toward or from the source of light. It is shown by these points that this type of response is not in agreement with JENNING’s theory (1906b), in which the process of orientation is of secondary importance, for neither the immediate nor the final body-orientation of lobster larvz to light Haney, Behavior of the American Lobster. 2.97 can be characterized as a “selection from among the conditions produced by varied movements” (JENNINGS 1906b, p. 452). Indeed there are no “‘varied movements” in the reactions by which the body-orientation to light is brought about. The only way in which the term ‘‘random movements” can, be applied to the orientation of the larval lobsters is in its relation to the variable extent of the revolutions or rotations. It cannot be denied that this degree may be dependent upon the physiological states of the larvee (for instance, fatigue or freshness), but, after all, this point is irrelevant to the present discussion, since it is the direction of the immediate turning and not the extent of it, which is the impor- tant consideration. The foregoing experiments throw but little light upon the ques- tion of intensity of light versus direction of light. Indeed it 1s probable that the latter phase of the problem is not of great impor- tance except in cases where the light rays are effective by passing through the body as in the case of the electric current, which, as the writer has shown elsewhere (HADLEY 1907a) causes reaction only when the direction of the current holds a certain relation to the longitudinal axis of the larva. It is clear, however, that the direc- tion of the light rays does modify the reactions of the larval in two ways: (1) By determining which of the two eyes shall be most stimulated, thus causing a body-orientation in which the longitu- dinal body-axis is thrown into line with the direction of the light rays, so that the eyes shall be equally stimulated; (2) by determin- ing what parts of the surfaces of the two eyes shall be stimulated equally, and thus producing a body-orientation in which the pos- terior lateral surface (Fig. 22, a.l.s.) of the eyes receives the strongest stimulation, and the anterior lateral surface (p.l.s.) the least. These reactions, and the consequent progressive orienta- tions of the larvz, the writer has called reactions to the directive influence of the light. That there may be, in addition to these responses, reactions to the intensity of light as Hotmegs (1901) and others have considered possible, it is still permissible to believe, and in the earlier pages of this paper the writer has pointed out some reactions of larval lobsters, which, although not perfectly understood, may be included under the head of photopathic response. The foregoing experiments were carried on at the Experiment Station of the Rhode Island Commission of Inland Fisheries at 298 ‘fournal of Comparative Neurology and Psychology. Wickford, Rhode Island, where exceptional facilities were found for obtaining material of all ages and stages. “The writer’s thanks are especially due to Prof. A. D. Meap of Brown University for making possible an opportunity for this line of inquiry and for material assistance; to Dr. R. M. YeErKEs of Harvard University, and to Dr. H. E. Watrer of Brown University for friendly criti- cism during the preparation of the paper; also to Mr. E. W. BaRNES, Superintendent of the Wickford hatchery, for many kind- nesses. VIII. SUMMARY. 1. Larval and early adolescent lobsters present both photo- tactic and photopathic reactions as these responses are defined on p- 201. 2. ‘There is no constant type of response for all larval lobsters, but a modification of reaction occurs through the metamorphosis of the larve. a. First-stage larvae, directly after hatching, give definitely positive phototactic and photopathic reactions oe endure for about two days, after which the phototactic reactions change to negative, becoming positive again shortly before moulting into the second stage. b. Both early second-stage and early third-stage larvae mani- fest a negative phototactic reaction, which usually becomes posi- tive shortly before moulting into the third and fourth stages, respectively. c. The photopathic reaction of the first three larval stages 1s commonly positive from the beginning to the end of the stage. d. The phototactic reaction of the fourth-stage lobsters is usu- ally (1. e., except in cases where intense light is used in connection with early fourth-stage lobsters) negative throughout the stage- period, and the photopathic reaction, positive during the early fourth stage-period, eventually becomes negative. é. During the fifth stage-period, and in all later stages, both the phototactic and the photopathic reactions are strongly nega- tive. 3. While the photopathic reaction of the larval lobsters re- mains constant, the phototactic reactions are subject to modi- fication as a result of changes in the intensity or in the direction of light. HADLEY, Behavior of the American Lobster. 299 a. During the early first stage-period no intensity of light used changes the index of the phototactic or of the photopathic response, but later an intense light may reverse the index of the phototactic reaction. b. Throughout the second and third stage-periods, the index of the photopathic reaction is not reversible, but during the early part of these periods the negative phototactic reaction, and dur- ing the latter part the positive phototactic response, may be reversed temporarily by using light of great intensity (suddenly introduced). c. During. the fourth stage-period the negative phototactic response can not be reversed (except in such instances as are noted in Exp. 24, Cases 5 and 6), but the positive photopathic reaction of the early fourth stage-period may be reversed tempora- rily by using light of very great intensity. None of the negative responses of the fifth-stage lobsters can be reversed by using light of any intensity whatsoever. e. Submitting larve to darkness for periods of 2 to 12 hours does not change the index of reaction. 4. The reactions to light can be modified by other factors; con- tact-irritability is first manifested in the middle or later part of the fourth stage-period, and henceforth determines (about equally with light) the behavior of early adolescent lobsters. Laboratory experiments explain some of the aspects of the behavior of the young lobsters under natural conditions of environ- ment: (1) The positive photopathic reaction, and the positive phototactic reaction (to lights of very great intensity) together with the, sponse to food stimuli may unite in determining the surface- swimming of the early fourth-stage lobsters. (2) The negative photopathic reaction, the negative phototactic reaction together with the response to contact-stimuli may unite in causing the late fourth, fifth and all later-stage lobsters to leave the surface water, and to burrow at the bottom of the sea. 6. The reaction of larval lobsters to light depends upon two factors; body-orientation and progressive orientation. 7. The body-orientation is invariably negative and is due to the difference in illumination of the two eyes of the larva. It is brought about by invariable reflex movements which tend to bring the longitudinal axis of the body parallel to the rays of light, with the head away from their source. 8. The progressive orientation may be either positive or nega- 300 “fournal of Comparative Neurology and Psychology. tive, and is due to the position (extension or contraction) of the thoracic appendages. If these have the ‘‘anterior position,”’ the reaction 1s positive ; if they have the “posterior position,” the reaction is negative. These positions appear to depend upon the intensity of light which strikes the posterior lateral surface of the eyes equally. The larve orient to screens and backgrounds of black and of white by reflex movements identical with those by which they react to direct illumination and shading. 10. The reactions by which the body-orientation to light is produced, are invariable motor-reflexes, quite in accord with the local action theory of tropisms. ‘The reactions by which the pro- gressive orientation to light is produced, although appearing to be simple reflexes, are not invariable or constant, but dependent upon “physiological states.” 11. In all the reactions to light (except the photopathic) the body-orientation 1 is of primary importance, since progressive orien- tation cannot occur until the body-orientation has been established. 12. None of the reactions to light can be interpreted as “a selection from among the conditions produced by varied move- LB) ments.” They are not trial (and error) reactions, in the sense in which this expression is used by JENNINGS and HoLMEs. IX. LIST OF REFERENCES. BLE peee 1906a. The reactions of the crayfish to chemical stimuli. Journ. of Comp. Neurol. and Psychol., vol. 16, p. 299. 1906b. Reactions of the crayfish. Harvard Psychological Studies, vol. 2, p. 615. Boun, GEorGEs. 1g05a. Impulsions motrices d’origine oculaire chez les Crustacés. Bul. institut gén. psychol., no. 6, p. 1-42. 1g0sb. Attractions et ocillations des animaux marins sous l’influence de la lumiére. Institut gen. psychol. Memoirs, i, p. 108. GRABER. 1884. Grundlinien zur Erforschung des Helligkeits- und Farben-sinnes der Thiere. Prag und Letpsig. Hap ey, P. B. 1906a. The relation of optical stimuli to rheotaxis in the American foberet Am. Fourn. of Physiol., vol. 17, pp. 326-343. 1906b. Annual report of the Rhode Island Commission of Inland Fisheries for 1905, pp.237- 257° 1907a. Galvanotaxis in larve of the American lobster. Am. Fourn. of Physiol., vol. 19, pp: 39-SI.- 1907b. Annual tee of the Rhode Island Commission of Inland Fisheries for 1906, pp. 181-216. 1908. Reaction of blinded lobsters to light. Am. Fourn. of Physiol., vol. xxi, pp. 180-199. Herrick, F. H. 1896. The American lobster. U.S. Fish Commission Bull., vol. 15, pp. 1-252. Hapvey, Behavior of the American Lobster. 301 Hormes, S. J. 1go1. PhototaxisinAmphipods. Am. Fourn. of Physiol.,vol. 5, p.211. 1905. The selection of random movements as a factor in phototaxis. ‘fourn. of Comp. Neurol. and Psychol., vol. 15, p. 98. Horr, E. Bo Ann Ler, ES; 1g01. The theory of phototactic response. Am. Fourn. of Physiol., vol. 4, p. 460. Jennincs, H. S. 1g06a. Behavior of the lower organisms. The Macmillan Co., New York. 1906b. Modifiability in behavior. II. Factors determining direction and character of move- ment in the earthworm. ‘Fourn. Exper. Zodl., vol. 3, pp- 435-455. Keeste, F., anp GAMBLE, F. W. 1904. The color-physiology of higher Crustacza. Philosophical Transactions of the Royal Society of London, Series B, vol. 196, pp. 295-388. Loes, J. 1893. Ueber kiinstliche Umwandlung positiv heliotropischer Thiere in negativ und umge- kehrt. Arch. d. ges. Phystol., vol. 56, p. 247. 1905. Studies in General Physiology. Decennial Publications of the University of Chicago. Lupggock, Sir Joun. 1881. On the sense of color among some of the lower animals. Fourn. Linn. Soc., vol. 16, p- 121. HEY ONe Eee 1906. Note on the heliotropism of Palemonetes larve. Biol. Bull., vol. 12, p. 21. Minxiewicz, R. 1906. Sur le chromotropisme et son inversion artificielle. Comptes Rendus de l’académie des Sciences, Paris, Noy. 19, 1906. Parker, G. H. 1902, The reactions of copepods to various stimuli and the bearing of this on daily depth migrations. Bull. of the U. S. Fish Comm. for 1901, pp. 103-123. Peart, R. 1904. On the behavior and reactions of Limulus in early stages of its development. ‘fourn. of Comp. Neurol. and Psychol., vol. 14, p. 138. ScHOUTEDEN, H. 1902. Le phototropisme de Daphnia magna. Annales de Société entomologique de Belgique, vol. 46, pp. 352-362. SPAULDING, E. G. 1go4. An establishment of association in hermit crabs. Journ. of Comp. Neurol and Psy- chol., vol. 14, pp. 49-61. Yerkes, R. M. 1899. Reactions of entomostraca to stimulation by hght. Am. Fourn. of Physztol., vol. 3, pp. 157-182. 1903. Reactions of Daphnia pulex to light and heat. Mark Anniversary Volume, pp. 361— Syilif SS yaa THE REACTION FOr EIGHT OF: THE DECAPEEAGTED YOUNG NECTURUS: ALBERT C. EYCLESHYMER. From the Anatomical Laboratory of St. Louis University. y y During the summer of 1904 a large number of young Necturi (15-18 mm.) were decapitated by “pinching with fine forceps. The heads were cut off, at slightly different levels, at about the exit of the common trunk of the seventh and eighth nerves. Although the percentage of fatalities ran high, many of the larve lived until the yolk was absorbed, usually about three months. The larve used in the following experiments were decapitated on July ro and in early September they had grown to a length of 30 mm. That the young and old Necturi are negatively phototropic is a matter of everyday observation both in the naturalenvironment and in the aquarium. In testing the effects of various kinds of light on the normal and decapitated larva they were placed in a small glass aquarium about 60 cm. long, 30 cm. deep and 25 cm. wide. One-half of this aquarium was then painted black and the top covered with a black board. The larva, both normal and decapitated, were then subjected to sunlight of varying degrees of intensity. The rays were condensed by a hand glass and by concave mirrors, and were also passed through ground glass. The light of the room was controlled by an opaque curtain so that varying degrees of inten- sity could be obtained. In order to test the effects of artificial light, the normal and decapitated larva were taken into a photographic dark-room and the aquarium was placed in such a position that a sixteen candle- power electric light illuminated one-half of the aquarium. In the same manner one-half of the aquarium was exposed to the light from anarclamp. Further experiments were made by controlling these lights with condensers and mirrors. In all cases both the 304 “fournal of Comparative Neurology and Psychology. normal and the decapitated animals, when together or separate, react in the same manner as they do in diffuse daylight and direct sunlight. ‘They are negatively phototropic. In case the normal larve are unable to escape a bright light they almost invariably orient themselves in such a position that the light falls with equal intensity upon the two sides of the body. It was also noted that in the great majority of cases the heads were turned toward the light. “The decapitated individuals showed the same orientation, except that the heads were about as frequently turned from the light as toward it. A sharp pencil of rays of either sunlight or electric light when thrown on the tail of the normal animal causes a quick response. This indicates that the tail is especially sensitive, which is in agreement with the observations of Dusois on Proteus. In the same manner the decapitated animals respond more readily when the rays are concentrated upon the tail than when they are concen- trated on other parts of the body. During the summer of 1902 larve were reared in glass aquaria, beneath which were placed pieces of black, white, red, yellow, green and blue paper. Although a large number of counts were made to determine the percentage over the different colors, at successive intervals, there seemed to be no decided preference for one color over another. A second set of observations, the follow- ing year, seemed to show that by far the highest percentage of larvee were found over the green, whether this was placed on the side of greatest or least diffuse daylight. In 1905 the same experiment was repeated with the decapitated larvee, but fifty-two counts showed nothing definite beyond the fact that the larva were most frequently found on the colors in the half of the spectrum toward the violet end. It is of interest here to recall that Dusots (’g0, p. 356) says: “I have observed that Proteus, under the same conditionas the blinded Triton, shows a preference for the following colors in a decreasing series: first, dark, then red, yellow, green, violet, blue and white light.” In the Proteus with normal eyes Dusots found the reac- tion towards the various colors was in the following decreasing series: first, dark, then yellow, then green, red, blue, violet. It should be added that these results were not obtained with mono- chromatic light. Concerning the reactions of Amphibia to light, there is some EYcCLESHYMER, Reactions of Necturus. 305 difference of opinion. ‘The earlier observations of GRABER (84, p. 121) seemed to show that Rana esculenta is negatively phototropic and Logs considered this probable. PLATEau (’89, p 82), however, found that R. temporaria is positively phototropic. PARKER (’03, p. 30) also found that R. pipens is positively photo- tropic, not only in the normal condition, but also when the eyes are removed. Later Miss TorELLE (’03, p. 487) discovered that Rana virescens and R. clamata are positively phototactic at ordin- ary temperatures, but that raising the temperature to 30° C. accele- rates the rate of positive response, while a lowering of the tempera- ture to 10° C. produces movements away from the light. Korany1 (93, p. 6) says that microscopical changes in the retina of Rana may be effected by the exposure of the skin, as well as the eye itself, to light. The results of experiments on Urodeles seem to be more uni- form than those of experiments on the Anura. COoNFIGLIACHI and Rusconi were probably the first to point out that some of the Urodeles are negatively phototropic. They noted that Proteus always retreats towards darkness. ‘These investigators thought the effect upon the skin, rather than upon the eyes, caused the animals to seek darkness. GRABER’S (’84, p. 96) experiments on the young of ‘Triton, in which he found them negatively photo- tropic, even when their eyes had been removed and their heads covered with black wax, led to the assumption that the skin can be stimulated by light. Dusois (’go, p. 356) who covered the eyes with gelatine and lampblack, concludes that Proteus distinguishes light from obscurity both by the eyes and skin, but that the der- matopteric sensibility is far less powerful than the ocular sensi- bility. Wuirman (98, p. 302) says of the young Necturus: “It is interesting to see how little the eyes are depended upon in finding a piece of meat. A bit dropped in front of a young Nec- turus receives no attention after it reaches the bottom. An object must be in motion in order to excite attention, and itis not generally the moving form that is directly perceived, but the movements of the water, traveling from the object to the sensory hairs, are felt, and in such a way as to give the direction of the disturbing center with most surprising accuracy. Ifa bit of beef is taken up adher- ing to the point of a needle and held in the water, the vibrations imparted to the needle by the most steady hand will be sufficient to give the animal the direction. If the meat falls to the bottom, 306 “Fournal of Comparative Neurology and Psychology. and the needle is held in place, the animal approaches the needle and tries to capture it without paying the slightest attention to the meat lying directly below. If, after the meat has fallen, the needle is withdrawn and touched to the surface of the water behind or at one side of Necturus, it turns instantly in the direction of the needle not because it sees, but because it feels wave motions coming from that direction. Long experience with Necturus, and with many of its nearer allies, enables me to speak very positively on this point. When it is remembered that in the higher animals the direction of sound waves is given by the auditory sense organs, which are pri- marily surface sensilla homologous with those in the skin of Nec- turus, it may not seem so strange that the animal directs its move- ments in the way described. Necturus can see, but it can feel (perhaps we should say hear) so much more efficiently that its small eyes seem almost superfluous.” All the facts thus recorded seem to show that the eyes of the young Necturus, as well as those of many other Urodeles, are not highly functional structures, and that when the animal is deprived of their use the dermatopteric sense adequately compensates for the loss. As PaRKER (05, p. 418) has well said, “The ability of the spinal nerve terminals to be stimulated by light may now be said to be established for certain fishes, amphibians and reptiles; and this fact is not without interest in connection with the theories of the origin of the vertebrate retina.”’ The many attempts to explain the inverted position of the verte- brate retina early led to hypotheses by LANKESTER (’80), BALFOUR (’85) and Brarp (’88) that the eyes are structures which have been evolved from light perceiving organs which were at one time located in the unclosed neural plate. BiscHorr, KOLLIKER, His, VAN BENEDEN and others long since observed in mammals a very early appearance of the optic vesicles. Heape (’84) observed the optic vesicles in the mole when the neural folds were widely open in the head region. Kerpet (’89) later observed that in the guinea pig a like early differentiation of the optic vesicles occurs. WHIT- MAN (’8Q) discovered that in Necturus there is a very early appear- ance of the eye, “its basis being discernible as a circular area long before the closure of the neural folds of the brain.”’ No one, however, had ever shown that the optic vesicles were present in the neural plate at the time the neural folds first appear, EYcLESHYMER, Reactions of Necturus. 307 until the writer (’93) showed that in Rana palustris the Anlagen of the optic vesicles not only appear as a pair of pigmented areas, but that these areas are made up of pigmented columnar cells so different from the cells in the remainder of the neural plate that there could be no reasonable doubt of their being specially differ- entiated areas. By following these areas step by step during the period of closure of the neural folds it was definitely established that these areas formed the bases of the future retinz. Shortly after the publication of the writer’s observations Locy (93) found a series of depressions in the unclosed neural plate of certain Elasmobranchs which he thought represented paired sensory structures, probably, of a visual character. In a word, it may be said that the evidence has been slowly accumulating from the morphological side in support of the hypothesis that the retina belongs to the cutaneous sensory system. The evidence from the physiological side is equally confirma- tory. ParKER (’05, p. 419) who has recently carefully reviewed the literature states that ‘“‘This sensitiveness of the vertebrate skin to light is probably a remnant of that primitive condition from which the lateral retinas were derived, and possibly served as a basis from which the temperature terminals of the skin in the higher vertebrates developed.” In conclusion, then, one may say all the evidence goes to show. as JOHNSTON (’05, p. 241) has well stated, that “the retina belongs morphologically, as well as physiologically, to the cutaneous sensory system.” BIBLIOGRAPHY. Barrour, F. M. 85. A Treatise on Comparative Embryology. London, Macmillan © Co. Bzarp, J. 88. The Old Mouth and the New. Anat. Anzeiger, Bd. 3, pp. 15-23. Dusors, R. ’g0. Sur la perception des radiations lumineuses par la peau, chez les Protées aveugles des grottes ‘de la Carniole. Comp. rend. Acad. Sci., Paris, Tom. 110, pp. 358-361. EyciesHyMER, A. C. ’93. The Development of the Optic Vesicles in Amphibia. Journ. Morphol., vol. 8, pp. 189- 194. GRABER. 84. Grundlinien zur Erforschung des Helligkeits und Farbensinnes der Thiere, Prag, pp. 1-322. ue Heaprr, W. 84. The Development of the Mole. Stud. Morp. Lab., Cambridge, Eng. Vol. 2, pp. 30-69. 308 “fournal of Comparative Neurology and Psychology. Jounston, J. B. ’?05. The Morphology of the Vertebrate Head from the Viewpoint of the Functional Divisions of the Nervous System. Four. Comp. Neurol. and Psychol., vol. 15,n0.3, pp. 176- 253. Kerset, F. Zur Entwicklungsgeschichte der Chorda bei Saugern. Arch. f. Anat. u. Phystol., pp. 329-338. Korany1, A. v. ’93. Ueber die Reizbarkeit der Froschhaut gegen Licht und Warme. Centralb. f. Physiol., Bd. 6. pp. 6-8. LankestTER, E. R. 80. Degeneration. London. Locy, Wo. A. ’93. The Derivation of the Pineal Eye. Anat. Anzeiger, Bd. 9, pp. 169-180. Parker, G. H. ‘ 03. The Skin and Eyes as Receptive Organs in the Reaction of Frogs to Light. Amer. Four. Physiol., vol. 10, pp. 28-36. ’o5. ‘The Stimulation of the Integumentary Nerves of Fishes by Light. Amer. four. Physiol. vol. 14, pp. 413-419. Prareau, F. I. 89. Recherches expérimentale sur la vision chez les arthropodes. Mémoires couromés de P Academe royale des sciences, des lettres et des beaux arts, de Belgique. Tom. 43, pp. I-91. Torette, E. ; ’03. The Response of the Frog to Light. Amer. Four. Phystol., vol. 9, pp. 466-488. Wuirmay, C. O. ”88. Some New Facts about the Hirudinea. ‘four. Morph., vol. 2, pp. 585-599. ’98. Animal Behavior. Biological Lectures. Ginn © Co., Boston, Mass. RECENT STUDIES UPON THE LOCOMOTOR RESPONSES OF ANIMALS TO WHITE LIGHT. BY E. D. CONGDON. During the last few years attention has been given to the light reactions of nearly all the large groups of inyertebrates. ‘The sudden appearance of data upon the photic responses of animals differing greatly in habits and in mechanism of locomo- tion has naturally resulted in a variety of opinions as to the proper classification of their orientations. The wide latitude as to precision of light control, amount of quantitative experiments, emphasis laid upon the mechanism of locomotion, and the like, exhibited by various investigators, has increased this diversity. Nevertheless recent discussions make good the claims of trial’ and phototaxis* as two mutually exclusive but closely associated categories within which most features of animal light response may find a place. Papers not concerned with these subjects may in most cases be best considered in relation to the animal group to which they refer. The period to be given attention extends from the year 1900 to 1907 inclusive. PHOTOTAXIS. Although some of the postulates of the mechanical phototactic theory of a few years ago have not survived, there can be no doubt that most of the animals to which it was applied have one characteristic in common. They align with the light by a movement whose direction has a definite relation to a localized photic stimulus. Some recent papers may help us to determine the accuracy and speed with which they align and the relation of bilateral symmetry to the procedure. Harper’s accounts (’05, 07) of the behavior both of the earthworm Pericheta and the larva of the insect Corethra have an important bearing upon the questions just suggested. The earthworm is found to react by the trial method if the light be of low intensity. Under greater illumination exploring movements in the direc- tion not aiding orientation gradually disappear. The animal then aligns itself with the light by a few quick turns. This procedure illustrates the fact that the turning provoked by localized stimulus may consume an appreciable amount of time and may consist of a series of movements. It might be mentioned here that ParKER found Planaria to orient phototactically by a curved course of some length. The larval Corethra has a discontinuous jerky locomotion. The successive advances are invariably in a path bending towards the source of light. Neverthe- 1 The expression “ trial and error” may be shortened to “trial” because the second term is implied in the first. ?-The view of Rapz is here adopted that the older term phototropism should be applied to all motor responses of animals which are produced by light as does geotropism to those produced by gravity, chemotropism to those produced by chemical stimuli, etc. 310 “Fournal of Comparative Neurology and Psychology. less they do not produce alignment because the animal always curves too far. In spite of its zig-zag path the larva always responds to the greater illumination of one side by turning in that direction. Alignment is defeated by a peculiarity in the method of locomotion. HarPER points out the inconsistency of applying to Corethra the mechanical theory of phototaxis as it was stated by Davenport for the earthworm. It was the suggestion of that author that orientation would result in a simple and mechanical way if we suppose, first, that light directly modifies the tonus of the muscle and, sec- ond, that optimal illumination gives the highest tonus. Under these conditions the side of the animal towards the more nearly optimal light would contract the most and the animal thus turn towards optimum. _ In spite of the fact the Corethra is a worm-like larva, the theory cannot apply to it because it contracts on the side away from the optimum. Rav (’03) is the author of the most complete account of phototaxis that has yet appeared. A considerable part of his monograph is occupied by his own study upon insects and other arthropods. A variety of interesting facts have been brought to light. Butterflies of various families may be found toward sunset perching upon flowers with body pointed away from the sun, wings outspread and head raised or depressed so as to bring the back of the wing as nearly perpendicular as possible to the sun’s rays. In the middle of the day certain species close their wings and align with the light. In general Ravi says: ‘‘Some butterflies so orient with the sun’s rays that in weak sunlight they expose the greatest possible surface, in strong sunlight the smallest surface of the wings.” He leaves the explanation for later investigators. Boun has described similar orientation in butterflies. Certain dragon flies persistently orient with the right side to the sun. Midges have a curi- ous way, little understood, of flying in a circle or spiral within a small area at some point near a light. ‘This place may be forsaken and a new position taken up, only to repeat the previous behavior. Actively moving Cladocera are found in dense swarms within the free spaces among the algal clumps in fresh water ponds. There is a clear band several centimeters wide between them and the shore. The face of the moving mass is clean cut and follows every irregularity in the lateral surface of the algal mass. A similar condition of things is not obtained in the laboratory and an explanation has not yet been discovered. Ravi also found that many aquatic arthropods show an orientation to the light divorced from their locomotor response. Daphnia, for example, regularly orients with its back to diffuse or direct sunlight, while at the same time moving about in a non-directive way. It will turn its back upward if the light be made to come from above or downward if the direction be reversed. Animals were kept in an inverted position for two weeks in this way with no diminution in the precision of the response. He also obtained that locomotor reaction described by Davenport, YerKEs and others, for Crustacea, which is characterized by rapid orientation to light and a symmetrical arrangement of the body in relation to the direction of the rays. ‘The conditions which determine whether orientation with back towards the light or with orientation with long axis in line with the light and accompanied by locomotion, shall control the animal have not been determined. Other peculiarities regarding the relation of body to locomotion have been recently described for arthropods. Pycnogonids (CoLE ’01) go towards the light with the head leading provided they are crawling, but swim toward it with the abdo- Concpon, Reactions to Light. 311 men in advance. Palamonetes larva swim with abdomen toward the light. Lyon (’07) caused them to move head first towards the dark by diluting the seawater. A considerable part of Rapt’s investigation, like that of Lores and Lyon at an earlier period, relates to the movements of insects and other arthropods placed upon disks rotating in various planes. Some animals remain standing upon disks and automatically turn their heads to maintain their orientation to the light. Some, if upon a slowly moving horizontal disk, keep in such a position that they do not lose their orientation to light or to the surrounding, fixed environment. ‘The rela- tion of these reactions to the explanation of light responses can best be made clear after recalling a view expressed by Lorn (’07, etc.). Binocular vision, he believes, is phototactic because a pair of eyes are always placed symmetrically in respect to the center of the field of vision by virtue of their adjustment so that it will fall upon the middle points of their retinas. Rapti conceives phototaxis as a response to localized stimulus resulting in symmetrical adjustment. He believes binocular vision is phototactic in his sense of the term phototaxis. At the same time he acknowledges that such phototaxis has two novel elements: namely, the substitution of the varied field for a simple source of light, and the orientation of organs instead of the whole body. In regard to the former, he admits that there has not as yet been brought forward any series of phototactic reactions to fields of gradually increasing complex- ity as a proof that orienting to them is essentially the same as orienting to a simple source of light. Rapi together with Lors and Lyon have found that orientation of eyes as well as head are shown by compensatory movements to be very common in insects. So frequently does it occur that Rant is led to say that the essential of arthropod phototaxis is the orientation of the eyes, and that the adjustment of the body follows only at times, and is of secondary importance. Haptey (’06, ’06a) has recently shown that young lobsters keep a constant posi- tion relative to the bottom while in moving water. This is partly due to orientation toward the fixed field about them. The optical portion of the process may be directly compared with compensatory locomotion upon a revolving disk. Mechan- ical compensatory movements due primarily to light, and resembling those of the young lobster, are described by Lyon (’o4) in a study of the rheotaxis of certain fish. Lors (07a) finds that marked compensatory head movements are made by the reptile Phrynosoma upon the revolving disk. His experiments show them to be in part due to optical reflexes. It is evident that the compensatory movements of vertebrates, in so far as they are optical in origin, have in them the qualities of similar arthropod movements. If the term phototaxis may be applied to the binocu- lar vision of arthropods, it also can rightly be used for vertebrates. Such a state- ment needs the corollary that phototaxis probably expresses only a tithe of the nervous activity involved in the binocular vision of the vertebrate. There has been presented a fair illustration in the variety of locomotion which may result from the response to localized stimulus as described by recent authors. We are therefore in a position to consider whether these different procedures have anything further in common. Opposite conditions in the complexity of aligning movements are illustrated by the earthworm and flatworm as compared with cer- tain crustaceans, as Daphnia. Some animals also stand in contrast with Daphnia because of the greater irregularity of their course to or from the light. Thus in Corethra peculiarities of locomotor mechanism produce a zigzag course. In_ spite of the great variety which these animals just mentioned show in their accuracy of 312 ‘fournal of Comparative Neurology and Psychology. orientation because of differences of locomotor mechanism and other factors, they have in common, that they align with the light more or less accurately as a result of its differential effect upon the opposite sides of a bilateral symmetrical body. There is thus a response to localized stimulus. The available evidence goes to show that animals responding to localized light stimulus have in general this same character. Even the bell-shaped jelly-fish and a spherical form such as Volvox come within the category inasmuch as radially symmetrical animals must be also bilaterally symmetrical. In the further use of the term phototaxis we shall there- fore imply alignment by the differential effect of light upon the sides of bilaterally symmetrical organisms. JENNINGS attaches little value to this view of phototaxis because it does not pre- tend to seek a full explanation of things as did the old mechanical theory. He says, “Tn order to retain any of its value for explaining movements of organisms, it would have to hold at least that the connections between the sense organs and the motor organs are of a perfectly definite character so that when a certain sense organ is stimulated a certain motor organ moves ina certain way.” It isto be granted that there is little of an explanatory character in phototaxis as defined above. Never- theless it has the value which attaches to all categories. It represents a certain stage in the classification of facts, and is a unit of behavior which will simplify further attempts at analysis in the same direction. Logs and Rapt rightly claim that there is a graded series between such a loco- motor response as we have just defined and the training of the two eyes of a verte- brate upon any object. The comparative anatomy of various types of eyes, as well as those experiments upon light response which bear upon the subject, strongly indicate that there is also a graded series between orientations to a single source and those to a varied field. The question of the practicability of applying the term phototaxis, which originally referred to locomotor responses of lower animals alone, to a series including the orientation of eyeless animals on the one hand and of the vertebrate eyes upon the other, is simply one of convenience in terminology. In this paper it will be used in the wider sense. Perhaps no contribution has appeared which shows more clearly the relation between phototaxis and the general nervous activity of an animal than does the study by Hormes (’oSa, ’07) of the reactions of the insect Ranatra to light. The behavior of the animal is dominated to a surprising degree by photic stimuli. It is marked not only by phototaxis of the body but its eyes and breathing tubes sway towards an alignment with the light even when the animal is not engaged in loco- motion. If various parts of the eyes be blackened there results the phototactic response which we would expect if the part of the environment dark to the animal were really devoid of light. Hotmes points out that this slavish and mechanical response is probably due to simple reflexes. But the behavior of Ranatra also reveals more complex nervous processes exist- ing side by side with phototaxis. Hemisection of the brain destroys light response almost completely. Therefore it is probable that the crossing optic fibers in the brain are part of the reflex arc. A number of stereotyped procedures such as hunt- ing food and cleaning the body may inhibit phototaxis. Of especial interest is the result of blackening all but a smal] posterior portion of one eye. There is a marked disturbance of orientation as one would expect. In spite of this fact, the animal in time learns to move towards the light quite accurately. HoLmes argues that no simple reflex can explain orientation under these conditions. Concpon, Reactions to Light. 313 The first experiment definitely directed to determining the relation of phototaxis and the image-forming power of the eye is described by Parker (’03a). He made use of the positively phototactic butterfly, Vanessa. The animal was placed in such a position between a window and a candle that the intensities of light from the two sources were equal where they fell upon the animal’s body. Under these conditions Vanessa flew towards the window, thus demonstrating that it can distinguish between the size of luminous fields. Phototaxis is preceded by a choice of the field to which it orients. The experiment, as PARKER points out, furnishes an answer to the query why positively phototactic winged insects do not fly towards the sun. They seek instead the larger mildly illuminated patches upon the earth’s surface. Coe (’07) employed ParKER’s test upon a number of terrestrial animals and thus increased our knowledge as to the relation of phototaxis and the power of forming primitive images. The animals were placed perpendicularly to the line joining two parallel screens and equidistant from them. The light given off by the screens per unit surface was inversely proportional to their size. ‘Therefore the total light intensities of their surfaces were equal. The dung worm Allolobophora, the insect larva Tenebrio, the cockroach Periplaneta, the European garden snail Helix, and the blinded cricket frog Acris did not give a greater number of turnings to one field than to the other. On the other hand the flatworm Bipalium, and the small crustacean Oniscus showed some little power of discrimination. Vanessa, Ranatra, and two species of frogs with eyes intact distinguished readily between the screens and always oriented to a particular one of them. A discussion of the relation between perception of detailed images and photo- taxis appears in a recent work upon vision by Nuet (04). TRIAL, JENNINGs was the first to apply the idea of trial, long recognized for vertebrates, to invertebrates as well. We shall consider the papers on this subject relating to the earthworm by ParKER and ARKIN, SMITH, ADAMS, HormeEs and Harper before turning to the protozoan studies of JENNINGS. The methods used by SmirH (’02) in studying the earthworm are valuable in giving, as it were, a birdseye view of its activities in light of rather weak intensity. She devised a means of plotting upon paper the path of the worm for a considerable distance. Exploring movements were shown by spurs upon the line indicating the animal’s course. When worms are started with their bodies perpendicular to hori- zontal light, they go in various directions, varying from directly toward to directly away from the light. In the great majority of cases the course is obliquely from the light. Exploring movements are especially common when the anterior end of the worm encounters stronger illumination or an unfavorable surface. Often they are preceded by a recoil. Aithough the fact is not emphasized by the writer, her diagrams show that exploring movements toward the light are not followed up so frequently as those away from it. We must turn to Hotes (’05) for the application of the trial idea to the worm. He makes the statement that the first effect of moderate light upon the earthworm is the production of exploring movements, of the anterior end, haphazard as to direction, with possibly a few more away from the light than toward it. ‘The sec- ond effect is to check the movements toward the light. As a result the animal 314 Fournal of Comparative Neurology and Psychology. pai roughly oriented negatively tothe light. He calls the process “the selec- tion of random movements,” and points out that it resembles the trial method of higher animals, with the reservation that there is here no learning by experience. Harper (’05) gives us a very reasonable explanation as to the mechanism of the exploring movements. He finds that the extension of the anterior segments of the worm presents more fully to light certain cells, probably photoreceptive, which lie near the dissepiments. An animal must Seri its anterior end well out in a certain direction, therefore, before light can produce inhibition of further move- ment. ParKER and ARKIN (oI) had published, previously to the appearance of the papers by SmirH and Hotmes, an account of the orientation of the earthworm Allolobophora. Their method of procedure was to tabulate the movements of the anterior end in a large number of trials made upon individuals placed trans- versely to the direction of the light. ‘There were 66 per cent of movements straight ahead, 4 per cent toward the light, and 30 per cent away from it. ‘The view was taken that the 4 per cent toward the light indicate disturbing influences of other stimuli, and so that it is probable that 4 per cent of those away from the light have a like cause. The remaining 26 per cent of those away from the light indicate a tendency of the animals to orient to the stimulation of light in the phototactic way. Another test of photic response was devised which gave very suggestive results. Light was thrown perpendicularly at different times upon the anterior, middle, or posterior thirds of the body. The percentages indicating the orienting effects are 10.2, 2.4 and I respectively as compared with 26 per cent of turns from the light when the entire body was illuminated. It is evident that the condition of the trial reaction as described by Hoimes is present when only the anterior end is illuminated. Yet if the rest of the body be also exposed to light the orienting response more than doubles in amount. ‘The experiment suggests the unreasonableness of thinking that this elongated animal, sensitive to light along its whole length, should make no use, in its orientation, of that wide difference of intensity which must often exist between its opposite ends. A recent experiment by Core (’07) suggests that the importance of antero- posterior differences of intensity could be found if a partial shadow were cast upon the earthworm’s anterior end when in a field of horizontal light perpendicular to the long axis. A difference of illumination of the two sides of the anterior end would exist such as would fulfill the conditions for a turning by the trial and error method. At the same time if the difference in intensity of the anterior as compared with the posterior end of the animal were effective we should expect a movement straight into the shadow. Apams (’03) applied the methods of PARKER and ArKIN to Allolobophora with the intention of determining the effect of twelve different intensities of light ranging from 192 candlemeters to .o12 candlemeters. At 192 candlemeters there were 41.5 per cent negative movements which showed the orienting influence of light. At 8 candlemeters there was an increase to a maximum of 59 per cent of negative reac- tions. The percentage decreased gradually to 3 per cent at .o12 candlemeters. The very low intensity of .oo11 candlemeters was found to produce a preponder- ance of positive movements. ‘This increasing proportion of precise movements away from the light tallies in a general way with the behavior of Pericheta when it forsakes all non-orienting movements in strong illumination. But Allolobophora Concpon, Reactions to Light. 315 shows a slight falling off of direct reactions from 8 candlemeters up to 192 candle- meters instead of the uniform increase seen in Pericheta. Of course it cannot be expected that the different genera of worms used by the two experimenters should agree in the details of their reactions. The trial method as described by Hotes with its production and checking of varied movements is confirmed by Harper as far as Perichzta is concerned, and itis hinted at by SmirH. ‘The observations of PARKER and ARKIN do not invali- date its occurrence, because we do not know that they attempted to record a check- ing of exploring movements. ‘There is, therefore, little doubt that there are both phototactic and trial phases in the behavior of worms, as well as that dependent upon the relation of the stimuli anterio-posteriorly along the animal. Only those parts of JENNINGS’ study (’00, ’04, '05, ’06, ’06a) of Protozoa need be considered here which refer to the method of orientation to light and to his con- ception of the trial reaction. He found that alignment takes place by a swinging of the anterior end of the animal away from a structurally defined side due to an unfavorable change of intensity. This he terms an avoiding reaction. In case it is initiated by an abrupt entry into a field of perpendicular light of unfavor- able intensity there is usually a quick return to the ordinary spiral course. The turn often serves to take the animal out of the unfavorable field. If it does not accomplish that end the process will be repeated until it gets out or becomes acclimated to the new conditions. If at any time it blunders into a field of favorable intensity it is evident that it will be held there as in atrap. A second variety of the reaction usually occurs if the animal be moving at an angle with hori- zontal light. ‘The beat of the cilia which produced the swing is then likely to con- tinue longer and the anterior end move around a larger circumference than usual. If forward motion be entirely stopped it may describe the surface of a cone or disk by whirling on its posterior end. Some part of the curve which is traversed by the anterior end of necessity leads into increasingly favorable light intensity and the stimulus for the swinging, which was an unfavorable change of illumination, is thus removed. The ordinary spiral course is resumed but the direction is now more nearly in line with the light. By a series of such turns, often very close together the protozoan soon becomes directed as nearly toward the light as its spiral motion will permit. The following definition of trial is given by JENNINGS (’06) which he applies to the protozoan methods and to that of the earthworm as well. “The organism performs varied movements, some features of which are not determined by the local- ization of the stimulus but by other factors; it then continues those movements which bring it into or toward a certain condition; this condition usually being a greater or less action of the stimulating agent as the case may be.”’ This statement of trial differs from that of HoLMEs in two of its features. JEN- NINGS does not confine varied movements to such as are produced by an unfavor- able change of illumination. A comparison of earthworm and protozoan varied movements will show whether the latter may be considered due to a change of light intensity. The exploring movements of the earthworm constitute its varied move- ments. ‘They may be clearly distinguished from the movements which carry the animal along because they are confined to the anterior end of the body. ‘The avoid- ing reaction of a protozoan, upon the contrary, may consist of ordinary locomotor movements modified by a swing from the structurally defined side due to an unfay- 316 9 “fournal of Comparative Neurology and Psychology. orable change of illumination. It is the avoiding reaction which constitutes the varied movement of the protozoan. All components of its motion are not evoked by change of light intensity. “Then why refer in a definition of trial to the method by which the varied movement is produced? Harper (’07) in a recent paper givesareason. ‘There are a great number of irregular movements, especially among lower animals, which by carrying their possessor into a large number of regions help them better to test the surroundings. Such, among others, are the spiral movements of the protozoan not involved in the poedine reaction, and certain writhings of insect larva. ‘These do not aid in orientation to light and in most cases do not result from unfavorable change of illumination. ‘The trial reaction is therefore to be considered as resulting from varied movements produced in whole or in part by change of light intensity. JeNNINGs does not make the checking of some varied movements an essential part of trial. He says merely: ‘Movements are continued which bring the animal into or toward the favorable condition.””» Amoment’s consideration of the method of the trial procedure in Protozoa makes the reason for his attitude clear. There is first an increase of the ciliary stroke producing the movement from a structurally defined side. When the anterior end of the animal in pursuing the enlarged spiral is brought into more favorable light intensity the increased vigor of stroke dis- appears. ‘The process is not a checking of any movement by unfavorable illumina- tion. The orientation of protozoan and earthworm plainly have some differences. Yet the two have sufficient in common to warrant their inclusion within a single category. Orientation by trial then consists in the production of varied move- ments which are at least in part produced by an unfavorable change of illumination, and the following up of those leading towards favorable illumination. ENNINGS’ account of protozoan behavior to light was soon followed by a paper from Masr (’06) upon the protozoan, Stentor. As the latter says: “‘ JENNINGS laid particular stress on the detailed movements of the individuals while I directed most careful attention to the regulation of the stimulus.” One carefully planned device which he employed gave him a graded field of ver- tical light. When subjected to it, Stentor, which is negatively phototropic, becomes directed in some path which does not lead into greater intensity. That is to say, it becomes oriented to such an extent that its head points within go° to one side or other of the line which would carry it most directly toward the dark. Mast raises a doubt as to whether the avoiding reaction of Protozoa is a trial response at all. His examination of the threshold of light stimulation for different parts of a Stentor shows that the peristomal region is probably much more sensitive than the rest of the surface. Therefore light stimulus is most likely to be received in this region. Inasmuch as the animal turns from the peristomal side in an avoiding reaction it is giving a definite response to a localized stimulus just as truly as is an insect which upon one eye being blinded turns away from the remaining one. The localization of light sensitiveness and the turning from the localized area cannot as yet be considered as an established fact. Does the protozoan show an alignment of a bilaterally symmetrical body to the light? It does so only imperfectly because of its spiral movement. Inasmuch as many phototactic animals only roughly approximate a straight course because of peculiarities in their locomotor mechanism, such a condition would not Bene CoNGDON, Reactions to Light. 317 the regarding of protozoan orientation as phototactic. ‘There is a consideration, however, that would do so, even though it were proven that a response to localized stimulus occurs. “There are no paired bilaterally symmetrical sensory areas through whose unsymmetrical stimulation orientation 1s accomplished. DIRECTION VS. INTENSITY. Rabi ('03) makes the statement that from a physio-chemical point of view there can be no question as to whether intensity or direction is the primary factor in the action of light upon an animal. ‘The amount of change produced in the protoplasm by light is due to the amount of energy given up by the light, and that in turn is a function of intensity, not of direction. ‘That this view does not exhaust the question is shown by a test which Hor and Lee (or) applied to the protozoan Lynceus, in imitation of the earlier experiments by Coun. ‘Their apparatus consists of a wedge-shaped tank containing dilute india ink suspended over an aquarium. Light from above produces in an imperfect way a field graded in intensity from one end of the aquarium tothe other. By varying the angle of incidence upon the prism the light is given an oblique direction within the aquarium and the gradation of the field is little changed. Lynczeus aligns itself with the light, and goes slavishly into either greater or less intensity according as the rays slant in the one or the other direction. ‘This kind of reaction had been previously used as an argument that direction is the essential factor of light response. Hott and LE applied in expla- nation of the reaction VERWORN’S suggestion that if an animal always turned toward the shaded side of its own body it would of necessity align with the light. Thus Lynceus is forced into either light or dark areas while responding in an un- varying way to the difference of intensity upon the sides of its body. Although Hott and Lee have thus explained the behavior of the animal satisfactorily by means of intensity changes, they did not settle the question of the relative merits of intensity and direction. We owe to Mast (’07) the first conclusive proof that orientation is due primarily to intensity. He used for his purpose the colonial protophyte Volvox. An individ- ual was first illuminated by two like pencils of light. As a result it took a course intermediate between them. ‘Then without changing the direction of either beam one of them was modifed in intensity. “The organism now changed its orientation, bending its course somewhat toward the beam that had become relatively stronger. Coe (07) illustrated the same point in another way upon the two worms Allglo- bophora and Bipalium. A partial shadow was cast upon the anterior end of a worm which has been pointed toward the nearly horizontal light. The creature in spite of the fact that it is negatively phototropic went into the shadow, thus moving almost directly toward the source of light. Serpulid larvz, though phototactic, were found by ZELENY (’05) to go into greater light intensity whether it led them in the direc- tion of the light or not. It is not necessary to seek for further evidence that light produces stimulation through variations of intensity. Direction plainly affects the intensity of light upon the body or the retina by the casting of shadows or by the complications introduced through eyes of varying position and visual angle. Torrey (’07) has recently recalled to mind the view that light may possibly show an orienting effect dependent upon direction in a way analogous to the action of an electric current. Such a theory would not explain the orientations of Volvox and Allolobophora. 318 fournal of Comparative Neurology and Psychology. PROTOPHYTA. Mast (’07) has produced a well rounded and thorough piece of work upon the photic reactions of Volvox. Although the form is classified as a plant its locomo- tion is of a protozoan type and so is of interest here. The first part of his report gives an analysis of its curious method of locomotion. His apparatus is carefully planned and the methods applied to determining its behavior are various. Equal attention is given to the reactions of segregated individuals and of large numbers taken together. Volvox is found to orient by phototaxis, although through a pecu- liarity of its locomotion its path is at a slight angle with the light. The light response is analyzed into a series of avoiding reactions of the individuals comprising the col- ony. Various factors such as previous condition of illumination, the stage of devel- opment of the individual, etc., are described as modifying the light reaction. COELENTERATA. Gonionemus is an interesting object of study as a type of the primitive and unique group of the jelly fishes. YERKEs (02, ’03a, 04, ’06) contributed a paper upon its light reactions in a series treating of different phases of its nerve physiology. Mors (’06, ’07) has also devoted some attention to the subject. According to YERKES ('03a) Gonionemus is decidedly phototactic under cer- tain conditions of illumination. The response to localized stimulus can be readily seen if the individual in a negative condition happens into a band of light of graded intensity such as may occur at the edge of a shadow. ‘The side of the bell toward the light which is most intensely illuminated contracts most strongly and the animal thus turns back into the shadow. The juxtaposition of contracting and stimulated regions results in a localized response reduced very nearly to its simplest terms. Morse has confirmed YERKES in the occurrence of directive response by observing single medusz in various conditions of illumination. A marked photokinetic effect occurs. As Los earlier found for Planaria the medusze will collect in a shadow because as soon as their active movements bring them there they come to rest. This method of non-orienting response to intensity of illumination has been termed negative photokinesis. It has been already stated that a graded field at the edge of a shadow may produce a phototactic orientation of stragglers which directs them back into the shadow. ‘Thus non- orienting light response and phototaxis cooperate. PLATHELMYNTHES. Three investigations have been recently published upon the flatworms by PARKER and Burnett, GAMBLE and KEEBLE and WALTER. ParKER and Burnett (’oo) so planned their experiments upon the negative Planaria as to determine the importance of the eyes in orientation, and to show the relative importance of light as compared with other factors in locomotion. Single animals were placed at the center of the horizontal surface marked with a circular scale and directed toward the zero point. The angle at which they emerged was recorded, as well as the time consumed in the trip. If individuals with eyes were started toward the light it was found that they would, on the average, bend 78° Concpon, Reactions to Light. 319 toward the right or left. Animals ina healthy condition, but with head cut off, showed a directive effect by an average bending of 57°. In case the initial direction coincided with that of the light the deviation from a straight line dropped to 24° for a normal animal and 35° for those without eyes. The conclusion is that phototaxis is only in part due to the eyes. The amount of non-directive wandering which takes place was learned from the ae obtained under vertical light. Animals with eyes wander on the average 27°. The bending of 78° by animals headed toward the light must be discounted by this much to obtain the directive effect of light upon them. ‘The course away from the light with 24° of wandering has a turning of only 3°, due to the directive action of light. The results of the comparison of the undirected with the directed course of Planaria are in point with the criticism made by Torrey ('07) upon JENNINGS’ view of the manner in which animals may move forward after they have once become oriented. ‘The latter believes that a straight course may be regarded as due in part at least to a lack of any stimulus of light or any other agent which would tend toturn it. Torrey takes the position that the straight course may be due to balanced rather than to non-stimulation. As a matter of fact, we have seen that Planaria’s course from the light is influenced only slightly by the light. Convoluta, to which GaMBLE and KEEBLE ('03, 03a) gave their attention, is a sedentary planarian containing a large amount of chlorophyl. ‘The animal gives a positive response in strong illumination which is markedly greater or less depend- ing upon whether the bottom of the aquarium is white or black. The conditions of tonus found in this creature are peculiar, very likely because of the presence of chlorophyl in its body. If kept in darkness fora while its muscles become contracted and its movements sluggish. Very strong light produces a similar effect except that the animal is now unusually susceptible to being broken to pieces if handled. Convoluta lives within the tide lines and periodically moves to the surface of the sand. The changes in tonus give GAMBLE and KEEBLE an explanation of this procedure. The study of planarian light reactions by WALTER (07) is one of the most exten- sive and many-sided contributions that have as yet appeared upon the light-reac- tions of any group. A comparison is made between representatives of several genera in regard to nine different varieties of response which he distinguishes in the animals. Diagrams are given of typical paths followed by the various species if allowed to roam in an aquarium until they come to rest. WALTER says of these, “It may be afhrmed that the generic differences are so pronounced that one could take a miscellaneous unidentified assortment of such records and correctly assign the great majority of them to the proper genera.”’ “Two species of one genus show a nearer relationship in behavior than do the different genera. Among the conditions of illumination which were applied to the worm are a series of intensities of non-directive vertical light, including zero intensity, changes in the strength of the entire field of non-directive light, two adjacent non-directive fields of differing intensity, directive light of constant and of varying intensities. Animals in the dark make many double turns which are termed “‘indefinite” as they evidently are not of orienting value. In non-directive light they are replaced by single turns. ‘The stimulating effect of simultaneous change of intensity over the entire animal varies with the rapidity of change. Decrease of illumination is more of a stimulus than an increase. 320 “fournal of Comparative Neurology and Psychology. A large number of observations upon the effects of other tropisms, physiological states and various internal factors are recorded. For example, some individuals were found to change from the usual response of the species for a time and then to return to it. By a certain arrangement of conditions it is shown that negative photokinesis 1s overcome by phototaxis. The tendency to wander may result in many excursions contrary to the phototactic influence. ‘This increases the effectiveness of negative photokinesis by bringing the animals into dark regions to which they would not come through phototaxis. CRUSTACEA. The photic reactions of crustaceans have received much attention. ‘Their pho- totaxis is characterized by quickness of alignment with the light and straightness of course. Photokinesis is often strikingly marked. One is especially impressed in looking over the papers upon the group by the variety of ways in which a reversal of phototaxis has been produced. Tow e (’00) found that the positive Cypridopsis could be readily made negative by squirting it through a pipette. Negative animals could less readily be turned to positive by the same means. In a series of papers upon entomostracan light reactions by YERKES (00, ’03) a similar condition of things is described for Cypris and Daphnia. Cypris is made positive in this way, and Daphnia faintly negative. In the latter animal it could not be determined whether the opposite effect could be produced, for the negative condition was at the best very weak and transitory. YERKES believed that in gen- eral the reversal most readily effected is from the less to the more common reaction for each species. ‘There is some probability that the stimulus producing the change is thigmotactic inasmuch as according to PARKER’s observation, the crustacean. Labidocera though affected in like manner to these others when squirted through a pipette, is not influenced as to its light response by vigorous shaking. YERKES attempted to find whether increase of intensity calls forth greater accu- racy of phototactic response. The question was answered by observing the duration of trips of constant length made by Daphnia and Cypris under various conditions of illumination. ‘There occurred a marked shortening of the period occupied by a trip if the illumination was increased. YERKES believes this partly due to a straight- ening of the course and therefore to more accurate orientation. ‘The difference between its phototaxis and that of Corixa, therefore, consists only to the degree of accuracy of the orientation. Daphnia was found to recoil and turn back into the light if its head came into a shadow somewhat as in the avoiding reaction of Protozoa. YerkEs has been able to obtain a physically perfect graded field of vertical light by means of a lens consisting of the segment of a cylinder. All light which passes through the bottom of the aquarium is deflected away by a mirror, thus avoiding reflected light. A Daphnia placed in the apparatus goes obliquely upward toward the lighter end at an angle of 45°; it is evident that this is partly due to an attempt at phototactic alignment with the vertical light. “The significance of the horizontal component of this motion is not stated. Daphnia does not seek an optimum but moves unhesitatingly into the most intense illumination it can reach. The harmful effects of strong light are shown Conopon, Reactions to Light. B21 by jerky and disorganized movements. PrarL and Cove (’o1) have described a like photokinetic effect in a variety of animals which they subjected to the light of a projection lantern. A leech, a nemertean worm and a small crustacean are rendered especially active by strong light until they show exhaustion by sluggish- ness and insensibility to tactile stimuli. Hoxtmes (o§a) finds that Ranatra acts like Daphnia in strong light, yet when it has been in the dark for a time it is not only sluggish but negative. The amphipod Orchestia which lives under drift seaweed is negative for a time when exposed to daylight, but turns positive much as does Ranatra. The beach flea Talorchestia, though a nocturnal animal, gives a positive Fesponse as strong as any that has been recorded. Ranatra also responds in a positive way with great vigor. The positivity of these dark-loving animals requires explanation. Increase of temperature hastens a change of Ranatra in a positive direction and accentuates the positive response when it is already present. Dupping into water gives a negative reaction which is probably a contact effect. Hoimes (or) dis- covered that the immersion of certain terrestrial amphipods will also effect a reversal. Labidocera was found by Parker to behave toward light differently from Daph- nia and Ranatra. It reacts positively in diffuse light, but turns strongly negative in direct sunlight. He cites a number of similar cases. ‘The possible adaptive value of the reaction does not need to be pointed out. SmitH (’05) brings forward a reasonable explanation of the gradual change of sense of response in a number of crustaceans, when subjected to a marked increase or decrease of illumination. It depends upon the fact that in Gammarus annulatus, as in many other crustaceans, the retinal pigment of the individual put from the dark into the light migrates distally at a rapid rate for about fifteen minutes, then moves more slowly for the remainder of an hour. ‘This mechanism protects the more sensitive parts of the eye from over illumination. A large part of a group of animals subjected to strong light change their response within fifteen minutes. At the end of an hour nearly all will be positive. A possible relation between pig- ment migration and photic response is evident. DIURNAL MIGRATION. PaRKER and Esterty contribute to the explanation of the movements of plank- ton crustacea and Harper of insect larve from their nocturnal position at the sur- face of the water to greater depths during the daytime. ParkER (’02) concerned himself with Labidocera zstiva, a typical marine plankton crustacean. He first made sure that geotropism could not account for the migration by any reversal through the agencies of temperature and density. Weak illumination gave a posi- tive response; daylight produced a negative reaction sufficiently strong to overcome the negative geotropism. He thus explains the migration: “*Females rise to the surface with the setting of the sun because they are positively phototactic to faint light and negatively geotropic; they descend into deep water at the rising of the sun because they are negatively phototactic to strong light, their negative geotropism being overcome by their negative photopism. ‘The males follow the females in migration because they are probably positively chemotropic toward the females.” A peculiarity of the method used by EstEerty (’07) upon Cyclops consisted in subjecting animals after a long period in the dark to a series of intensities in various 322 ‘fournal of Comparative Neurology and Psychology. orders of succession. By this means his records show the reaction of the animal to each intensity after exposure to each other intensity. This arrangement sug- gests a labor saving way of studying various kinds of previous stimuli upon light response. He finds that Cyclops is neutral to artificial lights of low intensity and negative to those of high intensity if it be subjected to them after confinement in darkness. Exposure for some time to light of any intensity makes it negative in all kinds of illumination. Especially interesting is the influence of light upon the geo- tropic response. Under illumination so diffuse as to be non-directive the animals are strongly positive in their geotropism. If light be removed they become negative. Esrerzy concludes that phototropism is of little importance in the diurnal migra- tion in a direct way. Light, however, probably produces some photo-chemical change in the animal, as a result of which positive geotropism occurs during the day. HarPER’s (07) work has to do with the insect larva Corethra. The animal is positively geotropic in strong light whether it come from above or below, and nega- tively geotropic in dim light. It is also distinctly phototactic. It is rae that the chief effect of the light upon migration must be due to its action upon geotropism. Harper thinks that it is likely that while the animal would go down in the day and come to the surface at night obedient to geotropism it would also respond phototrop- ically by collecting in well illuminated areas at whatever level it happened to be swimming. There are several extremely interesting and rather lengthy quantitative studies upon the distribution of plankton in various American and European lakes of which a recent example has appeared in the work of Jupay (04). It is not advisable to discuss them here as their interest is chiefly ecological. It may be said, however, of Jupay’s work that it shows conclusively that light is a very important though by no means the only factor in diurnal migration. It brings to light the fact that the downward migration of plankton begins long before sunrise if not before midnight. The reason of this early departure from the surface is not forthcoming. INSECTA. In his paper on the light reactions of the pomace fly Drosophila, CARPENTER ('05) gives us one of the first general analyses, by laboratory methods, of the light responses of a winged insect. Like many Crustacea, Drosophila is strongly photo- tactic as well as photokinetic. Like Daphnia it will go into any strength of light without reversal. Very great intensity produces not only rapid movement but apparent loss of coordination. By shaking the jar containing the flies they are rendered negatively geotropic. It is a suggestive fact that as in the case of plankton crustaceans light may affect the geotropism while not acting directively itself. Car- PENTER believes its effect is produced through a stimulating action much like that of the mechanical shaking. MOLLUSCA, FRANDSEN (’o1), Mirsukuri (’o1), WALTER (’06) and Boun have given more or less attention to the behavior of gasteropod mollusks toward light within the period of this review. It would not be profitable to consider their papers since not only has there been a lack of an extended recent study of the group but there is also investigation under way upon their light reactions. Conopon, Reactions to Light. 323 PISCES AND AMPHIBIA. Certain work upon the compensatory movements of vertebrates has already been referred to while discussing existence of phototaxis in binocular vision. ‘The atten- tion of several workers has also been recently given to locomotor light responses of fishes and amphibians, in particular those dependent upon the light sensitiveness of the skin. | Previously a few amphibians were known to possess this dermal function and blind newts of the genus Triton had been found to collect in the shade. Two primitive vertebrates, Amphioxus and the larval lamprey, have been exam- ined by ParKER (’05, ’06) with the resulting discovery that both can perceive light through the skin. Amphioxus is phototactic and negatively photokinetic. The larval lamprey has these same characteristics. It is somewhat startling to learn that the latter animal orients even when the head is removed. ‘The especial sensitiveness of the tail to light is correlated with a habit of burrowing head first until the rest of the body is covered. ‘The earliest study of the orientation of blind fishes in response to light was made by E1cENMANN (00) upon Ambylopsis. PAYNE (07) has within the year repeated and extended E1GENMANN’s observations. “The animals gather in shade by some other process than direct orientation. ‘They give a stronger re- sponse under vertical than under horizontal illumination. A photokinetic effect seems to be present along with movements suggesting discomfort. ‘The experi- ments employed are simple and not devised to carry very far the analysis of the com- plex nervous activities of the animals. ParKER (’03) demonstrates the occurrence of phototaxis for blind amphibians bymeans of frogs whose optic nerves have been severed. The animals can orient promptly, but only occasionally do they move toward the light. If the skin of a normal animal be covered orientation takes place readily by means of the eyes. TorELLE (’03) concerns herself with the behavior of the frog without reference to the relative activities of eyes and skin. Orientation is tested in certain experi- ments by placing the frog in a box 12 in. long with a glass window 9 in. wide and § in. high. It may be objected to this procedure that the animal was presented with a pattern of light and shade whose image possibly covered only a portion of the retina at once. ‘The only type of phototaxis which could be inferred from orienta- tion toward the window was that variety present in all binocular vision. ‘The other methods employed by Tore. te are not thus open to criticism, and her conclusions are well established. She, as well as PARKER, finds that orientation to light fre- quently takes place without locomotion. If one eye be covered the animal orients obliquely to the light when at rest. In spite of this fact it goes directly toward the light as did Ranatra when so blinded. When an individual is put in direct sunlight it will do one of two things. If there is a possibility of its walking into the shadow without losing its orientation to the sun it is likely to do so, but frequently it varies the process by hopping into the shadow and then turning around so as to come to rest with its head toward the light. The field toward which the animal will orient for the time being is thus chosen in the same manner as Cote describes for certain insects. Some features of the frog’s response are more mechanical than those we have just been considering. While sitting facing the light it may be made to raise or depress its head in an effort to keep its alignment with the rays if their angle of incidence upon it be changed. The behavior of the animal at low temperatures is probably related to its hibernating habit. Below 10° C. in air it becomes negatively photo- 324 “fournal of Comparative Neurology and Psychology. tactic and crouches down making feeling motions with its head. A very similar condition obtains when it is in water. THE REVERSAL OF PHOTOTROPISM BY MEANS OF CHEMICALS. A few scattered cases have been known where some substance in solution has changed the light response of an aquatic animal supposedly through its chemical effect. Los (’06) alone has attempted a duplication of this process experiment- ally. He has succeeded in making a number of organisms positive by adding a trace of acid to the water containing them. Fresh water Copepods, Daphnia, Gammarus, and Balanus larva, as well as Volvox, have been made positive in this way. Logs thinks it probable that the hydrogen ion is the active factor, because normal salts of effective acids produce no change. Alkalies affect the phototropism by destroying the activity of the acid. Volvox differs from the crus- taceans in its behavior toward alkalies in that they act directly upon it to make it positive. Hydrochloric, oxalic, and acetic acids reverse, but less quickly, than carbon dioxide. Low temperature has the same effect as acid upon most of the animals mentioned. It may also be made to reinforce the effect of acid. A hypothetical substance within the animals which is affected by the tem- perature and chemical condition of the water is invoked by Logs to explain these reversals. His theory is also extended to cover changes due to temporary physio- logical states, as for instance the reversal of the Porthesia larva upon becoming well fed. He argues that acid cannot favor the production of a chemical compound producing a positive condition because less acid is required to produce the positive state at 10° C. than at 20° while the velocity of a chemical reaction is more rapid at the higher than at the lower temperature. ‘Therefore a substance favoring nega- tive reaction is built up by the protoplasm and its formation or activity is hindered by acid. Or possibly a compound favoring positive reaction and situated in the | body may have its activity checked by a different one inthe retina. Acids by hinder- ing the formation of this last would produce positive phototropism. An increase in temperature would augment the velocity of its formation and so produce nega- tive response. Loers did not mention that a rise in temperature makes some ani- mals positive; this fact makes necessary a more general form of the theory. / Mast ('07) in his paper on Volvox makes use of the principle of reversible chem- ical reactions in much the same way as Logs. He further takes into consideration the significance of the substances on the opposite sides of the equation and recog- nizes that any theory must explain reversal in either direction for each kind of stim- ulus affecting the light reaction. He has especially in mind the reversal due to change of light intensity but applies it to other kinds as well. His reasoning is as follows for the case in which great intensity changes the usual positive reaction to negative. Let X stand for a substance, on the one side of the equation and 7 for one upon the other. Suppose an increase of X beyond a definite amount to produce a positive reaction and of Y a negative one. When X and Y are equal the animal is neutral. Since change of temperature produces a new equilibrium in any reversible chemical reaction, thus altering the relative amounts of the substances on opposite sides of the equation, it is reasonable to suppose that light changes can do the same, inasmuch as they also affect the amount of energy involved. If we suppose intense light to fall upon an animal in which the substances are of the proportion X = Y Concpon, Reactions to Light. 325 we would soon get a decrease of X and an increase of Y. ‘The equation would read X—=Y-+4+. Y being increased from the amount giving neutrality the animal is made negative. A reversal of this process would occur in sufficiently weak light. Acclimatization of the animal consists in changing the proportions of X and Y which give the neutral reaction. The correlation by Lors and Mast of reversal of light response and reversal of chemical reaction is suggestive and tempting. Unfortunately it is difficult to test its validity by experiment. Also, while it is beyond question that light may cause chemical change it is doubtful whether it can produce a reversal of reaction. A considerable number of agencies have been referred to by which reversal may be brought about. Among them may be named heat, mechanical and chemical stimuli, the various tropisms, condition of development of the individual, tempor- ary physiological states, such as hunger and sexual activity, previous stimuli, and certain stereotyped procedures. Inasmuch as two fairly definite types of light response have by this time become distinguished, there is encouragement to study the effect upon them of the various agencies which have just been named. LoEB and some others have already given a certain amount of attention in this direction. It is one of the tasks which lie next at hand in the comparative psychology of lower animals. BIBLIOGRAPHY. Apams, GrorcE P. 1903. On the Negative and Positive Phototropism of the Earthworm Allolobophora feetida (Sav.) as determined by Light of Different Intensities. Amer. Four. Physiol., vol. 9, pp. 26-34. Bett, J. CARLETON. 1906. Reactions of the Crayfish. Harvard Psychological Studies, vol. 2, pp. 615-644. CARPENTER, FREDERICK W. 1905. ‘The Reactions of the Pomace Fly (Drosophila ampelophila Loew) to Light, Gravity and Mechanical Stimulation. Amer. Nat., vol. 39, pp. 157-171. CHIMELEVSKY, V. 1904. Ueber Phototaxis und die physikalischen Eigenschaften der Kultur tropfen. Bes- hefte, Bot. Cent., vol. 16, pp. 53-66. Cote, L. J. 1901. Notes on the Habits of Pycnogonids. Biol. Bull., vol. 2, pp. 195-207. 1907. The Influence of Direction vs. Intensity of Light in Determining the Phototropic Responses of Organisms. Science (n. s.), vol. 26, p. 784. 1907a. Experimental Study of the Image Forming Powers of Various Types of Eyes. Proc. Amer. Acad. Arts and Sci., vol. 17, pp. 355-417. Deargorn, G. V.N. 1900. Notes on the Individual Psycho-physiology of the Crayfish. Amer. Four. Physiol., vol. 3, pp. 404-433. Dreyer, G. 1903. Influence de la lumiére sur les Aimbes et leurs Kystes. Ov. Danske Selsk., p. 399-421. Dvusots, RAPHAEL. 1905. Apropos Vheliotropisme. C. R. Soc. Biol., vol. 58, p. 299. EIGENMANN, C. H. 1900. The Blind Fishes. Biol. Lect. M. B. L., Woods Holl, for 1899, pp. 113-126. EIA G (C5 Ob 1907. The Reaction of Cyclops to Light and Gravity. Amer. Four. Physiol., vol. 18, pp. 47-54. FRANDSEN, P. Igor. Studies on the Reaction of Limax maximus to Directive Stimuli. Proc. Amer. Acad. Arts and Sct., vol. 37, pp. 185-229. 326 © “fournal of Comparative Neurology and Psychology. Game ie, F. W. anp Keepir, FREDERICK. 1903. The Bionomics of Convoluta roscoffensis, with Special Reference to its Green Cells. Proc. Royal Soc. Lond., vol. 72 pp-, 93-98. 1903a. The Bionomics of Conyoluta roscoffensis with Special Reference to its Green cells. Quart. Fourn. Mic. Sct., vol. 47, pp- 363-431. Garrey, W. E. 1904. A Sight Reflex shown by Sticklebacks. Biol. Bull., vol. 7, pp. 79-84. Hapiry, Puirir B. 1906. Observations on some Influences of Light upon the Larval and Early Adolescent Stages of the American Lobster. Preliminary Report. 36th Annual Rept. Comm’r Inland Fisheries, Rhode Island, pp. 237-257. 1g06a. The Relation of Optical Stimuli to Rheotaxis in the American Lobster, Homarus americanus. Amer. four. Physiol., vol. 17, pp. 326-343- Harper, E. H. 1905. Reactions to Light and Mechanical Stimuli in the Earthworm Pericheta bermudensis, Beddard. Biol. Bull., vol. 10, pp. 17-34. 1907. The Behavior of the Phantom Larve of Corethra plumicornis Fabricius. ‘four. Comp. Neurol. Psychol., vol. 18, pp. 435-456. Hermes, Witiiam B. 1907. An Ecological and Experimental Study of Sarcophagide with Relation to Lake Beach Débris. Four. Exp. Zoél., vol. 4, pp. 45-83. Houmes, S. J. 1901. Phototaxis in the Amphipoda. Amer. Four. Physiol., vol. 5, pp. 211-234. 1903. Phototaxisin Volvox. Biol. Bull., vol. 4, pp. 319-326. 1905. The Selection of Random Movements as a Factor in Phototaxis. ‘four. Comp. Neurol. Psychol., vol. 15, pp. 78-112. 1g05a. ‘The Reactions of Ranatra to Light. Four. Comp. Neurol. Psychol., vol. 15, pp. 305- 349- 1907. Observations of the Young of Ranatra quadridentata, Stal. Bzol. Bull., vol. 12, pp. 158-164. -Hott, E. B. anp Lex, F. S. 1go01. The Theory of Phototactic Response. Amer. four. Physiol., vol. 4, pp. 460-481. Jennincs, H.S. 1900. Studies in the Reactions to Stimuli in Unicellular Organisms. V. On the Movemerts and Reactions of the Flagellataand Ciliata. Amer. Four. Physiol., vol.3, pp.229-260 1904. Contributions to the Study of the Lower Organisms. Carnegie Institute of Washing- ton, Publication 16. 1905. The Method of Regulation in Behavior and in other Fields. ‘four. Exper. Zoél., vol. 2, PP: 473-494- 1906. Modifiability in Behavior. II. Factors Determining the Direction and Character of Movements in the Earthworm. ‘Four. Exper. Zoél., vol. 3, pp- 435-455- 1906a. Behavior of Lower Organisms. New York. 1907. Behavior of the Starfish Asterias farreri de Loriol. Univ. Cal. Pubs.,vol. 4, pp. 53-185. Jenninecs, H. S. anp Crossy, J. H. igor. Studies, etc. Will. The Manner in which Bacteria react to Stimuli, especially to Chemical Stimuli. Amer. four. Physiol., vol. 6, pp. 31-37- Jupay, C. 1904. The Diurnal Movements of Plankton Crustacea. Trans. Wisc. Acad. Sct. Arts Let., vol. 14, pp. 534-568. Jensen, Paut. 1904. Die physiologischen Workengen des Lichtes. Verh. Ges. d. Naturf. Leipzig, for 1903, vol. 75, pp. 240-254. Logs, J. 1900. Comparative Physiology of the Brain and Comparative Psychology. New York. 1904. The Control of Heliotropic Reaction in Fresh Water Crustaceans by Chemicals, especi- ally COs. Univ. of Cal. Pub., Physiol., vol. 2, pp. 1-3. 1g0§. Studies in General Physiology. Chicago. 1906. Ueber die Erregung von positivem Heliotropismus durch Saure inbesondere Kohlen- saure, und von negativem Heliotropismus durch ultraviolette Strahlen. Arch. f. ges. Physiol., vol. 115, pp. 564-581. Loes, J. 1907. 19074. Concpon, Reactions to Light. 327 Concerning the Theory of Tropisms. Four. Exper. Zodl., vol. 4, pp. 151-156. Ueber die Summation heliotropischen und geotropischen Wirkungen bei den auf der Dreischiebe ausgelosten compensatorischen Kopfbewegungen. Arch. f. ges. Phystol., vol. 116, pp. 368-374. Lonestarr, G. B. 1905. Lyon, E. P. 1904. 1907. Mast, S. O. 1906. 1907. Mirsuxur, K. Igol. Morse, Max. 1906. 1907. Nuet, J. P. 1904. Parker, G. H. 1902. 1903. 1903a. 1905. 1906. 1907. Heliotropism in Parage and Pyrameis. Trans. Entom. Soc. Lond. for 1905, pp. 28-29. On Rheotropism. 144-161. Note on the Heliotropism of Palaemonetes Larve. Biol. Bull., vol. 12, pp. 23-25. I. Rheotropism of Fishes. Amer. Four. Physiol., vol. 12, pp. Light Reactions in Lower Organisms. I. Stentor coeruleus. Four. Exper. Zodl., vol. 3, Pp. 354-394- Light Reactions, etc. II. Volvox globator. Four. Comp. Neurol. Psychol., vol. 17, pp- 99-180. Negative Phototaxis and other Properties of Littorina as Factors in Determining its Habitat. Annotations Zoologice Faponeses, vol. 4, pp. 1-19. Notes on the Behavior of Gonionemus. Four. Comp. Neurol. Psychol., vol. 16, pp. 450-456. . Further Notes on the Behavior of Gonionemus. Amer. Nat., vol. 41, pp. 683-688. La Vision, Paris. The Reactions of Copepods to Various Stimuli and the Bearing of this on Daily Depth Migrations. Bull. U. S. Fish Comm. for 1901, pp. 103-123. The Skin and the Eyes as Receptive Organs in the Reactions of Frogs to Light. Four. Physiol., vol. 10, pp. 28-36. The Phototropism of the Mourning-Cloak Butterfly, Vanessa antiopa Linn. Mark Anniversary Volume, pp. 453-567. The Stimulation of the Integumentary Nerves of Fishes by Light. vol. 14, pp. 413-420. The Reactions of Amphioxus to Light. 61-62 (213-232). The Interrelation of Sensory Stimulations in Amphioxus. Science (n. s.), vol. 25, pp. 724-725. Amer. Amer. Four. Physiol., Proceed. Soc. Exper. Biol. Med.,vol.3, pp. Parker, G. H. anp Arkin, L. IgOl. The Directive Influence of Light on the Earthworm Allolobophora foetida (Sav.). Amer. four. Physiol., vol. 5, pp. 151-157. Parker, G. H. anp Burnett, F. L. 1900. The Reactions of Planarians with and without Eyes to Light. Amer. Four. Physiol., vol. 4, pp. 373-385- PAYNE, FERNANDO. 1907. Reactions of the Blind-fish Ambylopsis to Light. Bzol. Bull., vol. 13, p. 317. Peart, RayMonp AND Cote, L, J. IgoI. Rant, Em. 1901. 1903. 1906. Reese, A. M. 1906. RotHert, W. 1903. The Effect of Very Intense Light on Organisms. 3d Rept. Mich. Acad. of Science, Pp: 77-78. Ueber die Phototropismus einiger Arthropoden. Biol. Cent., vol. 21, pp. 75-86. ‘Untersuchungen tiber die Phototropismus der Tiere, Leipzig. Einige Bemerkungen und Beobachtungen iiber den Phototropismus der Tiere. Byo/. Cent., vol. 26, pp. 677-690. Observations on the Reactions of Cryptobranchus and Necturus to Light and Heat. Biol. Bull., vol. 11, pp. 93-99. Ueber die Wirkung des Aethers und Chloroform und die Reizbewegungen der Mikro- organismen. Jahrb. f. wiss. Bot., vol. 39, pp. 1-70. 328 Fournal of Comparative Neurology and Psychology. ScHOENICHEN, WALTER. 1904. Die Empfindlichkeit der Nacht-Schmetterlinge gegen Licht-Strahlen, Prometheus, vol. 16, pp. 29-30. ScCHOENTEDEN, H. 1902. Le Phototropisme de Daphnia magna Straus (Crust.). Ann. Soc. Ent. Belgique, vol. 46, pp. 352-362. SmirH, AMELIA C. 1902. The Influence of Temperature, Odors, Light and Contact on the Movements of the Earthworm. Amer. Four. Physiol., vol. 6, pp. 459-486. SmitH, GRANT. 1905. The Effects of Pigment Migration on the Phototropism of Gammarus annulatus. Amer. Four. Physiol., vol. 13, pp. 205-216. ToreELLE, E. 1903. The Response of the Frog to Light. Amer. four. Physiol., vol. 9, pp. 466-488. Torrey, Harry BEAL. 1907. The Method of Trial and the Tropism Hypothesis. Science (n. s.), vol. 26, pp. 313- 3236 Tow er, Exizanetu W. 1900. A Study on the Heliotropism of Cypridopis. Amer. Four. Physiol., vol. 3, pp. 345- 365. Watter, Hergert EuGENE. 1906. The Behavior of the Pond Snail Lymnzus elodes Say. Cold Spring Harbor Mono- graph No. 6. j 1907. The Reactions of Planarians to Light. our. Exp. Zoél., vol. 5, pp. 35-162. Yerkes, Ropert Mearns. 1goo. ‘The Reaction of Entomostraca to Stimulation by Light. II. Reactions of Daphnia and Cypris. Amer. Four. Phystol., vol. 4, pp. 405-423. 1902. A Contribution to the Physiology of the Nervous System of the Medusa Gonionemus murbachii. PartI. The Sensory Reactions of Gonionemus. Amer. Four. Physiol., vol. 6, pp. 434-449- 1903. The Reactions of Daphnia pulex to Light and Heat. Mark Anniversary Volume, pp. 9-377: 1903. A Seats of the Reaction and Reaction-time of the Medusa Gonionema murbachii to Photic Stimuli. Amer. four. Physiol., vol. 9, pp. 279-397- 1904. The Reaction-time of Gonionemus murbachii to Electric and Photic Stimuli. Biol. Bull., vol. 6, pp. 84-95. 1906. Concerning the Behavior of Gonionemus. ‘four. Comp. Neurol. Psychol., vol. 16, pp. 457-463. ZELENY, C. 1g05. The Rearing of Serpulid Larve with Notes on the Behavior of the Young Animals. Biol. Bull., vol. 8, p. 308. LITERARY NOTICES. Pfungst, Oskar. Das Pferd des Herrn von Osten (Der kluge Hans). Ein Beitrag zur experiment- ellen Tier- und Menschen-Psychologie mit einer Einleitung von Prof. Dr. C. Stumpf sowie einer Abbildung und fiinfzehn Figuren. Pp. 193. Lerpzig: Verlag von Ambrosius Barth. 1907. Clever Hans has been in the public eye for four or five years and many charming magazine stories have been written about his wonderful and supermundane powers. Hans and his master, Herr von OsTEN, apparently were first brought to scientific and world-wide popular notice by the zodlogist, ScHILLINGs. So wonderful were the attainments of the horse that a ‘“‘ Hans commission” of thirteen men was chosen from widely different scientific fields and asked to solve the question as to whether there was any secret means of rapport between horse and master. “The commission reported that Herr von Osten did not, at least consciously, control the responses of the animal by means of signals. Srumpr’s investigations of the behavior of Hans began on the thirteenth of October and were continued until November 29, 1904. Herr O. Pruncsr and Dr. E. v. HornposteEx were present during these observations. “The main conclu- sion reached was to the effect that visual signs of one kind or another were utilized by the horse in making the proper responses. O. Prunest then continued the work in two ways. First, he made a thorough test of the various acts of Hans, then determined the sensory cues to which the horse reacted: Second, he substituted human subjects for Hans, who were required to answer questions (similar to those put to Hans) by utilizing the same kind of data which Hans employed. The experimental work was conducted partly in an open court and partly in a large, white tent. Carrots, sugar and bread were the rewards for correct answers. All questions asked were put in such a form that the answers could be given by tapping a certain number of times with the foot. 1. Can Hans read numbers? Printed or written numbers were placed on cards and exhibited to Hans. Hans was supposed to tap the appropriate number of times. Two methods were tried. First, the questioner himself was ignorant of the number displayed; second, the questioner knew the correct answer. When the questioner was ignorant of the answer, only 8 per cent of correct responses was returned. On the other hand, when the questioner knew the answer, 98 per cent of correct answers was returned. 2. Can Hans read words? Such words as “‘Hans,” “Stall,” etc., were printed on placards and arranged in a numbered series on a board. ‘The horse was asked to indicate by tapping on which placard any chosen word lay. When the word chosen was unknown to the experimenter, no correct answers were returned, when known to the experimenter, 100 per cent of correct answers was given. 330 “fournal of Comparative Neurology and Psychology. 3. Can Hans spell? The letters of the alphabet were arranged in horizontal rows on a board. Hans had to indicate first the row, and then the position in the row, of each letter called forinthe word. ‘The experimenter did not know the posi- tions of any of the letters of the alphabet except s and a (the positions of these were purposely ascertained). Hans was asked to spell such words as “Schirm,” “Arm,” “Rom” and “Hans.” Under these conditions, Hans was a complete failure. . Afterwards, when the questioner knew the positions of all the letters, the horse not only could “spell,” but also could answer questions involving several long words. 4. Can Hans make arithmetical calculations ? The method adopted in this test was as follows: Herr von OsTEN would whisper a number into the ear of the horse which was unknown to the rest of the observers. PFuNGsT would then give another number in the same way and then the horse was asked to add the two numbers. The answer, of course, was unknown to all. In 31 tests of the above type, the horse returned correct answers in three cases. In 31 cases where the questioner knew the answer, 29 correct responses were made. 5. Can Hans even count? The Russian kindergarten counting device (aba- cus) was used in this experiment. First, the questioner turned his back upon the machine and then shoved forward a certain number of balls. (The questioner in no case knew the number of balls which he had actually pushed forward.) The horse was then asked to indicate the number of balls which had been advanced. No correct answers were given. On the other hand when the questioner knew the answer, Hans in all cases responded correctly. 6. Memory tests. In the absence of the experimenter, a number, or the day of the week, was mentioned to the horse which he was to indicate to the experimenter when the latter returned. In ten trials, only two correct answers were returned. One of the two correct answers was the number three which Hans always “played” when in doubt. 7. Musical memory. A little one octave harmonica was operated in an adjoin- ing room. Hans was asked to indicate whether the first, second, or third, etc., tone had been played. When not attended by the experimenter, the horse always failed. When the questioner could be observed by the horse, all the answers were correct. In summarizing the results of these experiments, we find that when the questioner knew the answer to the proposed query, from go to 100 per cent of the horse’s responses were correct. On the other hand, when the answer was unknown to the questioner, the highest percentage of correct answers was 10. According to the author, these latter correct answers must be ascribed to accidents. PFUNGST concludes “‘that Hans can neither read, count nor perform calculations with num- bers. He can distinguish neither coins nor cards. He is not acquainted with the calendar nor with our system of time. He cannot even recall a number given him but a moment before. Finally, there is no trace of a musical ear. From all this, we must conclude that the horse is unable to work independently, but is dependent upon his environment for particular stimulations” (free translation). After the above data had been obtained, the author tested very carefully the means by which Hans gets his cue. Without going into detail in this part of the work, it may be said at once that if visual stimulation were cut off by means of blinders (the horse has a wonderfully wide field of vision ) the horse could no longer give the correct responses. In making his responses, it was observed that Hans never looked at the objects to which he was supposed to react, but always at his questioner. Literary Notices. Bai The sensory stimulations from which Hans took his cue consisted of certain slight movements of bis questioner’s body. After Herr von OstTEN had stated the problem, he tended always to bend the head and trunk slightly forward; where- upon Hans extended his right foot and began to tap without putting his foot back after each successive tap. When the desired number of taps was reached, Herr von OsTEN would give a slight upward jerk of the head. At this second signal, the horse would retract the foot to its normal position (this last movement was never counted). Now when the horse had ceased to tap, the questioner would raise the head and trunk to an upright position. ‘This second and more extensive movement (that is, more extensive than the slight upward jerk of the head) cannot be regarded as the signal for the retraction of the foot. If the larger movement, however, did not follow the slight upward jerk of the head, the horse would give a single vigorous tap with the /eft foot, without however first extending it. Horizontal movements were without effect in eliciting responses from Hans. All downward motions of the body, eyebrows, nostrils, arms, etc., were signs to begin the tapping movement, whereas the raising of these parts was a signal to cease tapping. The results of the experiments conducted in the laboratory upon human sub- jects in the role of Hans form an interesting contribution to the study of the psy- chology of involuntary movements. Surely, this careful and painstaking work of PrFuNGsT may be prescribed as an antidote henceforth and forever to those untrained but enthusiastic observers who may be filled with the desire to describe the doings of pet animals in glowimg anthro- pomorphic terms. J. B. W. Yale Psychological Studies. Edited by CHartes H. Jupp, n. s. vol. 1, no. 2. Psychological Review Monograph Supplements, vol. 8, no. 3, pp. 227-423. 1907. The second half of the first volume of the new Yale Studies contains five papers, at least four of which show that perfection of experimental technique which is char- acteristic of Professor JUDD’s laboratory. In Tonal Reactions, Dr. E. H. Came- RON gives an interesting study of tones as produced by the human voice, both with and without distractions. “‘The attempt to sing a uniformly sustained tone is not successful. ‘The beginning of the tone is markedly irregular and there is a tendency to raise the pitch towards the end of the tone. ‘There is usually a har- monious relation between the sung tone and the distracting tone.” Mr. F. N. FREEMAN contributes some Preliminary Experiments on Writing Reactions which connect interestingly with the Analysis of Reaction Movements contained in the first half of the volume. Both of these papers have important bearings on the mechanism of consciousness, of which the full significance, in the reviewer’s opinion, will appear only later. Mr. H. N. Loomis reports on Reactions to Equal Weights of Unequal Size. He finds that the weight of smaller size is usually raised later than the larger weight, and that the hand which lifts this latter has a much greater muscular tension. With practice the illusion tends to disappear, and so too these differences in the manner of lifting. In Studies in Perceptual Development Profes- sors Jupp and D. J. Cow inc describe experiments in which subjects learned to draw complex figures. Each figure was shown repeatedly for ten seconds, and after each view the subject reproduced once as well as he could what he had seen. The issue concludes with some remarkable Photographic Records of Convergence and Divergence, including a theoretical discussion of the mechanism of perceptual 332 fournal of Comparative Neurology and Psychology. unity, by Professor Jupp. In general, lateral movements of both eyes in the same direction are a more thoroughly established form of coordination than are move- ments of convergence and divergence; but many particular facts of movement are brought out which are well worth studying in detail. As is well known, the author denies the significance ordinarily attributed to sensations of movement in the forma- tion of spatial and other percepts, and his view 1s expressed in the very pregnant and, in the reviewer's opinion, just proposition: “‘ The only concept which is of any value in the clear explanation of perceptual unity is the concept of codrdination,” i. e€., the coordination of motor response. E. B. H. The Archives of Psychology. Edited by R.S. Woopworrn. New York, The Science Press. The Archives of Psychology is a continuation of the psychological part of the Archives of Philosophy, Psychology, and Scientific Methods, of which one volume, consisting of the following monographs, was published. Measurements of Twins. By Epwarp L. THornpike. Avenarius and the Standpoint of Pure’ Experience. By Wenpett T. Busu. The Psychology of Association. By Frirx ArNoxp. The Psychology of Reading. By Watrer Fenno Dearporn. The Measurement of Variable Quantities. By Franz Boas. Linguistic Lapses. By Freperic Lyman WELILs. The Diurnal Course of Efficiency. By Howarp D. Marsu. The Time of Perception as a Measure of Differences in Sensations. By Vivian ALLEN CuHarites HEeNMon. Below we give review notices of the numbers of the Archives of Psychology which have appeared. Norsworthy, Naomi. The Psychology of Mentally Deficient Children. Archives of Psychology, no. I, pp. iii t+111. $1.00. 1906. The author presents the results of an experimental study of groups of defective children, and discusses the scientific and practical significance of the facts which she has iiccnvered: She bnefly summarizes what little experimental work had been done in this field, previous to her own investigation, and insists upon the need of the exact measurement of a number of the important characteristics of normal and defective children. “T have sought to determine,” she writes, “(1) whether the mental defects of idiots are equaled by the bodily, (2) whetheridiots forma separate species or not, and (3) whether the entire mental growth is retarded, that is, whether there is a lack of mental capacity all around.’’ In order to get ars for fie solution of these problems she made measurements of the following traits. Mental Traits: Efficiency of perception; memory of unrelated ideas; ability in the formation of abstract ideas; ability to appreciate relationships and to control associations; perception of weight; and motor control. Physical Traits: Height; weight; pulse and temperature. The measurements which were made led the author to conclude: (1) That there is a decided difference between bodily and mental deficiency (p. 69); (2) that idiots seem not to form a special class or species, at least as far as intellectual traits are concerned, but that they are included as part of a large distribution (p.77); and (3) that there is not among idiots an equal lack of mental capacity in all lines (p. 82 Of special interest to educators, and to others who are interested primarily in Literary Notices. 333 applications, is the discussion of the education of defectives. It 1s the author’s belief that the difference between the defective and the normal child is one of degree and not of kind, and that for this reason the educational methods applied to the former should not differ in principle from those which are used for the latter. R. M. Y. Franz, Shepherd Ivory. On the Functions of the Cerebrum: The Frontal Lobes. Archives of Psychology, no.2, pp. 64. 50c. 1907. This monograph is one of a projected series on the functions of the cerebrum, particularly on those of the so-called association areas. ‘The first section (pp. 5-1 r) is introductory and historical; the second (pp. 12-28) summarizes and criticises previous studies on the frontal lobes; the third (pp. 29-34) gives the author’s methods and the fourth (pp. 35-62) his results. In criticising previous results the author concurs with others in giving slight weight to MuNK’s statement that dogs show motor disturbances of the trunk mus- cles after extirpation of the frontal Tate: He noticed no such disturbances, at any rate, in the cats and monkeys on which he operated. Nor do his experiments lend any support to FERRTER’S conclusion from experiments on monkeys (confirmed in part by GRUNBAUM and SHERRINGTON for the chimpanzee) that “frontal centers are concerned with the movements of the head and eyes” (p. 14). A somewhat detailed review of the evidence adduced by many to show that the frontal lobes are the centers of inhibition, attention or of higher mental processes leaves the impres- sion that this evidence is either inconclusive or is actually opposed to these infer- ences. His general criticism of such work is that the observations are too casual and that the accounts show too clearly the lack of “a careful analysis of the mental condition”’ (p. 24) to be taken as univocal proof. FRANZ attempts, in his own experiments, neither primarily to discover possible motor centers nor a connection between the frontal lobes and so-called higher mental processes, but “‘to determine whether or not animals with frontal lobe destruction retained simple associations or could form associations” (p. 30). The animal (a cat or a monkey) was placed in a box from which, by pulling a string or turning a button, it could escape and obtain food. For monkeys an_ intricate “hurdle” was sometimes used. ‘The habit was thoroughly formed while the animal was still in a normal condition and its retention tested after the lapse of some weeks or after severance of the frontal lobes, which were left in situ, from the rest of the cerebrum. In some cases the operation was first performed and then the attempt made to form the habit. “If the time for the performance of the act of turningthe button or pulling the string, etc. (after the operation), remained the same as when the earlier experiments were made, we are warranted in saying that the association is retained and the nervous connections for the performance of the habit have not, in the case of extirpation, been interfered with” (p. 34). In cats, the attempt was made to extirpate always in front of the crucial sulcus and often the section was made in the immediate neighborhood of the supraorbital fissure. For monkeys the endeavor was to limit the lesions to that portion of the cerebrum ante- rior to the precentral fissure. From neither of these extirpated regions did stimu- lation give any constant motor response. After the formation of the habit, but before the operation, the animals were put away for a week or more with no prac- tice, when their retention of the habit was again tested. 334. fournal of Comparative Neurology and Psychology. The results on four cats are first reported, all of which were practiced until they could release themselves from the box in from I to 6 seconds. Both frontals were then removed. During periods varying from seven to fourteen days after the opera- tion these animals were tested and were found to have lost the habits that they had formed. Inthese, and in the other cases as well, two minutes were given the animal in which to open the box. On ten monkeys the same operation (severance of both frontals), after the required habit had been formed, resulted in the loss of the habit by six of the animals and its retention by four, although the time of performance, in the latter cases, was somewhat longer than before the operation. As the result of the experiments designed to test the ability of the animals to learn a habit for the first time after the operation (on-both frontals) had been per- formed, or to relearn it after it had once been lost as a result of the operation, it was found that two cats easily acquired the box habit after both frontals had been severed from the rest of the cerebrum and that two of the cats and two of the mon- keys could relearn the habit lost after operation. In the case of one of the cats that learned the habit after operation the author remarks that “the curve of learning in this animal was about the same as that in an animal before the removal of the frontals” (p. 57). That the loss of newly acquired habits after the removal of the frontal lobes, which is the more frequent result in these experiments, is not due to surgical shock and does not result after the removal of other parts of the cerebrum is shown by the cases in which habits were retained even after the frontal lobes had been severed and by others in which the parietal lobes were removed without detriment. The inference that the author draws from his results and from those of other investigators is that “‘the frontal lobes are concerned in normal and daily associa- tional processes and that through them we are enabled to form habits and, in gen- eral, to learn” (p. 64). Four cases were mentioned, however, in which the formed habit was retained after cutting away both frontals, two in which the habit was learned for the first time after the operation and four in which it was relearned. The author suggests, in explanation, since the learning period, in those cases in which the habit was retained even after operation, was longer than in other cases, that it had become a reflex and was therefore due to the functioning of the lower cen- ters, identifying these cases with others in which he observed that habits of long standing, such as coming on call or jumping on the experimenter’s shoulder, were also retained after the operation. ‘The instances of learning and of relearning, after the removal of the frontal lobes, he supposes to have been due to the activity of the still uninjured parts of the cerebrum, in particular of the remnants of the frontal lobes still left intact after operation. Both suggestions are interesting but, as the author himself feels, further and more crucial experiments are needed to define the exact difference between a new habit (not retained after operation) and an old habit (retained). It is unfortunate, in this connection, that no exact record is given of the length of the whole training period for each animal, of the intervals between tests and of the number of trials at each test. YERKES" has recently shown the importance of such records in determining the efficacy of training. Further, if those portions of the frontal lobes which were severed from the rest of the brain are normally concerned in the formation of habits, ought habits to be learned 1 Yerkes, R.M. The Dancing Mouse. New York. 1907. Literary Nottces. 335 as quickly (as one case, at least, indicates) by the parts still left intact after the operation? In short, before the general inference from the experiments can be looked on as more than highly probable, further investigation and more exhaustive records, of the kind just indicated, are much to be desired. FRANz him- self intends to experiment further. ROSWELL P. ANGIER. Thorndike, Edward L. Empirical Studies in the Theory of Measurement. Archives of Psychology, RO. 3, Pp» 45- 59C. 1907. A discussion of statistical methods, in the light of the author’s experience: Measurements of type and variability, Smif ingame: relationships are con™ sidered with a view to convenience, economy, and directness as well as to precision. Lapisky, Abram. Rhythm asa Distinguishing Characteristic of Prose Style. Archives of Psychology, no. 4, Pp. ii+44. 50c. 1907. Ruediger, W. C. The Field of Distinct Vision, with Special Reference to Individual Differences and their Correlations. Archives of Psychology, no. 4, pp. 68. 1907. The author mapped out the field of acute vision in eighteen subjects, with a view to finding “‘characteristic individual differences” and to ascertaining whether the size of this field is correlated with “reading rate, the color zones, visual acuity, retinal inertia, and other phenomena of vision.”’ ‘The field of acute vision 1s defined as the area within which the letters » and u (of a certain font of type) are discrim- inated 75 (and again go) per cent of the cases, when exposed for a fixed length of time (less than the reaction-time of the eye). The shape of this field is found to vary “in different individuals from a “square- oval,’ about twice as long horizontally as wide vertically, to a circle;” and “‘the size a the field varies approximately as 2-I in the horizontal diameter, as 1.5—1 in the vertical diameter, and as 2-1 in area.”’ ‘There is some correlation between the size of this field and the acuteness of vision itself, which amounts, if the latter is determined by GatTon’s test, to nearly +.69 (PEARSON coefficient). In this corre- lation not eighteen but twelve subjects are used, and this value of the coefficient should not be further employed without a careful reading of the author’s text (pp. 46-49). “There is little or no correlation between the horizontal extent of distinct vision and the ‘A’ test, the number of lines that can be seen simultaneously, reading rate, and the number of pauses per line. Reading rate apparently does not correlate with any of the attributes of vision, but it correlates highly with the smallness of the number of reading pauses per line.” A simple method of Professor Woopwortu’s is described, for measuring correlation (pp. 37-39). It can be used wherever the individuals compared with regard to a character, can be ranked in ordinal series, and it takes into account this order of the individuals, but not the amounts by which they differ in regard to this character from one another. E. B. H. Jones, E. E. The Influence of Bodily Posture on Mental Activities. Archives of Psychology, no. 6, Ppp- 61, 50c. 1907. The author briefly sums up the chief results of his work as follows: “Pitch is discriminated better (with the body) in the vertical than in the horizontal position; 336 © “fournal of Comparative Neurology and Psychology. tactile discrimination is slightly more acute in the horizontal than in the vertical; visual memory is both more rapid and subject to fewer errors in the horizontal than in the vertical position; auditory memory shows the same result as the visual memory; adding can be done more rapidly and with greater precision in the hori- zontal posture; subjects show greater signs of fatigue in the horizontal than in the vertical posture; a greater number of taps per minute can be made in the vertical than in the horizontal position; and the vertical position is favorable to the strength of grip.” Wells, F. L. A Statistical Study of Literary Merit with Remarks on Some New Phases of the Method. Archives of Psychology, no. 7, pp. 30. 30c. 1907. Yerkes, Robert M. The Dancing Mouse: A Study in Animal Behavior. Animal Behavior Series, vol. 1, pp. xx1+ 290. New York: The Macmillan Company. 1907. It is not putting the matter too strongly to say that Dr. Yerkes has in this book given us the most valuable contribution that has yet been made to the study of animal behavior. Having become interested about four years ago in some speci- mens of the curious Japanese dancing mouse, and finding them readily tamed, easy to care for, and comparatively quick to learn, he undertook a thorough investi- gation of their sensory equipment and intelligence. The results are stated clearly and concisely in the present volume. Every step in the methods used, every stage in the reasoning processes by which the author’s conclusions were reached, is given, so that the book is a real text-book in experimental method. The dancing mouse, as is well known, gets its name from the fact that when placed in an open space it makes peculiar whirling or circling movements. ‘These movements have been thought to be due to a malformation of the equilibrium appa- ratus in the ear, and support seems to be given to the theory by the fact that the mice have defective hearing. Yet the statements of various experimenters who have examined the ear are so conflicting that no definite inference can be drawn from them. Dr. YERKEs concludes that to explain the peculiar movements of the dancer “the structure of the entire organism will have to be taken into account,” and at the same time he finds no “‘satisfactory ground for considering the dancer as either abnormal or pathological”’—an assertion the truth of which would seem to depend upon the meaning assigned to the term “abnormal.” ‘To account for the disagreement among different observers of the behavior of the animal, some of whom say that the mouse is markedly deficient in balancing power, while others find no striking defect in this respect, YERKES adopts the suggestion of Cyon that there are at least two varieties of the dancing mouse, and has observed evidences of the existence of two different strains among the specimens examined by himself. The net results of the author’s work with some four hundred individuals may be grouped under four heads: those concerning the mouse’s power of sense discrimi- nation; those concerning its learning capacity; those bearing on questions of experi- mental method, and _ those of interest to students of biogenetics. 1. Three classes of sensory discriminations: auditory, brightness, and color, were investigated. The mice of one of the two lines of descent represented were, with the exception of one litter, throughout their lives insensitive to sounds. ‘Those of the other line showed sensitiveness for a day or two during their third week. Literary Notices. 237 The mice displayed ability, varying with the individual, to discriminate different shades of gray paper, though their capacity in this direction was less than that of a human being. One mouse was subjected to tests of the validity of WEBER'S Law, in discriminations of the degree of illumination in different compartments; and the law was found to hold, the proportion lying between 1-10 and I-15. These discriminations were greatly improved by practice. As regards color discrimination, much of the behavior superficially to be classed under this head appeared on further investigation to be really based on the bright- ness value of the colors. This value is apparently quite different in the case of the mouse from what it is in the human subject. The red end of the spectrum is much darker to the mouse, being indistinguishable* from black and darker than any green or blue. ‘There is some evidence that the mice can discriminate green and red ‘“‘by some other factor than brightness,”’ but on the whole the problem of their color vision is not solved. The dancer was found to be incapable of distinguish- ing between two equal illuminated areas of equal brightness but different form. Mice that have learned a labyrinth path are little disturbed in traversing it by being made to do so in darkness, by washing the labyrinth so as to destroy smell clues, or by moving the labyrinth to one side so that the former track 1s removed. They were a good deal disturbed when the floor was covered with smoked paper, but Dr. Yerkes thinks this disturbance was a general one and _ not the result of loss of aclue. The rdle of the senses of sight, smell, and touch in the learning of a labyrinth path, quite a different problem from the effect of eliminating a sense after the animal has learned the path, was not experimentally tested; observation of the general behavior of the animals led to the conclusion that these senses are all used, but in different degrees by different individuals. 2. The results that bear especially on the mouse’s learning capacity are as fol- lows. The dancer is capable of forming habits that involve turning in one direc- tion or another (labyrinth habits), and habits that require in addition visual dis- crimination, but the former are acquired much more rapidly than the latter. A regular labyrinth, involving turns alternately in two directions, 1s learned with espe- cial speed. Useless habits occasionally persist for some time, a fact which several other investigators have noted. The mice did not learn by imitating each other. Putting the animals through one of the reactions which they learned, that of climb- ing a ladder, did aid the learning process. Dr. YERKEs’s conclusions regarding sex differences in learning capacity are less convincing than his other inferences from results. He says, ‘‘In labyrinth tests the female is as much superior to the male as the male is to the female in discrimination tests.”” Yet in the tables upon which the first part of this statement is based, although the average number of tests which had to be given before the labyrinth was perfectly learned was 18.7 for the males and 13.8 for the females, five of the ten males learned with fewer tests than did five of the females. “Of the five pairs of individuals whose records in white-black training appear in Table 43,” says the author, “not one contradicts” the statement that the males are superior to the females in discrimination experi- ments. This table contains the results of tests of black-white discrimination made at the rate of ten per day; but Dr. YERKEs himself points out that the females did better than the males when twenty tests per day were given. The experiments on the relation of docility to age were not completed. As 338 fournal of Comparative Neurology and Psychology. regards the persistence of the habits acquired, the white-black discrimination habit, it is concluded, “‘may persist during an interval of from two to eight weeks of dis- use,” but “is seldom perfect after more than four weeks.’’ ‘The color discrimina- tion habits never persisted more than two weeks. The white-black discrimination was re-learned, after all traces of it had disappeared, in a shorter time than had been required for its original acquisition, thus suggesting “‘the existence of two kinds or aspects of organic modification in connection with training; those which consti- tute the basis of a definite form of motor activity, and those which constitute bases or dispositions for the acquirement of certain types of behavior.’’ As Rouse found to be the case with the pigeon, experience with one form of laby- rinth made the learning of another form easier. 3. ‘The suggestions on method which the book contains are among its most valuable features. In the first place, Dr. YERKEs finds that the best motive to employ in studying the learning processes of mammals is not hunger, which is variable in intensity, unfavorable, in its extreme degrees, to the exercise of the ani- mal’s full powers, and inhumane; but the punishment of mistakes by slight electric shocks, given through wires on the floor of the discrimination box or labyrinth. So far as my recollection serves, the author first used this method in his experiments on the frog. It has certainly a decided advantage over any method where the motive is constituted by a continuous state in the animal, such as hunger or the desire to escape from confinement. Any continuous state is likely to vary in inten- sity, and discomfort under confinement 1s likely to diminish as the animal becomes used to its surroundings. An intermittent stimulus, given when mistakes are made, has a much better chance of producing a constant effect. Another interesting point in method concerns the evidence which was obtained that apparent color discrimination was really, in some measure at least, brightness discrimination. ‘This evidence consisted in the fact that mice which had been trained to choose a compartment illuminated by green light in preference to one. illuminated by red light, on being offered a choice between black and white com- partments, chose the white, although before the green-red training they had shown no such preference. ‘Thus it looked as if they had been choosing the green partly, at least, as the lighter of the two visual impressions. ‘This method might well be given a wider scope in the study of the sensory discriminations of animals. It is puzzling, by the way, in view of the evidence that red is much darker to the mouse than to the human observer, to find that a tendency to choose red rather than yellow in tests with colored cards is explained as the result of previous training to go to the brighter compartment in white-black tests. The results of training tests are throughout stated in terms not of the time re- quired to perform the act, but of either the number of errors made or the number of tests required before the formation of a perfect habit. The time required in ~ traversing a labyrinth, for example, is in the author’s opinion a poor index of the perfection of the habit. In this respect his position is the opposite of that taken by Watson, who states the results of his tests of the white rat wholly in terms of time. On the whole, the most favorable number of tests per day in the discrimination series, taking into account economy of time and fatigue for both experimenter and animal, was found to be ten. For labyrinth experiments, the author recommends the use of a standard maze in which “‘errors by turning to the right, to the left, and by moving forward should Literary Notices. 339 occur with equal frequency and in such order that no particular kind of error occurs repeatedly in succession. ” 4. Finally, Dr. YeERKEs made some studies on the phenomena of heredity in the dancing mouse. ‘The subjects of his experiments belonged to two separate lines of descent, which presented certain characteristic differences, the individuals of one line being more like ordinary mice than those of the other line. Observations on several generations indicated a certain inheritance in the latter line of descent of a tendency to whirl to the left in dancing, while those of the former line showed no such tendency. Four generations, a male and a female in each, were tested to see if the training of the parents in white-black discrimination facilitated the learning process in the offspring. ‘The results showed no evidence of the inheritance of this acquired character. From this superficial survey it will be seen how rich both in result and in sugges- tion the book is. No less admirable is the spirit in which the work has been carried on; a spirit of scientific conscientiousness, of modesty, and of humane sympathy, untinged with sentimentality, for the animals experimented on. Of comparative psychology, in the sense of an attempt to interpret the mental states of the subjects, there is very little in the book, and that little does not strike one as its most successful feature. For instance, when in labyrinth tests the procedure was adopted of allowing a mouse, as a preliminary, to traverse the maze and escape without getting an electric shock, it is said that this was for the purpose of allowing the animal “‘to discover that escape from the maze was possible,’’ but there is no discussion of the terms in which such a possibility may have functioned in the mouse’s consciousness in subsequent tests, whether as a memory image or merely as an increased tendency to movement. Again, when one method of reaction in the dis- crimination experiments is designated “‘choice by comparison,”’ one is left with the interesting problem as to what sort of process the comparison of two stimuli in the mouse’s mind may be, and it might perhaps have been better to use a term that would have had a less decided psychic implication. However, if there is but little attempt at interpretation of the mental aspect of the facts observed, the book is almost an ideal example of the kind of work which promises to put comparative psychology on a firm scientific basis. MARGARET FLOY WASHBURN. Davis, H.B. The Raccoon: A Study in Animal Intelligence. American Fournal of Psychology, vol. 18, pp. 447-489. 1907. ‘ This paper describes the habits and instincts observable in adult raccoons in captivity, and it presents the results of experiments to test learning, color perception, and imitation in these animals, together with comparisons of these results with those obtained by other investigators. In this review only the descriptions of experi- ments and the discussion and interpretation of results will be examined. ‘These may be taken up under the general headings learning, color perception and imita- tion, and comparisons. Learning. In the author’s experimental study of learning the raccoons were allowed to unfasten the door of a box, reach into it, and get food. Single fastenings, a group of two and a group of three latches, and finally, two combination-locks, each composed of four of the previously learned single fastenings, were used in the 340 “fournal of Comparative Neurology and Psychology. tests. [he combination locks demanded that their elements be operated in a fixed order. We are told that in these experiments each animal at first attacked the box with indiscriminate clawing, but finally settled down to a single habitual method of oper- ating the latch or latches. The formation of this habit was due to “the omission of unnecessary movements and the combination of those required,” exactly as described by THorNDIKE in the case of cats. “The steps by which perfection is reached are very short and blindly taken" (p. 468). Yet despite this gradualness and blindness of the learning process Mr. Davis’s adult raccoons showed a “nearly equal facility” with monkeys in learning to undo fastenings (p. 487), and_ their curve of ne follows closely the type of those for the higher animals and for man (p. 477) - : Mr. Davis states, “‘ Experience with former fastenings holds over in the case of new ones leading the animal, at least in certain cases, to begin his attack at the place on the surface of the food-box where he has been accustomed to work. (This has been found by THorNDIKE in the case of cats and denied by Cote in the case of raccoons).”” This very important conclusion is based, so far as can be judged from a very obscure statement, on only eight reactions of a single animal. During four of these trials the animal stood on his head and clawed where the latch had been. Presumably the vividness of this experience and Core’s remark concerning an easily discriminated fastening have led Mr. Davis to say that such performances are denied in CoLe’s paper, yet on p. 218 of that paper it is distinctly stated that one of CoLE’s raccoons clawed twice, another four times at the side of the door where a latch had been in the preceding test. Nevertheless CoLe’s results are characterized as ‘‘exceptional.”’ Are we to infer that his animals should have clawed eight times instead of six, or that they ought to have stood on their heads while doing so ? Notwithstanding the tremendous weight given by Mr. Davis to this performance of a single individual, we are told that the raccoons seemed to reach a sort of “‘gener-- alized manner of procedure” which enabled them to deal more promptly with any new fastening. ‘This half-subjective, half-objective term, “generalized procedure” is vague in the extreme. Does it mean, as pointed out by Cote (p. 218) that “in future new boxes the animals seemed to pick out the new latch and work directly at that as if experience led them to attack movable objects within the box, or else objects which gave a click or other sound when operated?” Coe continues: “These facts, with others to be mentioned, indicate, I think, that the raccoon’s learning to operate a latch includes something more than a mere mechanical coup- ling up of a certain instinctive act with a given situation.”” KINNAMAN (p. 122) says more boldly, ‘‘It looks very much like the possession of a general notion fairly well represented by projecting-thing- -has-something-to-do-with-it, and so they attacked the projecting thing and not something else.” If the conelacon as to ‘‘generalized procedure” does mean this, it seems to contradict point blank the conclusion based on the special procedure of the single animal which clawed eight times at the side of the door where a bolt had been in the preceding test. Probably THORNDIKE would be first to protest against confirmation by the exceptional behavior, super- or sub-normal of a single animal, when this behavior was con- tradicted by other records. 1 Ttalics are the reviewer’s. Literary Notices. 341 According to the author, “* Perception of the essential relations, if present at all, is dull and stupid in the last degree” (p. 468). Yet “there is an evident ability to respond fo small differences in complex relations. How far the perception of such relations really enters is, however, at present in doubt” (p. 477). Practical denial is weakened to doubt within a few pages, because of the contrast between what one raccoon did and what they all did. However, the study of the perception of re/a- tions in animals is a new field. It is enough for most workers at present if they can prove the perception of an easily discriminated object and say with certainty whether it is a visual, olfactory, or tactile perception. Perhaps, however, Mr. Davis means that the raccoons did not perceive the fastenings, though they responded to small differences in them, for his confirmation of ‘THORNDIKE commits him to the latter’s statement (p. 80) that “‘the loop is to the cat what the ocean is to a man when thrown into it, when half asleep.”’ ‘ This apparent conflict between conclusions is evident throughout the paper and it seems to be due to the old discrepancy between isolated observations and the final and impersonal result of systematic records, a conflict which THORNDIKE tried hard to terminate. In working the combination locks the animals learned “order’’ and “amount of effort’’ at somewhat different rates. ‘‘ The table seems to show that the memory of the order is more readily perfected than that of the muscular. adjustment required for each particular locking device” (p. 469). Does this mean two types of “‘memory,”’ as is indicated by this quotation, or merely two rates of habit form- ing, or a type of memory-and a case of habit forming, which we should expect to develop at two different rates? Varying the locking devices would doubtless have explained the phenomenon or analyzed it for us. If it is due to mere defect in method, varying the device would have eliminated it. So the observation seems significant for future tests. If we can find two widely divergent rates, we may find a distinction between habit and association. KINNAMAN, who tested monkeys with combinations very similar to those used by Mr. Davis, does not call our atten- tion to any difference in the rate of learning ‘‘order”’ and ‘“‘amount of effort.” This adds interest to Mr. Davis’s observation. An excellent table is given of the first forty trials of raccoon No. 1 with the single fastenings and groups. ‘The generalized curves are too greatly reduced to be of much value. A curve for KINNAMAN’S monkey’s is given, but KINNAMAN counted the entire time “no matter whether the monkey was before or behind the box, whether prancing around it or jumping up and down on top of it, so long as he was trying to open it. Some of these efforts were in nowise directed toward the latch”’ (KINNAMAN, p. 115). Davis, on the contrary recorded the time during which the animal.was 1m contact with the locking device (Davis, p. 465). Surely this differ- ence must be taken into account in valuing his conclusions that the raccoons show a nearly equal facility with KiNNaMAN’s monkeys in learning to undo fastenings, and that “the monkeys would seem to be a little less clever at the start” (p. 476). Cote had previously concluded that “‘in the rapidity with which it forms associa- tions the raccoon seems to stand almost midway between the monkey and the cat, as shown by the numerical records for those animals. In the complexity of the associations it is able to form it stands nearer the monkey” (CoLsg, p. 261). His method of timing agreed with KINNAMAN’s and with THORNDIKE’s, though his animals were young and exhibited “play trials.” Mr. Davis’s method of timing 342 “fournal of Comparative Neurology and Psychology. and his failure to mark intermissions in practice precluded the presentation of records of “play trials.” Although Mr. Davis finds marked differences in learning due to practice effects, we are nowhere told in what order he used the several fastenings. ‘This is a most serious omission and greatly impairs the value of his paper for comparative pur- poses. For example, in one case he tested a raccoon on fastening No. 3, then passed to No. g, and in the latter case finds remarkable stupidity. Now if fastenings No. 9 were really the ninth fastening this animal had tried, the result is new and unusual, but if it is the fourth, third, or second fastening, the animal’s behavior agrees closely with that of other raccoons, and entirely loses its marvelous character. Further, we read that while all the raccoons were “fully grown” when received, yet distinct differences in learning were found between the younger and the older animals. We should expect, therefore, a statement of the approximate age of each animal when received. Instead we are offered what seems to be the most useless possible statement, namely, “the approximate age of each animal” at death or escape or for the summer of 1907, some months after his work was completed (cf. pp. 462, 448). This defect greatly lessens the value of the experimental records. Fortu- nately reparation can be made by the publication of the date at which each ani- mal was received, the length of time during which it was tested, and the order in which the tests were given. ‘This addendum ought certainly to appear. Finally, so far as we can learn from the paper, only one box was used and the latches were all so fastened to it as to be most inconspicuous. ‘This, of course, tends to stamp in the box feature of the situation, and, therefore to make the animal more dependent on kinesthetic sensations. Varying the position and size of boxes and doors gives control experiments which rarely fail to modify an investigator’s first conclusions. The conflict between the author’s several conclusions leaves one in doubt whether the raccoons are, in intelligence, nearer the cats, which possibly have “no images or memories at all,”’ or nearer the monkeys which exhibit even “‘a low form of general notion.” Color Perception. ‘The color perception of the raccoons was tested, and it is con- cluded that they do not discriminate colors as such, but depend on differences in brightness alone for their successful reactions. While the tables seem to show this they may prove merely that discrimination of brightness is easier for the animals to make than discrimination of color, for the method employed is very defective. With the first piece of apparatus used the raccoons could both look into and reach into the vessel which contained the food, and into the five similar vessels which were empty. ‘The experimenter must have felt this disadvantage, for the second piece of apparatus “did not allow the animal to look into the container in which the food was placed” (p. 479), but the food could be obtained by reaching through an opening 2 by 1% inches, in the vertical slides. The food was placed back of one color and when this was moved every other color was given a new position also. Thus with the second device each container could be explored by touch. If the animal reached into a no-food vessel an error of color discrimination was recorded against him. ‘There seems thus no means of distinguishing true errors of color dis- crimination from the cases in which the animal paid no attention to the colors, except that brightness tests gave better results than color tests. “‘ The two pieces of apparatus were used indifferently.” Under these conditions there were 52 per cent Literary Notices. 343 of right choices in brightness tests, and 24 per cent in color tests. One of the four animals made 40.7 per cent of right choices in the color tests. ‘This fact is ascribed to brightness differences in the colors used. It must be remembered that by chance alone the animals would have made 17 per cent of right colors. It seems possible, therefore, that both averages are too low, due to the steady pressure of an instinctive impulse, for the reviewer has used the first piece of apparatus and found that apparently the raccoons could not pass a single food container without both reaching into it and looking into it. Instead, the animal would go to one end of the row of vessels, explore the first one carefully both by touch and sight, then the next, and so on until the vessel with food in it was found; then it would go on in the same way to the end of the row, and back again, rarely skipping a single vessel. “The raccoon has, then, a very strong instinctive impulse to reach into and to look into all sorts of openings. Imitation. No certain cases of imitation were discovered by the author. Comparisons. Mr. Davis “correlates” his results with those of BERRY on the white rat and of CoLE on the raccoon. Berry very properly compares the behay- ior of a rat which learns by trial and error with one given an opportunity to learn by imitation and concludes, “It seems to me that we ought to be able to say a priort, in the light of these facts, that no ordinary rat would be able to open a door by pull- ing a string, simply from having seen another do it, without first making a number of random movements.” ‘To this Mr. Davis replies, “It is upon such a slender basis that Mr. Berry infers imitation” (Davis, p. 483). “This seems quite unfair. It is upon no such basis that Berry infers imitation, but upon repeated experiments in which the imitator developed a tendency (not present before) to pull a knot after seeing another rat pull it many times. On such experiments as a “basis” with most carefully arranged control tests, which proved that the tendency was due to example alone, Mr. Berry makes Ths very conservative observation quoted, and first rate confumcition of its truth has been forthcoming. Watson has demon- strated the immense role that kinzsthetic sensations play in the life of the rat, and Berry has found an advance upon this grade of imitation in other animals. Why invert BERRy’s argument to the neglect of his recorded facts ? So Berry is said to “beg the whole question”’ because he “lays great stress on the visual sensation as the chief factor in what he calls the final imitative act.” Here again it would seem as if BERRY were, instead only allowing proper impor- tance to kinesthetic sensations, since the rat which learns by trial and error has them, while the imitator must depend first of all on sight. ‘The reviewer is unfamiliar with the behavior of rats, but he can say of raccoons that the experimenter had better lay very great stress on their visual sensations of movements for they are almost as skillful muscle readers as the trained dog, “ Roger,” of recent fame. ‘The danger is that the experimenter will not ascertain until too late how delicate are the movements which the animals can detect by sight. In a second correlation, what CoLe described as due either to imitation or to the presence of visual images in raccoons has, what seems to Mr. Davis, a third expla- nation. As this additional explanation offered is based on a complete misunder- standing of the conditions of the experiment we may pass it by with the remark that perhaps CoLe was not clear in his description. A third correlation with CoLe’s work, and one already referred to, is of so vital importance in interpreting the behavior of raccoons that all the relevant statements 344 fournal of Comparative Neurology and Psychology. must here be brought together. (1) “THORNDIKE (p. 80) is authority for the state- ment that “cats would claw at the loop or button when the door was open,”’ and ‘fat the place where the loop has been though none was there.” (2) CoLe, pp. 218, 253 found that raccoons did neither of these things, though they were given oppor- tunities to do both. (3) When the latch is fastened to the side of the box and on the opposite side of the door from that of the immediately preceding test the raccoons did claw a few times (COLE records six times by two young animals, in their earlier trials; Davis, apparently, eight times, one adult animal, whether earlier or later trials is not stated) at the place where the latch had been. If Mr. Davis had used an easily discriminated fastening like a loop or platform his results would have been more easily comparable with THORNDIKE’s and Coe’s. He does not say that the rac- coon ever clawed at a fastening when the door was open. Surely we must not expect the raccoon, in his early trials, to limit his efforts to projecting objects as he will do in his later trials. Do Mr. Davis’s records, then, really agree with THORNDIKE’S statement that “the loop is to the cat what the ocean is to a man when thrown into it when half asleep” (THORNDIKE, p. 80)? ‘This is a phrase meant to describe about as near a total lack of discrimination as “thought can pump out of itself.”’ Is it consistent with the raccoon’s responding to small differences in complex rela- tions? ‘Truly the small number of cases must be recorded, but they must not be overloaded with conclusions. It is, indeed, an ungracious task to find defects in another’s work and in a pre- vious résumé the reviewer largely refrained from it. Yet the first step in assigning the true value to the record of an investigation is to compare interpretations in the same paper. From such comparisons emerges a truth, well known to most investi- gators. In our early experiments with an animal his behavior suggests ambiguous or contradictory conclusions. ‘This is a hint from the animal that our apparatus or method or both need modification. Watch the animal closely and the direction the modification should take will be suggested. Refuse to modify the method or cling to apparatus already used with some other animal and you remain in the first stages of your work with contradictory or doubtful conclusions on every side. Care in varying the conditions seems to show, however, fairly consistent behavior in any one type of animal. Finally it appears that cats and monkeys are so widely different in intelligence that it is very difficult to interpret the behavior of raccoons as agreeing with that of both the other animals. L. W. COLE. The Journal of Comparative Neurology and Psychology VotumE XVIII OCTOBER, 1908 NuMBER 4 A COMPARISON OF THE ALBINO RAT WITH MAN IN RESPECT TO ]THE GROWTH OF, THE BRAIN AND GFE EHESSeINAL CORD. HENRY H. DONALDSON, Professor of Neurology at the Wistar Institute. With Prates II anp III anp One Cuart IN THE TExt. In this paper it is proposed to present data illustrating the growth of the brain and spinal cord of the albino rat, and also to compare their growth in this animal with that in man. As a preliminary to this study, it was necessary to determine for the rat the growth curve of the entire body. ‘The observations on this point were published in 1906 under the title “‘ A compari- son of the white rat with man in respect to the growth of the entire body” (Donatpson ’06). In that paper it was shown that the growth curve of the rat exhibited all the phases found in the human growth curve, and, further, that the curves for the two sexes were similarly related in both the forms examined. In the present study, therefore, we shall have the advantage of examining the growth of the nervous system in an animal, the general growth curve of which is similar to that of man, and this fact should enhance the significance of the results. The observations to be presented are unique, as the literature contains no extended record of the growth of the brain and of the spinal cord in any mammal below man. Moreover, the observa- tions on man are open to a good many qualifying criticisms, and it will be most advantageous, therefore, to postpone comment on them until the data from the rat have been presented. This study of the rat was begun thirteen years ago, and during the interval the records have been accumulating. ‘Throughout this period the rat colony has been composed always of the albino variety of Mus norvegicus (Harar ’07), although occasionally, 346 “Fournal of Comparative Neurology and Psychology. of course, the colony has been recruited from outside sources. By thus extending the observations over a long period the material has lost perhaps a shade in homogeneity, but on the other hand, something has been gained for the general value of the results. In collecting the data, I have been assisted by my students and members of the laboratory staff, and I desire on this occasion to acknowledge my indebtedness to those who have worked with me. I am indebted chiefly to my colleague, Dr. Harat, who has been of the greatest aid in the mathematical treatment of the observations, since without this assistance, the publication of the results must have been delayed still longer. In presenting the observations, the effort has been made to condense them as much as possible, while at the same time fur- nishing all the facts which would enable other observers to control the conclusions. ‘To this end, there is printed a complete table of the individual observations. (See General Table at the end of this paper.) All the formula and the descriptions of the meth- ods by which the data have been treated are of course given, and in addition, the results have been condensed as usual in the form of curves or tables. The formule are given only once in each instance, and then referred to by number when they reappear. It has not been deemed necessary, however, in view of the general table, to print at the same time correlation tables or the intermediate calculations. TECHNIQUE. It is to be expected that during so long a period the methods of observation should have changed somewhat and also should have been improved. In giving the technique for removing the brain and spinal cord and for making the other measurements the methods described are those now used, it being understood that if, in any instance, there was previously a deviation from the procedure which might modify the results, this fact has been taken into account. The procedure was as follows: Just before feeding time, i.e., when the stomach is comparatively empty, the rat was chloro- formed and notes made on the age, sex and any important con- ditions which might have modified the development of the animal. It was then weighed to the tenth of a gram, and the body length Dona.pson, Growth of Central Nervous System. 247 taken with calipers from the tip of the nose to the anus, the animal lying on its side, and being gently extended to its full length. The measurement was recorded in millimeters as the “body length.”’ From the anus to the tip of the tail, a second measure- ment was taken, which gives the length of the tail, and this was recorded as “tail length.”” The animal was then eviscerated. The spinal cord was next exposed, gently raised by the flum terminale, and the nerve roots clipped away (caudo-cephalad) close to the cord. ‘The division between the brain and the cord was made at the tip of calamus scriptorius or just caudad to it. The skull was then opened from the dorsal side, and the brain removed. Immediately after removal, the brain was put in one closed weighing bottle, the cord in another, and each weighed separately. The meninges of both brain and cord were left intact. Such blood as they contained, was therefore included in the weight. After the first weighing, the brain and cord were dried at a tem- perature between go° and 95° C. for a week or more, then re- weighed, and the percentage of water determined. In the following pages we shall discuss only the weights of the body, brain and cord, and their relations to one another, leaving for later consideration, the data on body length and on the per- centage of water in the brain and the spinal cord. The observations on the growth of the brain will be presented frst. GROWTH OF THE RAT’S BRAIN. Table 1 contains 680 records (462 male, 218 female) of the weight of the rat’s brain. ‘The changes in the weight of the brain are most readily appreciated when the records are arranged in relation to the increase in the total body weight. Such an arrangement is made in chart 1, plate ii, on which all the in- dividual records that could be entered without confusion are shown. To avoid confusion, however, it was necessary to omit a total of 37 records (26 males, 11 females). ‘The impression given by this chart is therefore somewhat less strong than that war- ranted by the observations. As can be seen by inspection, the “scatter”? of the individual entries is not very great. The entries on chart 1 suggest that the weight of the brain in the male rats is heavier than in the female. ‘To test this animals of 348 “fournal of Comparative Neurology and Psychology. like weight must be compared, and since the females run to only 255 gms., the numbers available for comparison are somewhat reduced (424 males,218 females). When the data are tabulated, the values given in table 2 show that the weight of the male brain exceeds that of the female in 84 per cent of the groups and is on the average I.5 per cent greater. TABLE 1. Giving the mean observed and calculated weights of the brain and of the spinal cord inthe albino rat. Sexes not distinguished. Brain 680 cases; spinal cord, 647 cases. js BraiN WEIGHT (IN Gos.) SPINAL CORD WEIGHT (IN GMS.) Cw 2 . BE | > a | No. of Ob q Reape: |Calculated | No. of @psesed renee: Calculated So — | cases. eaves | ayers @Jon 7th root} cases. beg hare (ced ean lle i 2.7 root. a) | [1]. [3]. A B C D E F. G H. I 5 58 0.333 ©2237) 9 58 0.036 ©.033 5} 15 60 0.977 1.009 58 0.103 O.115 | 25 52 1.285 1.244 47 0.180 0.178 35 53 1.367 1.362 47 0.227 0.228 45 42 1.441 1.442 42 0.254 0.269 BG || i Mie Wpey Waiter? 41 0.283 0.305 65 32 1.488 | 1.550 32 0.309 0.337 | 75 34 1.559 1.590 32 2.333 0.365 | 85 21 1.588 1.625 20 0.362 |= @23985)) 95 22 1.618 1.656 21 0.392 | 0.413 105 21 10745 Pee Ose 1.683 21 0.419 | 0.434 115 24 1.683 | 1.707 1.705 24 0.432 0.453 125 18 TOON seat 720 L725 16 0.465 0.471 135 nis 1.763 1.750 1.744 14 0.481 0.488 145 19 1.718 1.769 1.762 | 17 0.489 | 0.504 155 25 1.754 1.786 1.779 | 21 0.506 0.519 165 19 1.771 1.802 e705 aa 19 0.542 0.533 175 13 1.827 1.818 | 1.810 13 0.556 | 0.546 185 16 Di78t |) Us83g"| asa 14 0.530 | 0.559 195 15 1.803 | 1.846 1.838 15 ©.598 |) .O.57% 205 17 1.809 | 1.859 L.851 15 0.582 | 0.582 215 8 1.873 1.871 1.864 8 0.605 | 0.593 0.593 225 8 1.813 1.883 1.876 8 0.595 | 0.604 0.603 235 10 1.890 1.894 1.888 9 0.626 | 0.614 0.613 245 6 1.900 1.905 1.899 6 On6372 sie o. 624 0.622 255 4 1.900 1.915 1.910 4 0.620 0.633 0.632 265 7 1.921 1.925 1.920 7 0.653 | 0.642 0.641 275 6 1.983 1.934 1.931 6 0.690 | 0.651 0.649 285 3 1.950 1.943 1.941 3 0.710 0.660 0.658 295 3 1.950 1.952 1.950 3 0.683 0.667 0.667 305 3 PB HG) 1.960 1.960 | a 0.683 0.675 0.675 315 3 2.083 1.969 | | 3 0.737 0.683 ) Dona.pson, Growth of Central Nervous System. 349 TABLE 2. Showing the mean brain weight according to sex. 424 males, 218 females. Sain | BRAIN WEIGHT OBSERVED (IN Gms.) Oo le Percentage difference between female 5 E | brain weight and that of male taken as oe Pte: Males. | Bost Females. fhe: standard: oa) cases | cases. =| | | — + 5 37 0.356 16 0.324 8.9 BG lead 0.971 13 0.998 2.7 25 39 1.306 13 1.222 6.4 35 39 1.370 14 1.358 0.9 45 20 1.475 22 1.410 4-4 55 31 1.489 12 1.432 3.8 65 26 1.489 6 1.483 0.4 75 28 1.568 6 ou ger 85 17 1.591 4 1.575 1.0 95 9 ae tiBlxe) 13 1.595 Aaa 105 10 1.680 II 1.668 Q.7/ 115 14 1.664 | fe) iewfikey | 2.7 125 II 1 750m | 7 1.636 6.5 135 | 12 1.767 3 1.750 0.9 145 | II 1.722 8 Lag Ons 155 | 17 1.768 8 1725 2.4 165 | 9 | 4.783 sf) 1.760 gg) 175) | 7 1.821 6 1.833 0.6 185 | 9 1.783 7 1.780 0.2 195 | 6 1.833 9 1.783 | Pal 205 II 1.814 6 1.800 | On7 215 5 1.830 | 3 1.943 | 6.2 225 | | No females 235 | 5 1.930 5 1.850 4.1 245 2 I.900 4 I .900 0.0 255 MN eh eC es) z 1.900 0.0 Average percentage deficiency in the weight of the female brain 1.5 per cent. Although the absolute value here given is somewhat greater, this result accords with that of Hara1(’07A) who found the cranial capacity in the male greater by about 0.43 per cent. Boycorr and Damant (08) have found the fatty acids in the male rat to be on the average 4.4 per cent of the entire body weight, and in the female 5.6 per cent. “This datum, when applied as a correction to the body weight, would tend to reduce the difference between the brain weights of the sexes. It is further not improb- able that the thoracic and abdominal viscera are also proportion- ally different in the two sexes, and that as a consequence, there is a characteristic sex relation between the weight and length of the 350 ‘fournal of Comparative Neurology and Psychology. body, a condition which would also modify the results which we have obtained by using the crude body weights alone. In view of these circumstances, it seems permissible in most instances to treat the records for both sexes together, and so the statements which follow. are based on the total series of records without distinction of sex, except where such distinction is specially noted. The theoretical curve, about which the observations cluster, is represented by the continuous line in charts 1 and 3, plates ii and i, and was found by means of the logarithmic formula [1] y = .569 log. (x — 8.7) + .554 in which y is the weight of the brain in gms. and » the weight of the body in yrms. This formula has already been published by Haratr (08). The values obtained are given in column D of table 1. The formula [1] just given, was derived in the following manner. Assuming that the weight of the central nervous system is a func- tion of the body weight, we obtain at once the following general expression y = 4(x) An inspection of the curve of the brain weights, as plotted on the body weights, shows that the rate of growth of the nervous system decreases as the body weight increases. ‘This relation is. expressed by the following formula dy I dx x C where C is a constant. Hence we have dy =~ C, dx and y = Cfo ds = G@ lop eat The two constants C and A were determined by the method of the least squares. DoNALDSON, Growth of Central Nervous System. 351 When the foregoing formula is applied, the theoretical curve gives a very good graduation of the brain and cord weights for the larger values of x, but fails to adequately represent them for the smaller values of x. The values obtained by the formula are too high for the brain weight, and too low for the spinal cord weight. In order to meet this difficulty, the constant $ empirically determined, has been introduced, and the resulting formula becomes y =Clog(x +8)+A4 in which ? is the new constant. This is the general formula which we have employed for the present work, and it has been found very satisfactory, as will be seen from the tables and charts. Arranging the rats examined in groups differing by ten grams in body weight, and calculating the mean values of the observed weights of the brain for the mid value of each of these groups, we obtain the curve which is given in chart 3. The mean values (M = the broken line) obtained by so treating the observations, are given in column C of table 1. The table and chart show that the curve based on the means, fits closely with the theoretical logarithmic curve (C = continuous line). The coefiicient of correlation between brain weight and body weight in the case of the 680 records, was determined accordingly to the formula [2] ze (7 (xl yi) "\ r= Some) ot) n 0102 (Davenport ’04) and is high, being .7639 +.0108. For comparison with this result, it may be noted that PEARL (05) in the case of the total series of Bavarian brains, weighed by BiscHorr (80), found the coefficient of correlation between brain weight and body weight to be as follows: Male ee tererciciite © stataiate sate ee meenicuansde tay ya cenabaisis rg hic hrckaata ap eed More arent ce 0.1671 +0.0343 ermale dy ache cus, trate cy eevee esteten Vetchey aileron a rotT pS oe Bee OL2200 0.0412 In the case of Worcester school children 6 to 17 years of age, in which the measurements are more accurate than they could possibly be in the case of BrscHorr’s series, Boas (’05) found for 352 fournal of Comparative Neurology and Psychology. the following coefficients of correlation between body weight and head measurements: LENGTH WiptH OF HEAD. OF HEAD. ISON anne on Smict- Binks «ain Sania aa ucracioia ola icone SOG mAh doen a 0.43 0.32 NSIT ASS aly, «hte ahelcus egies auc «ht 2 ye RVE Ot Che eeate eo ROSE eens oe eae ee ©.41 0.33 Thus in both these series from man, the correlation is less per- fect than in the albino rat. However, it must be remembered that the determination of the true body weight, especially when it must be taken postmortem, is much more difficult to make in man than in the rat. In 535 records (357 male, 178 female) the age of the rat 1s known, and a similar calculation of the coefficient of correlation between age and brain weight in the male, gives a much smaller value, 0.5177 + 0.0261, a result which might have been expected fete eto cache body weight of the rat is so easily modified by food and other external conditions. In this case also the coe fh- cient of correlation for man is much less than for the rat. An examination of either of the charts (1 and 3) shows that between the body weights of 50 to 100 gms. the observations tend to sag below the theoretical curve. For this “sag” no expla- nation has yet been found. ‘There is of course no cogent reason for expecting that the increase in the weight of the brain must con- form to a simple formula, yet it does conform to such a formula, except at the body weights of 50 to 100 gms, and we are therefore justified in expecting that this deviation may sometime be ex- plained. In order to distinguish between the period of early rapid growth, and the later period of slow growth of the brain, a determination has been made of the limits within which the mature brain changes in weight in a simple relation to the body weight. Taking as a standard the theoretical brain weight of the heaviest group (315 gms.), as given in column VD, table 1, and calculating the values for each successive group below this, it is found that as far as the group with a body weight of 105 gms. the brain weight diminishes nearly in proportion to the 7th root of the body weight. The calculated values based on the 7th root of the body weight, are given in column E of table 1. For this distance the straight line formed by the 7th roots of the body weight runs as a chord, of which the logarithmic curve forms Dona.pson, Growth of Central Nervous System. 353 the arc. At 105 gms. the chord and arc intersect and a limit is obtained. ‘This point of intersection is arbitrarily chosen to indi- cate that at which the rapid growth of the brain ceases. Within the limits taken, the maximum deviation of the values obtained by the 7th root of the body weight is 0.5 per cent, the values on the logarithmic curve being considered as the standard. (Com- pare table 1, columns D and F&, for the body weight group, 185 gms.). Using the formula of DuBois (’98) | DR TET Dae where EF and E’ are two different encephalic weights, related as a given power of S' and S’, the corresponding body weights, it appears that the value of x (“the exponent of relation’’) taken as the 7th root, is in the present instance 0.143. LapicQue (’08) has en- deavored to show that where individuals of the same species but of different body weights are compared, we should expect the value of x to be 0.25, equivalent to the 4th root of the body weight. To explain why my results do not accord with those obtained by LapicQuE would require a long critique of his studies on this point. I prefer however to leave this till another occasion, as the intro- duction of it here would obscure the main point of the present paper. To explain the essennal differences between the rapid and the slow growth of the brain thus indicated, it will be necessary for us first to have information touching the changes in the percentage of water, the chemical composition, the ether-alcohol extract, the degree of medullation and the other histological modifications occurring during growth, so that it is hardly worth while to dis- cuss this question now. Before leaving the subject of the brain weight, there is still one point more to be presented. It is a familiar fact that rats, even of the same litter and reared together, grow very differently, and therefore at the same age may have widely different body weights. Moreover, either by underfeeding, or by the use of a monotonous and comparatively innutritious diet, animals otherwise normal, may be stunted in their growth. In the class first mentioned, we have designated those which grew to unusual size as “giants,’’ and those which remained small 354 fournal of Comparative Neurology and Psychology. s “dwarfs.’’ In addition also, we have records on rats experi- mentally stunted (Harat ’04, ’07B and ’08). In the accompanying table 3, there is given a summary of the observed and calculated weights of the brain and spinal cord in these three groups. The calculations are based on the weight of the body at the time of killing, and were made by the use of form- ula [1] for the brain, and formula [3] for the spinal cord. ‘The individual records used in forming this table 3 do not appear in the general table. TABLE 3. Data on special groups; condensed statement; all the measurements are averages. BRAIN WEIGHT. 9 |SPINAL CORD WEIGHT, g Novof ! |Body.[o0 0 28°) Be | 4 Crone: cases weight) “8°? | Calcu- a | -Cal | = aaa 8 days. Observed) oF |Observed|] 72°" | & | lated. fa) lated. | G = | | grams gram. | gram. |perct.| gram. | gram. | per ct Giants Males 38 | | | |179.8 79 1.728 | 1.755 | —I-5| 0.489 | 0.500 | —2.3 Females 7 | | Dwarfs | Males 32 | | | | 47.2 Pe ase) || GEES —2.5| 0.258 O25 2 |e oeg Females 14 | | | | | | Experiment-| Males 14 | ally stunted | | 92.5 | 203 | 1.622 | 1.620 | +0.1) 0.404 0.406) | tae Females 12 | On looking at the columns giving the observed brain weights, and comparing these with those calculated, it appears that in the case of the “giants” there is a difference of .027 gm., or I.5 per cent, in favor of the calculated weight. Inthe case of the “dwarfs,”’ a difference of .033 gm., or 2.5 per cent, in favor of the calculated weight, and in the case of the rats experimentally stunted, a dif- ference of .002 gm., or O.I per cent, in favor of the observed weight. Within the same range of body weights (47.2 to 179.8 gms.), as shown in table 1 and chart 3, the calculated values are on the average 1.6 per cent above the general observed means, so that the special groups in question show on the whole no greater deviation than that found in the larger series. From this it follows that the relations of the brain weight to the body weight are not modified by either excessive or deficient growth under the Donatpson, Growth of Central Nervous System. 355 Ul usual conditions, nor by the deficient growth which may be experi- mentally induced. From the foregoing observations on the albino rat we conclude: 1. That for albino rats between 5 and 315 gms. in body weight the mean weight of the brain as observed increases from .333 gm. to 2.083 gms., or 6.2 times, and as calculated, from .231 gm. to 1.969 gm. or 8.5 times. 2. That from birth up to a body weight of about 105 gms. the brain grows rapidly, and after that, more slowly, increasing in the phase of slow growth very nearly as the 7th root of the body weight. 3. That the weight of the brain is closely correlated with the body weight, the coefficient of correlation being 0.7639 + 0.0108, but less closely correlated with the age, the coefficient of correla- tion being 0.5177 + 0.0261. 4. That the relation of the brain weight to the body weight is not essentially modified in either “dwarf” or “giant”’ individ- uals, nor in those experimentally stunted. 5. That in these various relations there is no marked distinc- tion between the sexes, although on the average for animals of the same crude body weight, the male has a brain weight 1.5 per cent heavier than that of the female. The bearing of these results on the corresponding relations as recorded for man will be considered farther on. We pass next to the observations on the growth of the spinal cord. GROWTH OF THE SPINAL CORD. The general table contains 647 records (429 male, 218 female) of the weight of the spinal cord. Chart 2 shows how the individual observations are distributed when these are entered in relation to the body weight in the same manner as in the case of the brain. It has been possible to record clearly on the chart only a fraction of the total records, and so 65 males and 21 females have been omitted. The determinations of the values according to sex are given in table 4, and show a distinct tendency for the female to have a heavier spinal cord, as the cord is greater in weight in 68 per cent of the groups, and on the average exceeds that of the male by 356 “fournal of Comparative Neurology and Psychology. about 2.0 per cent. Although, of course, the absolute differences are here very small, the indications of a difference according to sex are unmistakable. TABLE 4. Showing the mean spinal cord weight according to sex. | SPINAL CORD WEIGHT OBSERVED | Percentage difference between Body weight In. of cases.| (in ous.) female spinal cord weight gms. : Bes: and that of the male taken Males. | No. of cases. | Females. as the standard. | aes 5 37 | 0.035 21 0.036 20 15 47 0.103 Il 0.103 25 33 | 0.178 | 14 0.184 Blog 35 33 | Slezee 1% D2 on: 45 20 | 0.251 22 | 0.256 2.0 55 27 0.283 12 | 0.281 0.7 65 2 0.307 6 | 0.315 2.6 AS 25 0.331 6 | 0.338 2.1 85 16 0.360 4 0.370 | eT) 95 8 0.395 13 0.390 Gee 105 10 0.426 II | 0.412 3.0 115 14 0.435 9 0.425 2A 125 8 0.473 | 7 0-447 5-5 135 10 0.486 3 ©.470 A3 145 Il le nOa77, 6 ©.510 6.9 155 II | Sevags 8 0.518 | 4.6 165 9 | 9-550. | 10 0.534 2.9 is 7 | 0.521 6 0.593 13.8 185 7 0.504 7 0.556 10.3 195 6 0.590 8 0.605 as 205 9 0.592 6 0.567 4.2 215 5 0.590 | a 0.630 6.7 225 | No | females 235 4 | ©4020) «| 5 0.630 1.6 245 2 0.630 4 0.640 1.6 255 | 2 0.630 2 0.610 qe Average percentage excess in the weight of the female spinal cord, 2.0 per cent. To discuss this result further observations are required, but pending a well grounded explanation, it must be remembered that Watson (’05) has shown that the bearing of young has the effect of increasing slightly the weight of the spinal cord in the female, and as many of the females recorded in table 4 had borne young, this is probably one factor in producing the result as it appears in females at or beyond the bearing age. The excess is found, nevertheless, even before puberty. Dona.pson, Growth of Central Nervous System. 357 As in the case of the brain, however, it seems justifiable to treat the sexes together. When so treated, the theoretical curve as shown by the continuous line (C) in chart 3 is found by the formula [3] y = .585 (x + 21) — 0.795 in which y is the weight of the spinal cord and x the body weight. This formula [3] was derived in the same manner as formula [1]. The means for the weight of the spinal cord, determined as in the case of the brain, follow this curve closely (see chart 3). The Sa i ee ie ie pinal 8564. f the body CORRECTION. ‘opos On page 357 of THE JOURNAL OF COMPARATIVE pe NevuroLogy anp Psycuotocy, Vol. XVIII, No. 4, ee 1908, Formula (3) is erroneously printed pele — 085 (x + 21) — 0.795. A The correct form is apid veo) os (x —- 2) —— 02790: ina 3 far viest ; the ssIVe the ee TTP EET EES OTT TE TOP ATION M111 C curve and those determined by the 2.7th root of the body weight become identical. As in the case of the brain, we consider this point of intersection of the two lines to mark the cessation of rapid growth. As far down as the 205 gms. group, then, the weight of the spinal cord is in a simple relation to that of the body weight. Using this fact as a criterion, we may look upon the earlier growth of the spinal cord up to the 205 gms. group as rapid, while after that it is slow. As in the case of the brain, so in the spinal cord, the varia- tions in the growth of the body which produce “giants” or “dwarfs,” or the stunting which may be brought about experi- 3560 = “fournal of Comparative Neurology and Psychology. about 2.0 per cent. Although, of course, the absolute differences are here very small, the indications of a difference according to sex are unmistakable. TABLE 4. Showing the mean spinal cord weight according to sex. | | | Percentage difference between female spinal cord weight and that of the male taken No. of cases. Females. as the standard. SPINAL CORD WEIGHT OBSERVED Body weight (iN GMs.) gms. No. of cases. Males. | | | 255 | eee | | | Average percentage excess in the weight of the female spinal cord, 2.0 per cent. To discuss this result further observations are required, but pending a well grounded explanation, it must be remembered that Watson (’05) has shown that the bearing of young has the effect of increasing slightly the weight of the spinal cord in the female, and as many of the females recorded in table 4 had borne young, this is probably one factor in producing the result as it appears in females at or beyond the bearing age. The excess is found, nevertheless, even before puberty. Dona.pson, Growth of Central Nervous System. B57 As in the case of the brain, however, it seems justifiable to treat the sexes together. When so treated, the theoretical curve as shown by the continuous line (C) in chart 3 is found by the formula [3] = .585 (x + 21) — 0.795 in which y is the weight of the spinal cord and x the body weight. This formula [3] was derived in the same manner as formula [1]. The means for the weight of the spinal cord, determined as in the case of the brain, follow this curve closely (see chart 3). “The numerical values for the means are given in table 1, column /7. The coefficient of correlation between body oe oh and spinal cord weight is still higher than that for the brain, being 0.8564 + 0.0071. As in the case of the brain, there is a “sag” of the observed means below the theoretical curve, between the body weights of 50 and 100 gms. and what has been stated apropos of this on p. 352 applies to the cord also. A moment’s inspection of chart 3 shows that the growth of the spinal cord differs from that of the brain in being on the whole more rapid, and also longer continued. ‘The details of the rela- tions will be taken up later, but the point of importance at this moment is that from the longer continued rapid growth it follows that the increase in the weight of the cord in a simple fixed relation to the body weight does not extend as far down the curve as in the case of the brain. From the heaviest group (315 gms.), the mean cord weight of which is taken as the standard, the weight of the cord diminishes in each successive group according to the 2.7th root of the body weight, until the 205 gms. group is reached, when the values on the logarithmic curve and those determined by the 2.7th root of the body weight become identical. As in the case of the brain, we consider this point of intersection of the two lines to mark the cessation of rapid growth. As far down as the 205 gms. group, then, the weight of the spinal cord is in a simple relation to that of the body weight. Using this fact as a criterion, we may look upon the earlier growth of the spinal cord up to the 205 gms. group as rapid, while after that it is slow. As in the case of the brain, so in the spinal cord, the varia- tions in the growth of the body which produce “giants” or “dwarfs,” or the stunting which may be brought about €xperi- 358 “fournal of Comparative Neurology and Psychology. mentally, do not modify essentially the relations of the spinal cord to the body, so that the weight of the cord as calculated by the formula [3] corresponds closely with that observed (see table 3). From the foregoing observations we conclude therefore: 1. hat for albino rats between 5 and 315 gms. in body weight, the mean weight of the spinal cord as observed, increases from .036 gm. to .737 gm, or 20.4 times, and as calculated from 0.33 gm. to .683 gm. or 20.6 times. 2. That from birth to a body weight of about 205 gms. the spinal cord grows rapidly, and after that more slowly, increasing in this phase of slow growth nearly as the 2.7th root of the body weight. 3. That the weight of the spinal cord is closely correlated with the body weight, the coefficient of correlation being 0.8564 + 0.0071. 4. That the relation of the spinal cord weight to the body weight, is not essentially modified in either “dwarf” or “giant” individuals, nor in those experimentally stunted. 5. That in these various relations there is no marked distinc- tion between the sexes, although on the average, the female spinal cord is about 2 per cent heavier than that of the male. This difference probably depends in part on the effect of the bearing of young. THE ENTIRE CENTRAL NERVOUS SYSTEM. While a detailed discussion of the weight relations of the entire central nervous system of the albino rat is hardly necessary, in view of what has already been presented concerning the brain and the spinal cord, nevertheless one or two points call for con- sideration. The values for the entire central nervous system are entered in table 5, in which the sum of the values for the brain and the spinal cord are given both as observed and as calculated by the formula [1] and [3]. The totals for the entire series of groups agree closely, the observed being 0.2 per cent less than that cal- culated by the formule.. By dealing with the entire system, we avoid any error which might depend on variations in the point of separation between the brain and the spinal cord. On determining the period of rapid growth for the entire nervous system and using the same general procedure as before (see pp. Dona.pson, Growth of Central Nervous System. Weight of the central nervous system in the albino rat, given in mean yaiues. TABLE 5s. 359 Cal= culations according to the formulz [1] and [3] and the 5th root of the body The heaviest group, 315 gms., is taken as the standard for the cal- culation according to the 5th root, and at,135 gms., the values by the 5th root and the logarithmic curve coincide. weight. No. oF CASEs. WEIGHT OF THE CENTRAL NERVOUS SYSTEM. | (IN Gs.) Body weight. | Gavcutanone Sse eas! Observed Br. Cd. ears By formule Boge [1] and fg). gel A. B. C. D. 10. Be 5 | 58 58 | 0.369 0.264 15 60 58 | 1.080 1.124 25 | 52 47 | 1.465 1.421 35 53 47 | ESS it | eRe) 45 42 42 | 1.695 Teun 55 43 41 1.756 1.807 65 32 32 1.797 | 1.887 75 34 32 | 1.892 | 1.955 85 21 20 1.950 2.015 95 22 21 | 2.010 2.068 105 21 21 | 2.093 2.116 | 115 24 24 2.115 2.160 | 125 18 16 Pe 2.201 | 135 15 14 2.244 2.237 2.238 145 19 17 2.207 2272 2.270 155 25 21 2.260 2.305 | 2.301 165 19 19 2.313 2.335 | 2.329 175 13 13 2.383 2.364 | 2.357 185 16 14 2.311 | 2.392 2.384 195 15 15 2.401 | 2.416 | 2.409 205 17 15 2.391 | 2.441 | 2.433 215 8 8 2478. 2." | 2.464 | 2-457 225 8 8 2.408 | 2.486 2.479 235 10 9 Patil. | 2.508 2.501 245 6 6 2.537 | 2.528 | 2.521 255 4 4 2.520 | 2.548 | 2.542 265 7 7 2.574 | 2.567 | 2.561 275 6 6 2.673 | 2.585 | 2.581 285 3 3 2.660 2.602 2.599 295 3 3 2.633 2.620 | 2.617 305 3 3 2.800 2.636 | 22635 315 2 3 2.820 2.652 | == 352 and 357), it appears that the weight of the central nervous system diminishes in proportion to the 5th root of the body weight, as far as the 135 gms. group. The rapid growth of the entire central nervous system ceases then according to this criterion, at 135 gms. of body weight. The sum of the values determined in % 360 = “Ffournal of Comparative Neurology and Psychology. accordance with the 5th root of the body weight (1.e., from the body weights of 135 to 305 gms.) is found to be 0.2 per cent less than the sum of the corresponding values determined by the form- ulae, all of which indicates substantial agreement between the three series. The following table 6 gives the weight of the central nervous system according to sex. In 68 per cent of the groups the male is the heavier, and the values for the male exceed those for the female by 0.8 per cent. ‘The difference is slight, but as already pointed out it seems probable that it is real. TABLE 6. Weight of the central nervous system according to sex. Those male groups which are heavier are marked with a star (*). WEIGHT OF CENTRAL NERVOUS SYSTEM OBSERVED. Body weight. _——$—$ $$ = - - | Male. Female. grams. grams. grams. 5 0.391% 0.360 15 1.074 1.103 25 1.484* 1.406 35 1.593* 1.593 45 1.726* 1.666 55 1.772* 7 65 1.796 1.798 75 1 .899* 1.855 85 1.951* 1.945 95 2.045% 1.985 105 2.106% 2.070 115 2.099 Zeiiias 125 22238 2.083 135 2. 2ha% | 2.220 145 2.199 | Dx D22, 155 2.263* 2.243 165 Dagar 2.204 175 2.342 2.426 185 2.287 2.336 195 2.423* 2.388 205 | 2.406% 2.367 215 | 2.420 | a AST Eh 225 | | No females 235 2.550% | 2.480 245 2.530 | 2.540 nv n nA is) n wo e} * 2.510 Donatpson, Growth of Central Nervous System. 361 WEIGHT RELATION OF THE BRAIN TO THE SPINAL CORD. The weight relations of the brain and spinal cord change with age. Using the calculated values, it appears that for a very short period after birth the brain grows more rapidly than the spinal cord (see body weight 15 gms., table 7) but at about the body weight of 15 to 25 gms., the cord begins to grow more rapidly than the brain, and from that time on the ratio of the brain weight TABLE 7. Showing the ratio of the weight of the spinal cord to that of the brain in the albino Tat. CALCULATED BY FORMULAE [3] AND [1]. Rateoreanleoad Body weight. SA en aan ; ; : 5 weight to brain weight: Cord weight. Brain weight. grams. gram. gram. 5 0.033 0.231 | 7.05 15 0.115 I .009 8.74 25 0.178 1.244 | 6.99 35 0.228 1.362 6.01 45 2.269 1.442 5-35 55 0.305 1.502 4-92 65 0.337 1.550 _ 4.60 75 0.365 1.590 4-36 85 0.390 1.625 4.17 95 0.413 1.656 4.01 105 0.434 1.683 3-88 115 0.453 | 1.707 shoGy/ 125 0.471 | 1.729 3.67 135 0.488 | 1.750 3-59 145 0.504 | 1.769 Bai 155 0.519 | 1.786 3-44 165 0.533 | 1.802 3-38 175 0.546 1.818 BEaa 185 0.559 | 1.833 3.28 195 0.571 | 1.846 3.23 205 0.582 | 1.859 3.19 215 0.593 | 1.871 3-15 225 0.604 1.883 ees) 235 | 0.614 1.894 | 3-09 245 0.624 1.905 3-05 255 0.633 1.915 3-03 265 0.642 1.925 3.00 275 0.651 I .934 | 2.97 285 0.660 1.943 2.94 295 0.667 1.952 2.89 305 0.675 1.960 | 2.87 315 | 0.683 1.969 2.85 362 Fournal of Comparative Neurology and Psychology. diminishes. The observed values indicate the same relation, although in a less marked degree. ‘The accompanying table 7 shows this ratio, determined for each of the several body weight groups. The phase in which the brain grows relatively more rapidly than the spinal cord is found also in man, but so far as the scant human records go it appears to pass over into the phase of the. less rapid relative growth of the brain some time before birth (Migs 93). Owing to the immaturity of the rat at birth, however, this earlier phase is just recognizable as a post-natal phenomenon in that animal. The mean values for the weight of the spinal cord at given brain weights are represented by the dots in chart 4, and are given under “observed” in table 8. In this same table under “calcu- lated”’ are given also the values for the weights of the spinal cord as determined by calculation. ‘These latter values were obtained in the following manner. ‘Transposing formula [1] to the form a Oye Tiog: (42> 89) == oS 7 One i -569 it was possible to calculate the body weights which belonged to the brain weight values used in this table. From the body weights thus obtained the corresponding weights for the spinal cord were calculated by formula [3]. The continuous line in chart 4, p. 363, is the curve based on these values, and the inspection of the chart shows that the observed values and those calculated agree very closely. On correlating the brain weight with the observed spinal cord - weight, using weight groups for the brain differing by 0.1 gms., the coefficient of correlation is found to be 0.8787 + 0.006, which is higher than for any relation which we have had occasion to deter- mine. PFIsTER (’03), in his studies on the spinal cord and brain in children, has also noted the close correlation between these two portions of the central nervous system. From the foregoing study of the weight of the entire central nervous system and of the relation of the brain weight to that of the spinal cord, we conclude: 1. That from the 5 to the 315 gms. weight group, the entire central nervous system as observed, increases in weight from Dona.pson, Growth of Central Nervous System. 363 1?) .20 40 60 .80 1.00 120 1.40 1.60 1.80 2.00 Gms. Cuart 4. The base line represents the brain weights from 0.20 to 2.00 grams. The corresponding values for the spinal cord weights are measured on the ordinates, and shown by a theoretical curve (con- tinuous line) determined by formule [1] and [3] and also shown by a series of dots indicating the observed mean values (see table 8). TABLE 8. Showing the mean weight of the spinal cord both observed and calculated through the range of brain weights in groups differing in brain weight by 0.1 gm. SPINAL CORD WEIGHT. Brain weight. : iS Ee E | Observed. Calculated. grams gram gram. 0.25 0.030 0.036 0.35 0.030 0.046 0.45 0.043 0.053 0.55 0.050 0.067 0.65 0.070 0.079 0.75 ©.070 0.085 0.85 0.076 0.094. 0.95 0.103 0.106 1.05 0.131 0.124 1.15 0.139 0.148 Ta 0.199 0.180 regells 0.223 0.222 1.45 0.282 0.274 1.55 0.345 0.336 1.65 0.422 0.408 1.75 0.505 0.488 1.85 0.561 0.575 1.95 0.614 0.666 22-05, 0.710 Polly 0.700 364 ‘fournal of Comparative Neurology and Psychology. 0.369 gm. to 2.820 gms., or 7.9 times, and as calculated, from 0.264 gm. to 2.652 gms., or IO times. 2. That for the central nervous system, the period of rapid growth extends up to the 135 gms. group, after which the system increases nearly regularly in proportion to the 5th root of the body weight. 3. When the mean weights of the central nervous system are determined according to sex, it appears that in 68 per cent of the records the weight in the male exceeds that in the female, but on the average the difference is small, amounting to only 0.8 per cent. 4. From birth to the 15 to 25 gm. group, the brain grows more rapidly than the spinal cord, but after that the spinal cord grows faster, so that using the calculated values, the ratio drops from 8.74 at 15 gms. to 2.85 at 315 gms. 5. The coefficient of correlation between the weight of the brain and the weight of the spinal cord is very high, being 0.8787 + 0.006. COMPARISON OF THE GROWTH OF THE BRAIN AND OF THE SPINAL CORD IN THE ALBINO RAT, WITH THEIR GROWTH IN MAN. With the foregoing data in hand, it is possible to make some comparisons between man and the albino rat in respect to the growth of the brain and of the spinal cord. Five points will be examined: 1. The form of the growth curve according to age. 2. The relative increase in the weight of the brain during the phase of rapid growth. 3. The time taken for this increase. 4. The cessation of the rapid growth of the brain in relation to puberty. 5. Weight of the brain and the spinal cord as modified by sex. To determine in the albino rat the growth of the brain with age, the calculation according to the formula [1] was made for the brain weight of each of the age groups used by me in constructing the growth curve for the entire body (DonaLpson ’06). ‘The results obtained are given in the following table 9 and are plotted in chart 5, plate 111. Donapson, Growth of Central Nervous System. 365 TABLE 9. Showing the weight of the brain at different ages in both sexes of the albino rar. Data on body weight taken from DonaLpson ’06, and brain weight deter- mined by formula [1]. Mates. FEMALES. Age Raa = Sie alae Pree Sey |e a te, y a SEV ist Body weight. | Brain weight. | Body weight. | Brain weight. | grams. calculated. | grams. | calculated. ° | 5-4 0.2589 | 5.2 | 0.2444 I 5.6 0.2744 | eae 0.2665 2 5.8 0.2909 | Soa 0.2825 8 6.3 0.3367 | 6.2 0.3276 4 6.9 0.4087 6.5 0.3592 5 8.3 | 0.5197 | el 0.4971 6 9.1 0.5887 8.5 0.5369 7 9.2 0.5938 8.7 0.5540 8 10.4 0.6851 10.6 0.7126 9 11.3 | 0.7902 | iit 0.7703 10 ee 0.8636 | 12.1 0.8564 Il. eA) 0.9311 12.8 0.9027 12 14.8 1.0008 | 15.1 1.0128 13 ria 1.0203 | rela 1.0128 14 15.2 1.0186 15.6 1.0313 15 16.5 1.0616 77, 1.0970 17 17.8 1.0906 19.2 1.1351 19 19.5 1.1420 20.6 1.1660 21 Die | 1.1782 22.6 | 1.2044 23 22.9 1.2097 24.9 | 11 a) 25 Dee 1.2483 27.4 1.2776 27 274. 1.2776 30.0 1.3099 29 29.5 | 1.3040 | Bi ch 1.3256 31 31.8 | 1.3299 | 32.9 1.3414 34 34.9 1.3611 | Aoy) 1.3685 37 B78 1.3870 39-5 1.4010 40 42.2 1.4218 | 43-7 1.4326 3 46.3 1.4503 47-9 1.4542 46 50.5 1.4765 | 52.0 1.4852 49 56.7 1.5106 | Se 1.5157 52 62.5 | 1.5388 | 62.9 1.5407 55 68.5 | 1.5149 | 68.4 1.5646 58 73-9 1.5863 | 74.6 1.5890 61 81.7 1.6142 78 .4 1.6028 64 89.1 1.6381 85.8 1.6278 67 99-3 1.6676 | 96.0 1.6588 70 106.6 1.6868 | 99.8 1.6690 3 113.8 1.7066 | 105.6 1.6842 76 12a | 1.7213 | 110.4 1.6858 79 128.2 1.7360 118.8 1.7158 82 135.0 1.7497 | 124.7 1.7287 85 143.8 1.7664 Heiitiols 1.7428 88 148.4 1.7747 | 136.0 1.7516 g2 152.3 1.7815 139.8 1.7589 97 160.0 1.7943 146.3 1.7709 102 | 168.8 1.8083 NG ae 1.7828 366 =“ fournal of Comparative Neurology and Psychology. TABLE 9—Continued. Mates. FEMALES. Age. == in days. | Body weight. Brain weight. Body weight. | Brain weight. | grams. | calculated. grams. | calculated. 107 177.6 1.8215 155-8 1.7874 112 183.8 1.8305 161.4 1.7966 117 191.4 1.8409 168.0 1.8069 124 197 .3 1.8488 | 172.6 1.8141 131 202.5 1.8555 181.0 1.8265 138 209.7 1.8645 185.0 1.8322 143 218.3 1.8749 186.6 1.8344 150 | PS 1.8831 188.2 1.8366 157 | 227.0 1.8849 188.0 1.8363 164 231.4 1.8899 189.5 1.8383 171 235.8 1.8947 192.2 } 1.8420 178 239.4 1.8986 197.0 | 1.8484 185 239.8 1.8990 200.0 1.8523 192 No Males 202.2 | 1.8551 216 252.9 1.9126 No Females 256 265.4 1.9250 No | Females 365 279.0 1.9377 226.4 | 1.8843 730 308 .5 1.9633 | As the calculated, values of the weight of the brain vary in the same sense as the body weights, it appears that from birth to maturity the curves for the brain weight in the two sexes are related to each other as are the body weights, and thus the brain weights in the females between the ages of 14 and 52 days are heav- ier than those in the males. This relation should be confirmed by direct observation before any value is attached to it. On the other hand, after the period of most rapid growth the brain weight of the male is always the heavier, because at like ages the male body weight exceeds that of the female. ‘This portion of the curves is therefore like that in man, and for the same reason. As previously pointed out, we consider the period of the rela- tively rapid growth in the brain to cease when it reaches the point where the further increase in weight is approximately in propor- tion to the 7th root of the body weight. ‘This occurs at about 70 days in the males, and 73 days in the females. In order to compare the amount of increase in the weight of the brain between birth and maturity in man with that in the albino rat, it is necessary to bring the data on man into the same form as that for the rat. “Taking as a basis the data compiled by VIER- DoNALDSON, Growth of Central Nervous System. 367 ORDT (’90), we give in the following table his observed values, and also the values obtained from a smoothed curve based on these data. The curve represented by V1ERoRDT’s observations is given in “The growth of the brain’”’ (DoNALDSON ’95) and also in the American Text-Book of Physiology (DoNnaLpson ’o1). The smoothed curve which passed with the least deviation through the rough curve has been drawn, and then the values given by the smoothed curve were determined for each year. ‘These values are entered in table 10 under “‘calculated”’ in columns D and F, and from these, of course, the smoothed curves can be reconstructed. To so reduce the values of the human records as to make them comparable when plotted with those from the rat, 1t was necessary to divide them by 7oo. In chart 5 the weight of the human brain thus reduced 1s compared with that of the rat, the span of human life being taken as thirty times that of the rat, and the time inter- vals entered accordingly. When thus plotted, it is seen that the two curves are similar in form. Moreover, if we determine the age at which the rapid growth of the brain ceases in the rat, which is at a body weight of 105 gms. (see p. 352), it is found to fall at about 70 days in the male, and 73 days in the female and it is evident that the average date, 72 days, corresponds very nearly with six years in man. Between birth and 72 days the rat brain has increased in weight (mean of both sexes combined) from .02517 gm. to 1.6823 gm. or 6.3 times, while in the corresponding interval, the human brain has increased in weight (mean of both sexes combined) from 383 to 1215 gms., or 3.2 times. We know, however, that the rat is born relatively much less mature than the child. ‘The comparison as it stands, is therefore hardly fair. If we determine for the rat the initial brain weight, which at 72 days would give an increase similar to that observed in man (3.2 times) we find the required weight to be .525 gm., or approximately the weight of the rat’s brain between five and six days. Therefore, between the age of five and six days—at which time the rat’s brain is certainly more comparable with the human brain than at birth—and 72 days, the brain of the rat increases in weight in the same proportion as does the human brain between birth and six years. This relation, although derived from a treatment of the data which is admittedly rough, is very suggestive, but it will be hardly 368 Journal of Comparative Neurology and Psychology. TABLE to. To show the increase in the brain weight of man with age. Encephalon weighed entire with pia. (Compiled by VierorprT). Mates. | FEMALES. Bratn IN GMs. BraIN IN GMs. aes No. of No. of cases. | Calculated. | Calculated. cases. | Geese (Donarpson) Seas (Dona.pson) A B C | D E F G © months 36 381 381 384* | 384 38 I year 17 | 945 945 872 850 II 532) 27 1025 1085 961 | 950 28 3 19 1108 1175 1040 1060 . 23 4 19 1330 1225 1139 1140 13 nS 16 | 1263 1290 1221 1180 19 6 10 1359 1325 1265 1205 10 7 14 1348 1360 1296 1220 8 8 4 1377 1380 1150 1235 9 9 3 GES) 139° 1243 | Wee) Z fe) 8 1408 1400 1284 1250 4 II 7 1360 1410 1238 1255 I 12 5 1416 1415 1245 1257 2 13 8 1487 1415 1256 1259 3 14 1 1289 1415 1345 1260 5 15 3 1490 1415 1238 1260 8 16 7 1435 1415 1273 1260 15 17 15 1409 1414 1237 1258 18 18 | 18 1421 1413 1325 1255 21 19 21 1397 1412 1234 1253 15 20 14 1445 1410 1228 1251 33 21 29 1412 1408 1320 1249 31 22 26 1348 1404 1283 1247 16 3 22 1397 1400 1278 1245 26 24 30 1424 1397 | = 1249 1243 33 25) 5) 1431 1395 Tea 1240 33 Motalnojoteasesst.1.3': / 2 te sn oe 415 Totaleno.voftcasess 7a - eee 424 *Tt appears probable that the weight here given in table 10 for the female brain at birth is too high (HanpMann ’06, S. 35); but it seemed best to hold to one table in this instance, and not attempt to revise any single entry init. Any lowering of the human brain weight at birth would tend to make the weight relations in man even more similar to those found in the rat than the calculations given farther on show them to be. . profitable to discuss it until we learn both for man and the rat, at what time cell-division in the brain ceases, and so can deter- mine when the increase in weight becomes the expression of simple enlargement alone. Nevertheless, it is of interest to note that while nearly the same fraction of the span of life is used for the rapid growth process in both forms, the actual period required by man is thirty times that for the rat. Donatpson, Growth of Central Nervous System. 369 The observation as it stands, represents a special instance of the phenomenon already observed by BuNcE (’02) and RUBNER (08 and ’o8A), that during the phase of rapid growth, immediately following birth, the smaller mammals double their body weight in a much shorter period of time than does man. ‘The present observation has moreover the interest of applying to an organ in which it is probable that cell division has nearly ceased, so that the increase in weight during this period, is due almost entirely to the mere enlargement of the elements which are for the most part neurones. It might be urged that to complete the demonstration, it should be shown that during this interval, the same percentage of the limit- ing brain weight had been attained by both forms. ‘The facts are these. The brain of the rat has a weight (calculated by formula [1]) at 72 days of 1.6823 gm., and at 303 days (corresponding to 25 years in man) a weight of 1.9020 gm., so that at 72 days it has attained approximately 88.4 per cent of its limiting weight. On the other hand, the human brain (mean of both Sees) has at six years a weight of approximately 1215 gms., which accord- ing to the value in table Io, is 92.2 per cent of its limiting weight at 25 years, and go.8 per cent of its calculated maximum weight at 16 years.'. Thus the human brain has attained a greater frac- tion of both its limiting and its maximal weight. ‘The discrep- ancy seems to depend mainly on the fact that while the early phases of body growth in the rat are similar to those in man, yet the rat continues to grow for a relatively longer period after matur- ity than man does, and at the same time, the weight of the brain and spinal cord continues to increase with that of the body. This differences in the later phase of body growth therefore is a point which needs to be investigated. At the same time although the early attainment of the maximum weight in man followed by a slow decline in weight through later life, as brought out by sev- eral investigators and specially studied by PEARL (’05), may be a normal biological phenomenon, yet it must be frankly aed that the human records as they stand, are distinctly influenced by the factors represented by the peculiarities of the “hospital population” on the one hand, and the effect of disease, especially ‘Tt may be noted in passing that HanpMANN (’06, S. 14-17) finds the maximum brain weights in both sexes between 15 to 17 years. 370 ©6fournal of Comparative Neurology and Psychology. chronic disease, on the other (GREENWOOD ’05, GLADSTONE ’05 and BLAKEMAN ’05). Turning next to the relations of puberty to the completion of the rapid growth of the brain, it is worthy of note that the comple- tion of rapid growth in the albino rat at about 72 days, coincides in this animal with puberty, which appears at 65 to 75 days. In man, on the other hand, it precedes puberty from 6 to g years. Any interpretation of this difference must await a determination of the finer anatomy of the brain in the two forms, at the time of puberty. Passing to the spinal cord, much less can be done in the way of comparison owing to the small amount of data on the spinal cord of man. ‘The human spinal cord at birth has a mean weight of about 3.2 gms. (Mires ’93) and at maturity of 27 to 28 gms. (ZIEHEN ’99). The body weight, length of trunk and sex prob- ably all have an influence on the weight of the cord, but we do not know how much (PFISTER ’03). Using the foregoing values (3.2 gms. and 27.5 gms.) it appears that between birth and maturity the human spinal cord increases in weight about 8.6 times. ‘Taking the calculated weight of the spinal cord in the rat (mean of both sexes) as 0.589 gm. at 303 days (equal to 25 years of human life), we find that the weight which would give an increase of 8.6 times is 0.068 gm. ‘This corresponds to the average weight of the cord between 7 and 8 days, which is nearly the same as the age (5 to 6 days) found for the brain by a like calculation. From this it follows that the cell elements in the spinal cord of the rat enlarge in the same propor- tion as do those in man, and that these two divisions of the central nervous system in the rat are similarly related to the cerrespond- ing parts in man. Calculation shows that the amount of enlarge- ment between birth and maturity is in both forms very nearly 2.5 times greater in the case of the spinal cord than it is in the case of the brain. Expressing this result in terms of neurones, it would mean that the average bulk attained by the neurones of the spinal cord was 2.5 greater than that attained by the nuerones of the brain. ‘The relatively greater weight of the cord of the rat, as compared with the brain, depends of course, on the initial plan of the central nervous system peculiar to that animal. With regard to the weight of the brain and of the spinal cord as modified by sex, a few words are in place. In the human records, Dona.pson, Growth of Central Nervous System. eh so largely has age been made the basis for the comparison of brain weights, that we have most of us fallen into the habit of thinking of them always in that relation. I wish therefore to emphasize the fact that it is my purpose here to consider the possible influence of sex on the weight of the brain and of the spinal cord in animals of like body werghts, age not being considered. As has already been shown in the case of the albino rat (pp. 349 and 355) when males and females of like body weight are compared, it is found that the weight of the brain is about 1.5 per cent heavier in the males, and the weight of the spinal cord about 2 per cent heavier in the females. Harat’s (’07A) studies on the cranial capacities of the male and female rats show even less dif- ference than we have found in the case of the brain itself. As already pointed out, it seems probable that when the crude body weights of the females are corrected for the excess of fat, and for the relation of stature to body weight, even this difference in the weight of the brain and cranial capacity will be further diminished. It should be noted moreover that the corrections which would tend to make the brain weights in the two sexes more nearly sim- ilar, would also tend to increases the weight of the spinal cord in the female. Such being the relations in the case of the rat, it is of interest to inquire how these matters stand in the case of man. Touching the weight of the brain as correlated with the weight of the body and the body measurements, I will cite only two recent investigations. BLAKEMAN (’05) on making the necessary calculations, finds that “The English man of the same age, stature, and diametral product as the mean woman, has 1235 gms. brain weight, or only 10 gms. more than the average woman” (1224.90 gms.) and fur- ther that ‘“The English woman of the same age, stature and dia- metral product as the mean man, has 1315 gms. brain weight, or only 13 gms. less than the average man” (1327.69 gms.). ‘The comparison is far from perfect, and other corrections, the need for which is recognized, would probably further reduce even this small difference. By a very different procedure LapicQue (’08) reaches a con- clusion which is quite similar. ‘Taking the values in the follow- ing table as given by him, Bovy WEIGHT. BRAIN WEIGHT. Miata siva sic ious soteereate dt iareia crore mer sictavsratnie ais 66,000 gms. 1360 gms. SHAH eGSOORM ab BU OCR ADE OrmOG aD miele 55,000 gms. 1220 gms. 372 fournal of Comparative Neurology and Psychology. he finds that the 0.56 power of the body weights, gives very nearly the brain weights as observed. The o. 56 power of the body weights represents the relation of the brain weights found by Dusors (’98) to subsist between animals of like form, but dif- ferent species. Leaving aside at this time any discussion of La- PICQUE’S general result, | wish merely to point out that the brain weights according to sex, as shown by these data of LapicQuE, are so related that when the body weight of the female is raised to that of the male, it calls for approximately the same brain weight as is found in the male. We may conclude, therefore, that in both rat and man the brain weight is nearly the same in both sexes, when the body weights are the same, such small difference as is still found being in favor of the male, but at the same time probably open to further reduction. If we turn now to the spinal cord, a direct comparison of the weights according to sex is blocked in man by the absence of suf- ficient data. Some light, however, can be obtained by examin- ing in the case of man the ratio Brain weight Spinal cord weight Mies (’93) gives the following: Mate. FEMALE. Age. ae ee ies Nee ir Aa ear pe No. vof B.W No. of B. W. Ratio — a Ratio = Cases | S.C.W SSIES S.C.W. SS helaly ahs he a Grae OIC OS cord Ce 10 | 116.42 II Tg) Milani tyusccntve npr violets aera ox egsier- 10 | sie) 4 49-47 which shows that in proportion to the brain weight both at birth and at maturity the weight of the spinal cord in the male is less, 1.e., gives a higher ratio than in the female. In a series of eight comparisons, extending in age from one month to 64 years, and based on 35 males and 38 females, PFISTER (03) finds the proportional value of the spinal cord weight in each of the eight comparisons, to be less in the male, indicating accord- ing to the average of the ratios, about 4 per cent of difference in favor of the spinal cord in the female. From what has been said concerning the weight of the brain and of the spinal cord in the Dona.pson, Growth of Central Nervous System. 272 rat when the sexes are compared, it follows that similar relations are found in that animal and the calculations show them. In view of these facts, and in view of the preceding determi- nations, that for like body weights, the human male and female have approximately the same weight of the brain, it necessarily follows that where the body weights are alike, the spinal cord in the woman is heavier than in the man; a conclusion which I be- lieve has not been heretofore explicitly stated. It thus appears that in both sexes of man and the albino rat, the relations of the weight of the brain and the spinal cord to that of the body are similar. From the observations presented in the later portion of this paper, we conclude that man and the rat are similar in the weight relations of their brain and spinal cord, in the form of the growth curves for the brain, in the fraction of the span of life taken for the rapid growth of the brain, and in the proportional develop- ment of the brain and cord during this phase. They differ, however, in the intensity of the general growth processes, which are some thirty times more rapid in the rat than in man, in the relation of the completion of the phase of rapid growth to the appearance of puberty and in the longer continuance of the phase of slow growth in the rat. | Nevertheless, in view of the similarities above named, it appears that by the study of the nervous system of the albino rat, it will be possible to obtain information bearing on certain growth phe- nomena in man, the direct study of which in the human nervous system is at present impracticable. 374. “fournal of Comparative Neurology and Psychology. GENERAL TABLE. Mus norvegicus var. albus (albino). The records are grouped according to sex, and in the case of each sex, every record carries its own serial number. In the present table, the records are arranged according to body-weight in two series, Series 1, normal, 458 males, 215 females, Series 2, injected with lecithin (Hata ’03), 4 males, 3 females. Both series were used in forming the special tables. If new observations are published in the future, each new record will bear its own serial number. In case series are to be formed for any purpose which involves the use of new records combined with those previously published, the latter will always bear the serial number given them when they were first printed. By this device, it is hoped that confusion between the new and old records may be avoided. : WEIGHT IN GMs. | acs ~ Sex. | Age in days | REMARKS. a Body. Brain. Cord. I M. I 3:8 0.2523 0.0242 | 2 M. AT 0.2092 0.0286 | At birth 3 M. 4-3 0.2348 0.0350 | At birth 4 M. 4-3 0.2400 0.0310 «=| At birth 5 M. 4-4 | ©.2092 0.0312 At birth 6 M. 4.5 0.2040 0.9309 | ~ At birth 7 M. 4.6 0.2179 | 0.0330 | ~At birth 8 M. I 4.6 0.2749 0.0306 9 M. 4.6 0.2240 | 0.0270 | 36 hours 10 M. 4.6 0.2096 | 0.0342 | At birth II M. 4-7 0.2150 | 0.0280 | 36 hours 12 M. 4-7 0.2310 0.0300 36 hours 13 M. 4-9 0.2052 | 0.0304 | At birth 14 M. 5.0 0.2286 0.0336 | At birth 15 M. I 5.0 0.3111 0.0335 | 16 M. ett 0.2088 0.0318 At birth 17 M. a7) 0.2324 0.0316 At birth 18 M. Go 0.2336 0.0324 | At birth 19 M. Get © 2220 0.0328 | At birth 20 M. 04 0.2326 0.0328 | At birth 21 M. 5-4 0.2034 0.0338 | At birth 22 M. 5.4 0.2750 0.0300 | 38 hours 23 M. | oly 0.2406 0.0320 | At birth 24 M. 5.6 0.2320 0.0350 | At birth 25 M. 5.8 0.2578 0.0342 14 hours 26 M. 2 5.8 0.2340 0.0330 27 M. 5-9 0.2752 0.0342 | At birth 28 M. | 6.0 0.2710 Oley | eNE lo yiinlan 29 M. | 6° 0.2722 || ©0370) | s eAt birth) 30 M. 2 | 6.2 0.2340 | 0.0320 | 31 M. | | 6.4 0.2758 | 0.0386 At birth 32 M. | | 6.6 0.2975 0.0409 20 hours 33 M. | 10 | eR 0.6982 0.0637 | 34 M. | 10 7-9 0.7087 | 0.0658 | 35 M. | 10 8.2 0.7430 | 0.0734 36 M. 5.3 8.3 0.5050 | 0.0540 37 M. 10 8.5 0.7498 | 0.0750 38 M. 9 10.7 0.7080 | 0.0764 Series I. No. 39 40 41 Dona.pson, Growth of Central Nervous System. B75 GENERAL TABLE—Continued. SSSSSSSSSSS5S5S5555 5555555555555 5255 55555555555 555555555 | Age in days. | WEIGHT IN GMS. REMARKS. Body Brain. Cord. 10 10.8 0.8010 0.0744 Io 10.9 0.7998 | 0.0685 Ke) Vitie@ 0.8494 | 0.0818 9 visi ge) 0.7450 0.0730 9 | 11.7 0.7404. 0.0752 10 | 11.8 0.8560 0.0890 10 | li.g 0.8410 0.0701 fe) ene 0.8082 ©.0750 10 12.0 0.8600 © 0960 9 | L2/or 0.7758 0.0784 10 | E28) 0.8415 0.0781 10 12.6 0.8271 0.0733 10 12.7 0.8992 0.0975 10 13-4 0.8656 0.0947 9 you 0.8010 0.0800 19 lols 1.0840 ° 0.1250 Io 13.5 0.8883 0.0898 10 13.8 0.8978 0.0895 10 13.8 0.8495 0.0825 14 13.8 1.1153 0.1062 14 13.9 I. 1099 0.0962 40 we 8) C9927 19 14.3 1.1580 0.1262 10 14.4 ©.goIo 0.0895 10 joeoanata 0.9550 ©. 1000 19 14.5 1.1812 0.1391 6 14.5 0.8180 0.0820 6 14.8 0.8380 0.0840 12 15.0 LLOZO" |) On 1240 10 15.5 I .0270 0.1060 17 15.8 1.1494 0.1218 65 16.0 1.0389 0.1236 21 | 16.4 1.0190 0.1132 19 | 16.5 1.2431 0.1439 38 17.0 1.0990 0.1453 40 17.0 1. 1081 41 17.0 | 0.9695 ©.1400 II Lez: 0.9968 0.1010 II We) 7] 0.9870 0.0961 15 17.8 1.1200 0.1180 fe) 18.0 I. 1017 0.0962 53 18.0 1.0367 0.1476 58 19.0 1.2039 0.1843 II 19.1 1.0438 ©.1050 21 19.5 I .3000 0.1718 19 20.0 1.1184 0.1300 40 21.0 1.2369 0.1745 65 21.0 1.2444 0.1603 45 21.2, 1.1661 0.1802 15 21.6 1.2339 0.1158 20 21.9 1.2284 0.1504 PEE 1.2420 376 “Ffournal of Comparative Neurology and Psychology. GENERAL TABLE—Continued. Series I. WEIGHT IN GMS. : i : REMARKS. No. a | ewe Body Brain. Cord. : | gl M. 50 24.0 1.2149 | 0.1881 g2 M. 50 24.0 1.2219 0.1939 93 M. 20 24.1 1.2764 0.1534 94 M. 24.6 1.2448 0.1751 95 M. 20 24.8 1.3336 0.1578 96 M. 22 25.2 1.2060 0.1690 97 M. sina] 1.2440 98 M. 20 DEG 1.3338 0.1605 99 M. 21 25.6 1.3790 0.1712 100 M. 20 25.9 ere a8 0.1694 101 M. 20 26.0 fi Thesiey cin 0.1626 102 M. 86 26.0 ly eetea7a4 0.2495 103 M. 22 26.2 | 1.3796 | 0.1806 104 M. 59 26.4 TG 2 al ROFL ay 105 | M. 21 26.7 Waceeiel mal | aug 106 | M. 21 27.0 Pe ti sghiiys) | 0.1700 107 M. 35 27.0 ) 97033047 0.1948 108 M. 45 Den lPietegos3 0.1938 109 M. 21 ps 1.3878 0.1734 110 | M, Disha 1.2940 111 M. 22 27g 1.3100 0.1726 112 M. 20 27.6 TAG Omen Ola 113 M. 21 28.3 1.4206 | 0.1856 114 M. 21 28.4 1.4458 0.1726 115 M. 20 28.4 1.3404 0.1690 116 M. 28.5 1.2850 ©.2000 117 | M. 45 28.5 [eg 462 On 2itais 118 M. 20 28.5 1.3348 0.1662 119 M. 22 28.7 1.3802 0.1732 120 M. 28.9 | 1.2840 121 M. 50 29.0 | 1.2879 0.2122 122 M. 29.6 | 1.2380 123 M. 21 29.9 | 1.4130 ~| 0.1792 124 M. 30 30.1 | 1.2956 0.2004 125 M. 30.2 1.4070 126 M. 30 30.6 1.3035 0.2774 127 M. 48 31.0 I .3000 0.2392 128 | M. 30 31.9 1.2803 0.1909 129 M. 38 32.0 I .3300 0.2560 130 M. 30 B20 1.3198 0.1983 131 M. 26 32.4 1.3169 0.1589 132 M. 22 2265 1.3650 0.2040 133 M. 33 R257 1.3470 0.2300 134 M. 30 32.8 1.3791 0.2087 135 M. 32.8 1.3130 136 M. 35 aR05 Ne tee ye) 0.2380 137 M. 42 34.0 | 1.4459 0.2426 138 M. 34.6 1.3120 ©.2020 139 M. 27 35-0 1.3020 0.2030 140 M. 42 35.0 1.4183 | 0.2427 141 M. 81 35.0 | 15 r6g890" 55" so:a4ih7, 142 M. 27 35-2 | 1.3480 0.1970 Dona.pson, Growth of Central Nervous System. 377 GENERAL TABLE—Continued. Series I. WEIGHT IN GMs. S 1 ; REMARKS. No. Cee eae eal satis: Brain. Cord. ga 143 M. 30 Ayia 1.3292 0.2246 144 M. a o/ 1.3920 145 M. 39 AIST) 1.3580 0.2430 146 M. 43 36.0 1.4249 0.2492 147 M. 31 36.1 1.3236 0.2158 148 M. 75 36.3 | ©2951 0.2453 149 M. 35 Ace) || Wer AGS 0.2640 150 M. 50 37.0 1.3407 0.2397 151 M. 39 aie 1.4015 152 M. 30 37 2 I .4090 0.2332 153 M. 31 erlaa) le 107 0.2122 154 M. 31 38.0 1.4172 0.2299 155 M. 38.1 1.3820 156 M. 38.5 1.3280 0,2400 157 | M. 39 38.5 1.4450 0.2300 158 M. 76 B9R3 1.2875 0.2424 159 M. 96 39-4 1.3654 0.2742 160 M. 39-5 1.3410 161 M. 30 39.6 1.5016 0.2322 162 M. 36 39.8 1.4060 0.2500 163 M. 30 40.0 1.4182 0.2228 164 M. 38 40.8 1.5143 0.2247 165 M. 51 41.0 1.5261 0.2902 166 M. 30 42.2 1.5286 0.2434 167 M. 26 43-2 1.4750 0.2150 168 | M. 43-3 1.3130 0.2490 169 M. 31 43.6 1.4580 0.2429 170 M. 30 43-9 1.4140 0.2330 171 | M. 30 44.7 1.5416 0.2324 172 | M. 30 45-5 1.5770 0.2274 173 M. 32 45-9 1.5550 0.2750 174 M. 30 46.2 1.5446 0.2448 175 M. 40 46.8 1.4220 0.2652 176 M. 25 47.0 1.3930 0.2970 177 M. 51 47-1 1.4555 0.2623 178 M. 47-5 1.4650 0.2870 179 M. 88 47.8 1.4726 0.2850 180 M. 40 48.6 1.4699 0.2800 181 M. 70 49.0 1.5383 0.2623 182 M. 88 49.4 1.3610 0.2637 183 M. 50.7 1.4300 0.2930 184 M. 30 50.8 1.5256 0.2602 185 M. 29 51.0 1.3800 0.2900 186 M. fits?) 1.5120 187 M. 88 51.6 1.4309 0.2805 188 M. 30 51.8 1. 5006 0.2580 189 M. 30 Bayi 1.5222 0.2612 190 M. 30 Bei 1.5244 ' 0.2652 191 M. 60 53-4 1.5445 0.3001 192 M. 30 eau) 1.4706 0.2832 193 M. g2 53-9 1.3675 0.2584 194 M. 31 54.0 1.6051 0.2680 378 “Ffournal of Comparative Neurology and Psychology. GENERAL TABLE—Continued. WEIGHT IN GMS. seals Sex. | Age in days. | | | Remarks. No. Body Brain. Cord. 195 M. 100 | 54.3 1.5056 0.2882 | 196 M. 55-6 E5220) | 197 M. 40 55-9 1.5338 0.2995 198 M. 40 56.4 1.4466 0.2560 199 M. 50 57-0 1.4412 0.2797 200 M. 30 ype 1.5670 0.2804 201 M. 30 57-2 1.5918 0.2888 202 M. 40 ee) 1.5072 0.2474 203 M. 30 57-6 1.5706 0.2804 204 M. fou 1.4200 0.3350 205 M. 57-9 1.4430 0.3286 206 M. 50 58.0 1.4452 0.2774 207 M. 96 58.4 1.4308 0.3207 208 M. 97 59.0 1.4382 0.2740 209 M. 59.6 1.4090 0.3278 | 210 M. 41 59-9 1.4424 0.2950 | 211 M. 96 59-9 1.4979 0.3150 212 M. 60.9 1.3800 0.2870 213 M. 50 61.0 1.4296 0.2756 214 M. 50 62.0 | Sr s6na2 0.3015 215 M. g2 62.6 |) arih 2773) 0.3105 216 M. 40 62.9 | 1,5854 0.3304 217 M. 97 63.0 1.4288 0.2911 218 M. 40 63.0 1.4023 0.2700 | 219 M. 89 63.2 1.5823 | 0.2986 220 M. 63.4 1.2850 0.2620 221 M. 41 63.5 1.4695 0.2923 222 M. g2 64.0 1.5338 0.3072 223 M. 78 64.1 1.6439 0.3169 224 M. 50 64.2 1.4891 0.2950 225 M. 78 64.3 1.4174 0.3205 226 M. 65.0 1.4480 0.3220 227 M. 38 65.0 1.4270 ©.3000 228 M. 65.1 1.5525 0.3353 229 M. 97 65.2 1.4659 0.2885 230 M. 60 65.6 1.4744 0.2869 231 M. 40 65.7 1.5039 0.3009 232 M. 40 67.2 1.4518 0.3048 233 | M. 41 67.8 1.4764 0.3139 234 M. 100 69.0 1.6307 0.3104 235 | M. 40 69.1 1.5738 0.3334 236 M. 96 70.0 1.5397 0.3380 237 M. 40 70.3 1.5188 0.3148 238 M. 70.4 1.6010 239 M. 97 70.4 1.4237 0.3067 240 M. 78 70.6 1.5201 0.3180 241 M. 70.7 1.4200 0.3480 242 M. 50 Tpice) 1.6326 0.3338 243 M. 60 71.8 1.5414 0.3083 244 M. 60 72.9 1.5244 0.3037 245 M. 40 7Tghou! 1.5984 0.3274 246 M. 51 Faher) 1.3864 0.2976 Donatpson, Growth of Central Nervous System. 379 GENERAL TABLE—Continued. | WEIGHT IN GMS. sae I. Sex Age in days. | REMARKS. No. | | Body. Brain. Cord 247 M. 40 73-9 1.5960 0.3298 248 M. 115 74.0 1.6012 0.3953 249 M. 78 74.1 1.5592 | 0.3188 250 M. 40 74.4 NeGAleyy © |) Calli 251 M. 40 75-5 1.5958 | 0.3410 252 M. 58 75-5 1.6013 0.3328 253 M. | 50 76.0 1.6272 0.3204 254 M. 40 76.1 1.6800 0.3460 255 M. 50 76.1 1.6813 0.3821 256 M. 97 76.3 1.7749 | 257 M. 76.6 1.4400 0.3280 258 M. 60 78.1 TeGQ Use Oral: 259 M. 51 78.4 1.4472 | 0.3060 260 M. 57 78.6 1.5407 | 0.3682 261 M. 125 79.0 1 te I LY | 262 M. 79.2 1.5520 0.3420 263 M. 48 79.8 1.6400 0.3320 264 M. 58 80.0 1.5817 0.3168 265 M. 40 81.3 1.6674 0.3308 266 M. 82.0 1.6540 | 267 M. 116 82.0 1.4691 0.3355 268 M. 12] 83.0 1.6656 0.4106 269 M. 57 83.3 1.6045 0.3833 270 M. 51 83.4 1.5864 0.3440 271 M. 51 83.6 1.5254 0.3402 272 M. 51 84.9 1.5090 0.3266 273 M. 59 85.1 I. 5003 0.3741 274 M. 96 85.5 1.5952 9.3733 275 M. 58 87.1 1.6381 0.3299 276 M. 52 87.4 1.5824 0.3574 Oiitl M. 87.4 1.7156 0.3579 278 M. 115 88.3 1.6955 0.3828 279 M. 58 89.1 1.5482 0.3354 280 M. 115 89.3 1.5668 0.3820 281 M. | 51 92.6 1.5614 0.3532 282 M. 131 94.0 1.6737 0.3700 283 M. 127 96.0 1.7341 0.4293 284 — M. 96.4 1.5400 285 M. 50 96.9 1.7744 0.4031 286 M. 115 97 -3 1.6957 0.4136 287 M. 96 99-3 1.5921 0.3778 288 M. 99-7 1.7029 0.4059 289 M. 130 99.8 1.6296 0.4119 290 M. 52 100.4 1.6774 0.4162 291 M. 158 101.7 1.7087 0.4388 292 M. 131 102.0 1.7388 ©.4141 293 M. 161 104.2 1.6268 0.4414 294 M. 115 105.8 1.6594 0.4012 295 M. 170 106.0 1.5837 0.3781 296 M. 300 106.9 1.6755 0.4762 297 M. | 115 107.0 1.7742 0.4274 298 M. 107.6 1.7790 0.4138 380 §=Fournal of Comparative Neurology and Psychology. GENERAL TABLE—Continued. Series I. No. Dn i) ‘a SEE | Il Chae cia » Age in days. 300 121 221 72 115 96 115 57 116 128 222 128 WEIGHT IN GMs. OOS HIKHIADKOS DAF OSV O KBHANAUHE O AYED ODO BVH wDWRKRONHOS MIDNOON DH Brain. -6445 -6934 -7765 | -4940 | 7444 .6784 | 7646 | . 5226 Sapa 5944 -8536 5661 O33 .6680 6671 -4621 -7656 8046 -7301 -7795 .6400 8213 . 5677 .7660 8255 .6950 -9465 8041 .6976 8024 7024. 8644 8831 -9649 7730 -7383 .7667 6390 6950 7823 .8470 -7549 .6150 -5990 7673 7590 -7333 6656 . 7003 .8975 8165 7271 Ln cn Bi Ie en ee ee e©oo000000000000909090909090900 0 ~ No P ° n ra lon ns) 00099900000 wal ie) > Ww fo} as XQ nA fe) oOo n> aw a eo) Ow REMARKS. Dona.pson, Growth of Central Nervous System. 381 GENERAL TABLE—Continued. | WEIGHT IN GMS. EES Sex. Age in days. ’ | Remarks. No. Body. Brain. Cord. 351 M. 79 150.3 1.6657 0.4547 352 M. 183 LS ORS 1.6952 353 M. 128 151.2 1.7604 0.4339 354 M. | 9 age 1.7280 0.5260 355 ] M. 152.4 1.7430 356 M. 126 153-0 1.7297 0.4713 357 M. Dae 7 1.7420 358 M. 222 iis} 1.8276 0.4856 359 M. 193 153.8 1.5666 360 M. 234 154.0 1.8167 | 0.5488 361 M. 222 155.7 1.8441 0.5307 362 M. 126 156.0 1.7551 0.4853 363 M. 158 158.0 1.8245 0.5232 364 M. 221 159.0 1.8364 0.5186 365 M. 72 159.6 1.8459 0.4984 366 M. 222 160.1 1.9153 0.5062 367 M. 161.6 1.7770 0.5890 368 M. 222 162.2 1.8040 ©.4740 369 M. 163.0 1.7250 0.6150 370 M. 234 164.3 1.8072 0.5424 371 M. 166.5 1.7925 0.5355 Over 6 months 372 M. 167.2 1.5924 0.5844 373 M. 222 eet 67709 1.8717 0.5164 374 | M. 169.0 1.7963 0.5769 375 | M. 85 | 169.4 1.7800 0.5240 376 M. a 7a.O 1.8291 0.6199 377 | M. 172.8 1.8322 0.4652 - 378 M. 176.6 1.8166 0.5232 Over 6 months 379 | M. 206 176.7 1.8321 0.5213 380 | M. 80 176.9 1.7290 0.4760 381 | M. 159 177.2 1.8590 0.5564 382 | M. 221 T7740 1.8080 0.5166 383 | M. 80 Wye LET: 1.7320 0.5000 384 | M. 128 | 180.6 1.9520 0.5017 385 | M. } UR 5 1.6420 0.5130 386 | M. lo 82735 1.6600 0.4800 387 M. 155 182.5 1.7519 0.5166 388 M. 185.0 1.8050 389 M. 182 186.7 1.6578 0.4862 390 M. go 186.9 1.7940 0.5510 391 M. “a 187.4 1.8000 0.5036 392 M. 188.0 2.0780 393 M. 190.5 1.9120 0.6380 394 M. 190.5 1.8400 0.6920 395 M. 202 192.1 1.7083 0.5327 396 M. 195.5 1.7693 0.4857 397 M. go 196.0 1.6530 0.5840 398 M. 198 .6 1.7250 0.5810 399 M. 186 199.0 1.9781 0.5829 | 400 M. 200.9 1.8340 | 401 M. ezore2 1.8140 0.6570 402 M. azo. 1.8840 382 =“fournal of Comparative Neurology and Psychology. GENERAL TABLE—Continued. SSSSSSSS5 5555555 a Age in days. | 113 113 120 159 216 120 106 113 120 120 140 140 140 | | WEIGHT IN GMs. Body Brain. 201.9 1.5220 202.1 1.8600 203.6 1.8714 204.2 1.8442 206.8 1.9538 207.7 1.7490 208 .6 1.7698 209 .6 1.8442 216.2 1.7790 2720 1.9337 218.0 1.8370 218.8 1.8050 219.9 1.7144 221.6 1.8124 DEVE 1.8496 223.7 1.7645 223.9 1.7988 224.7 1.9342 226.6 1.8900 229.2 | 1.9389 | 229.5 1.5766 | 234.8 2.1380 236.2 1.8102 236.5 1.9594 238.1 1.9300 238.6 1.7298 241.5 1.8849 242.1 1.9967 250.3 1.9230 251.0 1.9107 260.0 1.8740 260.0 1.8039 261.0 1.7661 ‘| 262.8 1.9057 | 264.5 1.8214 267.0 1.9391 267.0 2.0856 267.4 1.9700 269.1 1.9389 272.5 1.9444 275-3 1.9389 278.0 1.9780 278.2 1.9173 279.1 2.0713 282.7 1.8200 285.0 1.9000 | | 285.0 2.0954 291.0. 1.9000 294-5 1.9450 297.0 2.0599 305.0 2.1037 0000000000000 lon R Oo \o 0000000000000000099999090 90 n c we) “oO fo) REMARKS. Over 10 months |Over 10 months Over 10 months Over 10 months Over 10 months Over 10 months Over 10 months and fat ~ Over 10 months Over 10 months Over 10 months Dona.pson, Growth of Central Nervous System. GENERAL TABLE—Continued. 383 WEIGHT IN GMS. a e: Sex Age in days. ; REMARKS. oS Body. Brain. Cord. 454 M. 308.0 2.1791 0.6630 |Over 10 months 455 M. 310 .0 2.0610 0.6639 |Over 10 months 456 M. 310.2 1.9690 ©.7550 |Over 10 months 457 M. 316.0 2.1213 0.7626 |Over 10 months 458 M. 320.0 2.1527 0.6948 |Over 10 months WEIGHT IN GMS. See < Sex. Age in days. | : ReMaRKS. G: Body. Brain. Cord. 459 M. 50.6 1.4016 0.3340 (Injected with lecithin, Ha- TAI, 703. 460 M. Rise 1.3850 0.3050 ees 461 M. 63.3 1.4500 0.3500 be 462 M. 65.3 | 1.4690 0.3470 aS 2 WEIGHT IN GMS. eee oF Sex Age in days. | : REMARKS. eh Body. Brain. Cord. I 1 3.9 0.2300 0.0330 At birth 2 INE | 4.2 0.2070 0.0260 At birth 3 KF. I | 4.5 0.3023 0.0290 4 FF. | 4.6 0.2280 ©.0300 36 hours 5 1, 4.6 | ©.2110 0.0270 38 hours 6 EF. 4-9 | 0.2210 0.0210 36 hours 7 F. Gon We lolz 0.0280 38 hours 8 10), 2 Bez | 0.2260 0.0300 9 F. 2 | a 0.2260 0.0300 ite) F. Boy 0.2830 0.0350 38 hours II 1d, Say 0.3320 0.0340 36 hours 12 li 5 7.0 0.4520 0.0510 4 13 FE: 5 7.6 0.4610 0.0480 “iia BE. 5 ey 0.4680 0.0450 15 13 10 9.0 0.8101 0.0746 16 Re 10 10.0 0.8312 0.0709 17 F. fe) Tig 0.8470 0.0860 18 BR: fe) 11.6 0.8280 0.0810 19 10; 9 11.9 0.7120 0.0720 20 13 16 13.5 1.0530 0.1200 21 18 16 Poly 1.0870 0.1210 22 1; 9 14.0 0.9109 0.0864 23 12, 12 15.5 1.0550 0.1150 24 F: 16 Ga 1.0109 0.1028 25 F. 16 17.9 1.1480 O.1110 384 Fournal of Comparative Neurology and Psychology. GENERAL TABLE—Continued. Series I. No. oobi olleoN obo Reskoheo MeN Mele Mer Me leole Meo Hes tee lect Mas Boks: Wee ie Perllec lie Bele bee Be) lie ope lee Reon old Uae ecla esc ac So Age in days. WEIGHT IN GMs. 4 oo ie} Cal oo 00 Wnk DOD MDADSDODOSDODOOOMNOOKMODO0000SO0RDOOXVO0SD04H5000NNNO Brain. | -0479 -0580 | -0637 | -094I | 0832 1977 | -1420 22205, | 2850 | -2940 | 3765 | .3130 -2251 e352 2591 4015 3944 -3470 -4924 .2841 -4266 -3338 4311 -3467 433° aa 722 -3594 4042 4100 2598 N a 3501 -3680 -4420 3703 -4055 “4247 2625 -6100 © 5850 3943 -4440 .6070 -2810 .2800 -4028 3772 -4693 4194 -3587 3770 -3787 -3838 Po te en eT Te ee en een een nn ee oe CROROROOEONO ONG OMONON ONO VON OO ONONO ONO OOF ONO MONO FO FONONORONCVONONOSOHONOROROTO ORO OR OTORORC TC Dona.pson, Growth of Central Nervous System. 385 GENERAL TABLE—Continued. | | WEIGHT IN GMs. gee ae Sex. Age in days. | : REMARKS. 10% Body. Brain. Cord 78 | Be | 78 | 53-1 1.4486 0.2809 79 | F. | 50 | 54.0 1.3517 0.2602 80 | 136 130 54.2 1.4869 0.3224 81 De 78 eaece Gen 1.4829 0.2746 82 he 60 | 55-8 1.4103 0.2834 83 | FE. 30 57-4 1.5040 0.2820 84 | F. 60 | 58.4 1.4213 0.2802 85 | F. 95 } 59-0 1.5580 0.3042 86 Be 97 60.0 1.4600 2.2930 87 F. Ore7 1.4880 0.2975 88 | 1 167 63.0 1.3814 0.2837 89 | Ke 78 63.1 1.5745 0.3116 go | 185 64.6 1.5367 0.3062 gI | F. 130 64.8 1.4536 0.3387 2 | 18 97 68.9 1.4429 0.3211 93 | 13 69.6 1.4950 0.3470 94 | F. | 88 rp. 1.6030 0.3179 95 | FP. 97 Nite 7332 1.4795 0.3127 96 | 186 48 | Telos 1.6550 0.3350 97 F. WAT, | 1.4550 0.3430 98 1, 116 74.0 1.5665 0.3727 99 | F. 76.4 1.3700 0.3260 100 FE, Tie 1.5110 0.3359 101 18 96 80.5 1.5189 0.3542 102 | KF. 116 82.8 | 1.5950 0.3846 103 IP 116 88 .6 | 1.6002 0.4010 104 1M 167 89.1 1.5513 0.3528 105 1D 96 91.5 1.5325 0.3541 106 | 1ije 145 91.7 1g webeye! 0.4307 107 14 135 92.0 | 1.6823 0.3436 108 FP. 116 95-0 1.6614 0.3967 109 1d 95-4 1.5970 0.4280 110 | 10, I5I 96.1 1.4999 0.3989 III | 106 156 97-7 | 1.7433 0.4246 112 | IN 131 98.0 | unGeRy 0.3421 113 | 18 98.0 1.5640 0.3710 114 | 13 130 98.6 | 1.5646 0.3939 115 F. 116 99.1 1.5897 0.3775 116 1B 158 99-1 eet eOnkr see sO.3730 117 Re 130 99.8 Perey SN) lar tells 118 12 158 Neaeto2ziir (iy aa8228 oh a vonage 119 BE. |) ea lee baes 5780 0.4190 120 10s 135 104.1 | c/a 0.4012 121 | F. 159 104.3 1.8782 0.4294 122 E. IeeiO5/.0 1.6336 0.4035 | 123 FP. 166 | 106.5 1.6457 | 0.4451 | 124 F. 116 106.7 D.7353-1 ino On452 ae | 125 ie 131 | 107.0 1.6747 | 0.3678 | 126 KS 160 | 107.1 1.6549 | 0.4003 127 F. 130 | 107.8 1.4902 | 0.3712 128 19, 176 |) 7 iiehsiaie 1.5381 0.4164 129 E. 126 | 112.0 1.7040 | ©.4440 386 = Fournal of Comparative Neurology and Psychology. GENERAL TABLE—Continued. WEIGHT IN GMS. ae x Sex. Age in days. | ; REMARKS Oo: Body | Brain. Cord 130 Re 127 sig ig a 1.7698 0.4459 131 16 128 L1g.2 1.6488 0.3950 132 ie 114.7 1.7050 0.5340 133 F. 130 115.8 1.6299 0.4167 134 13 116.1 1.7605 0.4123 135 F. 128 Tey 1.7193 O.4114 136 PB: LiGos eo) kes 20 0.4120 137 19: 166 119.0 | 1.8465 0.4919 138 1); 130 121.8 | 1.6970 0.4397 139 108 224 122.2 1.6614 0.4841 140 196 204 122.4 1.5960 0.4204 141 1). 142 125.1 1.6988 0.4505 142 10. 109 125.7 1.7096 0.4116 143 F. 164 126.9 1.6859 0.4941 144 136 159 129.0 | 1.6740 0.4614 145 19, 175 129.2 1.5553 0.4520 146 | F. 176 134.6 1.5768 0.4459 147 | F, 186 137-9 eae exe 6207 0.4713 148 1 139.1 (ee Gene 0.5210 149 1M 166 139.9 1.8068 0.4836 150 F. 109 140.4 1.7858 0.4574 151 136 224 142.3 1.7380 0.5181 152 1) 143-7 1.6750 0.4540 153 F. 176 145-7 1.6798 0.5059 154 F. 147-7 1.7738 0.5467 155 ine 166 148.1 1.6555 0.4950 =| 156 1X 85 150.4 1.7500 ©.5100 157 12 151.7 1.8162 0.5546 (Over 7 months 158 12. 151.8 1.6350 0.5360 159 ine 152.3 r.5885 O.5112 160 1s 80 155.0 1.8150 0.4800 161 BE. 80 155.0 1.8500 0.5250 162 10, | 224 155.3 1.7707 0.5162 163 1D: 166 156.9 1.7954 0.5458 164. 10 | 157-5 1.6630 0.4950 165 1D 158.7 | 1.7900 0.5200 166 F. 109 161.9 | 1.8308 0.4420 167 iN 100 162.8 1.6800 0.4920 168 B. 186 163.7 I.go14 0.5113 169 F. 224 164.2 1.8892 Oasta 7 8 170 Ine go 164.3 1.7170 0.5760 171 18 100 165.9 1.6350 0.5320 172 1 328 166.1 1.6966 0.5896 173 10 211 | 166.7 1.8387 0.5398 174 F. 128 | 167.0 1.6921 0.5642 175 B. go | 168.0 1.7830 0.5360 176 ADS 305 | cagatieg 1.8010 0.6382 177 F. hes ety 1.7176 0.5491 178 F, 176 ee Rapes) 1.8342 0.5277 179 10 | 396 172.6 1.8003 ©. 6001 180 F, 328 174.0 1.7840 0.6329 181 | 194 176.0 1.9499 0.6677 |Over 10 months Dona.pson, Growth of Central Nervous System. 387 GENERAL TABLE—Continued. WEIGHT IN Gms. a I. Sa Age in days. Kap ; Remarks. Or: Body. Brain. Cord. 182 10 224 180.7 1.8190 0.5239 183 19, 181.0 1.6120 9.4990 |Over 10 months 184 1% 380 182.4 1.7803 0.5817 185 1D, IIo 183.7 | 1.6810 0.5390 186 F, 184.7 1.9290 0.6146 |Over 1o months 187 10, 186.5 Logue I CBG see 188 10; 211 188.4 | 1.8627 0.5310 189 Ey 190.7 1.7950 0.6380 190 1, 345 191.2 1.8007 0.5878 191 13. 328 191.7 1.8731 0.6302 192 IN 361 195.0 1.6944 |! 0.5746 193 18 110 195.2 | 1.7090 0.5210 194. 1 380 196.0 | 1.8426 0.6177 195 | 1 380 196.4 1.7878 0.6311 196 1 361 197.0 1.9005 0.6219 197 13, 200.9 1.7950 0.6100 |Over ro months 198 1D 165 202.7 1.7460 0.5680 199 1D 320 203.0 1.8426 0.5989 200 Ie 345 OREO} lo Tet 0.5718 201 F. 221 203i An eae | Sai OO75 0.6053 202 19, 165 205.5 1.7390 0.5990 203 12 309 = 212.0 1.9330 0.6375 204. 1% 309 212.0 1.9510 0.6205 205 16 345 219.4 1.8108 0.5945 206 1 320 231.0 ye 8205 0.6615 207 1), 380 231.4 ial ba7ZtZo 0.5807 208 1), 361 232.0 1.7740 0.6047 . 209 136 233-0 1.9350 0.6570 |Over 10 months 210 195 234.4 1.9800 0.6180 |Over 10 months 211 1 242.6 1.8610 0.6600 |Over 10 months 212 FE 320 243.0 1.8622 0.6185 213 196 309 245.5 1.9704 0.6340 214 136 309 247.0 | 1.9694 0.6370 215 F. 309 280.0 | 2.0130 || 0.7034 WEIGHT IN GMs. nae ti Sex. Age in days. f | | Remarks. Ce Body. Brain. Cord. 216 B. 53-8 1.4260 0.3386 Injected with | | lecithin Ha- | TAI, 703. 217 1, 60.4 1.3810 0.3520 Soames 218 Bs 62.1 1.4500 0.3220 Coe hes 388 = Fournal of Comparative Neurology and Psychology. BIBLIOGRAPHY. BiscHorr, T. von. 1880. Das Hirngewicht des Menschen. S.1-171, P. Neusser, Bonn. BLAKEMAN, J. 1905. A study of the biometric constants of English brain-weights, and their relationships to external physical measurements. Biometrika, vol. 4, pp. 124-160. Boas, F. 1905. Statistics of growth. Report of Commissioner of Education U.S. A., chapter 2, pp. 25- 132. Boycorrt, A. E. anp Damant, G. C. 1908. A note on the total fat of rats, guinea-pigs and mice.fourn. Physiol., vol. 37, pp. 25-26. Bunce, C. 1902. Physiologic and pathologic chemistry. 2d edition (edited by E. A. Starling). P. Blakiston’s Son & Co., Phila. Davenport, C. B. 1904. Statistical methods with special reference to biological variation. 2d ed., Fohn Wiley & Sons, N.Y. Donatpson, H. H. 1895. The growth of the brain: A study of the nervous system in relation to education. 4th ed., Charles Scribner’s Sons, N.Y. 1go1. Chapter on ‘‘central nervous system” in vol. ii, p. 279, of Am. Text Book of Physiol., Howell. W.B. Saunders & Co., Phila. 1906. A comparison of the white rat with man in respect to the growth of the entire body. Boas Memorial Volume, p. 5-26, G. E. Stechert F Co., N.Y. Dusors, E. 1898. Ueber die Abhangigkeit des Hirngewichtes von der Korpergrosse bei den Saugethieren. Archiv fiir Anthropologie, Bd. 25. Giapstong, R. J. 1905. A study of the relations of the brain to the size of the head. Biometrika, vol. 4, pp. 105-123. Greenwoop, M. 1904. A first study of the weight, variability and correlation of the human viscera, with special reference to the healthy and diseased heart. Biometrika, vol. 3, pp. 63-83. HanpMANN, Ernst. 1906. Ueber das Hirngewicht des Menschen auf Grund von 1414 im pathologischen Institut zu Leipzig vorgenommenen Hirnwagungen.. Archiv f, Anat [u. Physiol.],S. 1-40. Harat, S. 1903. The effect of lecithin on the growth of the white rat. Am. }. of Physiol., vol. 10, Pp 57-66. 1904. The effect of partial starvation on the brain of the white rat. Am. F. of Phystol., vol. 12, pp. 116-127. 1907. On the zodlogical position of the albino rat. Biol. Bull., Vol. 12, pp. 266-273. 1907A. Studies on the variation and correlation of skull measurements in both sexes of mature albino rats (Mus norvegicus var. albus). Am. F. of Anatomy, vol. 7, DPr4 235442 1907B. Effect of partial starvation followed by a return to normal diet, on the growth of the body and central nervous system of albino rats. Am. F. of Physiol., vol. 18, Indo Sieh 4er 1908. Preliminary note on the size and condition of the central nervous system in albino rats experimentally stunted. 7. of Comp. Neurol., vol. 18, pp. 151-155. LaricquE, L. 1908. Tableau général des poids somatique et encéphalique dans les espéces animales. Le poids encéphalique en fonction du poids corporel entre individus d’une méme espéce. Memoires de la Société d’ Anthropologie de Paris, p. 249-344. Mies, J. 1893. Ueber das Gewicht des Riickenmarkes. Centralbl. f. Nervenheilkunde u. Psychiatrie, Shieh Peart, R. 1905. Biometrical studieson man. I. Variation and correlation in brain-weight. Biometrika. vol. 4, pp. 13-104. Dona.pson, Growth of Central Nervous System. 389 Prister, H. 1903. Zur Anthropologie des Riickenmarks. Neurol. Centralb., Bd. 22, S. 757 und 819. Rusner, M. 1908. Das Wachsthums problem und die Lebensdauer des Menschens und einiger Saugetiere vom Energistischen Standpunkt aus betrachtet. Archiv fiir Hygiene. Bd./xvi. 1908A. Probleme des Wachstums und der Lebensdauer. Bezblatt zu den Mitteilungen der Gesellschaft fiir innere Medizin und Kinderheilkunde in Wien. VII. Jahrgang, No. 3, S. 58-82. Vierorpt, H. 1890. Das Massenwachsthum der Kérperorgane des Menschen. Archiv fiir Anat. [u. Physiol.], S. 62-94. Warson, J. B. 1905. The effect of the bearing of young upon the body-weight and the weight of the central nervous system of the female white rat. ‘F. of Comp. Neurol.,vol. 15, pp. 514-524. ZIEHEN, T. 1899. ‘Nervensystem” p. 10 in ‘Handbuch der Anatomie des Menschen,” von Bardeleben. Gustav Fischer, fena. 390 “fournal of Comparative Neurology and Psychology EXPLANATION oF Pirate II, Cuarri. The upper continuous line represents the brain weight according to body weight, calcu- lated by formula [1]. The separate entries (. males and X females) show the individual observations so far as they can be entered without confusion. The lower continuous line represents the spinal cord weight according to body weight, calculated by formula [3]. The same scale is used for the two curves. Cuart 2. The continuous line represents the spinal cord weight according to body weight. The separate entries (. males and X females) show the individual observations so far as they can be entered without confusion. The scale of the ordinates is twice that used in chart 1. BODY WEIGHT 20 40 ‘60 80 {00 120 140 160 ~——«*S80 200 220 240 260 280 300 320 Spe meee Chart 1. SPINAL CORD WEIGHT BODY WEIGHT Gms. 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 ’ Chart 2. ag L = a Pe ¥: ~s eb Z * ABE Coa) 392 “fournal of Comparative Neurology and Psychology. ExpLaNaTION oF Prare III. Cuart 3. In the upper curves, the continuous line (C), shows the weight of the brain according to body weight as calculated by formula [1], the broken line (/), the means of the observed brain weights. In the lower curves, the continuous line (C) shows the weight of the spinal cord according to body weight as calculated by formula [3], the broken line (7) the means of the observed spinal cord weights. The same scale is used for both curves. ; Cuarr 5. On the base line representing age, one day of rat life is given the same value as 30 days of human life (i.e., 1 day rat = 30 days man). The lower curves represent the weight of the brain according to age (in days) for the rat. The solid line for the male, and the broken line for the female. The upper curves represent the weight of the human brain (at yearly intervals) the actual values of the ordinates being reduced to 1-7ooth in order to make the curves comparable with those of the rat. Continuous line, male; broken line, female. 800 600 400 40 60 80 100 90 ee te eer Oto = Sa —e-— ——e- a =e iG BODY WEIGHT 120 2140 160 180 200 220 240 260 280 300. 320 Chart 3. MAN AGE YEARS © 9 "1 13. 15 Az 19 21 : 23 25 RAT Gms 2.00 ew ow we ww we om oe er ew ern ttre eee aloe co ee ae eS eee ee ae em ns oes me en 1.50 BRAIN WEIGHT 1.00 50 0 130 150 170 190 210 230 250 270 290 RAT AGE DAYS > Chart 5. THE MORPHOLOGICAL SUBDIVISION OF THE BRAIN. BY Cc. JUDSON HERRICK. (From the Anatomical Laboratory of the University of Chicago.) The great diversity in the internal organization of different parts of the nervous system makes demands on the morphologist for a much more minute regional subdivision than is necessary with most other organs; and at the same time this diversity, to- gether with the intricate interrelations between the various parts, makes such an analysis the more difficult. The subdivision of the human brain, as made by the first anato- mists on the basis of gross external form, has a certain functional as well as morphological basis; but when the attempt was made to study the regions so named comparatively, the morphological imperfections of the scheme became at once apparent. Any fur- ther attempt to utilize uncritically in morphology the “regions”’ as customarily defined in the older human neurology is misdirected energy. The clear recognition of this fact early led Professor His to seek in his embryological studies a safer guide to cerebral mor- phology, and the result of his labors as finally formulated is incor- porated in the BNA nomenclature. But the cerebral analysis of Professor Hts is based almost wholly on human embryology and therefore inevitably shares some of the same defects as a scheme based on the human adult; for the human embryonic brain at all stages is very far indeed from giving a true picture of ancestral phylogenetic conditions. And there can be no sound morphology which does not rest on a phylo- genetic basis. And moreover the dynamic element in modern morphology requires throughout a closer correlation between struc- ture and function than any purely embryological or anatomical scheme can effect. 394 “fournal of Comparative Neurology and Psychology. Accordingly, comparative anatomy, comparative embryology, and comparative physiology must be appealed to before we can feel that we are on safe ground in making a morphological sub- division of the nervous system. ‘The correlation of these subjects is attempted in the modern functional analysis of the nervous system as effected by recent students of comparative neurology. All of these subjects are now sufficiently far advanced to justify a reéxamination of the question of the subdivision of the brain from the phyletic standpoint and with especial reference to the application of the BNA terms in comparative studies. The earliest form of regional differentiation of the nervous system in the phylogeny was probably the concentration of a cen- tralized or integrated system from the primitive diffuse type. This differentiation appears in some form in all but the simplest metazoa. In vertebrates the diffuse system also exhibits a certain degree of integration on its own account and appears as the sym- pathetic system. It is not intended to imply here the specific homology of the ganglia of the sympathetic chain or any other part of the vertebrate sympathetic system with the diffuse nervous system of any particular invertebrate type—and much less with any invertebrate central nervous system. It is very probable that the highly complex sympathetic nervous system of vertebrates has been elaborated subsequently to the differentia- tion of the central nervous system. It is maintained, however, that the diffuse vertebrate nervous system, especially the peripheral sporadic ganglia (and possibly the sympathetic as a whole), is in a general way comparable with the diffuse nervous system of such animals as the Coelenterata. Even if it should prove, as now seems probable, that the entire sympathetic system is in the ontogeny differen- tiated from the same embryonic tissue (medullary plate) as the cerebro-spinal system, I think the com- parison will still hold, though we must recognize that the ontogenetic development deviates far from a recapitulation of the phylogeny of the sympathetic system. ‘This deviation is in the direction of a concentration of all of the embryonic nervous rudiments, looking forward to the functional intimacy between the cerebro-spinal and the sympathetic systems of the adult, and thus is parallel with the general trend of the evolution of the whole nervous system. Our primary subdivisions, then, are (1) the sympathetic (auto- nomic) and (2) the cerebro-spinal nervous systems. The cerebro-spinal or integrated nervous system in early phy- logenesis separated from the diffuse nervous system to serve three great types of bodily reactions, and gave rise to three systems of sense organs (receptors) and their associated centers and return motor paths. ‘These, adopting SHERRINGTON’S nomenclature, we may designate as follows: 1. Exteroceptors, systems for reaction to stimuli impinging upon the outer surface of the body. The source of the stimulus may not be in contact with the body, in which case the sense organs In question are termed by SHERRINGTON distance receptors. The Herrick, Subdivision of the Brain. 395 modalities of sense primarily represented here are: (1) cutaneous sensation (touch, temperature, etc.) ; (2) hearing; (3) vision. ‘These are termed the somatic, as distinguished from the visceral, senses, their most essential characteristic being the fact that the reaction evoked is somatic, 1. e., a movement of the body as a whole (in lower animals usually locomotor in type) with reference to the source of the stimulus. In certain cases, as relatively recent phylogenetic adaptations, sense organs of the visceral type have secondarily appeared in the skin and assumed exteroceptive functions, as in the cutaneous taste buds, of certain teleosts. But these exceptions must be recog- nized as such and need not confuse our primary subdivisions. ‘The organ of smell presems a somewhat similar atypical instance, which I have considered in more detail in another article.! 2. Proprioceptors——Vhese systems were evolved parallel with the exteroceptors and subsidiary to them. ‘Their sense organs lie chiefly in the organs of somatic response, i. e., in the muscles, joints, tendons, etc., and are adapted to assist in the correlation of the movements of he body, reporting to the central nervous system the exact degree of contraction of every muscle, the degree of ten- sion on the joints, tendons, etc. They are therefore indispensable to all delicate muscular adjustments involving accurate regulation of movement, strain, etc. “Their organs of response are obviously identical with those of the exteroceptors with whose functions they are associated. The most highly specialized member of the group is the mechanism of eauilibration in the auditory labyrinth. 3. Interoceptors—These comprise the visceral systems of sense organs chiefly concerned with stimuli received in the digestive tract, and exciting visceral responses thereto. The most typical sense modalities are taste and a group of ill-defined pneumo-gastric sensations (suffocation, nausea, hunger, thirst, etc.). Smell and taste (the chemical senses) are clearly related physiologically and probably have a common origin from a primitive undifferentiated chemical sense. The purpose of the differentiation in vertebrates of two chemical senses so closely similar physio- ogically and psychologically and so very dissimilar anatomically has given morphologists a world of trouble. SHERRINGTON suggests the most natural explanation when he calls attention to the fact that, while the organ of taste is a typical interoceptor, the olfactory organ is a distance receptor. In other words, the chemical sense has differentiated along two lines determined simply by whether the source of 1 On the phylogenetic differentiation of the organs of smell and taste. Journ. Comp. Neurol. and Psych., vol. 18,no.2. 1908. 396 “Ffournal of Comparative Neurology and Psychology. the stimulus is in contact with the body (taste) or at a distance (smell)—a practically important distinc- tion from the standpoint of the type of reaction which should follow, though one which may rest on a relatively trivial physico-chemical difference in the stimuli themselves. Accordingly, the cerebral centers for smell, which normally call forth locomotor responses, have differentiated far from those of taste, where typically visceral responses alone are involved. (Cf. tne article last cited, On the Phylogenetic Differentiation of the Organs of Smell and Taste.) Attention should be called in this connection to the fact that in the hypothetical ancestral vertebrate from which the olfactory and gustatory reflex systems were evolved both the effectors and receptors were in an unspecialized condition and in later phylogeny their elaboration occurred simultaneously. Responses to chemical stimuli of an unspecialized or “‘total” sort would followin such an animal and the differ- entiation of the responses into visceral and somatic types occurred pari passu with the functional differ- entiation of the sense organs into interoceptors and distance receptors. And of course the cerebral con- duction pathways for smell and taste became clearly defined and separate from the general unspecialized central gray only gradually as the functional need arose. Ina similar way all of the well defined reflex paths within the higher brains are shown by comparative studies to have taken form from the more diffuse type of central nervous structure found in the lowest vertebrates. The central gray and forma- tio reticularis grisea et alba are survivals in higher brains of this primitive unspecialized nervous tissue. The first two of SHERRINGTON’S physiological groups, then, compromise in general the systems of nerves and end organs designated by recent morphologists the somatic systems; his third group includes the visceral or splanchnic systems. From the preceding analysis it clearly appears that the basis for the most fundamental divisions of the cerebro-spinal nervous system is found in the contact of the organism with the environ- ment. In other words, the organization of the cerebro-spinal nervous system has been shaped by its peripheral end organs. Early in the process of the resultant differentiation the verte- brate central nervous system responded to these peripheral influ- ences by developing a series of structurally defined longitudinal zones. In the first place, the dorsal part of the nerve tube and the related nerves were devoted to the afferent or sensory limb of the reflex arc and the ventral part to the efferent or motor limb, sep- arated by the sulcus limitans (Hts). The early recognition of this relation in the spinal cord by Sir CHARLES BELL led to the formu- lation of BeL’s law of the composition of the spinal nerve roots. These have been further subdivided by GasKELt and his followers, so that in passing from the dorsal to the ventral surface of the spinal cord we now recognize successively, in both gray and white matter, the following longitudinal zones: 1. Somatic sensory, including exteroceptive and propriocep- tive centers and conducting paths. 2. Visceral sensory, including the interoceptive centers and their pathways. These are feebly developed and still very imper- fectly understood in the spinal cord. Afferent impulses enter by Herrick, Subdivision of the Brain. 397 the dorsal roots, probably by way of the rami communicantes of the sympathetic system. 3. Visceral, or splanchnic motor. The region of the inter- mediate zone and columna lateralis grisea. ‘The efferent fibers are pre-ganglionic sympathetic nerves, which leave the central nervous system mainly at least by the ventral roots and which excite the intero-effectors, including viscero-motor, vaso-motor, excito-glandular fibers, etc. 4. Somatic motor. The columna ventralis grisea and asso- ciated fiber paths. ‘The efferent impulses go out by way of the ventral roots to the extero-effectors (somaticor skeletal muscles). Parallel with this longitudinal differentiation of the neural tube a transverse segmentation took place called forth by the metam- erism of the body. In all vertebrates, especially in the spinal cord, this transverse segmentation is much more evident anatomically than the longitudinal divisions. Accordingly, morphologists in the past have devoted their attention almost exclusively to it in the elaboration of metameric schemata of nervous organization. But in reality transverse segmentation is far less important to cere- bral morphology save for convenience of anatomical description, as will appear from a consideration of the genesis of the two types of specialization in question. We cannot hope to elaborate a nomenclature reflecting perfectly the relations in a low type of brain like the lamprey’s which will at the same time be adequate for the human neurologist; but we should seek to devise a scheme which 1s sufficiently elastic to permit of adaptation to both with no change of fundamental plan. A sys- tem based on transverse segmentation, while in many respects better adapted for the lowest vertebrates, breaks down completely when applied in the Mammalia. Metamerism is primarily mesodermal in origin. It arose as an aid to locomotion of the vermiform type in very primitive animals. The segmentation of the skeletal, nervous and vascular systems, etc., is all secondary to that of the body muscles, and where these latter disappear, as in the head of higher vertebrates, the neuromeres lose their individuality also. The longitudinal functional divi- sions, on the other hand, are primarily nervous. ‘They represent the most fundamental factors in the architecture of the vertebrate body and exert a more potent influence on cerebral structure the higher we go in the evolutionary series. Metamerism is more 398 fournal of Comparative Neurology and Psychology. primitive and dominates the nervous system of lower animals, but becomes relatively less important as we pass up the phyletic series, whose higher types come into progressively more varied relation with the environment. Nevertheless the influence of metamerism is always apparent, even in the human brain; and the fact that two tendencies, independent in origin and often exerting antagonistic influences on the course of che differentiation, have operated in the architectonic of the vertebrate nervous system is a cause of great perplexity and confusion in attempting the analysis of cere- bral structure in higher animals. A purely metameric scheme can in the nature of the case be no more satisfactory than one based on adult or embryonic human structure, even though it is based on a correctly interpreted phylogeny. The matter is still further complicated by the fact that, either primarily in chordate evolution or secondarily, there appeared a difference between the metameres in the rostral part of the body and those in the more caudal part; viz: the presence of gills in the rostral portion. ‘The structural unit here is the branchiomere. The delimitation of the branchial region from the rest of the body gives the most fundamental plane of differentiation which crosses the mid-line of the body. Our problem, then, is ay to analyze the two elementary factors in the phylogenesis, metamerism and longitudinal functional dif- ferentiation, and then to endeavor to trace the influence exerted by each and to construct a scheme of cerebral structure which shall hold good both in lower and in higher vertebrates and take due account of both of these directive influences. In the spinal cord region, where the primitive relations seem to have suffered the least modification in the course of phylogenesis, the two factors referred to above can be quite readily distinguished. The primitive metamerism is highly modified in the peripheral distribution of the spinal nerves, but it is preserved almost un- changed at the surface of the spinal cord, as shown by the serial arrangement of the spinal roots and their ganglia. Again, inter- nally the demand for correlation between the different levels has produced longitudinal arrangements which largely obscure the transverse segmentation. Only in the early embryo is the internal structure of the neural tube evidently segmental. There is a stage when neuromeres are clearly defined in the neural tube as a transient beading of its contour. The internal longitudinal HERRICK, Subdivision of the Brain. 399 differentiation is however so nearly uniform in the adult through- out the length of the spinal cord that the subdivision of that struct- ure can most conveniently be effected in terms of the transverse segments, these being named after their nerves and the corre- sponding vertebra, as defined by the classic nomenclature. In the rostral end of the body the segmental plan is modified in all lower vertebrates, as we have seen, by the presence of gills. These are visceral structures and their innervation belongs wholly to the splanchnic systems.? In lower vertebrates this branchio- meric system may coexist with the typical somatic systems in the same segments, but in higher forms segments possessing gills, or their derivatives in land vertebrates, have usually lost the somatic components or else these latter have suffered so great modification as to be with difficulty recognized as such. The reduction in number of gills took place early in the phylogeny (they never exceed seven in gnathostomes, and usually are less than five) and the surviving members of the series are so closely associated with cranial structures that the whole gill region in gnathostomes may be considered a part of the head. é The branchiomeric type of nerve is preserved with least modi- fication in the region of the medulla oblongata, bounded rostrad by the isthmus; and this structural type 1s clearly evident, though ina highly modified form, in the human medulla oblongata. Ac- cordingly, the rhombencephalon of His is a natural subdivision phyletically as well as embryologically considered. The cerebellum and its associated pons are derivatives of the somatic sensory column in the cephalic part of the same region, called forth primarily by the vestibular apparatus (and allied sense organs in fishes). This gives a sound genetic basis for the meten- cephalon of Hrs, as distinguished from the remainder of the rhomb- encephalon (the medulla oblongata). The metencephalon should be limited to the cerebellum and its immediate dependencies, a structure which has been added to the much older primary rhombencephalon, or branchiomeric brain. This usage will necessitate some revision of the limits of the meten- cephalon as set by the BNA. It can no longer be regarded as a 2 These structures have suffered considerable secondary modification. For example, the gustatory system has been derived from the unspecialized visceral sensory, and the visceral motor has in part been specialized parallel with the development of striated branchial muscles from the splanchnic mesoderm. The branchio-motor nerves lack the post-ganglionic neurone and structurally resemble the somatic motor nerves in their mode of connection with their end-organs. 400 “fournal of Comparative Neurology and Psychology. transverse segment of the neural tube, but as a dorsal structure which reaches down into the lateral walls and floor of the older brain stem like a girdle. “The metencephalon should, therefore, include the cerebellum, pons, corpus restiforme, brachium con- junctivum and some of the nuclei in immediate contact with these structures. It should not include the longitudinal conduction paths in the brain floor above the pons, nor the nuclei of the cranial nerves of the same region. The term medulla oblongata should be applied to that part of the rhombencephalon lying between the spinal cord and the isth- mus, exclusive of the parts here enumerated as belonging to the metencephalon. ‘That portion “of the medulla oblongata lying caudad of the VIII nerves and their chief primary nuclei may be called the myelencephalon (which is practically the usage of the BNA), thus limiting this latter term to the region of the typical gill bearing segments in the true fishes. If a distinctive name 1s required for the preauditory part of the medulla oblongata coordi- nate with myelencephalon for the postauditory part, the term pars facralis medulle may be suggested. The region so designated includes that portion of the brain stem (exclusive of the meten- cephalon as I here define it) comprised approximately within the metencephalon and isthmus rhombencephali of the BNA, a region which receives the cerebral nerves of the skin and muscles of the face and facial skeleton. The medulla oblongata, as here defined, extends sufficiently far forward to include the roots and chief nuclei of the V, VI and IV cerebral nerves and the superior secondary gustatory nucleus (nucleus visceralis cerebelli, JoHNsToNn). It is bounded rostrad by a constriction, the isthmus, which marks the adult position of the groove between the embryonic second and third cerebral vesicles. The subdivision of the isthmus region is very difficult. I be- lieve that the use of that term for an encephalic region cannot be justifed. The word is, however, a convenient descriptive term for the constriction in question and if retained in our nomenclature at all it should be used only in that sense. Rostrad of the rhombencephalon the evidence of the primary metamerism has almost entirely disappeared from the adult human brain. In lower brains, even in their embryonic conditions, it 18 very difficult to decipher the vestiges of metamerism in these regions. Herrick, Subdivision of the Brain. 401 The primary longitudinal functional zones have likewise suffered extreme distortion by reason partly of the development of the organs of special sense but more especially on account of the elaboration of the massive organs of correlation. The diencephalon and the mesencephalon, from our present point of view, are not natural regions, nor can any other transverse division of the brain be made which will satisfy the conditions, for the primary metamerism has ceased to be an important factor in the problem. The terms mid-brain, thalamus, etc., will in any event of course continue in use as convenient topographic designations. But from the point of view of a broad compar- ative morphology, I believe that they are confusing rather than helpful. Functionally and genetically, the retina, optic nerves, chiasma and tracts and the optic thalamus (sensu stricto) should be asso- ciated with the optic tectum of the mid-brain to form an ophthal- mencephalon whose boundaries cross freely those of the classic encephalic regions. The principle upon which this term is based 1s the same as that which led Hts to adopt (in the BNA) the term fasciculus cerebro- spinalis in place of the older terms, pyramid and pyramidal tract; viz: the association of neurones belonging to the same functional system. he advantages of this usage over any purely topograph- ical designation are so clearly brought out in the discussion of the terms pyramids, etc., that we refer the reader here to the words of Fairs; The term ophthalmencephalon as proposed here is analogous with rhinencephalon as used by the BNA for the whole olfactory apparatus of the forebrain except the olfactory portion of the pallium.‘ Aside from the visual centers, there are in the midbrain the pedunculus cerebri, colliculus inferior and other correlation cen- ters less clearly defined and still imperfectly known. It would be premature in the present state of our knowledge to attempt a final detailed subdivision of this difficult part of the brain; but the follow- ing simple outline may serve as a working basis. In the mammalia the part of the brain between the tectum opti- cum and the cerebellum may best be divided into two regions, the 8 Archiv f. Anat. |u. Physiol.], Suppl. Bd., 1895, p. 163. 4 On the rhinencephalon, BNA, see beyond under the subdivision of the forebrain. 402 Fournal of Comparative Neurology and Psychology. pedunculus cerebri lying ventrally and the colliculus inferior dorsally. The colliculus inferior is in mammals chiefly an acoustic center, forming the brain roof (epencephalic area of Hrs, Entwickelung des menschlichen Gehirnes, 1904, p. 23) over a portion of the pedunculus cerebri. In the lowest vertebrates this region is feebly differentiated, if at all, from the tectum opticum (celliculus supe- rior). The latter structure in lower fishes contains other types of sensory structures besides the optic. But in higher fishes the dif- ferentiation of the optic centers (colliculus superior) from the other systems is practically es The tectum opticum of these higher hishes embraces a massive basal structure (the torus semicircularis or “colliculus” of the teleostean anatomists) which receives secondary sensory tracts other than optic—tracts which reach the tectum in the lower fishes. “These secondary tracts come chiefly from the tuberculum acusticum. Although the latter structure of fishes is not exactly homologous with the tuberculum acusticum of man, yet the relations are such as to justify us in regarding the so-called colliculus of teleosts as in a general way homologous with the colliculus inferior of the mammals. The latter organ attains its highest development in mammals parallel with the evolution of the cochlea. In the brains of the lowest vertebrates, where the colliculus inferior has not yet differentiated from the colliculus superior, the whole structure may be designated simply colliculus, a region which would include a part of the ophthalmencephalon as well as the rudiments of the colliculus: inferior. In mammals, where the colliculus inferior is well defined as an acoustic center, the question arises, Why not recognize an acusten- cephalon analogous with the rhinencephalon and ophthalmence ph- alon? This question has been carefully considered, but found very difficult of practical realization. ‘To carry out the analogy with the two systems last mentioned it would be necessary to include the peripheral auditory nerves and primary centers in the medulla oblongata. Such a region may be defined in terms of neurone systems and as a physiological unit, and has great value as such. But the acoustic (cochlear) pathways and centers are in all cases more or less confused structurally with the vestibular, and even in mammals their physiological independence seems to Herrick, Subdivision of the Brain. 403 be less than has sometimes been supposed.* Furthermore, as we pass down to the lower vertebrates, the cochlear and the vestibular systems not only become progressively less clearly separable from each other, but they are also related to other still less highly dif- ferentiated types of sensory systems, notably the organs of the lateral line, and still lower in the series to the organs of ordinary tactile sensation. In short, the acustencephalon in the lower mem- bers of the phyletic series possesses no individuality, and in the higher members where it is both structurally and functionally bet- ter defined the system as a whole is not structurally sufficiently separate from adjacent parts to justify giving it place in a scheme of regional subdivision, however valuable it may be as a physio- logical unit. “This suggests a consideration of the relative merits of two mor- phological standards which are not always easily reconciled, viz: the functional system of neurones as contrasted with topographic form relations of the nervous system. ‘The real unit of the nervous system is unquestionably the functional system of neurones and the fruitfulness of this unit in morphology has been well illustrated by the treatment adopted by Barker in his text-book on the Ner- vous System (New York, 1go1) and by the results attained by the students of the so-called functional morphology, especially in America. Any topographic subdivision of the brain will be fully satisfactory as a basis for both morphological and physiological work just in proportion as its divisions express the underlying functional relations. But such a subdivision must take also into account the phylogenetic history of these functional units and of the brain as a whole, primary metamerism, the influence of vari- ous mechanical factors which have affected the differentiation of the mesous system and also the practical consideration of anatom- ical and didactic convenience. ‘These factors are seldom in com- plete accord. ‘This indeed is what makes the problem of cerebral regional anatomy so difficult. ‘The relative weight to be given to the different factors of the problem is a matter calling for the exercise of the utmost skill and in the nature of the case the ques- tion will be answered differently by specialists in different depart- ments. The preceding discussion of the ophthalmencephalon 5 Cf. the recent results of C. Winker. The central course of the nervus octavus and its influence on motility. Verh. Kon. Akad. van Wettenschappen, Amsterdam (2 Sec.), Deel 14, no. 1, 202 pp., 24 pl. 1907. 404 “fournal of Comparative Neurology and Psychology. and acustencephalon illustrates my own view of the proper bal- ance to be struck between the claims of the functional systems and of convenience in the recognition of topographic landmarks for didactic and descriptive purposes, in a general scheme of the subdivision of the brain. The pedunculus cerebrt is a convenient, but purely artificial, topographic region, including the tegmentum, substantia nigra, basis pedunculi, III nerve, etc.—in short all of the mesencephalon of the BNA after the sch) pene of the colliculus superior and col- liculus inferior (or the single colliculus of lower vertebrates where there is but one). It will doubtless be found possible to subdivide it or distribute it to neighboring regions, but at present it may be better to use this term as a makeshift than to propose a new sub- division, on the basis of our very imperfect knowledge of the com- parative anatomy of this part of the brain. The nomenclature of the diencephalon, after the separation of the optic centers to form the ophthalmencephalon, requires very little modification of existing usage. The term medithalamus may be applied to such parts of the thalamus and metathalamus (BNA) as remain after subtraction of the optic centers (pulvinar, geniculatum laterale, etc.) The term hypothalamus. may be retained for all of the region so designated in the BNA save the optic chiasma. The epithalamus remains as defined by the BNA. ‘The medithalamus is a derivative of the central gray of the first, sec- ond and third neuromeres. “The hypothalamus includes the hypo- physis and important correlation centers, chiefly of visceral sen- sation (olfactory and gustatory). The epzthalamus includes the epiphysis and important olfactory centers in the habenula. The exact boundaries of these thalamic subdivisions for verte- brates in general cannot be defined in the present state of our knowl- edge. JouNnsTon has discussed the limits of these regions 1n lower vertebrates in his text book,* to which the reader is referred for a summary review of our present knowledge regarding this difh- cult subject. Much more extensive comparative study will be necessary before attempting anything but a provisional analysis of the thalamus region and classification of its nuclei and fiber tracts. The telencephalon is well pouedl It is terminal, not only in position, but also in point of time, having been added relatively late ® Jounston, J. B. The nervous system of vertebrates, Philadelphia. 1906, chapter 17: Herrick, Subdivision of the Brain. 405 in the phylogeny to the rostral end of the original neural tube. The BNA has done well to omit from it the pars optica hypothal- ami which was originally tabulated as part of this region by Pro- fessor H1s. Originally developed as primary and secondary olfac- tory centers, it has added successively more and more complexity during the whole course of phylogenetic history. The most ancient, or stem portion of the telencephalon we may term, following EpINGER,’ the hyposphzrium, and the dorsal cor- relation centers epispherium. The term rhinencephalon may properly be applied to the whole of the primary olfactory brain, including the olfactory bulbs, tracts and basal centers and also the anterior commissure and lamina terminalis. The only im- portant structure of the mammalian hypospherium not included in the rhinencephalon is the corpus striatum. ‘The epispharium is subdivided after ELtiot SmirH into archipallium and neopal- lium, the former including the olfactory cortex (hippocampus, etc. ) and the fornix, the latter including the more recently developed cortical representation of the other senses and their association centers and the corpus callosum. Our subdivision of the telen- cephalon, then, is as follows: ‘ Hypospherium: Rhinencephalon (incl. lamina terminalis, ant. com. etc.) Corpus striatum. Epispherium: Archipallium (including fornix). Neopallium (including corpus callosum). The confusion in the nomenclature of the forebrain is so great that one hesitates to recommend any of the old terms, for all have been used with diverse significations, and that too very often by authors who supposed they were using them similarly. “The BNA terms seem to have suffered especially from this latter form of misuse. Yet one shrinks from adding to the burden by coining new terms which would be free from these confusing implications. The best course is to select the most fit of the current terms and try to give them precision by accurate definition. One of the most valuable contributions in this direction is that of ELLIoT 7 Epincer, L. Ueber die Herkunft des Hirnmantels in der Tierreihe. Berliner klin. Wochenschr., 1905, no. 43. 406 ‘fournal of Comparative Neurology and Psychology. SmiTH.* He presents in the work cited a very cogent argument for extending the application of the word rhinencephalon to com- prise the whole olfactory apparatus, including the olfactory cere- bral cortex, or archipallium. ‘This course has much to recommend it, for the olfactory cerebral cortex is more intimately connected with the lower olfactory centers than are the cortical representa- tions of the other sensory systems with their lower centers. In the case of the latter functional systems the cortical centers are widely separated topographically from their respective lower centers, so that the cortex cannot be joined to the lower centers in a regional subdivision of the brain. For the sake of uniformity it seems to me better to treat the entire cerebral pallium in the same way, even though the limits between olfactory pallium and lower olfactory centers cannot always be clearly drawn, as ELLior SmirH has shown. I, therefore, recommend that the rhinencephalon be limited to the basal or stem portion of the olfactory system and that the olfac- tory pallium be excluded from the rhinencephalon. The olfactory pallium is indeed very distinct structurally as well as physiolog- ically, trom the remainder of the cerebral cortex and therefore the separation of the cortex into archipallium and neopallium is worthy of recognition in our nomenclature. ‘The usage here rec- ommended is apparently similar to that of the BNA, but ELLiot SmitTH has shown in the paper cited that neither Professor His as reporter for the BNA nor the neurologists who have subsequently adopted his terms are consistent in their use of them. Confusion of this sort can be avoided only by establishing a definition of pallium which is independent of accidental form rela- tions. “The term was first applied to the thin free forebrain roof, as contrasted with the more massive basal ganglia. In lower vertebrates this criterion is of no morphological value. KaAppEeRs and THEUNISSEN® have developed in a fruitful way a histological conception of the distinction between pallium and basal forebrain centers. In the case of the olfactory system the primary and sec- ondary olfactory centers are considered as belonging to the basal or stem portion of the telencephalon, while olfactory centers of 8G. Eruior Smirx. Notes upon the natural subdivision of the cerebral hemisphere. ‘fourn. Anat. and Physiol., vol. 35, 00. 4, pp. 431-454, 1901. ‘Zur vergleichenden Anatomie des Vorderhirnes der Vertebraten. Anat. Anz., Bd. 30, 1907; and Die Phylogenese des Rhinencephalons, des Corpus striatum und der Vorderhirnkommissuren. Folia Neuro-biologica, vol. 1, no. 2, 1908. Herrick, Subdivision of the Brain. 407 the third order are treated as pallium. ‘The application of this principle, however, proves to be very difficult, for there are many cases where olfactory tracts of the third order run to basal regions which have none of the other characteristics of pallium, and on the other hand the archipallium (hippocampus) of all higher verte- brates, including man, is said on good authority to receive olfac- tory fibers of the second order, as well as of higher orders. It is clear that in mammals the distinction between hyposphe- rium and epispherium 1 is capable of tolerably precise anatomical definition and is easily recognized. While accepting this as an important anatomical fact, the writer is of the opinion that our knowledge of both the histology and the phylogeny of the mam- malian pallium i is still too imperfect to permit of its final mor- phological interpretation. The phylogeny of the pallium is now under active investigation in a number of 1 important neuro- logical laboratories and until our knowledge of its early phylo- genetic stages is more complete it is better to avoid dogmatism and await fuller knowledge before attempting to elaborate in detail the morphology of the telencephalon. The unsettled state of opinion regarding the fundamental character of cerebral local- ization further emphasizes the need of caution in forebrain morphology. ; We may, then, summarize our scheme of subdivision of the vertebrate nervous system as follows :!° Systema nervorum sympathicum (BNA). Systema nervorum cerebro-spinale. Systema nervorum periphericum (BNA). Systema nervorum centrale (BNA). Medulla spinalis (BNA). Encephalon (BNA). Rhombencephalon (BNA). 10 Tt should be borne in mind that the terms adopted in this table are not codrdinate in morpholog- ical value from any standpoint. ‘They are offered simply as a practicable suggestion for a terminology which shall be available for all vertebrates and which deviates as little as possible from the most widely used standard of our time. The writer would add, moreover, that in recommending this subdivision and nomenclature he by no means pleads for its final adoption as a whole. This scheme is manifestly defective in many places, and it is hoped and expected that further discussion will clarify the more obscure points. These pages are offered primarily as a contribution to method and it is earnestly maintained that the principles here illustrated are vitally important and must be taken into account in all future morphological work in this field. The exact limits of the regions and the names to be applied to them are subsidiary considerations upon which unanimity of opinion can hardly be expected until our anatomical and physiological knowl- edge is far more complete. 408 fournal of Comparative Neurology and Psychology. Medulla oblongata (BNA). Myelencephalon (BNA). Pars facialis medullz. Metencephalon (BNA). Cerebrum (BNA). Pedunculus cerebri (BNA). Colliculus inferior (BNA). Ophthalmencephalon. Medithalamus. Hypothalamus. Epithalamus (BNA). Telencephalon (BNA). Hypospherium. Rhinencephalon (BNA). Corpus striatum (BNA). Epispherium ( = Pallium BNA). Archipallium. Neopallium. ON THE COMMISSURA INFIMA AND ITS NUCLEI IN THE BRAINS OF FISHES. BY C. JUDSON HERRICK. (From the Anatomical Laboratory of the University of Chicago.) With Twetve Ficures. It has long been known that the brains of fishes possess an extensive mass of fibers which cross the median line above the ventricle in the region of the nuclei of the dorsal funiculi where the medulla oblongata joins the spinal cord. This is the com- missura inima of Hatter. ‘The commissure discovered in a sim- ilar position in the mammals by CaJat (1896, p. 43) was at once recognized by fish neurologists as a homologous structure; and since the commissure of Caja And its associated nucleus clearly belong to the visceral sensory system (receiving sensory fibers from the visceral roots of the vagus and glossopharyngeus nerves), it has been commonly assumed that in the fishes the commissure is visceral sensory. Renewed examination shows that this assumption is correct, but itis not the whole truth. “The commissura infima includes two morphologically distinct elements : (1)a visceral sensory commissure, comprising a decussation of vagus root fibers and a commissure of secondary elements from the visceral sensory centers; and (2) a somatic sensory commissure, consisting of secondary fibers from the funicular nuclei and adjacent centers of tactile sensation. Each commissure has associated with it a nucleus. The visceral nucleus was discovered by Cajat and named by him the nucleus commissuralis. “The somatic nucleus was first reported in my paper (1906) on the tactile and gustatory centers of fishes, to which the reader is referred for the general topography of this region. In the paper last mentioned this commissure of Ameiurus, the common horned pout or cat-fish, was analyzed incidental to the study of the adjacent centers, and found to be very complex. ‘The 410 ‘fournal of Comparative Neurology and Psychology. purpose of this paper is the examination of a number of types of fishes in which the various elements of the commissure are dif- ferently developed, for the purpose of reaching a more complete understanding of this critical region of the brain. We shall begin with a review of the conditions in Ameiurus, where the visceral and somatic elements are about equally developed, and then examine other species showing various deviations from this type. The visceral commissura infima of Ameiurus.—The visceral commissural nucleus is a dorsal unpaired structure forming a pro- tuberance in the triangular space behind the vagal lobes and between the funicular nuclei. ‘The cells of the nucleus, which are rather small, are more thickly arranged near the external borders of the lobe (fig. 1). Their dendrites ramify through its whole sub- stance and freely cross the median line. ‘The fibers of the descend- ing vagus root, which enter the nucleus at its lateral borders, ter- minate chiefly uncrossed by widely branched aborizations, but some of these endings cross to the opposite side before terminating (fg. 3). This commissure also recefves short secondary tracts, either unmedullated or with slight medullation, from the vagal lobe, which end partly crossed and partly uncrossed (cf. HERRICK 1906, fig. 7). The cells of its mucleus therefore may receive vis- ceral impulses either directly from the periphery by way of the descending vagus root or indirectly by way of the descending sec- ondary visceral tract from the vagal ‘lobes. Both types of affer- ent fibers, as well as dendrites of abe cells of the nucleus, partici- pate in the formation of the commissure, which is diffuse and chiefly unmedullated. ‘The efferent tract from this nucleus is by tolerably compact bundles of unmedullated fibers which curve downward near the median line around the cephalic end of the median funicular nucleus to effect connection with the adjacent formatio reticularis under the vagal lobe (fig. 1). T he somatic commuissura infima of Ameturus. =e commis- sure lies ventrally of the preceding and dorsally of the ventricle. The two commissures are for the most part very distinct anatom- ically, though at the cephalic end there is some mingling of their fibers. The somatic commissure is chiefly, though by no means wholly, a commissure of the funicular nuclei (fig. 2). Its most dorsal part is a strong compact bundle from the dorso-lateral fas- ciculus and lateral funicular nucleus (fig. 2, y; fig. 3). Among these fibers and ventrally of them are dendrites of the cells of the Herrick, Commissura Infima. 411 median and lateral funicular nuclei and delicately medullated fibers connecting the two median funicular nuclei. Farther ven- trally and extending nearly down to the canalis centralis are fine fibers, chiefly unmedullated, passing between the formatio reticu- laris of the two sides (fig. 2). Among the latter fibers are nu- merous cells, some very small and some large (fg. 3; cf. fig. 5 of Catostomus). These cells of the somatic commissural nucleus constitute an extension of the adjacent formatio reticularis grisea which, accordingly, is broadly continuous across the median line above the canalis centralis. ‘The large cells of this nucleus send their neurites ventrally into the ventral cornu and _ perhaps the ventral funiculi. The smaller cells seem to connect with the adja- cent formatio reticularis. The splanchnic and somatic divisions of the commissura infima are thus seen to be very similar, save in the fact that the somatic division 1s not known to contain root fibers. Each contains com- missural fibers from adjacent primary centers and a median nucleus whose efferent tracts reach the adjacent formatio reticu- laris. ‘These nuclei seem to have been differentiated from the formatio reticularis grisea, the splanchnic nucleus being the more highly specialized. I have elsewhere described these commissures in Gadus (1907, p. 75-78) and found the typical relations with neither the somatic nor the visceral elements especially differentiated, the somatic com- ponent being considerably larger than the visceral (see figs. 3, 5, 6 and 7 of the paper cited). In Haploidonotus grunniens [ find the same conditions as in Gadus save that the visceral component is considerably larger. The commissura infma of cyprinotds.—In these fishes the visceral element of this complex is greatly enlarged, without a corresponding modification of the somatic element. In the carp, Cyprinus, the morphologic relations are the same as in Ameiurus with such modifications only as are caused by the larger vagal lobes. The nucleus intermedius vagi seems to be included in the motor layer of the vagal lobes (HERRICK 1905, p- 433). The visceral commissural nucleus is both larger and more distinct than in Ameiurus. It is continuous headward with the motor layer of the vagal lobes and under the caudal border of the vagal lobes appears as a pair of pyriform swellings whose larger ends are fused over the ventricle (fig. 4). The area of fusion con- 412 “fournal of Comparative Neurology and Psychology. tains the visceral portion of the commissure infima, consisting of sparse medullated fibers and numerous unmedullated tracts. ‘The narrow end of each nucleus 1s directed laterally and receives the most caudal (descending) sensory vagus root. This root is un- usually large and spreads throughout the substance of the lobe. Numerous fascicles of root fibers pierce the lobe to cross in the commissura infima above the ventricle. “These lobes receive, as in Ameiurus, large numbers of feebly medullated diffuse tracts from the layer of secondary tracts of the vagal lobes. ‘These end partly uncrossed and partly crossed. ‘These visceral nuclei pass forward into the nucleus intermedius vagi, as just stated, and ventrally they are bounded by the somatic sensory centers and their commissure. ‘The dorsal part of the somatic commissura infima is blended with the ventral part of the visceral commissure. ‘The visceral commissure is diffuse and chiefly unmedullated. ‘The somatic commissure contains numer- ous separate fascicles of heavily medullated fibers, some of which come from the dorso-lateral fasciculi, and also more lightly medullated fibers which connect the adjacent funicular nuclei and formatio reticularis. The somatic sensory centers are nearly as large as in Ameiurus, but do not show as much differentiation. ‘The lateral funicular nucleus is distinct; the median nucleus and nucleus of the spinal V tract are indisttnguishably fused. ‘They extend far forward under the visceral nuclei, the latter having been crowded back- ward by the enlarged vagal lobes. Both funicular nuclei receive descending secondary gustatory fibers from the facial lobe. Most of these fibers end in the median nucleus, while the lateral nucleus receives a much larger proportion of fibers from the dorso-lateral fasciculus. Both nuclei are, therefore, as in Ameiurus, correlation centers for tactile and gustatory sensation from the outer skin (Herrick 1906). Their secondary connections are as in Ameiurus and in addition there is a large tract of small medullated fibers from the median nucleus and the formatio reticularis ventrally of 1t, which crosses at once in the ventral part of the somatic commissura infima and then passes headward along the lateral border of the ventricle to end in the nucleus ambiguus. ‘This is evidently a direct path from the tactile-gustatory correlation center to the nucleus of the gill muscles, and may be termed the tractus funiculo-ambiguus (fig. 4). Herrick, Commissura Infima. 413 In Catostomus the general plan is much as in Cyprinus, but more compact. ‘The visceral commissural nucleus (nucleus of CajaL) is not well developed in the median line, but is a paired structure lying close to the meson at the ends of the commissura infima, whose visceral portion is short, thick and more compact than in the catp. The descending sensory vagus root is very large and most of its root fibers decussate in this commissure. The visceral commussural ancleus is not as clearly separate from the surrounding structures as in the carp. This nucleus and the adjacent parts, both forward and backward, are connected by a strong tract of unmedullated external arcuate fibers with the funic- ulus ventralis. The nature of this connection I have not been able to make out. It is present in Ameiurus and contains some feebly medullated fibers. “The dorsal end of this tract is shown in fig. 6 of my recent paper on Ameiurus (1906), passing down later- ally of the tracts marked 7. /. It seems to be the path from the visceral sensory centers to the motor nuclei of the muscles of the fins and trunk. The great enlargement of the visceral centers of cyprinoids is confined to the medulla oblongata. ‘The spinal visceral centers are even smaller than in some other fishes, and the commissural nucleus cannot be traced far back into a clearly defined area of the spinal cord. The somatic portion of the commisstura infima is less compact, being but little different from the dorsal commissure of the spinal cord, which is well developed. ‘The somatic commissural nucleus is developed about as in Ameiurus. One of its neurones is shown In fig. The gold fish, Carassius auratus, resembles the carp very closely, the chief difference being the greater distinctness of the visceral and somatic components of the commissura infima. ‘The tractus funiculo-ambiguus is well developed and there is a conspicuous well medullated descending tract from the visceral commissural nucleus, which passes directly back from the commissure close to the median line. It passes caudad among the transverse fibers of the somatic commissura infima and disappears before reaching the caudal end of the funicular nuclei. ‘This tract is present in all of the fishes which I have examined, but is exceedingly variable in size. Usually it is unmedullated. Gotcr sections of various species have shown sparse fibers passing from it ventro-laterally 414 “fournal of Comparative Neurology and Psychology. into the formatio reticularis. It probably is the path of conduction between the visceral sensory centers of the oblongata and the corresponding areas of the spinal cord. The commissura infima of the Anguillide.—The brain of the eel is strikingly selachian in aspect and by reason of its extreme elon- gation presents some features of the oblongata more clearly than any other type. My material consists of two series of the brain of Conger cut transversely and stained by WeicERtT’s method, two of Anguilla cut transversely and stained by DELAFIELD’s and Matiory’s hematoxylin respectively and two of Anguilla cut horizonally and stained by DELAFIELD’s and WeIGERT’s hema- toxylin respectively. The somatic sensory centers of these brains are very highly developed, the visceral sensory centers moderately. The vagal lobe is greatly elongated; it receives in front the visceral sensory root of the facial nerve, the sensory [X root about midway and the sensory X roots at the caudal end, beyond which it passes directly into the visceral commissural nucleus. ‘There is no specially differen- tiated facial lobe. The ascending secondary gustatory tract arises from the whole extent of the vagal lobe in the typical manner. From the cephalic or facial end of the lobe a descending tract appears to pass back ventrally of the spinal V tract into the dorso-lateral fasciculus for the funicular nucleus and spinal cord, like the de- scending secondary tract from the facial lobe of Ameiurus; but the sections do not make the relations perfectly plain. The vagal lobes at their caudal ends fuse and from the point of fusion the visceral commissural nucleus extends far backwards as a compact mass of dense neuropil containing few medullated fibers, many cells and unmedullated tracts running in various directions, many of which cross the median line. Some unmed- ullated vagus terminals probably reach this commissure, though the WEIGERT sections do not permit a demonstration of this. Strong unmedullated tracts pass from the whole ‘length of this nucleus into the formatio reticularis of the same side (figs. 6, 7, 8). This visceral nucleus extends far caudad, diminishing in size and sharply marked off structurally from the adjacent somatic centers. The nucleus ambiguus accompanies its lower border for some distance and can be followed back as far as the level of the second spinal nerve (figs. 6 to 10). With the enlargement of the funicular nuclei in this region the visceral area shrinks to a mere Herrick, Commissura Infima. 415 vestige which can, however, be followed more than five milli- meters back into the spinal cord (fig. 10). ‘This area corresponds to the descending tract from the visceral commissural nucleus described above for the gold fish. The somatic sensory centers of both the oblongata and _ spinal cord are greatly enlarged, as well as elongated. aie tuberculum acusticum is large and extends far caudad over the vagal lobes. From its lower end a somatic sensory field (fig. 6) extends back laterally of the vagal lobe to connect with the lateral funicular nucleus, which is well developed about as in Ameiurus. ‘The somatic commissura infima begins close behind the vagal lobes, over-arching the visceral commissure and its nucleus (fig. 6). This part of the somatic commissure contains a strong tract of medullated fibers which pass from the caudal end of the tuber- culum acusticum back through the lateral sensory field just referred to, crossing as the most cephalic fibers of the somatic commissure and terminating in the lateral funicular nucleus of the opposite side (fig. 6, com. tub. acust). I have not observed such a tract in any other fish which I have studied. Even in Gadus, which also has very large tubercula acustica, there is no field of gray matter extending between the tuberculum acusticum and the lat- eral funicular nucleus and no tract can be distinguished in this region for the commissura infima, though such a tract may pass from the tuberculum acusticum indistinguishably mingled with the others in the dorso-lateral fasciculus. In Gadus the tubercula acustica fuse dorsally over the ventricle and there is a strong med- ullated acoustic commissure in this area of fusion (see KApPERS 1906, figs. xcv to xcix). In Conger there is also a broad dorsal fusion of the tubercula acustica but no medullated fibers appear in it; nor is there an acoustic commissure of unmedullated fibers except at the extreme cephalic end. It may therefore be that the descending medullated tract for the commissura infima in Conger is a compensation for the absence of an acoustic commissure 1n the tubercula acustica themselves. But we should have more precise knowledge of the courses of these fibers before accepting this suggestion. The somatic commissura infima is larger than in any other fish which I have examined except Prionotus. Its cephalic part is large and very compact and lies dorsally of the visceral nucleus and commissure (figs. 6, 7, 8). Its commissural nucleus 1s not 416 ‘fournal of Comparative Neurology and Psychology. developed at this level. ‘The first part of the commissure con- tains, in addition to the acoustic commissural tract above described, more numerous finer fibers which connect the lateral funicular nuclei and the underlying dorso-lateral fasciculi (figs. 7 and 8). Even as far back as the first dorsal spinal root (fig. 8) the somatic centers are not greatly enlarged except the lateral funicular nucleus. The lateral funicular nucleus extends far caudad and behind fuses with the median funicular nucleus. The fibers of the first dorsal spinal root terminate chiefly in this lateral nucleus. A slender fas- cicle accompanies these root fibers and Looe farther ventrally to connect with the nucleus ambiguus (fig. 8, rx XJ?). These appear to belong to the spinal accessory nerve, trouah their peripheral destination is unknown. As we pass caudad from this level both the dorsal somatic com- missure between the lateral funicular nuclei and the visceral com- missural nucleus disappear, the place of the latter being taken by the somatic commissural nucleus and the commissure between the median funicular nuclei, which have meanwhile rapidly enlarged. The spinal V nucleus is indistinguishable from the funicular nucleus. The somatic commissural nucleus is only moderately developed (figs. 9, 10), and in this region the somatic commissura infima 1s represented by scattered fascicles of medullated fibers between the funicular nuclei and formatio reticularis. The fun- icular nucleus lies unusually far caudad and farther back passes over into the dorsal cornu, which continues to be large far back into the spinal cord, where it becomes enveloped by the large dorsal funiculus. Anguilla, the common eel, is essentially the same as Conger, the visceral system being relatively smaller. “Uhese fishes illustrate a very high development of the somatic longitudinal conduction paths of the somatic sensory centers of the medulla oblongata. The commissura infima of Prionotus 1 have elsewhere described (1907a). In this species, as in the other gurnards, the visceral sen- sory system is rather poorly developed, but the somatic sensory systems, especially the spinal tactile centers, are very extensive. The “‘accessory lobes”’ of the cephalic end of the spinal cord are enlarged dorsal cornua and the first lobe includes also the spinal V nucleus. ‘The funicular nucleus is very greatly enlarged. The visceral commissura infima and commissural nucleus are rather small but of the typical teleostean type. “The somatic commissura HERRICK, Commuissura Infima. Any, infima contains at the cephalic end a large, heavily medullated tract from the funicular nucleus, and farther back extensive more diffuse connections between the first and second accessory lobes. The somatic commissural nucleus is also very large and associated with the tracts last mentioned. “The commissural nucleus does not extend back beyond the cephalic end of the second accessory lobe, though there is a well developed medullated dorsal commissure between all of the accessory lobes. The commissura infima of Amia calva.—tIn this fish both the visceral and the somatic commissural systems are moderately developed and the whole region is simpler and probably more primi- tive than in any teleost examined. The vagal lobes are elongated and their caudal ends rise up to form the lips of the fourth ventricle (tania ventriculi quarti) in the calamus region, fusing together behind the ventricle to form the visceral commissural nucleus (fig. 11). Sparse unmedullated fibers cross the medial plane within this nucleus, constituting the visceral commissura infima. ‘This nucleus contains but few cells and is broadly connected with the homolateral formatio reticularis ventrally of the funicular nucleus. The funicular nuclei are elongated, extending from the level of the visceral commissural filers Galcecl toe aie ale spinal cord. The somatic commissural nucleus (fig. 12) contains many densely crowded cells extending from the ventro-mesial borders of the two median funicular nuclei and across the meson ventrally of the most caudal part of the visceral nucleus and close above the canalis spinalis. ‘There are no medullated fibers in the somatic commissural nucleus and very few unmedullated fibers. Kappers (1907, p. 490) has briefly referred to the commissura infima of Amia, but he was not able to demonstrate definite com- missural nuclei. He says, referring to the visceral commissural nucleus, “ Ich mochte thn lieber nicht als besonderen Kern betrach- ten.’ It is true that the visceral nucleus is not so large and clearly defined in Amia as in the teleosts which I have examined, yet its individuality is perfectly clear, as I have seen in an extensive series of sections of Amia kindly loaned to me by Prof. CHaRLEs BRooK- oveR. ‘These include preparations by the methods of WEIGERT, Nissi, Cayat, BretcHowsky and the iron hematoxylin method of HarenHain. I have chosen for illustration (figs. 11 and 12) a teries through a young specimen stained by the method last men- sioned. ‘The adult relations are similar. 418 “fournal of Comparative Neurology and Psychology. In young Lepidosteus about g cm. long the relations of the com- missura infima region are about as in the adult Amia as far as can be determined by the study of hematoxylin preparations. In the adult the disposition of the parts has been considerably altered. The adult vagal lobe does not reach back to the lower end of the fourth ventricle; but from its caudal end a diffuse tract of fibers, both medullated and unmedullated, extends caudad mesially of the funicular nucleus and adjacent to the wall of the fourth ven- tricle, to the commissura infima. Here this tract rises up inthe tania ventriculi quarti and decussates above the caudal end of the fourth ventricle to end in the visceral commissural nucleus farther caudad and ventrad. ‘These visceral fibers are the only elements in the commissura infima of this region so far as our preparations demonstrate. The visceral commissural nucleus does not lie in the median plane in association with its commissure, but some sec- tions farther caudad and ventrad as a paired structure lying ven- tromesially of the funicular nucleus of each side near the dorsal fissure. The efferent tract from this nucleus, consisting of both -medullated and unmedullated fibers, passes out ventro-laterally into the adjacent formatio reticularis. The funicular nucleus lies for the most part cephalad of the calamus region instead of caudad of it, as in Amia. Some fibers from the funicular nucleus or somatic sensory field may cross along with the visceral fibers in the commissura infima, though I have not been able to demonstrate them. ‘The size of the somatic commissura infima is reduced; possibly the strongly developed efferent tracts from the funicular nuclei forming internal arcuate fibers below the ventricle may compensate for the reduction of the dorsal commissure. The combined nucleus of the spinal V tract and funicular nucleus extends, as mentioned above, far cephalad of the commissura infima into a somatic sensory field laterally of the caudal end of the vagallobe. Itis quite sharply separate from the tuberculum acusticum, which occupies the somatic sensory field cephalad of it. The efferent fibers from the funicular nucleus can be easily followed. They leave the nucleus in compact strands of heavily medullated fibers which pass downward into the formatio reticu- laris, ventral cornu, and in still larger numbers cross the ventral raphé as internal arcuate fibers entering the fasciculus longitud- inalis medialis. The funiculus dorsalis. is unusually large in Herrick, Commissura Infima. 419 Lepidosteus and it terminates for the most part in the cephalic part of the funicular nucleus. For my preparations of the brain of Lepidosteus I am again indebted to the kindness of Professor BROOKOVER. CONCLUSION In effecting the functional analysis of the somatic and visceral centers at the lower end of the medulla oblongata difficulty has been experienced on account of the diffuse character of these nuclei and their tracts and the intricacy of their interrelations. At the time of the publication of my report on the central gustatory paths in fishes (1905) these relations were very imperfectly understood. Further comparative study showed that different fishes exhibit very unequal degrees of development of the somatic and visceral elements in the funicular nucleus region and that by comparing types with the maximal visceral elements, like the carp, with those showing maximal development of the tactile system, like the gurnards, the obscurity was largely cleared up, and forms with an approximately equal development of both systems could then be understood. For the convenience of the reader I have presented these results in the reverse order of that adopted in the research, having pub- lished the findings in Ameiurus (1906) before those in the more highly specialized species, like Cyprinus and Prionotus. ‘The latter type has proven especially helpful, since, while the brain is no- where very highly specialized, the spinal tactile path 1s greatly enlarged and may therefore be isolated for study simply by com- parison with other unmodified types of fishes. Accordingly I have made a more detailed examination of this species (1907). In the present paper I have brought together the data scattered through my previous articles so far as they bear upon this region, together with some new observations on these and other fishes. It appears that the commissura infima of fishes (HALLER) and of mammals (Cajal) and its nucleus, so far from being a purely visceral structure, as believed by recent critics, has an important somatic sensory component, which in some fishes far exceeds in size the visceral element. ‘The visceral commissure and its nucleus are extensions of the deep layer of the vagal lobes (nucleus inter- medius vagi) and also of an imperfectly known visceral zone of the 420 fournal of Comparative Neurology and Psychology. spinal cord, which probably sends some fibers into the dorsal com- missure of the spinal cord. If the nucleus dorsalis (CLARKE’s column) of the spinal cord represents the visceral sensory center of the spinal cord, as supposed by some recent anatomists, then the spinal root fibers which cross in the dorsal commissure to termi- nate in the heterolateral nucleus dorsalis are comparable with the sensory root fibers of the vagus which cross in the commissura infima. But our knowledge of the visceral sensory system in the spinal cord is still too imperfect to permit of final decision of any of these questions. The somatic component of the commissura infma is no doubt comparable with the somatic sensory fibers which make up the greater part of the dorsal commissure through- out the spinal cord. It is probable that in fishes (and in higher vertebrates) visceral centers which primitively were arranged, like the somatic centers, in a metameric way throughout the spinal cord have become con- centrated in the medulla oblongata, the intestinal branch of the vagus and various sympathetic connections of the cranial nerves having to a large extent supplanted the original segmental visceral nerves of the spinal cord. If, as appears probable, the primitive vertebrate ancestor had gills extending down the greater part of the length of the trunk region, as in Amphioxus, the explanation for this concentration of the visceral nerves is clearly apparent in the progressive loss of the more caudally placed gills as we ascend the vertebrate series. In the extensive region of the enlarged visceral sensory area of the medulla oblongata the roof plate is membranous and widely extended laterally. This feature prevents the visceral sensory commissural fibers of the medulla oblongata from crossing at their own level and necessitates their passage caudad to the region behind the calamus scriptorius, where they are concentrated as the visceral commissura infma. Both root fibers of the vagus and secondary visceral tracts from the vagal lobes are involved in this movement, which has carried with it a certain number of cells per- taining to these commissural fibers. These cells make up the visceral commissural nucleus and are probably mainly terminal nucleus cells for the vagus root fibers of the commissure. The secondary connections of this nucleus are substantially the same as those of the visceral sensory nucleus of the vagus in the medulla oblongata. Herrick, Commissura Infima. 421 The somatic sensory centers of the spinal cord have shown no tendency to migrate into the head, like that seen in the visceral sensory centers. Even in Prionotus, where the most cephalic seg- ments of the spinal cord alone are greatly enlarged, there is no especial tendency for them to be concentrated in the medulla oblongata. In the oblongata, however, the somatic sensory centers have always suffered extreme modification. ‘The somatic sensory zone in the cephalic end of the oblongata has given rise to the tuberculum acusticum and cerebellum and because of the crowding due to the presence of these structures, or for some other reason, in teleosts practically all of the tactile, or unspecialized somatic sensory nerves from the skin of the head pass back in the spinal V tract to terminate in the funicular nucleus region. In some fishes there is a separate and well defined spinal V nucleus; in others this is indistinguishable from the dorsal cornu and funicu- lar nucleus. The latter is a derivative of the formatio reticularis, which also gives rise to the somatic commissural nucleus. ‘The somatic commissura infima is a continuation of the commissure of the dorsal cornua and fasciculi proprii of the spinal cord. It receives also large additions from the funicular and spinal V nuclei. The commissure of the tubercula acustica in fishes like Gadus and Haploidonotus, where these fuse above the ventricle, is probably homologous, and also a part of the commissural fibers of the cerebellum. PITRE RATURE Ci ED: CATAL, Sa Rex. 1896. Beitrag zum Studium der Medulla oblongata, des Kleinhirns und der Ursprungs der Gehirnnerven. Trans. by Brester. Lezpzig. Herrick, C. Jupson. 1905. The central gustatory paths in the brains of bony fishes. Journ. Comp. Neur. and Psychol., vol. 15. 1906. On the centers for taste and touch in the medulla oblongata of fishes. Ibid., vol. 16. 1907. A study of the vagal lobes and funicular nuclei of the brain of the codfish. Jbid., vol. 17. 1907a. The tactile centers in the spinal cord and brain of the sea robin (Prionotus carolinus L) Tbid., vol. 17. Kappers, C. U. A. 1906. The structure of the teleostean and selachian brain. 3fourn. Comp. Neur. and Psychol., vol. 16. 1907. Untersuchungen tiber das Gehrin der Ganoiden Amia calva und Lepidosteus osseus. Abhandl. Senckenbergischen Naturf. Gesellschaft, Frankfurt, Bd. 30, Heft 3, 1907. 422 “fournal of Comparative Neurology and Psychology. Fic. 1. Parasagittal section through the oblongata of a specimen of Ameiurus nebulosus about 2 cm. long, showing the visceral commissural nucleus and the secondary tract from it to the formatio reticularis. Gotcr method. X 42. Fic. 2. Section through the widest part of the somatic commissura infima and funicular nuclei of the adult Ameiurus nebulosus. Method of Wericert-Pat. X35. From the Fourn. Comp. Neurol. and Psychol., vol. 16, p. 425 (Herrick ’06, Fig. 4). The lateral funicular nucleus appears external to the spinal V tract and its nucleus, receiving many fibers from the fasciculus dorso-lateralis and sending large tracts to the formatio reticularis and the com- missura infima. Thiscommissure receives also a large mass of fibers from the median funicular nucleus and probably also from the spinal V nucleus. Fibers are seen passing from the spinal V tract into its nucleus, and some pass through this nucleus to end in the median funicular nucleus. com. inf., somatic part of commissura; f.d./., fasciculus dorso-lateralis; f./., fasciculus lateralis; f.l.m., fasciculus longitudinalis medialis; f.r., formatio reticularis; f. v., fasciculus ventralis; .amb., caudal end of nucleus ambiguus; 1.fn./., lateral funicular nucleus; n.fn.m., median funicular nucleus; n.sp.V., spinal V nucleus; s., secondary tracts from spnial V nucleus and median funicular nucleus; sp.V .tr., spinal V tract; tr. sp.b.tect., rectus spino- et bulbo-tectalis (lemniscus); w. tractus bulbo-spinalis; x., tractus spino-cerebellaris; y., secondary tracts from lateral funicular nucleus and other elements for the commissura infima; cf. Fig. 3. Herrick, Commissura Infima. commissural vagal Jobe secondary tract Ufrom commis. muc. ae —— FF we: WW . é jt teeeeeee' formatio reticularis tr. spino-tectalis Fic. I. 423 424 “fournal of Comparative Neurology and Psychology. Fic. 3. Transverse section through the funicular nuclei and visceral commissural nucleus of CayaL of Ameiurus nebulosus. Gorci method. X75. The drawing is a composite of two adjacent sections, the right side drawn wholly from one and the left from the other. From the Fourn. Comp. Neurol. and Psychol., vol. 16, p. 437 (Herrick ’06, Fig. 13). The endings of the descending sensory vagus root in the commissural nucleus are shown and of the spinal V tract and dorso-lateral fasciculus in their nuclei. One big neurone of the somatic commissural nucleus is impregnated and a few neurones in the lateral funicular nuclei. Dendrites (and probably axones) of the latter accompany fibers from the dorso-lateral fasciculus into the somatic commissura infima in the tract marked y in Fig. 2. Cf. Herrick ’06, Fig. 14, for another similar section. Fic. 4. A transverse section through the middle of the visceral commissural nucleus of the carp, Cyprinus carpio, showing the decussation of fibers of the descending sensory root of the vagus in the commissura infima, also the decussation of fascicles from the dorso-lateral fasciculus (dec. f.d./.) and funicular nuclei in the somatic portion of this commissure. The area designated funicular nucleus contains also the spinal V nucleus and receives in this section thick bundles of fibers from the descending secondary gustatory tract from the facial lobes (desc. sec. VII). Method of Weicert-Pat. X30. Herrick, Commissura Infima 425 nuc.commiss. ES Ze ndde. tunic. lat. cr we! Vv nue. Ah=nuc. tunic. med. : F yi fasciculus a 2H ati part. dorso-/at. ; LT Ks sural nuc, ZZ \ SEG ey "A! tr. bulbo-. tectalis “ural nuc/eus A) att Dpscom. infime SER g SN tr funiculo- msambiguu s tevin tr bulbo- =tectalis ae f desc. sec YL ZS funie. dorso-/at.—__\- Spinal Vu rack 426 ‘fournal of Comparative Neurology and Psychology. Fic. 5. A neurone of the somatic commissural nucleus of Catostomus commersoni. Goxcr method. X 130. The cell body lies just to the right of the median line, in the same position as the neurone of Ameiurus marked somatic commissural nucleus in Fig. 2. Several dendrites extending across the meson soon pass out of the plane of the section. One large dendrite spreads throughout the whole ventral part of the combined funicular nucleus and spinal V nucleus; another spreads throughout the whole of the dorsal part of the formatio reticularis. Fics. 6 to 10. A series of transections through the region of the commissura infima in the adult conger eel (Conger conger), all drawn to the same scale. Wircert method. X26. Fic. 6. Section through the brain of Conger just caudad of the vagal lobes, passing through the visceral commissural nucleus which is composed of a dense mass of neuropil and a cluster of small cells in the middle. Unmedullated fibers cross the meson, constituting the visceral commissura infima; others pass as uncrossed secondary visceral tracts to the formatio reticularis. Dorsally of this nucleus is the most cephalic part of the somatic commissura infima, consisting of medullated fibers from the caudal ends of the tubercula acustica. The somatic sensory field laterally of the nucleus extends caudad from the tuberculum acusticum to the funicular nuclei. It contains both neuropil and fine medullated fibers diffusely distributed. Internal arcuate tracts pass from this field into the ventral commissure. Herrick, Commissura Infima. 427 funicular nucleus dors o> . ilateral yoo fasciculus \ idesc. psec. VIL ~~ meson lat. formatio reticularts 428 “fournal of Comparative Neurology and Psychology. Frc. 7. Section through the brain of Conger .22 mm. farther caudad, showing the visceral com- missura infima and nucleus, and the somatic commissura infima passing between the somatic sensory fields. The latter area at this level may be regarded as lateral funicular nucleus. Internal arcuate fibers pass from it to the ventral commissure. Frc. 8. Section through the brain of Conger .4 mm. farther caudad at the level of the first dorsal root of the first spinal nerve. At this level the visceral commissural nucleus is less sharply separated from the adjacent somatic centers. A root passes from the nucleus ambiguus out into the first dorsal spinal root (rv. XI?). Its peripheral course is unknown. The somatic sensory field is desginated nuc. funiculi lateralis, and the cephalic end of the median funicular nucleus appears ventrally of the spinal V tract. This nucleus receives termini of the spinal V tract and of the first spina] nerve and is related with the fasciculus dorso-lateralis. Internal arcuate fibers from both the lateral and the median funicu- lar nuclei cross in the ventral commissure and largely enter the ventral funiculi within which they turn caudad for the most part. Fic. 9. Section of the brain of Conger .3 mm. farther caudad, through the somatic commissural nucleus. The visceral commissura infima and its nucleus have disappeared, vestiges only being appar- ent dorsally of the somatic commissural nucleus. The portion of the somatic commissura infima which crosses between the somatic sensory fields dorsally of the visceral nucleus (Figs. 6, 7, 8) has also dis- appeared, but tracts passing forward into that commissure from the lateral funicular nucleus are seen at a. A broad diffuse somatic commissura infima appears ventrally of the visceral nucleus associated with the somatic commissural nucleus. The latter is also closely associated with the formatio reticularis and median funicular nucleus. Herrick, Commissura Infima. _somatic commis. infima somatic sensory field . _ spinal V tract __fase dorso. lat #1, _formatio reticularis nuctuniculi lateralis _Sp-Vtract nucfunieul; medialis fasc.dorso lat. RIX XT formatio reticularis _huc.funiculi lat. z ee vise.commis nuc. somatic commits. infima ae somatic commis nu Zn \ Spinal V tract SA _nucfunceult medialis \ 2 a ray formatio Fic. 9. 429 430 “‘fournal of Comparative Neurology and Psychology. Fic. 10. Section through the brain of Conger .6 mm. farther caudad, passing through the median funicular nucleus at its widest part and including the lowest spinal vestiges of the somatic and visceral commissural nuclei and the nucleus ambiguus. The funicular nucleus includes also the spinal V nucleus and passes caudad directly into the dorsal cornu. Fics. 11 AND 12. ‘Transverse sections through the commissural nuclei of Amia calva L. Drawn from sections of a young fish about 7 cm. long stained in iron hematoxylin, kindly loaned to me by Professor CHARLES BRooKOVER. Fic. 11. Section through the visceral commissural nucleus at the level of the most caudal rootlet of the vagus nerve. The area marked somatic sensory field contains the extreme cephalic part of the funicular nucleus and the fasc. dorso-Jat. contains the spinal V root in addition to other elements. X55. Fic. 12. Section through the somatic commissural nucleus at the level of the first dorsal spinal root. The visceral nucleus has entirely disappeared at this level. X55. ; Herrick, Commissura Infima. 431 . ‘ \ - 749 Vise. COmMLS. NUE. */ 2 ~ sp.V- Bee rx. dors. 2$p. rv somatic commis(Zé_ nucleus formatio nue. ambigquu reticularis VLSC, COMMLS. NWO Fi Fite J ° é . dors. — —~Wr= Isp eye funie. dorsajis_-_ —_ 1 *s_\ nuc.funi¢. medialis | GES es y . ‘ an Da Apa EVERSION AND INVERSION OF THE DORSO-LATERAL WALEED RE RENE PARTS OF THE BRAIN: BY C. U. ARIENS KAPPERS, Amsterdam. With Five Ficures. In the Anatomische Anzeiger, Bd. xxx, 1907, and in a more extensive way in the Folia Neuro-biologica, Heft 2, 1908, THEU- NISSEN and [| have given a comparative description of the dif- ferent forms of forebrain, as they occur in vertebrates, from which it resulted that in Cyclostomes and in Selachians the upper part of the lateral wall of the forebrain is bent in a medio-dorsal direc- tion, forming a sort of pallium, whereas in Ganoids and Teleosts this same part is bent ventro-laterally, so that the primitive brain- mantle which is inverted in the former is everted in the latter. I further called attention to the fact that this primitive mantle should be called paleo-pallium, as it is older than the archipal- lium, receiving only secondary olfactory fibers, whereas the archipallium receives tertiary olfactory fibers, and further that in those animals where the palao-pallium is everted it is always greatly reduced in size compared to the inverted palzo-pallium of Cyclostomes and especially of Selachians, and that this reduc- tion of the palzo-pallium gives rise to the formation of the medial epistriatum’ of Ganoids and Teleosts, which has a vicarious function. For this reason we find either a large and inverted palao-pallium and a feebly developed epistriatum or an everted palao-pallium and a large epistriatum. The ontogenetic development of the prosencephalon in Ganoids (ALLIs, Vv. KUPFFER) makes it probable tu me that these differences find their origin inthe form of the skull in embryos, which in a cer- tain stage of development probably pressed on the brain, so that an extensive growth of the dorso-lateral part of the forebrain wall was made impossible. The ventral part of it took then a great deal of its function by means of an enlargement of the striatum ' Not visible in Fig. 2, which is drawn after a section anterior to the epistriatum. 434 ‘fournal of Comparative Neurology and Psychology. (epistriatum) by which again the dorso-lateral wall was more pushed in a ventro-lateral direction. That really the large epistriatum is an important factor for the eversion of the dorso-lateral forebrain wall is clearly proved by the Teleosts, where the epistriatum on an average is larger than in the Ganoids, and consequently the eversion of the palzo- pallium is also more striking, ‘The same is seen in one of the bony Ganoids, Amia calva, where the epistriatum is larger in the middle of the forebrain, where consequently the eversion of the latero-dorsal brain wall is also more striking? than in the frontal IBiGeane Fic. 2 ~ oe Fic. 1. Frontal section through the posterior part of the forebrain of Galeus canis. Fic. 2. Frontal section through the anterior part of the forebrain of Amia calva. BYGs3 Fic. 4. Fic. 3. Frontal section through the medulla oblongata of Galeus canis. Fic. 4. Frontal section through the medulla oblongata of Hexanchus griseus. or caudal parts of the fore-brain. ‘These differences and homolo- gies were proved by an exact study of the course of the afferent forebrain tracts, which (namely, the tr. tania) proved that this interpretation was right. Nearly the same ideas about the different forms of forebrain have been published by StupnicKka, who however gave only morphological proofs for this conception and whose interpreta- tions were not generally, or rather were generally not, accepted, probably because the conception of a palo-pallium was never ? Chimera monstrosa has a forebrain of which the morphology shows both forms of development, as in the frontal part of the forebrain the palzo-pallium is large and inverted, whereas in the posterior part of it, it is everted and reduced. Kappers, Eversion of Brain Wall. 435 exactly defined; and he with FRizpricH Meyer regarded the olfacto-habenular tract, which in Cyclostomes for the greater part originates in the palzo-pallium, as a homologue of the cor- tico-habenular tract of Reptiles and Mammals, not making an exact distinction between the pallium of fishes and the archipallium of higher vertebrates, which was not right, an archipallium and archicortex being entirely absent in the former. Amongst others Prof. J. B. JoHNsTon criticised this point of STUDNICKa’s work and I can only join him in this.’ Referring for the description of the forebrain tracts in different animals (I studied the vertebrate series from the Cyclostomes to the Chiroptera) to my work in the Folia Neuro-biologica, | here only want to draw attention to the fact that the differences above mentioned for the dorso-lateral forebrain wall also occur in other parts of the brain. Fic. 5. Fic. 5. Frontal section through the medulla oblongata of Chimera monstrosa. If we compare figs. 1 and 2, which represent two different forebrain types (Galeus canis and Amia calva) with figs. 3 and 4 which are made after sections through the medulla oblongata of different Plagiostomes, we see at once that the same contrast concerning the form of the dorso-lateral wall is also present between the hindbrain of Galeus canis on one side and Hexanchus griseus on the other. The nucleus of the nervus lateralis anterior, which in most sharks is bent inward, so that it lies under the cerebellum, 1s turned outward in Hexanchus, and Chimera monstrosa (fig. 5) exhibits a character which keeps about the middle between these extreme forms, as the same nucleus, though inverted, is not nearly 3 On the other hand I do not consider Professor JoHNsTon’s nomenclature, as far as concerns this question, very happily chosen, as he would better make a difference between the epistriatum of fishes and the primitive mantle-portion, paleo-pallium, which morphologically are very different things. 436 “fournal of Comparative Neurology and Psychology. as far inverted in this animal as it is in Galeus, Mustelus, Scyllium and other sharks. Contrary, however, to what is seen in the forebrain, that the eversion always accompanies a reduction of the palao-pallium, the nucleus nervi lateralis anterior in Hexanchus is not smaller than in other sharks, or, better, this nucleus in Galeus and other Selachians is not larger than in Hexanchus, being never very large in transverse sections (in comparison with inverted palao- pallium forms) so that reduction of its size and a replacing of its function, for instance, by further development of the end- -region of the VIII and posterior lateral nerve seems not at all necessary in this case. It is not easy to say which factor exactly has caused this strange position of the nucleus lateralis anterior in Hexanchus; it might be a traction in the lateral direction by the anterior later- alis root, about which, however, we have no certainty. LITERATURE CITED. STUDNICKA. Beitrage zur Anatomie und Entwickelungsgeschichte des Vorderhirns der Cranioten. Sitzungs- berichte der bohmischen Gesellschaft der Wissenschaften. Mathem.-naturwissenschaft- liche Classe. 1895, 1896. Nach einige Worte zu meinen Abhandlungen iiber die Anatomie des Vorderhirns. Anat. Anzeiger, Bd. 13. 1898 . JouNsTON. The Brain of Acipenser. Fischer, Fena, 1901. The nervous system of vertebrates. P. Blakiston’s Son & Co., Philadelphia. 1906. ArRIENS KappeErs. The structure of the teleostean and selachian brain. ‘fournal of Comparative Neurology and Psychology, vol. 16. 1906. Untersuchungen iiber des Gehirn der Ganoiden Amia calva und Lepidosteus osseus. Abhana- lungen der Senckenbergischen Naturforschenden Gesellschaft in Frankfurt a/M. Bd. 30. 1907. ArIENS Kapprrs aa THEUNISSEN. Zur vergleichenden Anatomie der Vorderhirns der Vertebraten. Anat. Anzeiger. Bd. 30. 1907. Ariens Kapprrs (unter Mitwirkung von THEUNISSEN). Die Phylogenese des Rhinencephalons, des Corpus striatum und der Vorderhirn commissuren. Folia Neuro-biologica. Heft2, 1908. (W. Klinkhardt, Leipzig.) ALLIS. The cranial muscles and cranial and first spinal nerves in Amia calva. Fournal of Morphology, vol. 12. 1897. v. Kuprrer. Die Morphogenie des Central-nervensystems. (Abdruck aus dem Handbuch der vergleichen- den und experimentellen Entwickelungsgeschichte der Wirbelthiere von O. Hertwig. Bd. II). The Journal of Comparative Neurology and Psychology VotumE XVIII NOVEMBER, 1908 NUMBER 5 THE RELATIONS OF COMPARATIVE ANATOMY TO COMPARATIVE PSYCHOLOGY=2 BY LUDWIG EDINGER. (Translated from the German by H.W. Rand.) Wiru Five Ficures. The relation between animal psychology and human psychology constitutes an old problem. It has interested me since myearliest years of study. However, when I endeavored to learn from the literature more precisely how brain anatomy and psychic phe- nomena are related to one another in the lower animals, I dis- covered something very surprising. It is true that I found in all the text-books very promising illustrations of the brains of sharks, frogs, rabbits, and other animals, yet | remember as if it were today the lively undeception which I experienced when I found that in all the books, even in WunptT’s great work, the psycholog- ical part of the text made no reference to these illustrations. I discovered that psychology had made no further use of compara- tive anatomy than, so to speak, as a means of illustrating its texts. I gradually discovered the reason for this. In reality anatomy has had nothing to offer to psychology. The ideal goal of the study of brain anatomy is a very ambitious one. We desire so thoroughly to understand the organ with which psychic processes are associated that we shall be able to predict its functions, so that where observations are impossible— and that is really the case for a large part of the psychology of the lower vertebrates—we may even infer these functions. To be sure, we are still very far from this goal. When we consider what we know about the human brain, its overwhelming complexity seems even simple compared to what we have observed of its activities. But I hope today to be able to point out that, at least in the realm of comparative psychology, anatomy, pursued always in connection with observation of the living animal, can explain much 1 An address before the Third Congress for Experimental Psychology. 438 ‘fournal of Comparative Neurology and Psychology. which has hitherto been unknown, and that particularly it is a source of much stimulation and clarification in the realm of sense psychology. You will recognize with me that even today the constitution of the brain in the lower vertebrates enables us to predict most of the activities which we observe in these animals. I divide the brain into the pal@éncephalon and the neéncephalon. The palzéncephalon appears, with all its characteristic sub- divisions, from cyclostomes to man. No part is ever entirely absent; its type remains unchanged whether we have before us the brain of a shark or the brain of an elephant. It is the oldest portion of the entire central nervous system, and many animals possess nothing but it. The neéncephalon, however, develops ray lob acust lat a lob vagi Satcus —~ Ggl.mes.lat. Aypopk. “95° Fic. 1. Brain of Chimera monstrosa. above fishes. From very small beginnings in the selachians it increases to that enormous organ, the cerebrum, which in man fills almost the entire skull. I will illustrate the palzeéncephalon by reference to a figure of the brain of Chimzra monstrosa. This fish in reality possesses nothing but the paleéncephalon. From the nasal cavities in front, the olfactory nerves lead into the olfactory lobes and terminate there. Behind and above the olfactory lobes lies the corpus striatum covered by a thin plate whence in other animals the neéncephalon EDINGER, Comparative Psychology. 439 is developed. From these parts of the brain fibers extend back- ward through a long stalk, and in this stalk probably lie also tracts which lead into the forebrain from the peripheral region supplied by the trigeminal nerve. ‘Then ventrally there is a much folded sac, the hypothalamus, upon which lies the hypophysis, while dorsally there is a hollow sphere, the roof of the mid-brain, wherein termi nate the optic nerves which may be seenemerging from the chiasma just in front of the hypothalamus. The cerebellum rises in prominent folds over the roof of the mid-brain and behind it one sees a large lobe situated laterally on the oblongata. Here ter- minate the nerves for the sense of hearing and for the lateral line sense. Below is seen the oblongata which is very well developed, because even in Chimera the cranial nerves whichemerge from it are extraordinarily large. This apparatus is thoroughly suited by its inner connections, which are now well known, for the reception of sense impressions from the outside world and for conveying them to various places whence groups of motor ganglion cells send out their nerves to the muscles. It also includes a number of special regulatory mechanisms, amongst which the cerebellum is most important. The motor mechanisms are everywhere united into motor-com- plexes in such a way that a sensory impulse brings about the move- ment, not of a single muscle, but always of a group of muscles adapted for some special action. Even isolated parts of the palaéncephalon are capable of simple reactions. For example, a ring cut from the neck region of a male frog embraces the female, if the skin of the breast comes in contact with the skin of the female, exactly as the whole animal does (Gottz). In fact, the embracing reflex may be induced even if one rubs the skin of the male with the juice ofeggs. I need not in this place point out that all the mechanisms for movement— swimming, flying, and the like—are so lodged in the palaéncephalon that the animals are able to execute these movements for some time after the removal of the neéncephalon. ‘This was demon- strated two thousand years ago by the ostriches which ran about Rome’s arena with their heads pierced by arrows. No part of the palazéncephalon can be absent without a corre- sponding function becoming lost, and all parts develop in size according to the demands which the activities of the animal make upon them. A knowledge of the degree of development is of the 440 ‘fournal of Comparative Neurology and Psychology. highest importance for sense psychology, as may readily be shown by a single example. That part of the brain which in man and other mammals is undoubtedly concerned with the sense of smell exhibits a constant arrangement and microscopic structure, not only in them but in all vertebrates down to the cyclostomes. We are therefore thoroughly justified in the conclusion that an animal which possesses this part smells, even though from its behavior nothing may safely be inferred. Indeed we may judge of the importance of the sense of smell to the animal according as this organ is large or small in relation to the remainder of the brain. The olfactory lobes vary greatly amongst the mammals, and the following example which I select from the lizards enables you to see that here, too, very considerable differences in the sense of smell occur in different species. In Chameleon, which obviously seeks its prey by means of the eyes, the roof of the mid-brain, where the optic nerves end, is very large while the olfactory lobes are extremely small. ‘The nearly related lizards have enormous olfactory lobes. It has long been disputed that birds possess a sense of smell. Anatomy however shows us that they possess true, although small, olfactory lobes. ‘This simply and satisfac- torily settles the much discussed question, and in fact there are today observations enough which make the presence of an olfactory sense at least very probable. The vulture and the eagle are attracted by concealed prey and ravens find dead animals in a thicket, even when they are deeply buried or covered with snow. RoTHE saw in Lithuania, at a temperature of 24°, that the sea- eagle scented out a dead animal deeply covered with snow, uncovered it, and devoured it. “The woodcock finds worms which are deeply buried. It inserts the beak only to withdraw it with a worm. A blackbird pecks industriously at the ground and digs out a grub which lay fully five centimeters below the surface. It must be that our ducks smell under water, for they dive suddenly down into the mud and come up with full bills. “The refraction of the water must prevent their seeing anything on the bottom. The degree of development of the various parts of the palzén- cephalon will always give us information as to the possible activi- ties of the animal. If, however, anatomy solves one problem, it suggests, as the following shows, new problems in sense psychology. Probably EDINGER, Comparative Psychology. 441 in the lizards, and certainly in the birds, a large fiber-tract lead- ing from the nucleus of the trigeminus terminates in a field situated close behind the olfactory apparatus. ‘This field, the lobus par- olfactorius, attains an enormous size in birds and the question arises as to what function this structure can serve. he importance of the beak, which is innervated by the trigeminus, the extraordi- narily rich trigeminal supply about the mouth and in the tongue, and the further circumstance that stimulation of the lobus par- olfactorius produces movements of the beak, lead one to the con- clusion that we have here a center for the territory innervated by the trigeminal nerve, that is, a hitherto quite unknown feature of the brain. JI am now engaged, together with Dr. KappeErs, in tra- cing out this apparatus and we are able even now to declare that in all vertebrates up to the mammals there must exist an as yet ‘scarcely studied sense which 1s localized about the mouth and has its center in the lobus paroljactorius. In the chameleon, with very small olfactory nerves, this lobe is almost as large as in birds, and we should remember that this animal catches its food by extending its tongue. We know how significant in fishes is the investigation of food by means of the barbels and the tip of the snout, how serpents are guided by touching with the tongue, and as we trace these functions, which we may tentatively designate as the oral sense, upwards in the scale we find, not without sur- prise, that even the mammals possess in this same locality a brain structure which is small and atrophied in those whose snout plays no important role (man, the apes, and ruminants), but which becomes a giant structure in mammals, of the most diverse orders, so far as they make extensive use of the snout. In the brains of the hedgehog, the mole, the armadillo, also in swine and the elephant, the lobus parolfactorius is strongly developed. In man it has completely disappeared except for a vestige in the atrophied lamina perforata anterior. So much for the oral sense. It is little enough, yet it shows that sense psychology acquires an entirely new problem from anatomical studies. According to the degree of development of the olfactory lobes in mammals much may be inferred as to the condition of the olfactory sense. Since these matters have been well known from the time of Broca, I will now only briefly refer to the fact that these lobes in the lower mammals make up more than half of the entire brain, that in the beasts of prey they play an important 442 fournal of Comparative Neurology and Psychology, role, that in man and the apes they are reduced to a small structure, while in the aquatic mammals they are completely absent. No one will deny that the various degrees of development of the parts of the palaéncephalic olfactory apparatus furnish most impor- tant problems for psychology. I should like to show you by means of two more examples how the development of the paleéncephalon is dependent upon the demands of the outside world. The roof of the mid-brain, which receives upon the one hand the optic nerves and upon the other hand secondary sensory tracts, is much more strongly developed in birds and fishes than in any other vertebrates, but in blind animals it may be atrophied. In cases where we find such anatomical atrophy, we should be stimulated to investigate the capacity for sight. Then it appears that in animals (Proteus) which are entirely blind certain tracts of other sensory mechanisms are especially strongly developed. ‘Their mode of operation presents stull other problems. The size of the cerebellum is so completely dependent upon life habits that in some sedentary animals it has completely disap- peared, while in weak swimmers (eel, flounder) it 1s very small, but in the strong swimmers and fliers it attains enormous size. In so nearly related animals as the land and water chelonians the former have a cerebellum less than half as large as that of the latter. Much futile work on the physiology of the cerebellum would have been spared us if we had regarded these facts of comparative anatomy. Finally, let me refer again to the important apparatus of the lateral line sense of the fish. Because of the obviousness of its end organs in the skin, this sense fortunately has found many investigators and now we know through the investigations of Fucus, and of Huser that this entire apparatus enables the animal to detect changes of presstire in the water, particularly the resistance which it encounters in swimming. Here anatomy has led to physiological investigation. The paleéncephalon alone is present in the bony fishes. The activities which depend upon it we will designate as paleéncephalic activities. Since in all other vertebrates, with the appearance of the neéncephalon, quite different—neénce phalic— activities make their appearance, it is of the greatest importance to study thor- oughly the activities of fishes. The central nervous apparatus of the EDINGER, Comparative Psychology. 443 fish doubtless serves for all the receptions necessary to the animal, for all regulations, and for all the movements which the animal’s relation to the outside world demands, that is, for locomotion, for obtaining food, and for the reproductive activities. Not only all the activities which we commonly designate as reflex, but also all instincts, are localized in the paleéncephalon. Flight when sur- prised, migrations, nest-building, courtship, and many other activ- ities are to be observed in the bony fishes. On theoretical grounds it has particularly interested me to ascer- tain if fishes learn. From my own observations, from the litera- ture, and from hundreds of contributions which I have received in response to an inquiry, it 1s now well established that new kinds of receptions, provided that they affect the inherited motor mechan- isms with sufhcient intensity or sufhciently often, stimulate them. The animals /earn in a very moderate degree to modify their ac- tivities. One can tame them, and train them not to flee, so that they allow themselves to he held in the hand; or they may be called to food at a certain place or a certain time. ‘They can learn to swim to a particular person who feeds them. ‘These associa- tions become so well established that, for example, my Macropoda, which I never feed myself, swim up as soon as I appear because, five months before, they had always been fed by anyone who approached. A pike which has several times escaped the spear becomes more cautious and learns to avoid it. But fishes always return to the hook so long as the bait presents the same appearance, for it is not the fish which attracts the prey but the prey which attracts the fish. If the bait is unusual in appearance it does not attract. All the experience of anglers goes to show that fish will not go to poorly arranged bait. ‘That, however, does not neces- sarily indicate intelligence, for if they possessed the genuine intelligence which has occasionally been attributed to fishes, we should expect that sometimes they would be caught by inappro- priate bait. As a rule fishes respond to particular sensory stimuli by the execution of certain definite combinations of movements. But their brain is able to relate a new sense impression with a movement combination which formerly had not answered to it. I propose to designate this lowest kind of association by the term establishing of relations, but to reserve the term connecting of associations for those totally different processes of the brain which we observe after the appearance of the neéncephalon. Such very 444 ‘fournal of Comparative Neurology and Psychology. unlike mechanisms are required for the two processes that this distinction seems well justified. Since itis certain that the palaénce phalon persists quite unchanged even after a well developed neéncephalon has been added to it, there is no ground for regarding those activities which we recognize as palazence phalic in one class of animals as anything else or as other- wise localized in higher animals. Furthermore, we may regard an entire series of acitvities as common to all vertebrates, and we may then seek to ascertain how other activities are added to these when a new structure 1s added to the paleéncephalon. All sense impres- stons and movement combinations belong to the paleéncephalon. It ts able to establish simple new relations between the two, but it zs not able to form associations, to construct memory images out of several components. It 1s the bearer of all reflexes and instincts. Through the separation of palaéncephalic and neéncephalic activities we gain an entirely new pointof view and statement of the problem for sense physiology. Ifthe palaéncephalon can not form associations, then those animals which depend upon it entirely, or almost entirely, must remain unaffected by many sense impressions to which, according to our own experiences or according to our knowledge of the sense organs of these animals, we should expect them to give some response by movement. A lizard which listens to the slight rustling of an insect in the grass remains quite at rest, as my own investigations have shown, when one pounds upon a stone Just over its head, or when one calls loudly, sings, or makes an uproar. The animal, otherwise so shy that an unexpected shadow or a slight shaking of the ground caused by my step makes it disappear, does not flee. With these new sounds, which bio- logically it never encounters, it associates nothing, just as a warn- ing placard written in Clinesccouldinever seueane omen abyss. The mechanism for conveying new stimulations to the old inherited movement complexes is entirely lacking to it. The reptiles must all appear to us practically deaf, although they do hear. It is said that turtles react to music, but that is yet to be proved. YERKES has demonstrated to us that amphibians do not flee from noises and the sound of a bell. Yet his talented researches have shown us that the acoustic nerve is in some way stimulated by these sounds. It is well known, however, that frogs call loudly at mating time in order to attract the female, and Professor BorTrcHER has informed me that he was able to attract a tree-frog EDINGER, Comparative Psychology. 445 by imitating its cry with a metal mortar. Clearly, then, these ani- mals hear very well that which concerns them. It has also been shown by Pieper that in fishes, which according to all the accounts hitherto given, appear so deaf, negative variation in the auditory nerve is caused by the sounding of a tuning fork. How much work has been done entirely in vain because we have not as yet fully ap- preciated the fact that, in the absence of a mechanism for associa- tion, nothing but the biologically adequate stimulus can bring about movement! Why should a fish flee, as we have always hitherto expected, at the sound of a bell or of a tuning fork? Sounds of that kind mean nothing to the animal unless—and I consider this possible—it has been brought into relation with them by training. Thus we find ourselves compelled to divide sense stimuli into those which are biologically adequate and those which operate only by association. As one readily sees, here arise new problems for investigation. But now we have reached the limit of the possi- bilities of the palaéncephalon. I suspect that thus far in my address you have been under the impression that what I have been presenting is not psychology but physiology. [am entirely in accord with that, if we under- take to draw sharply the line between psychology and physiology upon the ground of our newly acquired anatomical knowledge. No objection can be made if, not for all time, but tentatively, we exclude all the above mentioned activities and also all instincts from purely psychological consideration. As a knowledge of the literature continually reminds me, the instincts hitherto have rendered difficult a consideration of the truly psychological phe- nomena of animals. In the literature—and one need think only of what has been written about birds—they are continually intruding to pervert our general views. ‘This proposition to regard the simple activities and the instincts of animals as sharply separated from the other psychological processes, a proposition to which I have been able to come only through a comparison of the anatomy with the activities, is not a fundamental one but only methodological. It will call forth your objection. But I hope in the second part of this discussion, which will concern itself with the neéncephalon, to be able to show you that it is not so entirely impracticable. The neéncephalon, the bearer of the cortex, develops in the roof of the brain, beginning as a rudiment which is evident even in the 446 ‘fournal of Comparative Neurology and Psychology. selachians and becoming more and more conspicuous in am- phibians and especially in reptiles. By reference to fig. 2 one may see how the palaéncephalon persists unchanged underneath the very important neéncephalon. In the neéncephalon of reptiles there appears for the first time, and very definitely, a mechanism which by means of numberless connections within itself provides the possibility for association. In the first rudiment of the cortex these connections are already so numerous that they can scarcely be overlooked. Even in the lizards the number of associations rendered possible by their net- work is inconceivable. Fic. 2. Acat brain and the brain of Chimera (see fig. 1) combined in order to show the increase resulting from the addition of the neéncephalon. Investigations which have occupied me for years make it pos- sible to declare with certainty that the oldest cortex becomes con- nected with those parts of the paleéncephalon which serve the sense of smell and the oral sense, and subsequently other cortex regions are gradually superadded to this. With the appearance of the neéncephalon the behavior of the animal becomes completely changed. Let us first consider the obtaining of food, because that is the best of the activities to study —indeed the lower animals present to the observer no other form of activity so often as this. We have recognized as the characteristic of the palaéncephalon that when stimulus and disposition are the same, the same activities always result, so that they may be predicted. EDINGER, Comparative Psychology. 44.7 Hungry animals if they possess only the palzéncephalon seize food under all circumstances, provided the stimuli which proceed from it are appropriate, but only then. An animal which is incited to seizing only by a moving body never recognizes the Amphibian. Reptile. Mammal. Fic. 3. The evolution of the neéncephalon (black) and the regression of the paleéncephalon (gray). same body if it is at rest. All of these animals can be caught with bait if one has ascertained the proper stimulus. Fishes which, like the trout, go toward swiftly moving and glittering insects can easily be caught by imitations of such insects constructed of metal 448 “fournal of Comparative Neurology and Psychology. and feathers, providing the angler rightly imitates the hopping movement. The entire art of angling, concerning which we possess large volumes, depends upon knowledge of the proper stimulus and upon the excluding of disturbing stimuli, such for example as a thick fish-line. Frogs may be caught by means of heath-berries dangled before them ona string. Even the frog has a rudimentary neéncephalon, but so far as my observations go, it plays no part in the obtaining of food. It still eats palaéncephalically. No matter how hungry a frog may be, it seizes the earthworm only when it crawls, or catches the fly only when it makes some move- ment. One may lay a worm on the frog’s snout or may in any way bring the two in contact, but eating does not result. ‘The worm acts as a stimulus only when crawling, otherwise it is not recognized. One can very clearly observe how the entire operation of eating results from the addition of very definite reflexes. “The crawling worm first induces, by way of the optic nerve, possibly also by way of the acoustic nerve, a turning of the head; if it crawls further a new stimulus is added, and then the body is turned, the head sinks and, if the stimulation continues, the seizing results. If, as frequently happens, the animal misses the prey it does not immediately strike at it again. The worm must crawl further and the entire series of reflexes must be repeated. If the worm stops crawling, the series is at that moment interrupted. Upon the other hand, an object which is not eatable gives rise to the seizing act provided that the same stimuli proceed from it as from the worm. HAanau saw a toad follow and repeatedly snap at a blind-worm’s tail for hours. The sense stimuli which lead reptiles to the obtaining of food are not materially different from those just described. Most ser- pents, all lizards, and the carnivorous turtles appear not to see motionless prey. However, they do not rush recklessly at moving prey as does the frog at the heathberry, but they orient themselves with respect to their food by sniffing or by touching with the tongue. In some cases the stimulus is received through the sense of hearing. But the serpents appear not to use this sense, for a very hungry animal does not change its attitude when a mouse squeaks or a bird calls. What, then, are the differences in behavior which depend upon the presence of the cortex in serpents? Is it possible from the structure of the cortex to formulate problems for observation, and EpINGER, Comparative Psychology. 449 how far does observation of the behavior of the animals accord with the fact that a new mechanism has been added to the palzén- cephalon? The cortex of serpents consists of several layers of cells which are manifoldly connected by means of countless fibers. Judging from our knowledge of mammals, we should naturally take the view that such a mechanism renders possible the holding back of an impression and the associating of one impression with another. The tracts which lead to this association mechanism come from the center for the olfactory and oral senses. Others, such as tracts from the center for the optic nerve, have not yet been found in the animals which have been studied. ‘This is in accord with the fact that the reptiles recognize prey optically usually only as some definite combination, such as the mov- ing mouse, the moving frog. The optic impression of the resting mouse does not by itself suffice to induce seizing. But one readily sees that these animals use the olfactory and oral senses very differ- ently from the amphibians. A serpent, by touching with the tongue, determines whether it has an animal of one kind or of another. It marks where a food animal has been resting and finds it by following it to its lair. By testing the surface of the water with the tongue the ringed-snake determines if there are fish in the water. The oral sense is very much used. Occasionally the ani- mals try to devour pieces of wood upon which prey has rested and left its odor, but after touching they turn away. Zamenis, by touch- ing, selects a pigeon egg from amongst a number of turtle eggs of the same size. “The hungry serpent is restless, it makes slight movements, touches the ground, it seeks food—something which the frog is never observed to do. In another respect reptiles differ from those animals which do not possess a cortex. If the latter fail to obtain the prey which has stimulated them to eat, they remain quiet until a new stimulus appears. Not so with reptiles. Serpents, once stimulated by a jumping frog or a running mouse, follow their prey at least for a time and, guided by the olfactory and oral senses, they are able amongst a number of holes to find that particular one into which the prey has crept. Finally, there first appears in reptiles some- thing which indicates that they occasionally foresee what may follow from a certain experience. Many lizards and serpents assume an attitude of defense when danger threatens. ‘They direct the head toward the enemy, raise the forward part of A 450 ‘fournal of Comparative Neurology and Psychology. body, and open the mouth to bite. I have never observed any- thing of that kind in a palzéncephalic animal. Probably it is due to the neéncephalon, too, that first in the reptiles we meet with individual differences. Within the same species there are indolent and excitable, dull and lively individuals. Everyone who has kept many mud turtles knows this. Reptiles learn more easily and quickly than fishes. One can teach turtles to come to be fed at the sound of clapping. They also learn to follow correctly the path which leads to good food and will work all day long against obstacles. StEGWART’s turtles worked themselves repeatedly through successively narrower grat- ings to an aquarium containing Proteus. ‘They even climbed over fences which were interposed and placed themselves on edge in order to get between the bars. Finally, reptiles which naturally follow only jumping prey learn to recognize resting prey. Aside from the obtaining of food, the life of reptiles consists merely in resting and sunning themselves. ‘Therefore, in so far, we recognize no very marked differences between reptiles and amphibians. Most important in the psychological behavior of reptiles is the fact that the animals are no longer always dependent upon the sense impression of the moment, but that earlier impres- sions influence them. Further, they associate certain sense impressions which lie within the realm of the olfactory and oral senses, and turn them to account; they learn more easily than fishes and amphibians; occasionally they foresee; and they exhibit individual differences. ‘There can be no doubt that all of these facts are referable to the appearance of a cortex in the néen- cephalon. So far as our observations go at present, genuinely psychological processes make their appearance at this point in the animal series. It is certainly possible that they may occur even in the selachians and particularly in the amphibians in connection with the begin- nings of the cortex, but they are so rudimentary that they will probably be found only when attention is especially directed toward them. From the brain of the reptiles two different types of brain are derived. One, the type found in the lower mammals, develops by increase of the cortex; the other is the avian type. In birds the cortex is more highly developed than it is in reptiles. The increase in the bulk of the brain, however, actually results Epincer, Comparative Psychology. 451 from the enlargement of the palazéncephalon whose various parts here reach a perfection which they attain nowhere else. We know that in birds nearly all parts of this palaéncephalon are connected with the cortex; that particularly the brain-part connected with the oral sense (the lobus parolfactorius) is of enormous size; and finally, that from the optic termini anespecially large number of fibers lead to the cortex. A priori one would infer from this structure that the instinctive actions must be of much greater variety and perfection, and that also the capacity for forming associations must be much greater than in reptiles. As a matter of fact, the investigation of the psychic behavior of birds—I am speaking now of nest-building, migration, and courtship—has met certain difficulties in the numerous strong instincts whose perfection is so great that it has not always been possible to distinguish them from activities which are dependent upon the cortex. Although we possess many works dealing with the behavior of birds, the observers have only very seldom en- deavored to maintain an objective point of view. I regard the works of WuRM and GREPPIN as among the best. If one leaves out of account instinctive actions, one is struck with the fact that the new (as compared with reptiles) connections of the palzen- cephalic optic termini with the neéncephalic cortex play the all important role in the behavior of the animal. Birds see and recognize; a single visual characteristic of the object often enables them to judge of the whole. Their actions are for so longa time influenced by a thing seen that one must infer that they possess and make use of memory images. Ducks soon recognize the hunter’s screen and avoid it after several of their number have been killed. Ermer relates that on the first day he caught thirteen sparrows in a newly constructed sparrow trap, but afterwards no more. ‘Two years later the trap was again set up but not a bird went into it. Game birds learn so well to recognize the hunter that they distinguish him from wood-choppers, wagons, horses and the like, just as do wild mammals. Upon this fact are based many of the tricks of hunting, such as stealing up behind a horse or arranging a trap under a screen upon which is painted a cow. When partridges see the falconthey crouch downanxiously. ‘Thus it is often the practice to arrest a scattered covey by means of a painted paper kite and then to kill the birds (WuRM). Only birds 452 fournal of Comparative Neurology and Psychology. can be frightened from fields by scarecrows, only the bird of prey recognizes its victim in the far distance, only amongst birds do we find creatures which, like the carrier pigeons, retrace the path once seen. Everyone who in winter strews crumbs of bread from a window observes how upon all sides the birds watch his action, but approach only after he has closed the window. Accordingly these animals, which are the first to possess an optic tract leading from the palzéncephalon into the cortex, are likewise the first to so far understand and retain optic impressions that they may long afterward be employed to bring about rela- tively complicated actions depending upon associations of many kinds. But when ScHRADER deprived his falcon of its cortex it fell at once into the condition of a palzéncephalic animal. Running mice were readily caught by the injured bird, but mice which had crept under the falcon’s wings remained unrecognized and gradu- ally devoured their host, which, as a merely palaéncephalic animal, could no longer recognize them associatively. Birds hear very well. It is probably only a palzéncephalic hearing when the female follows the call of the male; but magpies, ravens, and parrots learn to come when their names are called and birds of many kinds learn to imitate whistled melodies or even pronounced words. In spite of many anecdotes, there is as yet no conclusive proof that parrots understand language, but there can be no doubt that they employ the same words upon similar occasions. It is anatomically uncertain if the oral mechanism is connected with the cortex, and the behavior of the animals scarcely indicates that it is. The action of a bird in digging up worms which are six centimeters under ground can just as well be accomplished through the mechanism of the palzénce phalon. Quite new as compared to the reptiles are certain indications of true intelligence. Of course it is difficult here to avoid being deceived as to the significance of acts. But when a parrot learns always to plunge its hard bread into water before eating, and when animals which have been repeatedly disturbed at one nesting place remove the nest and seek a place inaccessible to the danger first experienced, we can find no other name for this kind of associa- tion-formation than intelligence. This intelligence is very clearly EDINGER, Comparative Psychology. 453 seen when an animal assures itself of safety, a matter which GrePPIN has especially studied. Every bird before alighting or before taking food looks about on all sides very knowingly. This inspection is not an inherited habit but, as shown by GReEPPIN’s observations on young blackbirds, is acquired. Very young birds at every Jar, every noise, stretch out the head and open the bill. It is only later that they learn the opposite behavior. Ground birds acquire the habit of assuring themselves much earlier than birds of the air. Visual images and scociations surely play an important role in this assurance. Crows, which remain quietly at rest as one approaches, fly away as soon as one of them is shot, and thereafter they can be shot only from ambush. Birds very carefully seek out a place for their nest and often reinforce it purposefully with very remarkable supports. It is not conceivable that all these actions should take place without the participation of the cortex, for they involve numerous memories and associations. It must also depend upon the presence of the cerebral cortex that birds are particularly easy to tame and that they may be trained to a large number of performances. ‘Thus, they learn to modify the old hereditary behavior; in fact such activity rules in close relation with instinct, as one may see in the feeding of nestlings by the mother, or in the teaching of young storks to fly. What the anatomy of the bird brain leads one to expect is in excellent accord, as one may see, with the results of studying the behavior. The differences between reptiles and birds are easily referable to anatomical differences in the brain. ‘To be sure, it must be the task of further observation to elaborate what is here set forth; above all things, to determine what activities of the lower vertebrates are palaéncephalic and what are neéncephalic. Ac- cordingly, reptiles and birds must be studied much more thor- oughly than they have been hitherto, because we have demon- strated the first appearance in them of activities which depend upon a cortex and these activities occur in relative simplicity. It is also an important question whether neéncephalic reflexes and instincts exist. We have come to know fishes as strictly palaéncephalic animals. In reptiles and birds a small neéncephalon coéperates. Finally, in the mammals we meet a brain which has so large a neénce phalon that we may well expect a subordination of reflexes and instincts 454 | pean? 2. ee 1 es 3 4 5 6 5) 8 9 fe) Series ¥ | . A i r 1 r ] r 1 r ] r B rem || eeall TaN al i l r ] r l Ree ONS ONI AnNHhW WY HF OW CON ANAW WD Re WR iS as) Rw bs ie els eee Mos iS eS | Ce el ll ll ells Me Ae Oe Se en BO HR eH er Hee BO RH RH ee eee ee He lel eoetn Miels Wile Miles Mie MMS i | ti Mlle Mlle Well ets Mes SS a er oy in le Mle Melle Millis Mes MS i: i i a re Oe ee ea iin Mien Mie ie Mls Mis MS MS i i: a | ee ee ee ie) side of the box and the other on the inside, as fig. 1 indicates. The latter consisted of three sections of which two constituted linings for the sides of the box and the third a cover for a portion of the open top of the box. In no case did these inside cards extend the entire length of the electric boxes. The white and black cards were readily interchangeable, and they never were left on the same electric box for more than four consecutive tests. The 462 ‘fournal of Comparative Neurology and Psychology. order in which they were shifted during twenty-five series of ten tests each, in addition to the preference series 4 and B, is given in table 1. In case a mouse required more than twenty-five series of tests (250 tests), the same set of changes was repeated, beginning with series 1. In the table the letters r and / refer to the position of the white cards; r indicates that they marked the electric box which was on the right of the mouse as it approached the entrances of the electric boxes from the nest-box; / indicates that it marked the left electric box. The way in which this apparatus was used may be indicated by a brief description of our experimental procedure. A dancer was placed in the nest-box by the experimenter, and thence it was permitted to pass into the entrance chamber, B. The experi- menter then placed a piece of cardboard between it and the door- way between 4 and B and gradually narrowed the space in which the animal could move about freely by moving the cardboard toward the electric boxes. ‘This, without in any undesirable way interfering with the dancer’s attempts to discriminate and choose correctly, greatly lessened the amount of random activity which preceded choice. When thus brought face to face with the en- trances to the boxes the mouse soon attempted to enter one of them. If it happened to select the white box it was permitted to enter, pass through, and return to the nest-box; but if, instead, it started. to enter the black box the experimenter by closing the key, upon which his finger constantly rested during the tests, caused it to receive an electric shock which as a rule forced a hasty retreat from the black passage-way and the renewal of attempts to dis- cover by comparison which box should be entered. Each of the forty mice experimented with was given ten tests every morning until it succeeded in choosing the white box cor- rectly on three consecutive days, that is for thirty tests. A choice was recorded as wrong if the mouse started to enter the black box and received a shock; as right if, either directly or after running from one entrance to the other a number of times, it entered the white box. Whether it entered the white electric box or the black one, it was permitted to return to the nest-box by way of the white box before another test given. Escape to the nest-box by way of the black box was not permitted. A male and a female, which were housed in the same cage between experiments, were placed in the experiment box together and given their tests turn about YERKES AND Dopson, Habit Formation. 403 Almost all of the mice used were between six and eight weeks old at the beginning of their training. ‘The exact age of each, together with its number, is stated in table 2. This table shows also the general classification of our experiments. ‘They naturally fall into three sets. “These are designated by the roman numerals TABLE 2. Age in days, at the beginning of training, of each mouse, with a statement of the conditions of training. s | Mates. FEMALES. é IN, Sen trength of | Condition of discrimination. | ctimulus. Number. | Ageindays.| Number. | Age in days. : Weak | 128 50 127 50 Medium 125+ 10 134" 4) 250 133 43 Set I Medium 192 47 191 47 3oot25 | 194 47 193 47 | reer Strong | 130 36 129 36 Soot 50. 132 | 44 131 37 | 268 | 52 267 52 135 7a) lee Se 269 52 Great : 266 50 263 50 95 418 48 265 50 | 260 43 259 | 43 Set I 255 262 43 261 43 396 48 189 41 Easy ue 398 | - 195 | 43 Ane 280 40 279 40 412 | 74 281 43 135 | 290 44 199 53 Slight 195 288 45 223 25 sige 255 286 42 285 42 Difficult 375 284 42 283 42 I, Il, and II] in the table, and will throughout the paper be referred to as the experiments of set I, set I] and set III. As is suggested by the heading “condition of discrimination,” at the top of the first vertical column of table 2, these sets of experiments differ from one another first of all as to condition of visual discrimination or, more explicitly stated, in the amount by which the two electric 464 ‘fournal of Comparative Neurology and Psychology. boxes differed from one another in brightness. For set I this difference was medium, in comparison with later conditions, and discrimination was therefore of medium difficultness. For set II the difference was great, and discrimination was easy. For set III the difference was slight, and discrimination was difficult. It is clear, then, that the series of words, medium, great, slight, in the table refers to the amount by which the electric boxes differed in brightness, and the series medium, easy, difficult, to the demand made upon the visual discriminating ability of the mice. For the sake of obtaining results in this investigation which should be directly comparable with those of experiments on the modifiability of behavior in the dancer which have been conducted during the past three years, it was necessary for us to use the same general method of controlling the visual conditions of the experi- ment that had previously been used. ‘This we decided to do, not- withstanding the fact that we had before us methods which were vastly superior to the old one with respect to the describability of conditions and the accuracy and ease of their control. ‘To any experimenter who wishes to repeat this investigation with other animals we should recommend that, before recourse is had to the use of cardboards for the purpose of rendering the boxes distin- guishable, thorough tests be made of the ability of the animal to discriminate when the boxes are rendered different in brightness by the use of a screen which excludes a measurable amount of light from one of them. We have discovered that the simplest and best method of arranging the conditions for such experiments with the dancer as are now to be described is to use two electric boxes which are alike in all respects and to control the amount of light which enters one of them from the top. _ It 1s easy to obtain satis- factory screens and to measure their transmitting capacity. We regret that the first use which we wished to make of our results in this investigation forced us to employ conditions which are rela- tively complicated and difficult to describe. For the sake of the scientific completeness of our paper, how- ever, and not because we wish to encourage anyone to make use of the same conditions, we shall now describe as accurately as we may the conditions of visual discrimination in the several sets of experiments. The cards at the entrances to the electric boxes were the same in all of the experiments. Each card (the black and the white) YERKES AND Dopson, Habit Formation. 4.65 was 11.5 cm. in height and 5.4 cm. in width, with a hole 3.5 by 3-5 cm. in the middle of its lower edge as is shown in fig. 1. ‘These entrance cards were held in place by small metal carriers at the edges of the electric boxes. ‘The area of white surface exposed to the view of a mouse as it approached the entrances to the elec- tric boxes was 49.85 sq. cm. and the same amount of black sur- face was exposed. The white cardboard reflected 10.5 times as much light as the black cardboard. Special conditions of set I. ‘he inside length of each electric box was 28.5 cm. the width 7 cm. and the depth 11.5 cm. The inside cards extended from the inner edge of the front of each box a distance of 13.5 cm. toward the back of the box. Conse- quently there was exposed to the view of the mouse a surface 13.5 cm. by 11.5 cm. (the depth of the box and of the cardboard as well) on each side of the box. ‘The section of cardboard at the top measured 13.5 cm. in length by 6.5 cm. in width. The total area of the white (or black) cardboard exposed on the inside of an electric box was therefore 13.5 X 11.5 X 2 (the sides) + 13.5 X 6.5 (the top) = 398.25 sq. cm. If to this we add the area of the entrance card we obtain 448.10 sq. cm. as the amount of surface of cardboard carried by each electric box. But another condition, in connection with the amount of card- board present, determined the difference in the brightness of the boxes, namely, the amount of open space between the end of the inner cardboards and the end of the experiment box. The larger this opening the more light entered each box. In the case of the experiments of set I this uncovered portion of each electric box was 15 cm. long by 7 cm. wide; its area, therefore, was 105 sq. cm. Special conditions of set IJ. Both the outer and the inner card- boards were precisely the same in form and arrangement as in the case of set I, but in order that discrimination might be rendered easier, and the time required for the acquisition of the habit thus shortened, a hole 8.7 cm. long by 3.9 cm. wide was cut in the mid- dle or top section of the white cardboard. This greatly increased the amount of light in the white electric box. The difference in the brightness of the boxes was still further increased by a reduc- tion of the space between the end of the cardboard and the end of the box from 15 cm. to 2 cm. or, in terms of area, from I05 sq. cm. to 14,.sq.cm. This was accomplished by cutting 13 cm. from the rear end of the experiment box. For the experiments of set 406 ‘fournal of Comparative Neurology and Psychology. II the black box was much darker than it was for those of set I, whereas the white box was not markedly different in appearance. Special conditions of set III. “The experiments of this set were conducted with the visual conditions the same as in set II, except that there was no hole in the white cardboard over the electric box. This rendered the white box much darker than it was in the experiments of set I], consequently the two boxes differed less in brightness than in the case of set II, and discrimination was much more difficult than in the experiments of either of the other sets. In the second column of table 2 the values of the several strengths of electrical stimuli used in the investigation are stated. To obtain our stimulus we used a storage cell, in connection with gravity batteries, and with the current from this operated a PORTER inductorium. ‘The induced current from the secondary coil o- this apparatus was carried by the wires which constituted an inter- rupted circuit on the floor of the electric boxes. For the experi- ments of set I the strengths of the stimuli used were not accurately determined, for we had not at that time discovered a satisfactory means of measuring the induced current. These experiments therefore served as a preliminary investigation whose chief value lay in the suggestions which it furnished for the planning of later experiments. The experiments of sets I] and III were made with a PorTER inductorium which we had calibrated, with the help of Dr. E. G. Martin of the Harvard Medical School, by a method which he has recently devised and described.’ On the basis of the calibration measurements which we made by Martin’s method the curve of fig. 3 was plotted. From this curve it is possible to read directly in “units of stimulation” the value of the induced current which is yielded by a primary cur- rent of one ampere for any given position of the secondary coil. With the secondary coil at 0, for example, the value of the induced current is 350 units; with the secondary at 5.2 centimeters on the scale of the inductorium, its value is 155 units; and with the second- ary at 10, its value is 12 units. [he value of the induced current for a primary current greater or less than unity is obtained by multiplying the reading from the calibration curve by the value 17Martin, E.G. A quantitative study of faradic stimulation. I. The variable factors involved. Amer. Four. of Physiol., vol. 22, pp. 61-74. 1908. II. The calibration of the inductorium for break shocks. Ibid., pp. 116-132. YERKES AND Dopson, Habit Formation. 467 of the primary current. The primary current used for the experi- ments of sets II and III measured 1.2 amperes, hence the value of the stimulating current which was obtained when the secondary coil stood at 0 was 350 X 1.2 = 420 units of stimulation. Fic. 3. Calibration curve for Porter inductorium. The numbers below the base line refer to the position of the secondary coil with reference to the primary. The positions are read, as on the scale of the inductorium, in centimeters. The numbers in the margin represent values of the induced current in terms of Mart1n’s unit of stimulation. As conditions for the experiments of set I, we chose three strengths of stimuli which we designated as weak, medium, and strong. [he weak stimulus was slightly above the threshold of stimulation for the dancers. Comparison of the results which it yielded with those obtained by the use of our calibrated inducto- rium enable us to state with a fair degree of certainty that its value was 125 + 10 units of stimulation. ‘The strong stimulus was decid- 468 ‘fournal of Comparative Neurology and Psychology. edly disagreeable to the experimenters and the mice reacted to it vigorously. Its value was subsequently ascertained to be 500 +50 units. For the medium stimulus we tried to select a value which should be about midway between these extremes. In this we succeeded better than we could have expected to, for comparison indicated that the value was 300 + 25 units. Fortunately for the interpretation of this set of results, the exact value of the stimuli is not important. By the use of our calibrated inductorium and the measurement of our primary current, we were able to determine satisfactorily the stimulating values of the several currents which were used in the experiments of sets II and III. The primary current of 1.2 amperes, which was employed, served to actuate the interrupter of the inductorium as well as to provide the stimulating current. The interruptions occurred at the rate of 65 + 5 per second. We discovered at the outset of the work that it was not worth while to attempt to train the dancers with a stimulus whose value was much less than 135 units. We therefore selected this as our weak- est stimulus. At the other extreme a stimulus of 420 units was as strong as we deemed it safe to employ. Between these two, three intermediate strengths were used in the case of set II, and two in the case of set I{I. Originally it had been our intention to make use of stimuli which varied from one another in value by 60 units of stimulation, beginning with 135 and increasing by steps of 60 through 195, 255, 315, 375 to as nearly 425 as possible. It proved to be needless to make tests with all of these. We may now turn to the results of the experiments and the inter- pretation thereof. Before the beginning of its training each mouse was given two series of tests in which the electric shock was not used and return to the nest-box through either the white or the black box was permitted. These twenty tests (ten in series A and ten in series B) have been termed preference tests, for they served to reveal whatever initial tendency a dancer possessed to choose the white or the black box. On the day following preference series B, the regular daily training series were begun and they were continued without interruption until the dancer had succeeded in choosing correctly in every test on three consecutive days. Results of the experiments of set I. The tests with the weak stimulus of set I were continued for twenty days, and up tothat time only one of the four individuals in training (no. 128) had YERKES AND Dopson, Habit Formation. 469 acquired a perfect habit. On the twentieth day it was evident that the stimulus was too weak to furnish an adequate motive for the avoidance of the black box and the experiments were discontinued. A few words in explanation of the tables are needed at this point. In all of the tables of detailed results the method of arrange- ment which is illustrated by table 3 was employed. At the top of the table are the numbers of the mice which were trained under RAB Eas The results of the experiments of set I, stimulus weak (125 + 10 units). Mates. FEMALES. Gat Series. | Average. No. 128 No. 134. | Average. | No. 127. | No. 133. Average. A 6 7 6.5 | 4 5 Aas 5.50 B 5 5.0 6 4 5.0 5.00 I 3 5 4.0 4 4 4.0 4.00 2 6 6 6.0 6 7 6.5 6.2 3 5 4 4.5 * 2 5 Zhaly 4.00 4 4 5 4.5 6 4 5.0 4-75 5 3 u 5-0 3 5 4.0 4-50 6 2 5 arsy, || 4 4 4.0 375 V 3 4 3-5 | + 7 5-5 4-50 8 2 2 2.0 2 3 Dik 2.25 9 5 5 5.0 3 B 3.0. 4.00 10 I 2 | lials 4 2) 250 225 II ° A Tels 3 is 4.0 ail 12 I I 1.0 3 2 Pr A/S 13 I 3 ely 2 2 {0} 1.75 14 I I | Wa! ° 3 ig 125 15 I 3 2.0 I 3 2.0 2.00 16 fo) fo) O. I fo) 0.5 0.2 17 ° I Ons ° fo) O. 0.2 18 ° xe) oO. D I 1.5 0.75 19 I | 0.5 | 2 I Tals 1.00 20 Ss eee ee ee 2 3 2785 2.00 the conditions of stimulation named in the heading of the table. The first vertical column gives the series numbers, beginning with the preference series A and B and continuing from 1 to the last ‘series demanded by the experiment. In additional columns appear the number of errors made in each series of ten tests, day by day, by the several subjects of the experiments; the average number of errors made by the males in each series; the average number of errors made by the females; and, finally, the general 470 ‘fournal of Comparative Neurology and Psychology. average for both males and females. In table 3, for example, it appears that male no. 128 chose the black box in preference to the white 6 times in series A, 5 times in series B, 3 times in series 1, 6 times in series 2. After series 15 he made no errors during three consecutive series. His training was completed, therefore, on the eighteenth day, as the result of 180 tests. We may say, however, that only 150 tests were necessary for the establishment of a perfect habit, for the additional thirty tests, given after the fifteenth series, served merely to reveal the fact that he already possessed a perfect habit. In view of this consideration, we shall TABLE 4. The results of the experiments of set I, stimulus medium (300 + 25 units). Mates. FEMALES. . General Series. | PECMEOwe MILA AL DIISe yi hee. No. 192. No. 194. Average. No. 191. No. 193. Average. A 4 8 6.0 3 7 5.0 _ 5-50 B 6 6 6.0 4 6 5.0 5.50 na 4 4 4.0 4 5 Tefen a 4.25 2 3 3 3.0 4 2; 3.0 3.00 3 4 5 4-5 5 6 5-5 5.00 77g eae 4 3-5 6 3 4.5 4.00 5 2 4 3.0 5 7 6.0 4.50 6 | 2 ° 1.0 2 2 2.0 1.50 7 2 2 2.0 ° 3 Ts 75 8 I ° 0.5 I ° 0.5 0.50 9 ° 2 1.0 ° ° °. 0.5¢ 10 ° fo) oO. ° ° oO. °. II ° ° oO. ° oO. °. 12 ° O°. °. take as a measure of the rapidity of learning in these experiments the number of tests recetved by a mouse up to the point at which errors ceased for at least three consecutive series. Precisely as the individuals of table 3 had been trained by the use of a weak stimulus, four other dancers were trained with a medium stimulus. The results appear in table 4. All of the subjects acquired a habit quickly. Comparison of these results with those obtained with the weak stimulus clearly indicates that the medium stimulus was much more favorable to the acquire- ment of the white-black visual discrimination habit. In its results the strong stimulus proved to be similar to the weak stimulus. All of the mice in this case learned more slowly YERKES AND Dopson, Habit Formation. 471 than did those which were trained with the medium strength of stimulus. The general result of this preliminary set of experiments with three roughly measured strengths of stimulation was to indicate that neither a weak nor a strong electrical stimulus is as favorable to the acquisition of the white-black habit as is a medium stimulus. TABLE 6s. The results of the experiments of set I, stimulus strong (500 + 50 units). Mates. FEMALES. : General Series. Average. No. 130. | No. 132. | Average. | No. 129. No. 131. Average. A 6 6. 5 3.0 4-75 B 6 + 5.0 + 4 4.0 4-50 u 3 5 geo 5 5 5-0 4-50 2 3 I 2.0 3 3 3.0 2.50 3 5 3 Ge 3 3 joo) seule 4 3 2 Des 2 3 25 2.50 & 2 2 2.0 2 4 3:0 2.50 6 3 I 2.0 2 2 220 2.00 7 2 ° Hal 2 4 3.0 2.25 8 4 ° 2.0 I 2 | Hint 175 9 3 2 2ia5 2 I | Mes 2.00 10 2 3 2715 I I 1.0 oily II I I 1.0 2 ° 1.0 1.00 12 I 2 io ° fo) @p = 0.75 13 I I 1.0 2 2 2.0 | 1.50 14 fo) fo) O. 2 2 2.0 | 1.00 15 2 ° 1.0 ° I 0.5 | 0.75 16 ° ° O. | fo) 2 1.0 || “o.5o 17 fo) O. fo) I 0.5 || nOEzs 18 ° QO. 2 1.0 0.50 19 | I 0.5 0.25 20 | I 0.5 0.25 21 = | ° O. O. 22 | ° oO. O. 23 | fe) O. Oo. Contrary to our expectations, this set of experiments did not prove that the rate of habit-formation increases with increase in the strength of the electric stimulus up to the point at which the shock becomes positively injurious. Instead an intermediate range of intensity of stimulation proved to be most favorable to the acquisition of a habit under the conditions of visual discrimination of this set of experiments. 472 “fournal of Comparative Neurology and Psychology. In the light of these preliminary results we were able to plan a more exact and thoroughgoing examination of the relation of strength of stimulus to rapidity of learning. Inasmuch as the training under the conditions of set I required a great dealof time, we decided to shorten the necessary period of training by making the two electric boxes very different in brightness, and the dis- crimination correspondingly easy. This we did, as has already been explained, by decreasing the amountof light which entered the black box, while leaving the white box about the same. The influ- ence of this change on the time of learning was very marked indeed. With each of the five strengths of stimuli which were used in set II two pairs of mice were trained, as in the case of set I. The detailed results of these five groups of experiments are presented in tables 6 to 10. Casual examination of these tables reveals the fact that in general the rapidity of learning in this set of experi- ments increased as the strength of the stimulus increased. The weakest stimulus (135 units) gave the slowest rate of learning; the strongest stimulus (420 units), the most rapid. TABLE 6. The results of the experiments of set II, stimulus 135 units. Mates. FEMALES. : General Series. | Average. _ | No. 268. | No.274. | Average. | No. 267. No. 269. | Average. A 9 7 ° 8 7 7-5 7-75 B 8 6 7-0 4 6 5.0 6.00 I 6 4 5.0 6 4 5.0) etl eo 2 2 3 Deals 2 4 3-0 2.75 3 2 4 3.0 4 6 5-0 4.00 4 I 4 Dials ) I 0.5 1.50 5 ° 3 Ta 2 2 2.0 Des 6 fo) 2 1.0 fo) fo) oO. 0.50 7 ro) I O-50 4 I I 1.0 0.75 8 ° | Oo. | ° ° °. O. 9 ) | 9. fo) ° O. °. Io fe) | oO. 2 ° 1.0 0.50 Il | I 0.5 0.25 12 | I 0.5 0.25 13 | fo) oO. oO. 14 | ) °. oO. 15 | | I 0.5 0.25 16 | ° °. oO. 17 fo) °. oO. 18 fo) oO. O°. | | Yerkes AND Dopson, Habit Formation. 473 TABLE 7. The results of the experiments of set IT, stimulus 195 units. Mates. FEMALES. Ganka SEEES Average. No. 266. | No. 418. | Average. No. 263. No. 265. Average. A Geil ro 6.0 4 5 5-50 B 6 7 6.5 8 3 Gok 6.00 I 6 7 6.5 5 7 6.0 6.25 2 5 I 3.0 I I 1.0 2.00 3 g 5 ze) I 4 2-5 S25 4 2 2 2.0 2 I res 1.75 5 I I 1.0 ° 2 1.0 1.00 6 2 I Tits I ° 0.5 1.00 7 I I 1.0 fo) ° O°. 0.50 8 I ° 0.5 fo) ° O. 0.25 9 ° ° O°. ° °. °. Lo ° fe) O°. °. II ) °. ro TABLE 8. The results of the experiments of set II, stimulus 255 units. Mates. FEMALES. General Series. Average. No. 260. | No.262. | Average. | No. 259. No.261. | Average. A 5 sec 525 Bie25 B 7 6 6.5 5 5 5.0 5-75 I 6 7 6.5 9 3 6.0 6.25 2 4 7 525) 4 3 3-5 aS 3 I 4 Phy 3 I 2.0 2.25 4 ° 2 1.0 4 ° 2.0 1.75 5 ° 2 1.0 fe) 2 1.0 1.00 6 ° ° O. ° I 0.5 0.25 7 ° O. fo) I 0.5 0.25 8 ° °. I 0.5 0.25 9 ° O. oe 10 ° oO. O°. II ° °. °. 474. ‘fournal of Comparative Neurology and Psychology. TABLE 9. The results of the experiments of set II, stimulus 375 units. Mates. FEMALES. Series. General. No. 396. No. 398. | Average. | No. 189. No. 195. Average. BO A 6 6 6.0 6 7 6.5 6.25 B 5 3 4.0 5 6 5-5 4-75 I 6 6 6.0 4 5 4.5 5-25 2 F I | 3.0 5 3 4.0 3-50 3 5 3 | 4.0 8 2 5.0 4.50 4 co) 4 2.0 3 I 2.0 2.00 5 ° 3 Te5 I 4 Aas 2.00 6 ° ° O. ° ° O. O°. 7 I 0.5 fo) ° °. e25 8 fo) 2. ° ° O. O. 9 I 0.5 25 10 ° O. °. II ) O. °. 12 fo) °. ro TABLE io. The results of the experiments of set II, stimulus 420 units. ae. Mates. FEMALES. Gate éries. | je Average. No. 280. | No. 412. | Average. | No. 279. No. 281. Average. A 5 5 4 6 5.0 5.00 B 6 6 6 6 4 5.0 5.50 I & 5 5.0 5 5 5.0 5.00 2 4 5 4-5 | I ° 0.5 2.50 3 2 5 325 2 4 3-0 3-25 4 I 3 2.0 fe) 2 1.0 1.50 5 ° 3 Tish ° I 0.5 2/00 6 ° fo) oO. ° ° Oo. oO. 7 ro) ° °. ° Oh °. 8 fo) oO. ° O. O. The results of the second set of experiments contradict those of the first set. What does this mean? It occurred to us that the apparent contradiction might be due to the fact that discrimination was much easier in the experiments of set II than in those of set I. To test this matter we planned to use inour third sei of experiments a condition of visual discrimination which should be extremely difficult for the mice. The reader will bear in mind that for set YERKES AND Dopson, Habit Formation. 475 II the difference in brightness of the electric boxes was great; that for set III it was slight; and for set I, intermediate or medium. For the experiments of set III only one pair of dancers was trained with any given strength of stimulus. The results, how- ever, are not less conclusive than those of the other sets of experi- ments because of the smaller number of individuals used. The data of tables 11 to 14 prove conclusively that our supposition was correct. [he varying results of the three sets of experiments are explicable in terms of the conditions of visual discrimination. In TABLE 11. | TABLE 12. | The results of the experiments of set III, The results of the experiments of set stimulus 135 units. | III, stimulus 195 units. | Mate. FEMALE. || Mate. FEMALE. Series. ———_——_———_|————— | Average. | ————___—_ Average. No. 290. No. 199. | No. 288. No. 223. | A 6 | 4 5.0 | 4 4.0 B 4 | 7 [ences | 7 | 8 7-5 I 4 6 5-0 y 5 | 7 6.0 a 5 2 3-5 || 3 6 4-5 3 3 6 4.5 || 5 6 5-5 4 4 2 3-0 | 6 3 4.5 5 7 4 5-5 || 6 7 6.5 6 4 4 4.0 | + 4 4-0 7 7 7 7.0 || 5 3 4.0 8 7 5 6.0 2 2 2.0 9 4 4 4.0 ° ° O. 10 4 2 3.0 3 I 2.0 II 4 I ahr el 2 I Tas 12 5 3 4.0 I ° 0.5 13 3 2 als I co) 0.5 14 2 4 [> Bee) ° ° °. 15 4 3 355 ° 0. 16 3 fe) it als ° QO. 17 2 2 2.0 18 ° 2 LiQwlier Sag s ope Ce en Le 19 I I 1.0 20 3 3 216) 21 I I 1.0 22 I fr) 0.5 23 2 °o 1.0 24 I fr) 0.5 25 3 #5 26 I 0.5 27 I 0.5 28 ° O. 29 fe) O. 30 2 1.0 476 fournal of Comparative Neurology and Psychology. TABLE 13. TABLE 14. The results of the experiments of set III,) The results of the experiments of set stimulus 255 units. III, stimulus 375 units. 2 Mate. FEMALE. Mate. | FEMALE. Series. SS SSS SSS] Atta | No. 286. No. 285. |Average. No. 284. | No. 283. A 4 7 | 5-5 4 | 5 4-5 B - 5 4-5 3 = 3-5 I 5 6 te 6 6 6.0 2 | Z| 3 3.0 B 2 2 I 3 | = 3 2a || 4 3 3325) 4 | 5 5 | 5-0 || 4 2 3.0 5 | 2 4 j 3-9 | 2 5 5}05) 6 | 2 3 2.5 || a] 2 Pols 7 | 3 2 2.5 || 6 5 5-5 8 I I ihre) || 4 2 3.0 9 I 2 ela I I 1.0 fe) 2 I 1.5 | I 2 1.5 II 2 3 2.5 |i I 2 res 12 3 ° ras 3 I 2.0 13 2 ° 1.0 I I 1.0 14 ° I 0.5 I I 1.0 15 3 I 2.0 I ° 0.5 16 I fo) ely | I I 1.0 17 ° fe) oe. || ° I 0.5 18 ° ° O. | ° I 0.5 19 ° On II ° I 0.5 20 | fe) °. 21 | 2 1.0 22 ) °. 23 | 2 1.0 24 ° O. 25 \| ° O. 26 \| ° O. }) set III both the weak and the strong stimuli were less favorable to the acquirement of the habit than the intermediate stimulus of 195 units. It should be noted that our three sets of experiments indicate that the greater the brightness difference of the electric boxes the stronger the stimulus which is most favorable to habit- formation (within limits which have not been determined). Fur- ther discussion of the results and attempts to interpret them may be postponed until certain interesting general features of the work have been mentioned. The behavior of the dancers varied with the strength of the stim- ulus to which they were subjected. They chose no less quickly in the case of the strong stimuli than in the case of the weak, but they were less careful in the formercase and chose with less delib- YERKES AND Dopson, Habit Formation. 477 ERRORS SERIES a Bee fe Be maw a Kal Peas Beas) AZ se Sea eeneesS Fe a i eo a ieee IS a Le Pa fee El Secceea bones DES Rea Ree es ase ee ee a a i eae eae PS [a ee Pease ae St gla See = ee ble ya = Kee oe ata naka eS | ~~ T+ A B 1 2 3 4 5 6 7 8 9 10 u 12 1s 14 15 16 17 18 19 20 21 Fic. 4. Curves of learning. Ordinates represent series of ten tests each, and abscisse represent the average number of errors for four mice in each series. W, designates the error curve for the individuals which were trained under the condition of weak electrical stimulation; M, designates the corresponding curve for the medium strength of stimulation; and S, that for the strong stimulus. 478 “fournal of Comparative Neurology and Psychology. eration and certainty. Fig. 4 exhibits the characteristic differences in the curves of learning yielded by weak, medium, and strong stimuli. These three curves were plotted on the basis of the aver- age number of errors for the mice which were trained in the experi- ments of set 1. Curve Wis based upon the data of the last column of table 3, curve M, upon the data in the last column of table 4; and curve S upon the data of the last column of table 5. In addition to exhibiting the fact that the medium stimulus yielded a perfect habit much more quickly than-did either of the other stimuli, fig. 4 shows a noteworthy difference in the forms of the curves for the weak and the strong stimuli. Curve WV (weak stimulus) is higher throughout its course than is curve S (strong stimulus). This means that fewer errors are made from the start under the condition of strong stimulation than under the condition of weak stimulation. Although by actual measurement we have demonstrated marked difference in sensitiveness to the electric shock among our mice, we are convinced that these differences do not invalidate the conele sions which we are about to formulate in the light of the results that have been presented. Determination of the threshold elec- tric stimulus for twenty male and twenty female dancers proved that the males respond to a stimulus which is about Io per cent less than the smallest stimulus to which the females respond. Table 15 contains the condensed results of our experiments. It gives, for each visual condition and strength of stimulus, the number of tests required by the various individuals for the acquisi- tion of a perfect habit; the average number of tests required by the males, for any given visual and electrical conditions; the same for the females; and the general averages. Although the numbers of the mice are not inserted in the table they may readily be learned if anyone wishes to identify a particular individual, by referring to the tables of detailed results. Under set I, weak stimulus, for example, table 15 gives as the records of the two males used 150 and 200+ tests. By referring to table 3, we discover that male no. 128 acquired his habit as a result of 150 tests, whereas male no. 134 was imperfect at the end of 200 tests. ‘To indicate the latter fact the plus sign is added in table 15. Of primary importance for the solution of the problem which we set out to study are the general averages in the last column of the table. From this series of averages we have constructed the curves of fig. 5. ‘This figure 150 100 Stim. 100 200 300 400 500 Fic. 5. A graphic representation of the relation of strength of electrical stimulus to condition of vis- ual discrimination and rapidity of learning. Ordinates represent value of electric stimulus in units of stimulation; abscissee represent the number of tests given. Curve I represents the results of the experi- ments of Set I. Each dot indicates a value of stimulus which was used in the experiments. For example, the first dot to the left in curve I signifies that the stimulus whose value was 125 units gave a perfect habit, in the case of the four individuals trained, with 187 tests; the second dot, that for the stimulus value of 300 units 80 tests were necessary; and the third that for the stimulus value of 500, 155 tests. Curves II and III similarly represent the results of the experiments of sets II and III, respectively. 480 Fournal of Comparative Neurology and Psychology. very clearly and briefly presents the chiefly significant results of our investigation of the relation of strength of electrical stimulus to rate of habit-formation, and it offers perfectly definite answers to the questions which were proposed for solution. In this figure the ordinates represent stimulus values, and the abscissee number of tests. “The roman numerals J, //, [//, desig- nate, respectively, the curves for the results of set I, set II, and set III. Dots onthe curves indicate the strengths of stimuli which were employed. Curve I for example, shows that a strength of stimulus of 300 units under the visual conditions of set I, yielded a perfect habit with 80 tests. TABLE 15. The number of tests required by the mice for the acquisition of a perfect habit of discrimination. Set. Stimulus. Mates. Average. FEeMALEs. Average. Gen. Av. Weak 150 200+ 175+ | 200+ | 200+ | 200+ | 187+ lM yoenaoceponoooT Medium 80 go 85 80 7o AS 80 Strong 150 130 140 140 200 170 155 135 40 70 55 150 7o 8 Ko) 82.5 195 80 7O 75 60 50 55 65 ION sopsnadcoon aud 4 255 30 50 86} =640 40 80 60 5° 375 30 go | - 60 50 50 5° 55 420 40 50 45 30 50 40 42.5 135 300+ | 210 255 I 195 130 110 120 sop degonexer 26s ae 150 155 375 160 230 195 From the data of the various tables we draw the following conclusions: 1. In the case of the particular habit which we have studied, the rapidity of learning increases as the amount of difference in the brightness of the electric boxes between which the mouse 1s required to discriminate is increased. ‘The limits within which this statement holds have not been determined. The higher the curves of fig. 5 stand from the base line, the larger the number of tests represented by them. Curve II is lowest, curve | comes next, and curve III is highest. It is to be noted that this 1s the order of increasing difficultness of discrimination in the three sets of experiments. YERKES AND Dopson, Habit Formation. 481 2. The relation of the strength of electrical stimulus to rapidity of learning or habit- fcmacion depends upon the difficultness of the habit, or, in the case of our experiments, upon the conditions of visual discrimination. 3. When the boxes which are to be discriminated between differ very greatly 1 in brightness, and discrimination is easy, the rapidity of learning increases as the strength of the electrical stimulus 1s increased from the threshold of stimulation to the point of harmful intensity. This is indicated by curve II. Our results do not represent, in this instance, the point at which the rapidity of learn- ing. begins to decrease, for we did not care to subject our animals to injurious stimulation. We therefore present this conclusion tentatively, subject to correction in the light of future research. Of its correctness we feel confident because of the results which the other sets of experiments gave. he irregularity of curve II, in that it rises slightly for the strength 375, 1s due, doubtless, to the small numbers of animals used in the experiments. Had we trained ten mice with each strength of stimulus instead of four the curve probably would have fallen regularly. 4. When the boxes differ only slightly in brightness and dis- crimination is extremely difficult the rapidity of learning at first rapidly increases as the strength of the stimulus is increased from the threshold, but, beyond an intensity of stimulation which 1s soon reached, it begins to decrease. Both weak stimuli and strong stimuli result in slow habit-formation. A stimulus whose strength is nearer to the threshold than to the point of harmful stimulation is most favorable to the acquisition of a habit. Curve III verifies these statements. Itshows that when discrimination was extremely difficult a stimulus of 195 units was more favorable than the weaker or the stronger stimuli which were used in this set of experiments. 5. As the difficultness of discrimination is increased the strength of that stimulus which is most favorable to habit-forma- tion approaches the threshold. Curve II, curve I, curve III is the order of increasing difficultness of discrimination for our results, for it will be remembered that the experiments of set III were given under difficult conditions of discrimination; those of set I under medium conditions; and those of set I] under easy condt- tions. As thus arranged the most favorable stimuli, so far as we may judge from our results, are 420, 300, and 195. This leads us to infer that an easily acquired habit, that is one which does not 482 ‘fournal of Comparative Neurology and Psychology. demand difficult sense discriminations or complex associations, may readily be formed under strong stimulation, whereas a difh- cult habit may be acquired readily only under relatively weak stimulation. hat this fact is of great importance to students of animal behavior and animal psychology is obvious. Attention should be called to the fact that since only three strengths of stimulus were used for the experiments of set I, it is possible that the most favorable strength of stimulation was not discovered. We freely admit this possibility, and we furthermore wish to emphasize the fact that our fifth conclusion 1s weakened slightly by this uncertainty. But it is only fair to add that pre- vious experience with many conditions of discrimination and of stimulation, in connection with which more than two hundred dancers were trained, together with the results of comparison of this set of experiments with the other two sets, convinces us that the dancers would not be likely to learn much more rapidly under any other condition of stimulation than they did with a strength of 300 + 25 units of stimulation. Naturally we do not propose to rest the conclusions which have just been formulated upon our study of the mouse alone. We shall now repeat our experiments, in the light of the experience which has been gained, with other animals. SOME REACTIONS OF DROSOPHILA, WITH SPECIAL REFERENCE TO CONVULSIVE REFLEXES. BY FREDERIC W. CARPENTER (Zoélogical Laboratory, University of Illinois.) WitH One Ficure. The behavior of the pomace fly (Drosophila ampelophila) in respect to several kinds of stimulation has already been the sub- ject of investigation. Barrows (’07) has recently shown that the insect is positively chemotropic to certain strengths of odorous substances occurring in fermenting fruit, such as alcohol, acetic and lactic acids, and acetic ether. ‘To light varying in intensity from 5 to 250 candlepowers Drosophila is positively phototropic; and under the influence of gravity it is negatively geotropic (CaR- PENTER 05). In the present study of the reactions of Drosophila to stimuli other than those just mentioned, attention was first directed to the behavior of the insects when they pass from a region of opti- mum temperature into regions relatively warm or cold. The flies were confined in a flat glass box, 38 cm. long, 23 cm. wide, and 8 mm. deep. The edges of the box along the two sides and one end were sealed with aquarium cement and enamel, and thus made water-tight. At the unsealed end of the box a small opening was left through which the flies could pass into the interior. All the movements of the insects could readily be observed through the glass, and the short distance that separated the roof and floor of the box permitted the use of a hand lens when desired. In the temperature experiments the box was partially immersed in water as shown in the accompanying sectional view of the apparatus. The water could be heated by means of an alcohol lamp placed beneath the vessel containing it, or it could be cooled by placing in the vessel small pieces of ice. By arranging the apparatus so 484 fFournal of Comparative Neurology and Psychology. that the immersed end of the box was directed toward a window the positively phototropic flies, introduced into the elevated end, could be made to creep toward the hot or cold region, since this region lay in the direction of the source of light. Reaction to increased temperature. The water surrounding the immersed end of the box was raised to 45° C., a temperature that is soon fatal to Drosophila. Flies introduced into the oppo- site end of the box, which was practically at room temperature, crept more or less steadily toward the light. ‘This movement brought them gradually to a region of increasing temperature. Upon arriving near the lower water-line (D) the creeping flies turned about, describing curved paths, and headed back toward the cooler end of the box, their positive phototropism apparently being overcome by the repelling effect of the heat. In no instances did creeping flies, whether on the floor or the roof of the box, pass ft hE iS Fic. 1. Sectional plan of apparatus. A B, glass box, 38 cm. long, 23 cm. wide, and 8 mm. deep, partially immersed in water; C, upper water-line; D, lower water-line. beyond this lower water-line. Occasionally one would creep along the line in a zigzag manner, as though alternating between the two antagonistic directive influences, but finally it would yield to the negative stimulus, and creep back to the region of lower temperature. ‘The majority of the return excursions were made as the result of a uniform and continuous deflection from the heated area. Since there was no satisfactory evidence of random movements involving a ‘‘trial and error’? method of reaction, this behavior may conveniently be spoken of as a “tropism.” ‘This term is here used merely in a descriptive sense for an orderly turn- ing away from a stimulating region. It does not carry with it an implied theoretical explanation of the precise effect of the stimulus on the organism. Reaction to decreased temperature. When the water in which one end of the glass box was immersed was cooled with ice, the other CARPENTER, Reactions of Drosophila. 485 conditions of the experiment remaining the same, a similar tropic reaction followed. ‘The flies were consistently negative to a tem- perature of from 5° to 6° C. Occasionally the creeping excursions toward the light were prolonged beyond the lower water-line, but only in very infrequent cases did the flies reach the upper water-line. As a control for both this and the previous experiment the water vessel of the apparatus was filled with water at nearly room tem- perature. ‘The flies then, following the light, crept to the end of the immersed portion of the box. Reaction to unilateral light stimulation. ‘The regular curved paths described by Drosophila in its response to the repelling effect of heat and cold suggested the possibility that this reaction might be explained by the “local action theory of tropisms.” It was conceivable that the unsymmetrical stimulation might act locally on the organs of locomotion, presumably through the nervous system. ‘Those locomotor organs on the side subjected to the greater stimulus might move more rapidly than those on the opposite side until the insect should be turned so as to head directly away from the region of stimulation. ‘The two sides of the body would then be equally affected by the heat or cold, and the organs of locomotion would, therefore, move with equal rapid- ity, and carry the fly away in a straight line. The adequacy of this simple explanation of the temperature reactions might have been tested if the stimulus could have been confined to one side of the body only. ‘The tropism theory would call for circus movements by the fly as long as the unilateral stimu- lation was maintained. No satisfactory method for applying this test to the temperature reactions occurred to me. The light re- action, however, presented fewer difficulties, and furnished quite as critical a reflex for the purpose. ‘The light stimulus is effective through the paired eyes of the insect. If one eye is covered circus movements are to be expected under the theory of tropisms, with the uncovered eye toward the centers of the circles, since Droso- phila is positively phototropic. Such reactions in insects with one eye blinded have been recorded by Hoimes (’or) for the blue- bottle fly, two species of bees, a robber-fly, a horse-fly, and a species of syrphid. PARKER (’03) has observed similar behavior in the mourning-cloak butterfly (Vanessa antiope). In preparation for this test experiment, one eye of each of several insects was covered by an opaque cap of lampblack and 486 “fournal of Comparative Neurology and Psychology. mucilage. To reduce the flies to a temporary state of insensi- bility and quiet, during which the covering to the eyes could be applied, recourse was made to what might be called a natural anesthetic. If Drosophila is exposed for a short time to a tem- perature of o° C. its movements cease, and it becomes apparently insensible. If then brought into the ordinary temperature of the laboratory several minutes will elapse before it recovers, and during this time the operation of covering the eye may be per- formed under a dissecting microscope. When the recovery takes place it appears to be a complete one, the fly responding in a normal way to all stimuli. Since a low temperature must often be present in the insect’s natural environment, it may be supposed that the action of cold will be attended with less risk of altering the nervous system than that of the chemical anesthetics usually employed.'! Repeated trials made with flies thus deprived of the sight of one eye showed that under such conditions of unsymmetrical stimu- lation they, nevertheless, crept in a fairly direct path toward the light, although a tendency to deviate toward the side of the normal. eye regularly occurred. ‘The insects generally moved in a peculiar, jerky manner. The tendency to diverge from the direct path toward the side of the uncovered eye was overcome by a series of short, quick turns in the opposite direction, which kept them headed toward the light. Normal flies, used as a control, pursued straight courses, and usually reached the end of the container before the experimental flies. Now and then one of the partially blinded flies performed circus movements; but this conduct was exceptional, and was never persisted in except in the case of a single insect, which had long been active, and showed signs of fatigue. It is clear that the tropism theory, with its assumption of a local action of the stimulus on the side exposed to its effect, does not furnish a complete explanation of these reactions. ‘Though the persistent tendency to turn toward the side of the functional eye gives some evidence of a purely mechanical reaction to a local canauinen:, such a reaction is evidently inhibited and dominated 1 The resistance of Drosophila to cold is rather remarkable. I have buried a glass vessel containing thirty-three flies in a snow-bank over night, exposing them thus to a temperature of about 0° C. for seventeen hours. Of these thirty-three, all except five recovered when brought again into the ordinary temperature of the laboratory. CARPENTER, Reactions of Drosophila. 487 by another and more complicated one. The latter belongs in that category of reactions included under the somewhat vague designation of “pleasure-pain” behavior. (For a discussion, see JENNINGS ” 04, pp. 248-249, and ’o6, pp. 332, 340.) Of reactions of this kind JENNINGS and others have pointed out abundant examples among the lower organisms. HoLMEs(’05) has described in Ranatra, after one eye had been blinded, conduct nearly similar to that observed in Drosophila. He concludes that the “phototaxis” of Ranatra seems in many ways to be “intermediate between purely reflex conduct on the one hand, and conduct of the pleasure-pain type on the other.’’ This conclusion applies equally well to Drosophila. The production of convulsive reflexes.—In the experiments with an increased temperature, as above described, it sometimes hap- ened that an insect, instead of creeping along the floor or roof of the box, would fly or hop toward the light. If it were under con- siderable headway it might, in spite of its negative thermotropism, be carried by its momentum into the immersed portion of the box. This rapid form of locomotion could often be induced by tapping on the exposed end of the box. A fly thus carried into a tempera- ture of 45° C. soon became violently active. The high tempera- ture evidently acted as a powerful kinetic stimulus, so that nervous impulses overflowed, as it were, from the sensory nerves concerned with temperature into the entire motor nervous system, producing a convulsive reflex. “The wings vibrated with great rapidity, and the legs, abdomen, head and mouth-parts were affected by spas- modic contractions of their muscles. ‘These activities often resulted in a peculiar spinning motion, and carried the fly rapidly about from place to place. Owing to the inclination of the box the insects usually tended toward the lower or immersed end, where they shortly succumbed to the heat, often dying in a charac- teristic attitude, with wings rigidly extended. Occasionally, how- ever, the energetic, haphazard motor reflexes carried a fly out of the heated area into the cool, elevated region of the box, where its convulsive movements ceased, and it shortly began to creep about, restored, apparently, to its former condition. When the experiments with reduced temperature were being performed, flies were introduced into the cold portion of the box. Many of these also gave the convulsive reflex before settling down into the quiet, benumbed condition eventually brought on by the 488 ‘fournal of Comparative Neurology and Psychology. low temperature. ‘The reflex, though generally of shorter dura- tion than when produced by heat, was, nevertheless, unmistakable. The characteristic spinning motion, and the final rigid extension of the wings could often be observed. ‘These flies soon became motionless, but they did not die. ‘They could be revived by rais- ing the temperature. Since extremes of both heat and cold produced, through the nerves concerned with temperature, such marked motor reflexes, I decided to try the effect of intense light acting through the optic nerves. he positive phototropism of Drosophila to light of various intensities has been described in a former paper (CARPEN- TER ’05). In using the highest intensity at that time available, an arc light of 250 candlepower, it was noted that after continued exposure at a distance of 40 cm. an insect became extremely active, flying and hopping about irregularly, and giving little or no evidence of a directive control. It seemed probable that this excessive activity might have led to a true convulsive reflex had the intensity of the light been still further increased. For the purpose of testing this Prof. C. W. Horres, of the Botanical Department of the University of Illinois, kindly placed at my disposal an arc light of 480 candlepower, conveniently suspended in a dark room. A small glass box was constructed, consisting of two compartments separated by a vertical glass plate. In one of these compartments the flies were placed; the other was filled with water to serve as a heat screen. A thermometer was placed just behind the heat screen in contact with the vertical glass plate separating the two chambers. When flies contained in this apparatus were brought to a dis- tance of from 2 to 3 cm. from the arc light their movements at first, while rapid and irregular, were not true convulsive reflexes. The front wall of their compartment had an initial temperature of 25° C.; after about a minute this temperature rose, in spite of the heat screen, to 30° C. The flies then gave the convulsive reflex, tumbling and whirling about on the floor of the compart- ment, and showing no signs of orientation. Up to this time there had been no evidence of a reversal of their phototropism from positive to negative. Removed from the influences of the light and heat they resumed their ordinary activities. To determine whether or not the intense light was a factor in inducing this convulsive reflex the flies were subjected to the same CaRPENTER, Reactions of Drosophila. 489 temperature in ordinary daylight. ‘Ten insects were placed in a water-tight glass vessel with thin walls, and the latter was immersed in water which had previously been heated to 30° C. The con- vulsive reflexes did not appear. The temperature was then eradually raised. The flies showed the first convulsive reflexes between 36° and 38°, and these became general between 38° and 40°. The experiment was twice repeated with the same results. It follows, then, that the light of a 480 candlepower electric arc, at a distance of from 2 to 3 cm., calls forth the convulsive reflex at a temperature at which, in ordinary daylight, this reaction does not occur. In view of the above-described effects of excessive temperature and light stimulation, it seemed probable that certain volatile substances, acting through the end-organs and nerves concerned with chemical sense, might also prove sufficiently stimulating for the production of convulsive reflexes. ‘The following experiment was, therefore, made. The floor of the glass box used in the temperature experiments was moistened near one end along a line drawn from side to side, first with aqua ammonia, and after- ward with glacial acetic acid. This end of the box was in each instance turned toward a window, and the flies, at first assembled at the other end, crept in the direction of the light. There was little or no evidence of a negative tropic reaction. But when the insects came close to either fluid the irritating vapors produced violent convulsive reflexes. Some of the insects were whirled into the fluid where they perished; others were carried to a distance and soon recovered. One fly spun about for fifteen seconds dur- ing a convulsive reflex induced by acetic acid, and finally reached a position outside the stimulating area. Its excessive activity then ceased, and it was soon creeping about in the usual way. The student of animal behavior will ask himself how this con- vulsive reflex is related to other reactions of animals. It deserves this consideration since it is, in Drosophila, a normal reaction. The conditions necessary to call it forth are, it is true, extreme, and usually cause the death of the fly if allowed to continue. ‘The reflex, however, is not a death struggle due to pathological changes in the body. If it removes the insect from the stimulating region the excessive activity gives way to ordinary movements, and the insect appears to be none the worse for its experience. 490 ‘fournal of Comparative Neurology and Psychology. Mainly through the recent writings of JENNINGS attention has been directed to the relative importance and widespread occur- rence of “trial and error’ behavior among the lower animals. This kind of behavior is characterized by a repetition of “random movements,” certain of which, under ordinary circumstances, are selected and followed up to the advantage of the organism. The convulsive reflex of Drosophila appears to be an instance of behavior of this character, in which, under excessive stimulation, random movements are made with extraordinary vigor and rapidity. ‘There is, however, little evidence of the selection and repetition of those movements which carry the insect in favorable directions. Escape from the stimulating region seems to depend on chance alone. The haphazard “trials” that are made during the convulsive reflex are the result of a complex reaction which seemingly involves all the movements of which the animal is capable. Mast (’03) saw in planarians subjected to a high temperature nearly all the reactions the worms have at their command appearing one after another. In Drosophila, with its more highly organized and specialized nervous and muscular organs, the reactions are simul- taneous, each movable part performing its special function to the limit of its capacity. Summary. 1. Drosophila is negatively thermotropic to high and low temperatures. 2. When one eye is covered so that the light stimulus is uni- lateral, Drosophila moves toward the source of light in a fairly direct path, but tends to deviate toward the side of the functional eye. A “pleasure-pain” reaction appears to inhibit and dominate a “‘tropic’’ reaction. 3. A violent, uncodrdinated motor reaction or convulsive reflex. may be induced in Drosophila by stimulating the insect either by a high temperature, or by a low temperature, or by intense light, or “by the vapors of such irritating chemical substances as ammonia and acetic acid. 4. The convulsive reflex thus obtained in Drosophila may be regarded as an instance of trial and error behavior, characterized by acomplex of vigorous random movements, involving, apparently, all the movable parts of the insect’s body. The escape of the insect from the region of stimulation appears to depend on chance. CaRPENTER, Reactions of Drosophila. 491 LITERATURE CITED. ARRows, W. M. 1907. The reactions of the pomace fly, Drosophila ampelophila Loew, to odorous substances. . Fourn. Exper. Zoél., vol. 4, no. 4, pp. 515-537- ARPENTER, F. W. 1905. The reactions of the pomace fly (Drosophila ampelophila Loew) to light, gravity, and mechanical stimulation. Amer. Nat., vol. 39, no. 459, pp- 157-171. Homes, S. J. 1go1. Phototaxis in the Amphipoda. Amer. Four Physiol., vol. 5, no. 4, pp. 211-234. 1905. The reactions of Ranatra to light. Journ. Comp. Neurol. and Psychol., vol. 15, no. 4, PP 3055349: Jennincs, H. S. 1904. Contributions to the study of the behavior of lower organisms. Carnegie Institution of Washington. Publication no. 16, 256 pp. 1906. Behavior of the lower organisms. New York, 366 pp. (Columbia University Biological Series, vol. 10.) Mast, S. O. 1903. Reactions to temperature changes in Spirillum, Hydra, and fresh-water Planarians. Amer. Four. Physiol., vol. 10, no. 4, pp. 165-190. Parker, G. H. 1903. The phototropism of the mourning-cloak butterfly, Vanessa antiope Linn. Mark Anni= versary Volume, article no. 23, pp. 453-469. PHOTOTAXIS IN- FIDDLER CRABS AND ITS, REVA- TION TO]THEORIES, OF ORIENTATION: BY S. J. HOLMES (From the Zoélogical Laboratory of the University of Wisconsin.) In the phototactic movements of animals which orient them- selves definitely to the light it is almost always the longitudinal axis of the body which is kept parallel to the rays. It is therefore not without interest in relation to the much discussed “theory of tropisms’’ to find an animal which orients itself sidewise instead of in the usual manner. Such an animal is the common fiddler crab of the Atlantic coast, Uca pugnax (Smith), which shows a very decided positive phototaxis, especially in strong light. Like many other crabs the members of this species run sidewise, and in fact they are so constructed that they would find great difficulty in any other form of locomotion. When recently brought into the laboratory they seem remarkably attracted bya bright light. They gather on the side of their enclosure nearest the light and often struggle for a long time to get nearer the source of attraction. By changing the position of the light the crabs may be made to follow it about in any desired direction, changing their course promptly whenever the light is moved. ‘There is lateral instead of longi- tudinal orientation to the direction of the rays. When the crabs reach the side of the dish they usually do not maintain their lateral orientation. ‘They frequently face the light, holding their eyes erect and moving from side to side in the en- deavor to get as near the light asthey can. Very often they settle down facing the light, remaining there for a long time as if spell- bound. ‘There seems to be no tendency to get into a position of lateral orientation once the animal attains to a position of prox- imity to the light. ‘This orientation is necessary if a certain object is to be followed, but, so far as I can determine by watching its behavior, the crab does not tend to assume it except during loco- 494 fournal of Comparative Neurology and Psychology. motion. When it has gone as far toward the light as it can it settles down preferably in a position of longitudinal orientation. When a crab that is facing the light is subjected to very strong illumination it will often raise its body so as to stand supported on the tips of its claws. If the light is withdrawn a short distance the body comes to rest again upon the bottom of the dish. The crab may be made to repeat this act many times by causing the light to approach and recede. ‘The behavior of the animal is apparently the involuntary result of the increase in the tension of the leg mus- cles brought about by strong illumination. Similar increase in muscular tone by light is shown in the be- havior of the eye-stalks. When a fiddler is seized the eye-stalks are drawn back into the orbits and tightly held there. If, how- ever, the crab is brought very close to a strong light the eye-stalks are erected. If the animal is removed a little further from the light the eye-stalks are pulled back into their orbits again. When brought into strong light the crab is apparently no longer able to hold the eye-stalks down and they come up in spite of the instinct to hold them in a protected situation. If the cornea of one eye is blackened over usually only the unblackened eye rises upon exposure to strong illumination, but the blackened one sometimes does so to a greater or less extent, owing perhaps to the fact that the two eyes usually make associated movements. The experiment of crossing the eye-stalks was tried in order to see what effect would be produced on the animal’s reactions to light. ‘The eye-stalks of the fiddler crab are long and they may readily be crossed like the parts of a letter X and tied in the middle. Crabs treated in this way show great confusion in their reactions to visual stimuli. When approached they give signs of alarm and frequently run directly towards the source of danger. When a light is moved suddenly they often run towards it instead of away as they usually do from all moving objects. Normal phototaxis, however, is mainly destroyed. ‘The crabs neither go directly to- ward or away from the light with any regularity; in fact, they seem to pay little attention to the light, owing perhaps to the discomfort of their unusual predicament. ‘There is no definite reversal of pho- totaxis, which I thought might occur under the circumstances, although there is often a reversal in the responses to moving objects. The crabs’ actions, however, are hesitating and uncertain; often they move a distance one way and then in another as if the result Hoimes, Phototaxis 1n Crabs. 405 of their movements were something unexpected. In a crab with crossed eyes the behavior of objects in its visual field consequent on its movements is different from what itis accustomedto. Under normal conditions fiddler crabs probably possess binocular vision so far as may be judged by the behavior of the eye-stalks and the arrangements of the facets of the eyes, but when the eyes are crossed the animals have two visual fields which give quite dif- ferent impressions, thus adding further to their confusion. ‘The visual world of such crabs doubtless seems a hopelessly mixed up affair, and it is not surprising that the animals often sulk as if dis- couraged with their efforts. Crabs kept for several days in order to ascertain if they would improve in the appropriateness of their responses gave only negative results. The phototactic reactions of fiddler crabs are very easily checked or overcome by fear. When a light is brought near the animals they often scurry away in great haste, and at first one might be led to interpret this behavior as a manifestation of negative photo- taxis, but it is a very different phenomenon. Even when showing a strong positive reaction the fiddlers often flee in apparent alarm upon a slight movement of the light. If the movement is a sudden one they are more apt to beat a retreat, while they follow slower movements without fear. When exposed to strong illumination for some time they become more insensible of their surroundings and are dominated almost entirely by the stimulus from the light without regard to movements made near them which at first would send them scurrying off in great haste. ‘They get, as it were, “warmed up” to the work, becoming not only less responsive to other stimuli, but more vigorous in their phototactic activity. I have described similar phenomena in the water-scorpion, Ranatra, and other observations have shown that it is a not uncommon trait in tropic responses. I do not wish to add further to the confusion that exists in the use of the term tropism, but I believe that the retreat of the fiddlers from a moving light cannot properly be described as a tropic reac- tion. It may be related to tropic reactions as vision is according to Rap1, but it is not so much a response to the light per se as to a sudden movement or appearance of the light. If we described as negative phototaxis all movements however caused which were directed away from the light we should have to include the flight of the fiddlers under this designation, and say that a sudden move- 496 fournal of Comparative Neurology and Psychology. ment of the light caused a reversal in the sense of the response. But will anyone maintain that when a wild animal runs away in alarm from a sudden blaze it manifests a negative phototaxis? It is with such an action as,this, rather than with the reactions com- monly included under the head of negative phototaxis that the retreat of the fiddlers is more closely related. ‘The flight of the crabs from light has all the characteristics of their flight from moy- ing objects in general. Whenever one enters a room where the crabs are kept or makes a small movement in their vicinity they promptly scuttle away; and they often detect one’s presence ona beach for a distance of several rods and make for their holes. These reactions we commonly attribute to fear, whatever physio- logical explanation we may offer for them, and anyone who has observed the fiddlers scurrying away from a moving light can hardly fail to ascribe their behavior to the same cause. The point of principal interest in the phototaxis of the fiddler crabs is the relation of their lateral orientation to the theories of tropisms. Can we regard orientation as a direct response in which the animal is involuntarily forced into line, or is it rather to be considered as coming under the pleasure-pain type of behavior, and as therefore related to the voluntary seeking of a certain end which is exhibited in the behavior of higher forms? In order to explain the orientation of a highly organized form like an insect or crustacean in which, in most cases, response to light takes place through the eyes, we may assume that light falling more strongly on one eye sets up impulses which are transmitted more orless directly to the leg musculature. We may assume that the exten- sors of the opposite side are stimulated, or the flexors on the same side, or both, and that in consequence of this distribution of im- pulses the animal moves until its body is in line with the rays. In such a case the movements involved in orientation are the same as those employed in ordinary locomotion only the activity of the legs on one or the other side 1s accentuated according to the posi- tion of the body in relation to the direction of the rays. In the fiddler crab, however, the case is different, and we can- not explain the phenomenon in this way. ‘The legs of the fiddler move in a plane approximately at right angles to the sagittal plane of the body, but they are capable of a certain amount of for- ward and backward motion which may be employed to change the direction of locomotion. The movements involved in orienta- Homes, Phototaxis in Crabs. 497 tion are different from those employed in ordinary running. ‘They are special movements employed to check deviations from a cer- tain course, a circumstance which would greatly complicate any attempt to explain orientation as a comparatively direct response. The results of observations on fiddler crabs tend to confirm the conclusion reached in studies made on the phototaxis of Ranatra,' namely, that light is followed much as an animal pursues any other object of interest such as prey, or its mate, and until we can give a physiological explanation of these phenomena we are not, | believe, in a position to give a satisfactory explanation of orienta- tion to the direction of the rays of light. 1 The reactions of Ranatra to light. Four. Comp. Neur. and Psych.,vol. 15, 1905. pe ig a et = Try LIVES SOF SEDUCABILITNY “IN PARAM GClwU Me BY STEVENSON SMITH Wiru Four Ficures. The theory of the phylogenetic development of adaptive behav- ior in animals has given interest to the question of the develop- ment of consciousness in animals, and to the possibility of the two developments having been coexistent throughout. A synthetic study of animal behavior, beginning with the lowest form, points out the possibility of an adaptive phylogenetic development, becoming more and more complex as we ascend in the scale of life, and all this without the coexistence of consciousness. If we start with the lowest possible form and determine that all its behavor may be described solely by mechanical laws, it may be possible to interpret the more complex behavior of the higher forms as the action of a more complex mechanism. As we have empirical evidence of such facts as inheritance and_ individual variation we may assume these as factors in evolution and still exclude consciousness as in no way explaining them. Some writers have looked upon natural selection as involving consciousness in that some organisms, possessing better memory than others, would be educated more easily and so adapt them- selves sooner and better to their environment than the rest. But these writers fail to see that memory has another than a psychic side. ‘Uhis is memory as we observe it in others; when a stimulus has acted upon an organism one or more times the next stimulation, of a like kind, produces a different reaction from that which the previous stimulus occasioned. ‘This form of memory is observed in inorganic manifolds as well as in organic. For instance, through continued use an old lock acts differently from the ame lock when it was new. ‘The action of any mechanism is subject to such a change. ‘This change may be to the advantage or to the disadvantage of the organism, but it is still memory. Thus, more complex and more advantageous memory, though accounted for by evolution, may in no way involve consciousness. 500 =‘fournal of Comparative Neurology and Psychology. Evolution depends upon those organisms being selected which have that certain kind of memory which enables them to cope with the conditions of their surroundings. Whether this memory is evolved through the inheriting of acquired aptitudes or through the selection of the best adapted variants, or mutations, does not bear on the question. With such factors given, and they are universally accepted laws in biology, the evolution of an adaptive behavior follows of necessity. It is probable that an explanation in these terms seems inadequate only because of the scarcity of empirical data. Observation of the physiological economy and gross behay- ior of animals is the basis for such a theory of the genesis of adap- tive behavior, but the only starting point for a study of conscious- ness 1s the consciousness of the observer. The observer, however, finds that other organisms of his own species have solved problems relating to, and have systematized, this very matter of consciousness, and other matters, which he, though possessing consciousness, might hardly have done. ‘This at first seems one of his strongest grounds for assuming conscious- ness in his fellows. But by such an assumption he implies that consciousness is an aid to this solving and systematizing and that he without it, could not solve and systematize. ‘This assumption he can make only by a denial of parallelism, for if consciousness in him has an invariable physiological accompaniment it may then be only the indicator of his ability and not an aid to this ability at all. But if the individual wishes, for convenience or any other reason, to assume consciousness in his own species, he may next consider what grounds he has for attributing it to other species. It 1s obvious that the probability of the other species possessing con- sciousness is directly proportional to the similarity of their behav- ior to that of the species assumed to possess it. In so far as inves- tigation follows this line it is valid. “As the behavior of any species most nearly approximates that of the species next to it in the scale of genesis any speculation as to the origin of consciousness may best be made by studying the species in inverse order of their development. The question then presents itself, does consciousness belong to every order of life? If not, what is the lowest order that possesses it Many criteria of consciousness have been suggested by the various writers in this field, and their motives and the value of SmiTH, Educability of Paramecium. 501 their assumptions must be considered and agreed upon by animal psychology before we can have an exact classification in that science. Lioyp Morean' says that consciousness is present wher- ever we find profit byexperience. He feels justified in assuming that pleasurable consciousness is associated with those modes of behavior which through repetition become more vigorous, and dis- agreeable consciousness with those that are checked. In man most education takes place in the highest level of the brain, the functions of which are synchronous with consciousness. ‘Hence, in man, profit by experience usually implies consciousness. In many lower animals no such level exists and education is a modi- fication of the lower centers or even of the somatic tissue. If our inference of animal consciousness is based on analogy, is it analogy with the gross behavior of man or with the nervous mechanism ne man? If profit by experience is our criterion it would seem that the analogy was to man’s gross behavior. But all profit by expe- rience in man is not necessarily accompanied by consciousness. Many adjustments are brought about unconsciously and many more are arrived at without involving our choice, and this is what Morean really has in mind. We certainly do not think that the profitable adaptation of our muscle tissue to new conditions ren- ders the muscle “a conscious mechanism.’’ But much adapta- tion in animals may be of this kind, and in animals possessing no differentiated nervous system any adaptation, or profit by wear and tear, must be a modifcation of body tissue. How then shall we justify ourselves in saying that all profit by experience is evidence of consciousness in an organism! This special case of inference by analogy is usually described in such words as these: “I infer consciousness in others because I ob- serve their behavior to be similar to that behavior in myself which is accompanied by consciousness.’ But is the similarity of gross behavior our only ground of inference ? If a race of beings should appear whose gross behavior was similar to our own but whose central nervous system was entirely different would the analogy of gross behavior alone justify the inference of their consciounsess ?~ Though it might do so for the unreflective man, it would not for the ontologist. Why is the doll more than a puppet to the child? Because of the analogy of 1 Animal Behavior p. 45 ff. 502 ‘fournal of Comparative Neurology and Psychology. shape, of facial expression, and of general human appearance. The closer the analogy the stronger is the child’s illusion that the doll possesses a consciousness like her own. Hence the desire for movable limbs and closing eyes. For the child the analogy of shape isenough. For some zodlogists the analogy of gross behav- ior suffices. If analogy is to be used at all should not the analogy be complete? If the analogy is made complete the criterion of consciousness will involve the possession of a cerebral cortex. One motive for assuming subjectivity in creatures like our own bodies is the ease of description resulting from the use of subjec- tive terms. The hypothesis is further fixed by our social instincts, of pity for an injured fellow man, of gratification in his welfare, of envy of his good fortune, etc., all of which states in him recall to us the mental accompaniment which we would have were we to experience them. ‘The usefulness of the concept disappears when we extend the theory to apply to the lower forms of animal life. JENNINGS? calls attention to MUNSTERBERG’S suggested criterion of consciousness, namely, that consciousness exists where it 1s use- ful to assume it in order to help us to understand and anticipate the behavior of others. We do not speak of choice in inorganic manifolds for this would be animistic. Water does not choose to run down hill rather than up and an acid does not choose to combine witha metal. ‘The water and the metal follow certain physical and chemical laws and to apply consciousness to them is improper. Yet when the proto- plasm of a living organism contracts in one way, on being affected by a physical stimulus or a chemical reagent, rather than in an- other, some scientists at least® are willing to claim that these selec- tive contractions and resulting changes of space relations to the stimuli are evidence of mind in the organism. What is the meaning of the word selective as used by Morcan ? Certainly it means selective of the most favorable conditions for the life processes of the individual and its community. Some permanency of organization is a feature of living things. Dyna- mic biology has only begun to solve the question how this structure is maintained. The choosing of conditions is a factor in such maintaining of organization. Bad conditions drive the creature away while good conditions retain or attract it. It is adjusted so ? Behavior of lower organisms, p. 335 ff. 3 Morcan and RoMaAngss, e.g. SmiTH, Educability of Paramecium. 503 as to react in these ways. The conditions are physical and the thing’s movements are physical. *Isthe adjustment somethingelse, something half psychical? If it can be shown that a little mind would help in making the movements, then we may busy ourselves in describing the behavior of mind as it lends a helping hand to clumsy protoplasm. But what seems unphysical is not the con- traction but the purpose which the contraction serves. The purpose that some contractions serve is regulation or read- justment and we may call behavior regulatory when a process hav- ing proceeded too far is the cause of its own remedy. Such readyust- ment is not without parallels in the world of inorganic manifolds. For instance, I put my coffee pot on an open camp fire, the fire becomes too hot, and the water boils over. But the boiling over of the water regulates the fire so that a fire of nearly constant heat is kept up as long as there is a certain amount of water in the pot. So a pond is kept from freezing to the bottom in winter by a regu- lation based on the densities of water at different temperatures. As it changes from a temperature of 3.9° C. it becomes, up toa certain point, less dense. “Therefore, when the whole pond 1s at a temperature of 3.9° and the top is cooled, the warmer water from the bottom does not rise. So many machines have been made involving a regulatory principle, such as the burglar alarm or the differential valve, that no mystery surrounds it. There is a difference most valuable for classification between living organisms, which through metabolism return after some time to, or nearly to, the original state which existed previous to an experience, and those inorganic manifolds which do not return to a normal state but which remain indefinitey changed after they are acted upon. It is this reversion to a normal state in all but the highest nerve centers of living organisms which makes possible their adaptation to often recurring stimuli of the same kind, and the stability of those vital economies which we call adjustment and adaptation. For instance, let an organism at birth be capable of giving N reactions (a, b, c,—N) to a definite stimulus S and let only one of these reactions be appropriate. If only one reaction can be given at a time and if the one given is determined by the state of the organism at the time S is recevied, there is one chance in N that it is the appropriate reaction. When the appropriate reaction is finally given the other reactions are not called into play, S 504. ‘fournal of Comparative Neurology and Psychology. may cease to act, but until the appropriate reaction is given let the organism be such that it runs through the gamut of the others until the appropriate reaction is brought about. As there are N possible reactions the chances are that the appropriate reaction will be given before all N are performed. At the next appearance of the stimulus, which we may call §,, those reactions which were in the last case performed, are, through habit, more likely to be again brought about than those which were not per- formed. Let uw stand for the unperformed reactions. ‘Then we have N—w probable reactions to S,._ Habit rendering the previously most performed reactions the most probable throughout we should expect to find the appropriate reaction in response to: S, contained in N. S, contained in N-w,. S, contained in N-w,-w,. S, contained in N-nu, which approaches one asa limit. Thus the appropriate reaction would be fixed through the laws of chance and habit. ‘This law of habit is that when any action is performed a number of times under certain conditions it be- comes under those conditions more and more easily performed. There are two main roads leading to the hypothesis of animal consciousness. One is traveled by the psychologist in his effort to extend the limits of the introspective science, and the other is followed by the biologist who would find in the conscious fiat some explanation of selective movements or of regulation in behavior. Hence the criteria of consciousness applied by the two investi- gators are different. Loes‘ holds that a psychology of the lower forms must be a science of tropisms, and that even in the higher forms conscious- ness is no explanation of behavior but merely a function of the mechanism of associative memory. Whether or not the behavior of any form of life has a definite significance to the psychologist, the complexity of its functions must decide its rank in a science of behavior, and for this classification the limits of such complexity *Lorz: Dynamics of living matter, p. 158. 5 Ibid., p. 6. Smith, Educability of Paramecium. 505 must be discovered. With this in view the present study has sought to define the limits of educability of Paramcecium. EXPERIMENTS IN EDUCABILITY.® The purpose of the following experiments was to determine what kind of modifiability is shown by Paramcecium due to recur- ring experiences of the same kind. Less interest attaches to that modification of behavior due to fatigue, which is usually a retarda- tion of movement, than to that modification supposedly due to a rearrangement of structure more suitable to perform the move- ment, which may be called adaptation through practice, and which is usually characterized by more rapid or exact movement. Aside from the results bearing on modifiability, there are noted below certain movements made by Paramcecium under the condi- tions of the experiments which, to the best of my knowledge, are not spoken of by other observers. The experiments fall into three groups: (1) Those in which the animal was stimulated by touch (the meniscus of a capillary tube) the conditions being such that it could react in but two ways in order to escape; and (2) those in which the animal was stimulated by change in temperature; and (3) those in which the animal was fre- quently made to experience two conditions—say A and B which at first occurred simultaneously, and later made to experience con- dition A alone, any difference being noted between the reaction to condition A before it had been combined with condition B and the reaction to it after it had been combined with and again sep- arated from condition B. Reactions to touch. The difficulty of observing Paramcecium, or any such free-swimming organism, when it is allowed to swim unrestrained about a slide is known to all who have attempted it. The uncertainty of any results obtained is proportional to this difficulty. It is not important in these experiments to imitate the conditions of real life, so it was decided to make as fixed as pos- sible the conditions of the experiment. | For this purpose a capillary tube was selected of a bore smaller than the length of the Paramcecium and larger than his width. The animal was caught by the upward suction of the tube and the 8 These experiments were carried out mainly in the Laboratory of Psychology of the University of Pennsylvania. 506 Fournal of Comparative Neurology and Psychology. tube was then placed on a movable carriage, so the animal could always be kept in the field of the microscope no matter what part of the tube it might be swimming through. Once in the tube the Paramcecium swims to the forward end and upon reaching the meniscus jerks backward for several times its own length, then approaches again in a wider spiral than before. This backing and approaching takes place at least a dozen times and later the Paramcecium settles down to a pecking movement, revolving anti-screwwise about the meniscus and attacking about five places in its circumference. In the original approaching and retreating both movements may be either screwwise or anti-screwwise. In approaching, both the screwwise and anti-screwwise movements give about the same width of spiral; namely, a very slight one. If the retreat is made anti-screwwise a relatively straight course is followed, the spiral being hardly noticeable. If the retreat is screwwise a very wide spiral results. Fic. 1. Paramcecium turning in capillary tube. In most cases the animal after a varying time bends its anterior end around toward the aboral side (fig. 1), forming a “U”’ with its body, and after a number of jerks succeeds in reversing the posi- tion of its body in the tube. In all cases it turns toward the aboral side, thus using the long creeping cilia near the buccal groove to obtain a hold on the side of the tube. Due to these movements being of no fixed type but varying greatly from time to time under the same conditions, a satisfactory explanation cannot be made in terms of tropism. The “trial and error’ explanation, although the principle is no doubt involved, as it is in the gross movements of all animals, does not seem to satisfy, because the movement of reversing in the tube requires a great deal of effort and perseverance on the part of the Paramoecium and a relatively long time to accomplish. The law of trial and error describes the organism as avoiding any great difficulty and turning to a more easily accomplished movement. ‘The summa- tion of stimuli of many failures probably becomes adequate to cause this unusual reaction. SMITH, Educability of Paramecium. 507 As this facing about in the tube is repeated, the time taken for each turn may be longer than for the last, the animal finally dying of apparent fatigue, or, if the tube is not so small that too violent an effort is required of the animal, the time may gradually be _ shortened and a most surprising aptitude of turning be developed. Parameecia from a vigorous culture give better results than poorly nourished ones. Under optimum conditions | have found a redue- tion of turning time, after the animals have been in the tube for twelve hours or more, from four or five minutes toa second or two, which is the minimum time in which the turn can be made. Often the Paramcecium will rest for a long period at one menis- cus, slowly circling around with its buccal groove resting against the air surface. When, however, the effort is made to reverse, the shortening of time in the practiced individuals is very apparent. Fic. 2. A and J’, tubes through which water of alternating temperatures passes and on which the capillary tube rests. B, beaker of boiling water in which pipe coil is immersed. C and C’, cold water supply tubes. HH, hot water supply tube. O and O’, interrupters. S, switch which alternates tem- peratures in 4 and A’. T, capillary tube containing Parameecium. At O and O’ are two interrupters so arranged that a single lever raises one and lowers the other. If the interrupter at O presses on the pipes the water flows through the loops, the hot water (from #) flow- ing through J’ and the cold water (from C’) flowing through A. If the interrupter at O’ presses upon the pipes the hot water flows through 4 and the cold water through 4’. The temperature and flow of the water supply are kept constant so that the alternating temperatures at 4 and d’ do not vary. Reactions to temperature. In these experiments a capillary tube was selected large enough to allow the Parameecia to reverse their direction without touching its sides, and in which two Parameecia could pass each other without difficulty. A number of individuals were taken up in this tube and the tube was placed on a carriage having two large glass supporting tubes through which water of different temperatures was passing and on which the capillary tube rested (fig. 2). While hot water was flowing through one support and cold water through the other the temperatures could be reversed, by a 508 “fournal of Comparative Neurology and Psychology. single movement of the key, so that the cold water would flow through the one and the hot water through the other. Thus the distribution of temperature in the capillary tube could be reversed at will. By cold water is meant water at normal temperature to which the animal gives no reaction. As soon as the capillary tube is heated at one end by contact with the hot support the Parameecia at that end dart about at random until they are headed toward the cool end of the tube and even then do not swim to the cool end at first but often turn back to the hot end several times before finally swimming over to the cool water. Once arrived at the cool end the Parameecia do not stay there but turn and start back to the hot water. In this way a Paramoecium may traverse the length of the tube a dozen times or more before coming to rest at the cool end of the tube. If + Fic. 3. J, L-shaped tube containing Parameecia. R, Brass rod heated and in contact with T, B, Bunsen burner used to heat R. now the switch (fig. 2) is turned so that the cool end becomes hot, the animal will dart about much as it did when first stimulated and only after many trials will it reach the cool water. As the animals leave their resting place at the warm meniscus in obedience to the repeated reversing of temperatures in the tube, their movements become slower and more regulated and they seldom turn more than once toward the cold water before swimming in that direction. It is not significant to express this modification of behavior in terms of time for, although the time involved in getting away from the heated end of the tube is somewhat reduced as the stimulus recurs, it is the suitability of the movement to accomplish the result which characterizes the later reactions. In these the actual locomotion is slower but the random movements give place to more determined ones. The influence of an associated past experience upon the reaction to a given stimulus. Although in the following experiments the SmirH, Educability of Paramecium. 509 observations gave nothing but negative results, these results serve to fix the limits of educability in Paramcecium. Although Para- moecium profits by experience, as seen in the above sections, it does not show associative memory such as Lors would demand as the criterion of consciousness. The conditions of the first experiment were these. Parameecia were placed in a trough having an extremely thin glass bottom and this trough was immersed in a partitioned box containing hot and normally cool water on the two sides, so that the bottom of the trough was kept cool on one half and warm on the other (fig. 4). There was a distinct line, not corresponding exactly to the parti- tion of the under box, at which the Parameecia approaching from Fic. 4. A,alum bath heat screen. BB, light screens. C,cold water supply pipe. H, hot water supply pipe. L, electric light. P, Knife edge partition. R R, overflow return pipes. SS, supports for trough. T, trough. the cool side would turn back. A light was fixed above the trough and a screen interposed so that a shadow fell covering the warm area and a minute part of the cool area beyond the reaction line. The white Paramcecium gives no reaction to light or darkness and it was hoped that by allowing the animals to experience darkness whenever they experienced heat they might, when the heat was removed, react negatively to darkness. This they did not do, however, though one group of Parameecia were allowed to experi- ence the two conditions together for fifteen hours, one for twenty- four hours, and one for forty hours. Another experiment of a somewhat similar kind was performed in which it was tried to bring about the association of heat and # 510 © “fournal of Comparative Neurology and Psychology. gravity. [he conditions were these (fig. 3). A small tube was bent into an L shape and, after some Parameecia had been drawn up into it, was placed so that one leg was horizontal and the other, rising from this, was vertical. At the top of the vertical leg was placed a hot metal rod in contact with the glass and kept at a con- stant temperature. If Paramcecia show geotropism,’ this irrita- bility to gravity should be more easily associated with heat than could light, which, although it must make some impression on the organism, does not cause normally an avoiding reaction. Whenever the Paramcecia swam up the vertical leg of the tube they received a heat stimulus which caused them at first to jerk backwards and after many random trials to swim downward to the cool water. Although these conditions were kept unchanged for as long as three days the Parmacecia never learned to avoid the vertical leg of the tube. In the end they did not react as vio- lently to the heat and did not, as at first, swim occasionally past the hot metal rod. Also they seem later to develop greater sensi- tivity, reacting to the heat before getting as close to the metal rod. If chemicals were not so diffusible and the conditions so hard to govern, an association might be produced between temperature and some chemical stimulus. CONCLUSION. Paramcecium is educable in that its behavior may be modified to show the results of practice, both in a reduction of the time involved in performing a movement and in the increase in suit- ability of the movement to accomplish the appropriate result. In so far as the tests here apply, there is no evidence of associa- tive memory in Paramcecium. The reversing movement above described is in the nature of a positive reaction. Hampden-Sidney College, Virginia. ™Moore: Am. Four. Phys., vol. 9, pp. 238 ff. FRENCH WORK IN COMPARATIVE PSYCHOLOGY FOR, VHE, PAST TWO: YEARS. The zeal with which investigations in comparative psychology are being pursued in France is testified to by Wile contents of the Bulletin de P'nstitut général psy- chologique, whereof the reports of the Groupe d’étude de psychologie zoologique form something like four-fifths. It is further witnessed by the long bibliography attached to this paper, the extent of which, however, is partly due to the fact that many of the titles refer to short communications in the Comptes rendus of the Société de Biologie and the Académie des Sciences. In some cases the contents of these are repeated in the longer articles. The work of GEorcEs Boun is, as usual of late years, the most voluminous and the most important French contribution to the science. ‘This writer’s earlier papers may be found summarized by Professor YERKES in this fournal, vol. 16, p- 231. During the two years since the appearance of that summary, BouNn has devoted himself especially to experiments and observations on actinians and starfish. He has gained what he considers to be new confirmation of one of the cardinal facts upon which he has long insisted: the influence upon the present reactions of an animal of the conditions which haye acted upon it in the past, /es causes passées. Further, he has definitely rejected JENNINGS’ conception of “trial and error” in favor of the position of LorB, and maintains that the oscillations and variations in tropisms which have given rise to the former idea are the effect partly of the influence of past conditions, partly of that “‘sensibility to difference,’ or susceptibility to changes in the intensity of a stimulus, which LorB assumes in addition to the tropism, and which, in Boun’s opinion, LoEs’s critics have too much ignored. A special case of the influence of past causes is to be found in the preservation under laboratory conditions of certain oscillations in tropisms which coincide with tidal rhythms and with the alternation of day and night. The study of these oscillations, to which he and others had previously called attention, has been continued by Bown, and observations bearing on the matter have been made by PizRoN and by Drzewina. Boun’s statements regarding the preserva- tion of the tidal rhythms in the laboratory have been received with some scepticism by L. Lapicgue. Of the other contributors whose names are to be found inthe bibliography, PrERon, in addition to his work on actinians, has been making studies of the sensory factors which play a part in the life of ants, and has also been investigating the phenomenon of “‘autotomy,” or the amputation by an animal of one of its own members. A discussion has arisen in connection with this point between him and Drzewina, the nature of which will be later explained. FAuR&-FREmiET has been observ- ing the behavior of certain protozoa. L£caILLon has been continuing his studies of the instincts of spiders. HAcCHET-SOUPLET, pursuing his conception of animal education, for which he has, with the approval of two members of the Academy, adopted the word “‘zoopédie,” has succeeded in obtaining the vote of the Institut 512 fournal of Comparative Neurology and Psychology. général psychologique for the establishment of a Section d’étude de dressage sctenti- fique, the actual formation of which, however, appears to have been postponed. We shall now take up in order the titles in our bibliography, referring to them by number, and try to indicate the important points brought out in each paper. 1. Of this article by Boun, the substance is as follows: ‘Those animals which show most rapid transmission of nervous impulse from one segment to others would seem to have most psychic individuality, but this is a vague and obscure concept. ‘The degree of codrdination depends on the development of the receptive sensory apparatus. 2 and 3. Acanthia lectularia is a negatively phototropic insect. BoHNn shows that when it undergoes a change of illumination, its tendency is to rotate through 180° in a direction which is constant during the day, and changes towards evening. This reaction is but poorly adaptive, since under certain conditions it may lead the animal to turn toward the light. For instance, if the insect 1s moving along a shadow directly away from the light, and comes to the end of the shadow, it will turn through 180° and thus be brought to face the light. Again, it may either approach or move away from a dark screen, as a consequence of its turning always in the same direction at a given time of the day. The mollusc Littorina, on the other hand, is always, at a given hour, attracted by a dark screen. ‘The superior adaptiveness of Littorina’s behavior may be due to the fact that in nature it is accustomed to seek shade, while Acanthia does not come out on bright surfaces at all during the day. 4 and 5. The results stated in these papers were published later in 27. 6. The results of this paper are stated in paper number I5. 7. As between the “‘teleological” interpretations of JENNINGS and the mechanical explanations of Lors, BouHN would insist on taking account of the past experience of the animal in determining tropisms. 8. This paper must be taken in connection with that by P1ERon numbered 59 in the bibliography, and with the paper by Bonn and Préron numbered 28. Actinia equina closes when the sea withdraws, and opens when the sea returns. Pizron found that the specimens he kept in the laboratory opened under the following conditions: when sea-water was made to run over them, when the water was agitated, when it was reoxygenated, when food substances were brought near. ‘They closed when they had been some little time dry, when the water was deoxygenated, when they received mechanical shocks, and after grave lesion by toxic substances. In the pools from which they were taken, they expand at the mechanical agitation caused by the first wave of the rising tide that reaches the pool. They close, at falling tide, before the pool is stagnant. They thus show “anticipation,” in closing before there is actual need of it. PrE£Ron did not find, however, that rhythmic opening and closing in accord with the tides persisted in the laboratory (59). BouN and Préron, in their joint paper (28), explain the difference between their results in regard to this last point,—Bouwn having found a persistence of the tidal rhythm in the laboratory with Actinia equina as with Convoluta roscoffensis,—by the difference in habitat between their specimens. Boun’s were taken from high on the side of a vertical wall, where the contrast be- tween the conditions at high tide and those at low tide was very marked. PIERON’s were taken from pools not wholly dry even at low tide. The “anticipation” noted by P1£RON is a step towards the development of such a rhythm as that WasHBuRN, Comparative Psychology. 513 observed by Boun. The actinian first responds to the stimulus of loss of oxygen or drying; then, by anticipation, to a stimulus which regularly precedes this (diminished agitation of the water), and finally to an internal, periodically occur- ring stimulus (28). In paper number 8 of the bibliography, Bown gives a further account of the persistence of the tidal rhythm in Actinia. “The specimens observed by him spontaneously opened and closed in the laboratory for two or three days. That the rhythm still existed after this time was revealed by the following facts: if an actinian was placed in a current of water, after expanding, it closed, but it closed much more readily at the time of descending tide; when kept in a current for a long time, the actinians remained closed, but opened irregularly and tem- porarily at the next high tide, and quite generally and persistently at the one after that; mechanical shocks had a tendency to make them open at rising tide and close at falling tide. L. LapicgugE, in paper number 43, expresses doubt as to the reality of the periodicity thus observed. He raises the point that the rhythm impressed upon the actinians should be that of the tides on the last day of their sojourn under actual tidal influence, and that this would in the course of the next week bring them quite out of accord with the contemporary tidal periodicity. Boun replies in paper number g by showing that the oscillations correspond in a general way to the contemporary tidal rhythm; and in paper number 38, with FauvEL, demon- strates that certain diatoms (Pleurosigma aestuarii) exhibit a tidal rhythm in emergence and disappearance which continues in the aquarium. He admits that mathematical exactness in plotting the curves of such periodicities is impossible (12) (13) (18); Laprcgue, unreconciled, suggests that Boun had better give Op the attempt at it, if this be the case (44) (45). 10. Boun’s study of certain seaside butterflies concerns the relations between phototropism and anemotropism. Satyrus janira orients itself when at rest with head to the wind; its flight is determined by the position of the sun. The more the posterior portion of the eyes is illuminated, the more the wings are spread apart when the insect is at rest, and the more ene recucally they beat in flight; hence the insect flies away fon the sun, especially when it is low. Vanessa cardui shows the same relation between the illumination of the eyes and the beat- ing of the wings, only more strikingly; V. io also shows it, but the relation is the reverse in the case of V. urticz. 1. This article is a discussion, more or less historical, of the relations between tropisms, instincts, and intelligent acts, in which the conclusion is reached that “JENNINGS is wholly right in considering supposed tropisms as phenomena in general very complex. But these tropisms depend not only on the connections between organs, but on the state of the matter composing the organs. Living matter has a whole history which is responsible for the fact that its reactions are made in accordance with determinate rules. Selection, as JENNINGS conceives it, has but little upon which to exercise itself. The ideas of JENNINGS, far from invalidating those of LorsB, merely supplement them.” 14, 15, 16, 17. These papers on the reactions of actinians may be considered together. Paper 15 includes the results of the other three. Actinia equina, as we have seen, was found to preserve a tidal rhythm in the laboratory. A day and night rhythm, usually that of opening at night and closing by day, also showed itself. The influence of habitat was indicated by the fact that the day and night 514 ‘fournal of Comparative Neurology and Psychology. rhythm was observable in actinians taken from pools where the tidal changes were less important. It was masked by the tidal rhythm in specimens from high rocks, but might be observed in these when the tidal rhythm had disappeared. The effect of habitat was further shown by the fact that actinians collected from sunny laces showed a reverse day and night periodicity, opening by day and closing at night, while those taken from dark places seemed to suffer under the influence of light. The effect of light is exhibited by the fact that actinians display more activity, the more light they have been subjected to in the past. Impurity of the water increases the effect of light. Mechanical agitation seems to destroy a state of inertia in the animals, and may reveal a tidal rhythm. Anthea cereus and Actinoloba dianthus show a more marked response to light than Actinia equina, the former probably because it contains chlorophyll-bearing alga. A. cereus converges its tentacles towards the light; A. dianthus orients its column in the same direction, but the orientation is reached only after a series of oscillations which suggest trials and errors, but in Boun’s opinion are the absolutely determined effect of past causes, combined with “sensibility to difference” in LoEB’s sense. There is a general tendency for actinians to expand under a thin layer of water; this is doubtless connected with the fact that the food supply is best near the sur- face. Tealia crassicornis shows the same general features of behavior as the other actinians mentioned. 19. The most important point in this paper is as follows. The leech observed is positively phototropic; at the outset of its movements toward the light, its orientation is precise, but the further it advances, the more it waves its body from side to side. If these deviations were “trials,” they ought, BouHNn contends, to diminish rather than increase in number. ‘They are, rather, the effect of the progressive weakening of the light’s attraction. 20 and 21. These communications may be summarized in the author’s own words. ‘‘An animal which has just been immersed in still water or undergone mechanical excitation, if it moves in a restricted area of a constant luminous field, shows in general a progressive and more or less rapid weakening of the effects of phototropism and of sensibility to difference. This weakening is connected with the progressive return of the animal to a state of rest. We should see in this return, not the consequence of ” fatigue or an alteration in external circumstances, but “the progressive exhaustion of the nervous effects of the initial mechanical excitation, which momentarily overcame the inertia of the animal.” “In a lumin- ous field, phototropic animals follow fatally, in a given direction, certain lines. But during a change of illumination, the animals tend to turn about upon the lines and follow them momentarily in the opposite direction, hence they may deviate for atime. Many of the supposed “trials” of JENNINGs might be explained by apply- ing this law.” 22. This is a summary of recent work in America and elsewhere. 23, 24, 25, 27. The echinoderms studied by Boun were the following: Asterias rubens, Asteriscus verruculatus, Astropecten irregularis, Ophiolepsis ciliata, O. albida, Ophiothrix fragilis, Ophiocnida brachiata. ‘The salient results may be grouped under three heads. (a) Sensibility to difference is shown by the tendency of sudden changes of illumination or of slope to change the sign of phototropism and geotropism, producing oscillations which are not properly “‘trials,” but are as fatally determined as the tropisms themselves. Further evidence that these WasHBurn, Comparative Psychology. 515 oscillations are not “‘trials” is to be found, Boun thinks, in the fact that young starfish show them to a much less extent than older ones; trials should diminish with age. (b) The eyes are essential in phototropism; a starfish with one or more eyes sectioned acts as if a black screen were brought near, that is, it moves toward the wound, a tendency which conflicts in an interesting way with the general tendency to move away from a wounded point. (c) The formation of habits in the starfish is shown by the following observations. A starfish on a sunny bottom far from any shade converges its arms towards the light in order to protect itself. Those which live normally in sunny regions do this more readily than those which are accustomed to be near shade which they can seek. Further, the starfish is capable of changing the direction of its movement in two ways: by changing the leading arm, and by rotating on itself so as to give its arms a new direction. An individual may be taught to use the latter method by cutting off one or more arms, or by repeatedly stimulating an arm. 26. ‘This paper contains notes on the reproduction of actinians by fission. 29. This article is a more or less popular lecture by BonntER on the habits of the honey-bee, in which he maintains the singular thesis that individual bees have no intelligence whatever; that intelligence is for the bee a function of the social state, and that it is displayed to a marvelous degree by a “secret committee” which regulates the affairs of the hive. 30 and 31. These articles by Mlle. DrzEwina will be discussed in connection with numbers 62-67, as they are concerned with P1EzRoN’s ideas on autotomy. 32. Here Drzewina shows that the fortnightly tidal fluctuations are repre- sented by changes of phototropism in the laboratory on the part of the crab Cli- banarius misanthropus. 33. Carcinus moenas put down anywhere on the beach will turn and make for the water, even with eyes blackened, and with the wind from any quarter. This, Drzewina thinks, is a case of attraction by humidity, and the influence of past causes is shown by the fact that crabs from high levels are specially sensitive. 345 35, 36, 37. FauRE-FREmIET in these articles first surveys the differentiations of structure and of sensory and motor apparatus to be found in the Protozoa. He then classes the reactions of this group under four heads: local and direct response to stimulation, as the withdrawal of a pseudopod; more extended response, involving a considerable portion of the body; general response, involving move- ment of the entire body; and local but indirect response, such as the retraction of the stem in Vorticella when another part is stimulated. In papers number 36 and 37 the reactions of Colpoda cucullus and Urostyla grandis are described, and the attempt is made to show that they are the resultants of the various ciliary bene. 39. Forex thinks the following fact shows that bees have memory for time. Some bees learned to visit an out-of-doors dining-table at certain hours of the morning and afternoon during which there were sweets on the table. They con- tinued for several days to come at these hours, although the sweets were no longer placed on the table; then gradually desisted. ~ 40. HACHET-SOUPLET suggests that we may be sure of the purely instinctive, i.e., non-intelligent, character of an act when an animal persists in trying to per- form it though one of the essential conditions for its performance is lacking, as when, for example, a hermit crab tries to introduce itself into a smooth glass ball without an opening. 516 “fournal of Comparative Neurology and Psychology. 41. In presenting his request for the formation of a special section for the study of animal education, HacHET-SouPLET makes some observations on the method which he considers best adapted to bring out the highest mental powers of animals: that of persuasion, consisting in explaining to the animal, by voice, gesture, or arrangement of surroundings, what it is expected to do. 42. The same writer discusses the method by which dogs are taught to rescue drowning persons. 46, 47, 48. The most important results of the last two papers are included in the first. ‘The instincts treated are the uses of the web, the care of the young, and the courting processes. LEcAILLON finds that the spiders observed by him show little discrimination in regard to the cocoon, but will accept cocoons of other species and different form from their own; that they are not disturbed if, while they are carrying a cocoon, its wall is cut, allowing the eggs to fall out and decidedly alter- ing the weight of their burden; that they can distinguish at some little distance a strange female occupying their nest. 49. MaraceE places himself on the negative side of the discussion regarding the hearing of fishes. He tested Gobio fluviatilis, Anguilla vulgaris, Esox lucius, Tinca vulgaris, Cyprinus carpio, and Leuciscus ite in the aquarium, and, in free water, Alburnus lucidus. The sounds used were the vowels ou, 0, a, é sung successively on notes from C2 to G6, with energy varying from 0.00045 ‘Kem. to 0.05 kgm., communicated through rubber tubes, the fish not being able to see the experimenter. No response ies er was Sheed: though a diver 80 m. away could hear and distinguish the sounds. 50. The chief contribution made by Martin to the study of the tidal rhythm in Convoluta is the fact that various influences, such as repeated mechanical shocks, prolonged darkness, colored light, chemicals, etc., may inhibit the rhythm, causing “‘amnesia,” and that “‘non-amnesic C mingled with a greater number of amnesic C lose their memory, while amnesic C mingled with a greater number of non-amnesic C imitate the oscillatory movements of the latter.” 51. This is an unimportant because inexact observation of the attraction of ants to food at a distance. 52. This paper contains definitions of morphological terms and a statement of unsolved problems with regard to the instincts and mental powers of birds. 53 and 55. Pi£RoN’s study of Actinia equina begins with the question as to what stimuli provoke reaction: he finds, unlike Boun, that light has no effect, nor has auditory stimulation. There is some response to food held very close to but not in contact with a tentacle. Contact with food produces the feeding reaction; some individuals will attach themselves to any mechanical stimulus, while others give withdrawing movements to any but a food stimulus. A portion of another actinian will not be swallowed. As regards the localization of sensibility, the tentacles are sensitive to both mechanical and chemical stimuli, as are the peri- stome and mouth; the foot is very sensitive to mechanical stimuli, and the column insensitive to both mechanical and chemical excitants. Varieties, individuals, and ages differ in sensibility. Foul water and drying affect the response to stimu- lation, as do certain internal factors, such as digestion, regurgitation, and _parturi- tion. Reaction ceases when a mechanical stimulus is repeated. Paper 55 is a study of the movements of A. equina and of their synergy. 54. This paper discusses, without reaching a positive conclusion, the problem WasHBuRN, Comparative Psychology. 517 as to whether the crab or the actinian started the fashion of the latter's taking up its abode on the former’s back. 56, 57, 58, 61. The first of the reports by PiERoN to the Society of Biology regarding his studies on ants states that he has confirmed with eighteen hitherto untested combinations of species, BETHE’s experiment in which an ant was received into a foreign nest when dipped in the juices of ants from that nest. In the second paper (57), he notes various circumstances which modify the reaction to strangers. Certain species are inclined to be tolerant, such as Aphznogaster barbara nigra and Formica cinerea with regard to other nests of the same species, and Myrmecina latreillei with regard to other species. Sometimes an ant of the same nest is attacked “erroneously.” Attacks are more frequent near the nest than at a distance from it. A solitary ant tends to run away rather than to attack, save in the case of a very small one meeting an ant of a larger species, when the former clings to the legs of the latter. Males do not distinguish strangers from nestmates, and a female after the nuptial flight is received in a foreign nest. ‘There are also individ- ual differences in reaction. Most of these modifying circumstances have an adaptive significance (58), for instance the tolerance of Formica cinerea is doubt- less connected with the fact that its nests are ordinarily built close together, and that of Myrmecina may be due to its hard chitinous armor. As regards the problem of nest finding, PrzRoN would distinguish three types of ants: visual (Formica fusca, e.g., which cannot find the nest when blinded), olfactory (Lasius fuliginosus, e.g.), and muscular (Aphznogaster barbara, which if carried out of its path will continue, when set down, until it reaches a point where the opening of its nest would have been found if the ant had not been moved). 59, 60, 63. We have already noted under (8) the contents of paper 59 and Pi£Ron’s distinction between “‘anticipation,’ or reaction which is made ahead of time because it has become associated with an an external stimulus occur- ring before the original stimulus to the reaction, and rhythmic reaction, where the response is made to an internal state of the organism, which has come to be period- ically produced. In papers 60 and 63 this distinction is amplified and the general significance of physiological rhythms considered. 62, 64, 65, 66, 67. ‘The chief point of importance brought out in the discussion of autotomy or self-amputation is PIERON’s differentiation of a form of the phenome- non which he calls “psychic autotomy,” unlike reflex autotomy in the facts that it is made in response to slight stimulation, such as merely holding the member fast, and that it does not occur if the commissures connecting the cerebral ganglia with the ventral ganglia are cut. DRzEWINA (30, 31) sees no reason to distinguish this phenomenon from ordinary reflex autotomy, and has found it occurring after section of the commissures. 68. ReTTERER states that actinians in northern seas where the effect of the tides is less marked do not show a tidal rhythm in the laboratory. 69. This paper is a study of the manner in which certain seaside Diptera are adapted to their surroundings. ‘The bodies of most of them are impervious to water; those which are by their manner of life exposed to the wind have a marked tendency to orient to it, or to hide behind shells when it is very strong; other forms resist it by taking very short flights or by bracing themselves with their legs. 70. The following three points are brought out in this study of Actinia equina. (a) ‘lhe actinian tends to resume the position it had in nature when placed in 518 Fournal of Comparative Neurology and Psychology. the reverse position in the laboratory. (6) An actinian would not swallow a bit of mollusc attached to a morsel of cork until the cork was removed. A bit of mollusc different (c) The between Boun, G. ie fon mn PW vv Bonn, G. 28. and a piece of another actinian, of a different species, being placed on parts of the disk, the former was swallowed and the latter rejected. foot ‘prefers’ to attach itself to a rough surface if offered the “choice” this and a smooth one. BIBLIOGRAPHY. L’individualité psychique chez les Vers, les Echinodermes, et les Insectes. Bull. Inst. gén. psych., vol. 6, p. 115. 1906. Sur le photrotopisme de l’Acanthia lectularia Fabr. C.r. Soc. Biol., vol. 60, p. 520. 1906. Sur ladaptation des réactions phototropiques. C.r. Soc. Biol., vol. 60, p. 584. 1906. Sur les courbures dues a la lumiére. C.r. Soc. Biol., vol. 61, p. 420. 1906. Sur des mouvements de roulement influencés par la lumiére. C.r. Soc. Biol., vol. 61, p. 468. 1906. Mouvements en relation avec l’assimilation pigmentaire chez les animaux. C.r. Soc. Biol., vol. 61, p. 527. 1906. La finalité dans l’étude des mouvements. C. 1. Soc. Biol., vol. 61, p. 570. 1906. La persistance du rythme des marées chez l’Actinia equina. C.r. Soc. Biol., vol. 61, p. 661. 1906. Le rythme des marées et la matiére vivante. Réponse a M. Lapicque. C.r. Soc. Biol., vol. 61, p. 708. 1906. Observations sur les papillons du rivage dela mer. Bull. Inst. gén. psych., vol. 6, p. 285. 1906. Les tropismes, les réflexes, et V’intelligence. Ann. psych., vol. 12, p. 137. 1906. Quelques chiffres rélatifs au rythme vital des Convoluta. C.r. Soc Biol., vol. 62, p. 51. 1907. Sur Pimpossibilité d’étudier avec une précision mathématique les oscillations de J’état physiologique chez les animaux littoraux. C.r. Soc. Biol., vol. 62, p. 211. 1907. L’influence de l’éclairement passé sur la matiére vivante. C.r. Soc. Biol., vol. 62, p. 292. 1907. Introduction 4 la psychologie des animaux 4 symétrie rayonnée. I. Les etats physiolo- giques des Actinies. Bull. Inst. gén. psych., vol. 7, pp. 81, 135. 1907. L’influence de l’agitation de l’eau sur les Actinies. C.r. Soc. Biol., vol. 62, p.395- 1907- Le rythme nycthéméral chez les Actinies. C.r. Soc. Biol., vol. 62, p. 473- 1907- A propos du procés-verbal. Le ralentissement et l’accélération des oscillations des Con- voluta. C. 7. Soc. Biol., vol. 62, p. 564. 1907. Les tropismes, la sensibilité differentielle, et les associations chez le Branchellion de la a Torpille. * C. r. Soc. Biol., vol. 63, p. 545. 1907. A propos des lois de P’excitabilité par la lumiére. I. Le rétour progressif 4 l’état d’immobi- lité aprés une stimulation mécanique. C.r. Soc. Biol., vol. 63, p. 655. 1907. A propos des lois, etc. II. Du changement du signe du phototropisme en tant que manifes- tation de la sensibilité differentielle. C.r. Soc. Biol., vol. 63, p. 756. 1907. L’acquisition des habitudes chez les animaux. Ann. psych., vol. 13, p. 170. 1907. Sur la réle et la protection des organes des sens chez les échinodermes. C. r. Soc. Biol., Biol., vol. 64, p. 277. 1908. Sur les mouvements rotatoires des Etoiles de mer et les Ophiures. C.r. Soc. Biol., vol. 64, Pp. 532. 1908. c De lacquisition des habitudes chez les Etoiles de mer. C.r. Soc. Biol., vol. 64, p. 633. 1908. Scissiparité et autotomie chez les Actinies. C.r. Soc. Biol., vol. 64, p. 936. 1908. Introduction 4 la psychologie des animaux 4 symetrierayonnée. II. Les essais et erreurs chez les Etoiles de mer et les Ophiures. Bull. Inst. gén. psych., vol. 8, p. 21. 1908. and Piéron, H. Le rythme des marées et le phénoméne de l’anticipation réflexe. C.r. Soc. Biol., vol. 61, p- 660. 1906. WasHBurn, Comparative Psychology. 519 Bonnier, G. 29. Le socialisme chez les abeilles. Bull. Inst. gén. psych., vol. 7, p- 397- 19°7- Drzewina, A. 30. Sur la prétendue autotomie psychique. C. r. Soc. Biol., vol. 63, p- 459- 1907- 31. Ya+t-il une différence effective entre la prétendue autotomie psychique et Pautotomie réflexe? Réponse a M. Piéron. C. r. Soc. Biol., vol. 63, p- 493- 1907- 32. Les variations périodiques du signe du phototropisme chez les Pagures misanthropes. C. r. Acad. Sci., Paris, Dec. 9, 1907- 33- De Vhydrotropisme chez les Crabes. C.r. Soc. Biol., vol. 64, p. 1009. 1908. Faurt-Freémiet, E. 34. Organisation, fonctionnement, et réactions individuelles chez les Cytozoaires. Bull. Inst. gén. psych., vol. 6, p. 305: 1906. 35. L’organisation, le fonctionnement, et les réactions individuelles chez les Cytozoaires. Bull. Inst. gén. psych. vol. 7, p+ 75+ 19°7- 36. Réactions de deux Infusoires ciliés. Bull. Inst. gén. psych., vol. 7, p- 308. 1907. 37- Les conditions organiques de comportement chez les Cytozoaires: PUrostyla grandis. Bull. Inst. gén. psych., vol. 7, Pp» 441+ 1907. Fauvet, P. and Bonn, G. 38. Le rythme des marées chez les Diatomées littorales. C.r. Soc. Biol., vol. 62, p. 121. 1907. Foret, A. 39. La mémoire du temps et association des souvenirs chez les Abeilles. Bull. Inst. gén. psych., vol. 6, p. 258. 1906. Hacuet-SouP.et. 40. Le critérium de instinct. Bull. Inst. gén. psych., vol. 7, p- 72+ 1907- 41. Sur un projet de création d’une Section d’étude expérimentale de dressage scientifique a VInstitut général psychologique. Bull. Inst. gén. psych., vol. 7, p. 187. 1907. 42. Les chiens sauveteurs et la Zoopédie. Bull. Inst. gén. psych., vol. 7, p. 451. 1907. LaricquE, L. 43. Sur les fonctions rythmiques des animaux soumis 4 l’alternance des marées. Observa- vation sur la note de M. Bohn. C. r. Soc. Biol., vol. 61, p. 7°7- 1906. 44. Sur la précision dans la question du rythme des marées. C. r. Soc. Biol., vol. 62, p. 302. 1907. 45. Réponse a M. Bohn, GC. r. Soc. Biol., vol. 62, p. 475. 1907- LécalLion, A. 46. Les instincts et le psychisme des Araignées. Bull. Inst. gén. psych., vol. 6, 127. 1906. 47. Notes complémentaires sur les moeurs des Araignées. I. Influence de la nutrition sur la réproduction d’Ageléna labyrinthica Cl. C. r. Soc. Biol., vol. 62, p. 334. 1907- 48. Notes complémentaires, etc. I. Nature et importance des soins que certaines femelles donnent a leur progeniture. C.r. Soc. Biol., vol. 63, p- 668. 1907. MaracE. 49. Contribution a étude de Paudition des poissons. C.r. Acad. Sci. Paris, vol. 143, P. 852. 1906. Mart, L. so. La mémoire chez Convoluta roscoffensis. C.r. Acad. Sci., Paris, vol. 145, p- 555+ MéneEGaAux, A. 51. Une observation sur le sens olfactif A distance chez les Fourmis. Bull. Inst. gén. psych., vol. 6. p. 302. 1906. 52. Questions de morphologie et de psychologie chez les oiseaux. Bull. Inst. gén. psych., vol. 7, p- 427- 1907. Pitron, H. 53. Contributions 4 la psychologie des Actinies. Bull. Inst. gén. psych., vol. 6, p. 40. 1906. 54. Contribution a étude des rapports éthologiques des Crabes et des Actinies. Bull. Inst. gén. psych., vol. 6. p. 98. 1906. 55. Contribution 4 la psychophysiologie des Actinies. Les réactions de l’Actinia equina. Bull. Inst. gén. psych. vol. 6, p. 146. 1906. 56. Généralité du processus olfactif de reconnaissance chez les Fourmis. C. r. Soc. Biol., vol. 61, p. 385. 1906. 57. Exceptions et variations dans le processus olfactif de reconnaissance chez les Fourmis. C. r. Soc. Biol., vol. 61, p. 433- 1906. 520 ‘fournal of Comparative Neurology and Psychology. Piéron, H. 58. 59: 60. 61. 62. 63. 64. 65. 66. 67. RETTERER, 68. Roupaup. 69. Le mécanisme de la reconnaissance chez les Fourmis. Réle des données olfactives. C.r. Soc. Biol., vol. 61, p. 471, 1906. La réaction aux marées par anticipation réflexe chez Actinia equina. C.r. Soc. Biol., vol. 61, p. 658. 1906. La question des rythmes spontanés et des phenoménes d’anticipation en biologie. C. r. Biol., vol. 62, p. 51. 1907. L’adaptation 4 la récherche du nid chez les Fourmis. C.r. Soc. Biol., vol. 62, p.216. 1907. Autotomie et ‘autospasie’. C. r. Soc. Biol., vol. 63, p. 425. 1907. Des phenoménes d’adaptation biologique par anticipation rythmique. C. r. Acad. Sci., Paris, vol. 144, p. 138. 1907. Sur une prétendue réfutation de Pautotomie psychique. Résponse 4 Mlle. Drzewina. C. r. Soc. Biol., vol. 63, p. 461. 1907. L’autotomie protectrice réflexe chez les Orthoptéres. C. r. Soc. Biol., vol. 63, p. 463. 1907. aan volontaire des décapodes. Quelques idées et quelques faits. C.r. Soc. Biol., vol. 63, p. 517- 1907. L’autotomie évasive chez les Orthoptéres. C.r. Soc. Biol., vol. 63, p. 186. 1907. E. A propos du rythme des marées et de la matiére vivante. C.r. Soc. Biol., vol. 62, p. 186- 1907. Instincts, adaptation, résistance au milieu chez les Mouches des rivages maritimes. Bull. Inst. gén. psych., vol. 7. p. 60. 1907. VAN DER Guinst, I. 70. Quelques observations sur les Actinies. Bull. Inst. gén. psych., vol. 6, p. 267. 1906. MARGARET FLOY WASHBURN, LIDERARY NOTICES. Pricer, Jno. L, The Life History of the Carpenter Ant. Biol. Bull., vol. 14, pp. 177-218, 1908. This paper. which is interesting to both the biologist and the psychologist, embod- ies the results of a year’s study of the carpenter ant (Camponotus pennsylvanicus and C. ferrugineus). ‘The contents of numerous nests collected during the winter were examined and counted, and colonies were raised from individual females cap- tured immediately after their nuptial flight. The subject is treated under the fol- lowing heads: “Life history of the colony,” “‘ polymorphism, ” “division of labor,” “food,’’ “relation to light and color,” “guests and parasites,’’ “instinct and intel- ligence. ” The author confirms the statement of Dr. WHEELER! and others that the fertil- ized female fasts from the time it enters its brood chamber until its first offspring have reached maturity. He also agrees with Dr. WHEELER’ that the polymorphism of this ant is onto- genetic. At the time of laying, all eggs of fertilized females are essentially alike. The size of the resulting offspring depends upon the quantity of food fed the larve. Mr. Pricer’s observations seem to support the view that sexually mature indi- viduals are not produced until the colony is more than two years old, and that the brood of females produced one summer remains in the nest until the following spring. The food of the ants consists chiefly of honey dew obtained from aphids. But this is supplemented by insect food and plant juices. “The aphids are never domes- ticated, nor are their eggs stored in the nest over winter. Insects are never captured alive and the head is the only part of insects fed upon that is ever carried into the nest. In his experiments on light the author employed the much used devise of a cen- tral corridor, on each side of which are rooms illuminated by light passing through glasses of different colors He used deep red, green, deep blue, indigo-blue and a cell of carbon disulfid (this latter to exclude the ultra-violet rays). At the begin- ning of the experiment these glasses were arranged in reverse order in the two sets of rooms. During the experiments the glasses were manipulated in various ways. As a control he used ants the eyes of which had been rendered opaque. The ants preferred to collect under the red glass, and they avoided the blue and light of shorter wave length. In this respect his results harmonize with those of Lussock and Miss F1ELDE; but Pricer’s experiments seem to show that the ants perceive the red, etc., whereas Miss Fre.pe’ claims that ants are blind to all rays of greater wave length than the violet. 1Wueeter, WM.M. On the founding of colonies by queen ants, etc., Bull. Am. Mus .of Nat. Hist., vol. 22, p. 39, 1906. ?Wueeter, WM.M. The polymorphism of ants. Jbid., vol. 23, pp. 66-75, 1907. $Fierpr,A.M. Notesonanant. Proc. Acad. Sci. Phil., vol. 54, p. 615, 1902; Effects of light-rays onanant. Biol. Bull., vol. 6, p. 309, 1904. 522 fournal of Comparative Neurology and Psychology. He demonstrated that ants enclosed in a wire gauze cylinder could be exposed to an arc light, at a temperature of 40° C., for an hour without being injured. From this he concludes that the nocturnal habits of this ant are the result not of necessity, but of preference. This is a broader conclusion than the experiment seems to warrant. McCook and others have held that this ant has an architecture of its own, and some have claimed that it damages trees and timber. ‘The observations of Mr. PRICER seem to show conclusively that it injures neither trees nor timber and that it has no architecture of its own, but lives in the abandoned burrows of wood borers and, unless the wood is rotten, it never alters the shape of these burrows. Five experiments upon instinct and intelligence led to the following conclusions: 1. Ants are capable of tracking themselves and others of the colony; but they are incapable of distinguishing the direction in which the trail was first laid down. 2. Ants do not depend entirely upon following trails in finding their way about, but are guided often by memory of the location of things and probably depend, as a last resort, on a sense of direction. 3. Ants ordinarily pay very little attention to trails when traveling from the nest. In the main the above conclusions harmonize well with the results stated in my paper on the Homing of Ants.* He also claims that there is no evidence of anything akin to reason. From the standpoint of comparative psychology, probably the most interesting portion of the paper is the record of the experiments on the power of communica- tion. The author placed a number of larva upon a small island which was con- nected, by means of bridges, with the food chamber of the nest. | An ant discoy- ered these and returned, empty handed, tothe nest. There it butted against several workers and then retraced its steps to the larve. The ants thus saluted, and no others, followed it. This was repeated several times with practically the same result. Once, however, two out of eight ants saluted reached the larve before the ant that discovered them had retraced its steps that far. ‘This most interesting experiment led to the conclusion that ants can communicate. One cannot help wishing that the author had devised an experiment which precluded the possibility of the response being due to an odor conveyed by the ant from the discovered larve to the ants saluted. The following epitome of an unpublished experiment of mine upon an allied species (C. herculeano-ligniperdus) will emphasize the importance of this precau- tion. The colony, which was housed in a JANET nest, usually kept a guard in the entrance. One day some strange ants (Formica fusca var. subsericea) forced their way past the guard to some food which I had placed just inside the nest. The guard, after fighting them for a while, retreated into the inner chamber, rushed about among the ants and then returned to the fray, followed by several others. ‘This looked like communication. To test the matter the following experiment was devised. I heated dissecting needles and glass stirring rods red-hot, to destroy any odor, and, as soon as they were cool, fought the guard with them. Soon it retreated into the inner chambers, rushed about among the ants and then returned, alone, to the outer chamber. ‘Then | dipped the needle or the stirring rod into oil of cloves and again fought the guard. It again retreated to the inner chamber, 4Turner,C.H. ‘our. of Comp. Neur. and Psy., vol. 17, p. 423, 1907- Literary Notices. oe. rushed around among the ants, and returned to the outer chamber. In this case, however, it was followed by several of itscompanions. ‘This was repeated several times with similar results. So interested was I in this experiment that I called in Professor Mean, of the University of Chicago, and performed it before him. Evi- dently, in this case, the following reaction wasa response to an odor. Whether ants do or do not communicate in any other way is a subject upon which I have no opin- ion that I am prepared to publish. I mention this experiment merely to show that this question is too complex to be solved by any experiment which is not so planned as to preclude the possibility of the reaction being a response to an odor. The author is to be complimented for the originality displayed in devising apparatus. C. H. TURNER. Jennings, H.S. Behavior of the Starfish Asterias forerri de Loriol. Univ. of Calif. Publ. in Zoélogy, vol. 4, nO. 2, pp. 53-185, 19 text figures. 1907. The present investigation on the Pacific Coast starfish, Asterias forreri, is another thorough, analytical contribution to the subject of animal behavior, in which field Professor JENNINGS has already done such masterly work. His general plan of investigation here is the same as that which first gave him an insight to the behavior of Paramecium and the Protozoa in general, and which led to the conception of the “motor reaction” as a stereotyped, almost universal mode of reaction to stimuli among these lower oragnisms—namely, a preliminary careful, minute, descriptive study of the behavior of the animal. The list of the headings which cover the descriptive portion of his paper will give an idea of the range of the investigation; these are: “‘ Respiration and its pro- tection by the pedicellariz,” “Detailed behavior of the pedicellariz,” “‘Capture of food,” ‘‘ Behavior of the starfish in selecting conditions of existence,”’ “Reaction to light,” “ Positive reactions,” ‘The righting reaction,” and “* Formation of habits in the starfish.” Of these most attention is directed to the righting reaction, while the reactions to light are least fully worked out. ‘There is such a wealth of detailed observational results that only the barest selection can be made in a review of this character. ‘They form, however, most interesting reading, in spite of their detail and of the fact that the author has in places relapsed somewhat from his usual liter- ary care, as, for example, in the description of the capture of food, where the tense changes with confusing rapidity. Frequent reference back and forth to the inter- related phenomena assists, even at the expense of some repetition, to keep in the reader’s mind the relationship of numerous factors which go to make up the com- plicated behavior of the starfish as a whole. For the author comes very decidedly to the conclusion—and the reader can hardly disagree with him—that the behavior of the starfish cannot be attributed to simple direct responses to obvious stimuli. On the contrary, besides the external stimuli, internal factors, depending upon past actions, etc., may determine the method of behavior. ‘The author himself states that perhaps the most important thing developed in his paper is “‘the demonstra- tion of the variability, modifiability, unity and adaptiveness in the main features of the behavior of the starfish.” The unity of the parts of the starfish in performing its various actions is an impor- tant point, upon which much emphasis is placed. Thus the behavior of the pedicel- 524 ‘fournal of Comparative Neurology and Psychology. lariz remind one very strongly of the behavior of individuals in a colony, such as of bees or ants, all of which work together to accomplish a definite end. When a starfish is placed in a new situation, where there is a problem to solve, the move- ments are at first varied, but soon a definite impulse to act in a certain way appears to be formed, after which all the parts work together with a unity to bring about the results on this line. JENNINGS calls this the unified impulse. When this is once established the movements tend to continue along this course, even if the con- ditions be changed and new stimuli introduced. ‘This latter tendency the author believes is “evidently akin to the formation of a habit.”” Moreover, he has actually been able to demonstrate habit formation in the starfish by training individuals to use different rays in righting themselves from those which they naturally employ. The effect of this laborious training, however, soon disappears. Considerable space is devoted to a iiscnesion Mol hese eau in relation to Driescu’s postulation of a “Psychoid” or “‘Entelechy,” a sort of vitalistic prin- ciple, which that author believes the only way of explaining these adaptive reactions. While JENNINGS does not claim to have analyzed all the factors which enter in, he nevertheless maintains—and very properly, it seems to the reviewer—that DriEscu’s would-be explanation is “merely a way of collecting all the difficulties together and giving the bundle a name.” “‘The Entelechy would be a problem not a solution, ” while “to accept the Entelechy unanalyzed and unexplained is merely to give up the problem as insoluble.” ‘The author’s alternative answer to the question is pregnant with suggestion and may well be quoted: “The only other answer that can be given is that the precise way each part shall act under the influence of the stimulus must be determined by the past history of that part; by the stimuli that have acted upon it, by the reactions which it has given, by the results which these reactions have produced (as well as by the present _rela- tions of this part to other parts, and by the immediate effects of its present action). In other words, this complex harmonious working of the parts together is only intel- ligible on the view that there is a history behind it; that it is a result of development. We can not look upon it as a final thing (‘etwas Letztes, Naturgegebenes’), because there zs a history behind it, and we know as solidly as we know anything in physiol- ogy that the history of an organ does modify it and its actions—in ways not yet thoroughly understood, doubtless, yet none the less real. ‘The starfish that we have before us has an actual history of untold ages, in which it has existed as germ plasm or otherwise, and there can be no greater mistake in physiology than to leave this out of account. ‘The modifications induced in organisms by their experiences, either while existing as germ plasms or as individuals, are as clearly a part of physi- ology as is the study of digestion, and their existence is not less doubtful.” LEON J. COLE. Buttel-Reepen, H.v. Are Bees Reflex Machines? An experimental contribution to the natural history of the honey-bee. Translated from the German by Mary H. Geister. Pp. 48, $0.50. The A. I. Root Company, Medina, Ohio. 1907. Students of animal behavior and comparative psychology will welcome this translation of VON BuTTEL-REEPEN’s noteworthy discussion of the behavior and psychology of the bee. The monograph may now be used to advantage in connec- tion with introductory courses in Animal Psychology. Apparently the translator Literary Notices. 525 has done her work with commendable care, but despite this fact many minor errors appear in the text. It is to be noted in this connection that voN ButreL-REEPEN has recently pub- lished,’ in the form of a monograph, the results of several years of work on the biology of the honey bee. Cole, Leon J. An experimental Study of the Image-Forming Powers of Various Types of Eyes. Proc. of the Amer. Acad. of Arts and Sciences, vol. 42, pp. 335-417. 1907. The image-forming power is here studied not directly, but indirectly by means of the responses of the animals in question to light-stimuli of equal intensity but unequal areas. ‘The apparatus was so arranged that the individual under investigation was free to move either toward a small source of light or (in the opposite direction) toward a luminous field of about 10,000 times the area but of the same total inten- sity. ‘This intensity varied in the course of the experiments from 5 to 1.25 candle meters. ‘Thus an animal which can form no optical image of a source of light and which responds therefore to intensity alone, would respond to either of the stimuli here offered, indifferently. And this was found to be the case in an eyeless form, the earthworm. Animals having “direction eyes” (Bipalium kewense, Periplaneta americana, larva of Tenebrio molitor, and larva of the wood-borer) were found to respond almost wholly to intensity of light. The few doubtful cases are explicable, since certain forms and arrangements of direction eyes “may be considered as the beginning of a crude i image- forming apparatus” (p. 362). Animals with image- forming eyes (Vanessa antiopa, Ranatra fusca, Acris gryllus, and Rana clamata) were found to be mostly positive; they move toward the stimulus of larger area. Whether positively or negatively phototropic, their preference for the smaller or the larger simulus was well marked. . The author studies and discusses many more than the above-mentioned species, both experimentally and from the available literature. In pp. 402-412 are pre- sented several interesting theoretical considerations, particularly those relating to three types of response, to intensity of light, to luminous area, and to “definite objects.” ‘The investigation is ingenious, careful, and suggestive. E. B. H. 1Apistica. Beitrige zur systematik Biologie, sowie zur geschichtlichen und geographischen Ver- breitung der Honigbiene (Apis mellifica, L.), ihrer Varietaten und der iibrigen Apis-Arten. Mitth. d. kgl. Zool. Museums, Berlin. 1906. The Journal of Votume XVIII DECEMBER, 1908 NuMBER 6 THE CRANIAL NERVES OF AMPHIUMA MEANS. BY H. W. NORRIS. Wirtu Prates IV, V, VI, VII anv VIII. (5 IEXGO YOLKS wad dovioneddot0 6c 00ID AO dA CETUS UU CO HIE. SUIOO0 Joo Qo MAnOUSonOGOdUnooos 527 2a Mb Ey OL HACTOR YEON VIE svar tare eke ter elarel ouetseratteh siohav ete niche Sefietofaieloiela)=\eheva.sfolshe1efetai oleteyereieteter rs 528 aed NEG Gren KhaN ola Ta 50 Godin anaes ob odo dU EpONGUO DOD Adon Robe Qo CeDE Me snOOWdua ste Oias o 528 Ap) HUE SE VE-MUSCLESNIER VSN clatalo(atelateePeiete!s «1 elec (els) e\e1+{2"o1ei«lotal= =) #1) s\oje/e\erele=y-12)» o1=/e/ehe) =) ofolalal aleve ele 529 DLE) ORUGEMIN AT NOR VIE tote tetete velar feet ladet fell +sele elela re) elelele elelela afallers) siete sioie)-fal-reloie1ofehelelelo| ole! +l el=1=\-fotsieh-T= 530 6 Uhemammnsrmandibmlariem Viewer trctrstierdratsisteer sale ceetelerele aleleeleielehelctel etal cict=ickalc(el-ateieneletorar= 531 Gi Lhe rantus: ophthalnirens pron ditsy Wi jeesetete ofeletel~ toy tnbaca yp (olele|evelaleye\ els) a\s leet =) ele f-l-l-fat-ta-Ts 533 d. Erigeminall fibers entering) the dorsal VME it f.20 fei 21sec ojo = 2 ove moles wieleieleiele © een t= 536 Gre L Ae SrACTAT CAN DAU DIT OR Vi NOORGVIES ferret raretetel siete aial tevelolaicleletelatore sisiekel sole ele) >) oyaieye elerernreraaieh 536 a. Ehe roots of the facial and fauditory Mervesec jer tlle.» clare oreo Ae ©) ol vle/s\e\e) |» i= lala ini ood 536 6» (he) lateral line; componentsiom the tacial nerves. semcicl cli
  • cela t= eelaiel eels stele 537 G Lhe ramus) buccaliss Vill yamderamas x axdllaris | Vics le ajele let elem ele a< + eieiela del ave i=er 538 d. 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The present paper is an outline of the more salient features of the origin and peripheral distribution of the cranial nerves of Amphiuma means with reference to their components. Inas- much as the nervous systems of but two of the urodele amphibians have been analyzed into their components (see BoweERs 1900, and COGHILL 1902), it seems to the writer that the time is not ripe for making detailed comparisons. For that reason the present account deals chiefly with facts of description. The material studied consisted of individuals varying from 55 to 300 millimeters in length, sectioned through the head trans- versely and sagittally. Fixation was for the most part in voM RatH’s picric-acetic-osmic-platinic mixture. Plate IV is from plottings of a series of cross-sections, ten micra in thickness, pre- pared by the parafin method, supplemented and checked up by a number of series sectioned io celloidin. Plates V to VII are chiefly from material sectioned in celloidin, sections fifteen and twenty micra in thickness. Counter-stains, when used, were either gold-orange or acid fuchsin. As individuals small enough to make sectioning of the entire body feasible are seldom obtained, there is still lacking detailed information regarding some of the cranial nerve branches that pass back into the trunk of the body. The nervous system of Amphiuma is favorable for study because of the differential staining that results from fixation in voM RaTH’s fluid. The lateralis components become intensely black; motor fibers are a dark gray; general cutaneous fibers are brown-black; and the communis system with slight development of myelin is but lightly colored. As the methods employed do not differen- tiate the sympathetic fibers, no description of the sympathetic system is attempted here. There is evidently a need for a thorough revision of the nomen- clature of the sub-divisions of the cranial nerves of Amphibia, but more facts are needed upon which to base comparisons. In this paper the older names are employed as far as consistent with the existing state of information upon the subject. 2 DHE SOREPACTORY SNERWE- Little need be added to the account given by KINGsLey. A little anterior to the level of the posterior border of the eyeball fibers begin to arise from the olfactory glomeruli on the dorso- Norris, Nerves of Amphiuma. 529 lateral border of the brain (figs. 13 and 20). From this point to the anterior end of the brain the emerging fibers constitute a dorsal part of the olfactory trunk. A ventral smaller part is formed by fibers that leave the more ventral glomeruli. Anteriorly, before the nerve leaves the brain, the two portions have become indistinguishably united; in fact there appears to occur an inter- lacing of fibers. Other smaller roots join these two main portions. As the nerve passes into the nasal capsule (fig. 3) it is seen to con- sist of about eight branches, arranged in two or three bundles. The ventral branch in the more ventral of the three bundles passes to JACOBSON’S organ (figs. 2 and 20) giving off also some branches to the ventral olfactory epithelium. ‘The nerve to JAcoBson’s organ passes to the anterior lateral ventral border of that structure, thence dorsally and posteriorly along its dorsal wall. The other branches in the ventral group innervate the ventral olfactory epithelium; the fibers of the middle bundle supply the median wall of the olfactory epithelium; and the dorsal bundle goes to the dorsal wall, except that immediately on entering the nasal capsule one of the dorsal branches sends a large twig to the ventral wall (fig. 20). It may be true that the branch innervating Jacos- SON’S organ comes from the ventral portion (or root) of the nerve, but it is certainly too small to contain all the fibers that arise by that root. It will thus be seen that the condition in Amphiuma contributes little in answer to the query whether or not there are two morphologically distinct elements in the olfactory nerve. 3: SEE OPTIC NERVE. The account given by Krncspry is confirmed throughout. Myelinic sheaths are not inevidence. Sagittal sections show that as the nerve leaves the brain a small ventricular diverticulum reaches out to the point of emergence of the nerve, but apparently the cavity has no peripheral extension. Ao ELE SEEMS Clb INE ROVE Si Of these KiInGsLEy was able to find but one, the oculomoto- rius. I find that the oculomotorius, the trochlearis and the abducens nerves arise in the typical manner, butare much reduced in size. [he oculomotor nerve leaves the lateral wall of the anterior 530 ‘fournal of Comparative Neurology and Psychology. part of the medulla oblongata, although its deep origin is ventral (fg. 13). Soon after its emergence it comes into intimate relation with the gasserian ganglion and more anteriorly with the ramus ophthalmicus profundus V, for some distance being embedded in the median border of these structures (figs. 13 and 6). Passing through its own foramen in the skull (fig. 5) it runs a short dis- tance to the vicinity of the origins of the eye-muscles and there divides into two branches, the dorsal of which supplies the superior rectus muscle, and the ventral the inferior and internal rectus and the inferior oblique muscles (fig. 22). It will be seen (fig. 13) that the dorsal branch passes dorsal to the main trunk of the r. ophthalmicus profundus while the ventral branch runs ventral to this nerve. ‘The trochlear nerve, consisting of two or three fibers, arises at the extreme posterior border of the dorsal part of the mid-brain (figs. 13, 7 and g) and passes anteriorly to its foramen of exit closely pressed against the inner wall of the skull (figs. 5 and 6). It ends in the superior oblique muscle (fig. 22). The abducens 1s extremely attenuated. It takes its exit from the ventral surface of the brain a little posterior to the level of the origin of the seventh nerve as a few fibers, usually two in number (figs. 7 and 13). ‘These I have been able to follow but a short distance. But anteriorly at the point where the r. mandibularis of the fifth nerve leaves the gasserian ganglion (figs. 6 and 13) there may be found leaving the ganglion or the r. mandibularis a nerve of two fibers that passes out of the skull along with the r. ophthalmicus profundus and ends in the external rectus muscle (fig. 22). Before reaching the muscle the abducens nerve 1s sometimes in very intimate ‘relation with a small nerve that inner- vates two small muscles which have their insertions upon the antorbital cartilage. But there seems to be no exchange of fibers between the two nerves. The incomplete development of the eye-muscle nerves precludes any more extended account of their relationships. Of ciliary nerves or ganglia I have found no traces. 5. THE TRIGEMINAL NERVE. a. The roots of the trigeminal nerve.-—The fifth nerve derives its fibers from four sources: (1) From the spinal V tract whose fibers may be traced as far posteriorly as the level of the second spinal nerve. (2) From fibers just dorsal to the spinal V tract. Norris, Nerves of Amphiuma. 531 It is doubtful whether this should be considered as a source dis- tinct from the preceding. (3) According to Kincssury (1895a) and to Osporn (1888) there occurs in Necturus a tract of fibers from the so-called trigeminal nidus in the roof of the mid-brain that passes in part into the spinal V tract near the exit of the fifth nerve. I find in Amphiuma a similar tract of large fibers from the mid-brain passing into close proximity to the spinal V tract and apparently giving off fibers to the latter near the motor root of the fifth nerve, but the fibers so given off are few in number, the greater number passing apparently posteriorly mesal to the spinal V tract, as many do in Necturus. (4) From motor fibers in one or two rootlets that come from a nidus of cells lying in the floor of the medulla. KINGSLEY speaks of the fact that the fifth nerve leaves the brain as three roots: dorsal and ventral small roots and a median large one. ‘The small dorsal root is made up of fibers that com- pose (2) above. In this region the spinal V tract is reinforced by numerous fibers from the adjoining cinerea. ‘This small dorsal root appears to be merely some of these fibers that delay the union until after emergence from the brain. ‘The small ventral root is the motor component. As it leaves the brain the fifth nerve contains only motor and general cutaneous fibers. b. The ramus mandibularis V.iYhe fibers of the fifth nerve leave the gasserian ganglion in three groups. ‘There is first given off the r. mandibularis, composed of motor and general cutaneous fibers, innervating the temporal, masseter, pterygoid, interman- dibular (mylohyoid anterior), retractor bulbi and levator bulbi muscles, and supplying the skin of the lower jaw and the side of the head (in part). The r. mandibularis passes out of the cranium through a foramen common to it and the “dorsal VII.” It emerges at the posterior dorsal border of the pterygoid muscle, at first enters the masseter muscle, then passes anteriorly, ventrally and laterally between the pterygoid and masseter muscles, finally out through the masseter. On emerging from the skull it gives off a number of small twigs to the pterygoid and masseter muscles. As the main trunk of the nerve is passing through the foramen there is given off a large branch which rising rapidly between the pterygoid muscle and the internal portion of the masseter and giving off branches to the anterior part of the pterygoid muscle passes around to the dorsal side of the cranium and runs _pos- 532 fournal of Comparative Neurology and Psychology. teriorly to supply the temporal muscle on the top of the head. While this branch to the temporal muscle is passing anteriorly there is given off from it a short distance from its origin from the main trunk a small branch which running mesally into the pterygoid musclg gives off twigs to the latter and descending applies itself so closely to the outer border of the r. ophthalmicus profundus as to be with difficulty distinguished from it. Leaving the r. oph. prof. nerve at the ventral border of the latter, it runs anteriorly to innervate the two small muscles, previously men- tioned, which have their insertion upon the antorbital cartilage (figs. 5, 13 and 22, mb.). These two muscles appear to have escaped the notice of previous writers. One of these (figs. 4 and 22, rtb.) has its origin on the posterior part of the maxillary bone and the anterior part of the pterygoid cartilage. As seen in the illustrations, its action is to depress the antorbital cartilage. From the position of the tip of the latter ventral to the eyeball the contraction of the muscle will bring about a retraction of the eye, or it acts as a retractor bulbi muscle. Its position and origin make such an homologizing not improbable. The other muscle (/vb.) has its origin on the orbito- sphenoid and parietal bones. Its contraction opposes that of the retractor muscle, or elevates the antorbital cartilage. It is here designated as levator bulbi muscle. As previously noted, the nerve supplying these two muscles sometimes comes into intimate relations with the abducens nerve. But that there is no funda- mental anastomosis between them is shown by the fact that this small branch to the retractor and levator bulbi muscles sometimes arises directly from the gasserian ganglion and passes out of the cranium through the foramen of the oph. prof. nerve and lateral to the latter, thence anteriorly through the pterygoid muscle dorsal and mesal to the oph. prof. without coming in contact with the latter, and nowhere approaching closely to the abducens nerve (fig. 22). As the r. mandibularis passes out through the masseter muscle it gives off twigs to the latter. One large branch, composed of motor and general cutaneous fibers, runs for some distance nearly parallel with the main nerve. Its motor fibers finally pass to the anterior part of the masseter muscle; its general cutaneous fibers run as a large branch nearly to the level of the mandible, and a little anterior to the angle of the jaw break up into twigs that run Norris, Nerves of Amphiuma. 533 in all directions to supply the skin on the side of the head. The main mandibular nerve on reaching the mandible enters a groove on the dorsal side of the latter (fig. 5) and soon divides into two branches. ‘The ventral of these passes directly down through the jaw between the dentary bone and Meckel’s cartilage and on emerging between the angulo-splenial and the dentary bones divides anteriorly and posteriorly into branches that supply the mm. intermandibularis (mylohyoideus anterior) anterior and pos- terior and the skin of the ventral surface covering these muscles. The dorsal division runs along in the groove above Meckel’s cartilage between the dentary and the angulo-splenial bones, and soon divides into two branches. ‘The larger of these, of darker staining fibers (md (3a)), occupies a canal in the dentary bone (hig. 4) “aaa in turn divides into two divisions. Small branches to the skin pass out from the canal, but the two chief divisions (repre- sented as one nerve in fig. 1) do not emerge from the dentary until well near the tip of the jaw where they supply the skin. ‘The smaller lighter stained division of the ramus in the mandibular groove (md (3b)) shifts mesally and ventrally from the larger division and runs along dorsal to Meckel’s cartilage in a groove between the dentary and angulo-splenial bones (fig. 4). There unites with it a branch of the r. alveolaris VII (alv. (4)), the combined nerve passing anteriorly just ventral to the teeth and apparently supply- ing the latter and possibly the lateral floor of the mouth. It may be traced as far as the extreme anterior teeth and always in close relation to the latter. An anastomosis between that part of the mandibularis supplying the intermandibular muscles and the por- tion of the r. jugularis VII innervating the interhyoideus muscle, such as CoGHILL describes in Amblystoma, I do not find in Am- phiuma, but it is certain that the two nerves in question approach very close to each other. KINGSLEY was inclined to believe that branches of the ramus mandibularis in Amphiuma supply lateral line sense-organs. I can state with certainty that no such relation- ship exists. c. The ramus ophthalmicus profundus V.—The ramus ophthal- micus profundus leaves the extreme anterior portion of the gas- serian ganglion and after passing anteriorly and somewhat dorsally into the region of the eye divides into a number of branches, of which there may be said to be five that are fairly constant in their occurrence and relationships. Of these the first given off, the 534 fournal of Comparative Neurology and Psychology. naSalis internus (op. (Z)), arises as a group of nerves, or asa single nerve, that soon divides into branches. ‘The larger of these branches (op. (ra)), that goes up through the edge of the cranium in a passage-way between the frontal and the prefrontal bones and then runs along in a canal in the edge of the frontal as far as the nasal capsule, was called by KincsLey “ethmoideus caudalis.” Anteriorly this can be traced along the upper surface of the frontal bone to a point halfway between thé eye and the tip of the snout. As it passes along its canal and on the surface of the frontal it gives off numerous twigs to the overlying skin. Arising from the posterior part of the nasalis internus, or directly from the trunk of the oph. prof., are one or two branches (0p. (zb)) that pass to the skin of the dorsum dorsal and a little posterior to the eye. The main portion of the nasalis internus passes anteriorly and enters the dorsal portion of the nasal capsule near its mesal border. A little before its entrance to the nasal capsule it gives off a branch (not figured) that passes forward in the capsule and emerging dorsally from the skull is distributed to the skin near the tip of the snout. After entering the nasal capsule the nasalis internus anas- tomoses with the r. ophthalmicus superficialis VII, then passing nearly to the ventral side of the nasal capsule divides, one branch ascending and uniting with the r. ophthalmicus superficialis in a second anastomosis, and the other passing out of the anterior end of the capsule to be distributed, like the dorsal division anasto- mosing with the oph. spf., to the skin of the tip of the snout. It will thus be seen that the distribution of the nasalis internus and its branches is to the skin of the dorsal side of the head from the extreme anterior end to a point some distance posterior to the eye. In its distribution it seems to answer approximately to the ophthal- micus superficialis V of fishes. It probably gives off fibers to structures in the nasal capsule, but I have deeeted none such. It evidently does not supply the nasal epithelium. A second branch of the ophthalmicus profundus (op. (2)) 1s one that arises usually in part from the nasalis internus and in part from the main trunk. It was designated by WILDER as r. glandu- laris IT, on the supposition that it innervates the lateral nasal gland. It and its branches, of which there are commonly two divisions, anastomose with each other and with the nasalis internus, enter the lateral dorsal portion of the nasal capsule, run anteriorly and emerging from the capsule are distributed to the skin of the side Norris, Nerves of Amphiuma. 535 of the snout from near the anterior end of the latter posteriorly about halfway to the eye. The fibers, if any, given off to the lateral gland are certainly few in number, for I have been unable to detect them. The ramus is characteristically cutaneous and the name, r. glandularis II, is a misnomer. Theyneet branch given off from the oph. prof. ((op. 3)) is the one that anastomoses with the r. palatinus VII. ‘The union occurs at the posterior border of the nasal capsule. ‘The palatine rapidly ascends from its ventral position and the trigeminal ramus descends to meet it. As the two nerves approach each other each divides into two parts, and the union occurs between the branches in pairs, so that there result two nerves, each containing general cutaneous and communis fibers (fig. 26). ‘The dorsal of the two nerves thus formed ascends slightly and divides into three branches. The dorsal one of these three branches (op.-pal.d.) from its mode of formation and from the appearance of its fibers consists of general cutaneous fibers only. It may divide and its two divisions on entering the nasal capsule run along the lateral wall of the nasal epithelium on the dorsal border of JacoBson’s organ to the extreme anterior end of the latter. The posterior wall of the nasal epithelium is supplied by branches (op.-pal.pn.) derived from this same source, of general cutaneous fibers only. The ventral pos- terior nasal epithelium is supplied by a branch from a division with mixed components (op.-pal.mn.), and its exact composition has not been determined. ‘The other two branches of the dorsal of the two nerves resulting from the palatine-trigeminal anastomo- sis (op.-pal.l.) pass to the lateral portions of the roof of the mouth innervating the lateral teeth, etc. ‘The ventral branch of the anas- tomosis (op.-pal.m.) passes ventrally 1 into the inner ventral angle of the nasal capsule and running forwards supplies the median series of teeth, etc. From it branches are also given off to the posterior ventral nasal epithelium (op.-pal.mn.). According to the figure given by WILDER this ramus of the trigeminus that anastomoses with the palatine comes from the nasalis internus. The origin of the two from the main trunk of the ophthalmicus profundus is such that it is not improbable that in some cases they may arise by a common branch. The mode of anasto- mosis, it will be seen, is like that described by CoGHILt in Am- blystoma. The remaining portion of the ophthalmicus profundus divides 530 “fournal of Comparative Neurology and Psychology. into two large branches. Of these the larger lateral one (op. (4)) fuses with one (buc. (1)) of the two main divisions of the buccalis VII. Sometimes the fusion occurs between the two undivided trunks, but more often each divides into three or four branches which then fuse in pairs or approximately so (fig. 25). The resulting mixed nerves (r. nasalis externus of WILDER) supply the neuromasts of the infraorbital series and the skin of the side of the snout. The other profundus branch (cp. (5)) comes into close relation with the second division of the buccalis VII (duc. (2)), but I can find little evidence of actual anastomosis. The combined nerves (r. glandularis | of W1LDER) supply the skin and the infra- orbital series of neuromasts at the side and tip of the snout. KINGSLEY refers to this union of branches of the ophthalmicus profundus with the buccalis (maxillaris according to him) asa con- dition reported only in Amphiuma. A casualexamination of the figures which WILDER gives of Cryptobranchus (Menopoma) and of Siren will show that similar (if not identical) anastomoses occur in these forms. ‘The prediction may be safely made that careful study of these forms will reveal the fact that as in Amphiuma it is a union between lateral line (buccalis) and general cutaneous (oph- thalmicus profundus) components. d. Trigeminal fibers entering the dorsal VII.—A third group of fibers leaving the gasserian ganglion is made up of general cutaneous fibers that at once associate themselves with rr. oph- thalmicus superficialis VII and buccalis VI]. Their subsequent course will be considered in connection with the facial nerve. 6. THE FACIAL AND AUDITORY NERVES. a. Roots of the facial and auditory nerves.—The fibers of this complex arise by two groups of rootlets. ‘The more dorsal group comprises the lateral line fibers of the seventh nerve and is formed by three rootlets. Of these the dorsal rootlet (VJIb (z)) enters that portion of the medulla oblongata which in Necturus is desig- nated by Krncsgury as the “dorsal island,” a mass of alba occupy- ing the extreme dorsal part of the medulla (figs. 7-10, //.) ‘This “dorsal island’ suggests an homology to the lateral line lobe (lobus linez lateralis) of cyclostomes, selachians and ganoids, although JoHNSTON (1906) asserts that the lateral line lobe and the dorsal root of the “dorsal VII” are absent in aquatic amphi- Norris, Nerves of Amphiuma. eur bians. The other two rootlets (V/Jb (2) and VIIb (3)) enter the sensory column ventral to the dorsal island. In the second and more ventral group of rootlets we find true facialis and acusticus fibers. ‘There may be recognized five rootlets, three belonging to the auditory and two to the facial nerve (figs. 1, 7 and 8). Of the auditory fibers there are four groups: (1) medium and large fibers that pass posteriorly into the spinal VIII tract (VIII (1)); (2) medium fibers that pass anteriorly in the so-called (incorrectly) “descending VIII” tract (VIII (2)); (3) medium and small fibers that pass into “tract b” (Necturus, Kincssury) (VIII (3));(4) large fibers forming atract at first distinct from (1) but posteriorly passing into the spinal VIII tract or into very close proximity to it (VJJJ(4)). (1) forms an anterior rootlet; (2) and (3) form a larger posterior rootlet; (4) forms a rootlet dorsal and intermediate to the other two (figs. I and 23a). Of these rootlets (1), (2) and (3) supply the sacculus, lagena, macula neglecta and the posterior canal; (4) supplies the utriculus and the anterior and horizontal canals. ‘The peripheral divisions of the auditory branches will not be considred here. The two facial rootlets consist of a dorsal one of communis fibers (VIJaa) ent2ring the brain at the anterior dorsal border of (4) above mentioned, and passing into the fasciculus communis, and a ventral motor rootlet (V/Iab). The relative positions of these rootlets of the facial and auditory nerves are subject to some variation. b. Lateral line components of the facial nerve.—From the points of entrance of its fibers into the brain the root of the lateral line portion of the seventh nerve passes anteriorly as a flattened band closely compressed between the brain and the earcapsule. Most if not all of the fibers of its dorsal rootlet, together with part of the fibers of the ventral rootlet, pass ventrally into the acustico-facial ganglion and thence out in the main trunk of the ventral portion of the seventh nerve. ‘The fibers of the middle rootlet and part of those of the ventral rootlet pass anteriorly as the “dorsal VII’ into the lateral line ganglion lying dorsal to and confluent with the gasse- rianganglion. Passing anteriorly from this dorsal lateralis ganglion the lateral line fibers are joined by general cutaneous fibers from the gasserian ganglion (the third group of fibers mentioned under the head of the trigeminal nerve). These general cutaneous fibers are in two distinct bands, one of which is applied to the ventral 4 538 “fournal of Comparative Neurology and Psychology. and the other to the mesal surface of the lateralis trunk. As the combined nerves pass anteriorly the general cutaneous components shift their positions, the median one becoming dorsal and the ventral one shifting to a lateral position. The main combined trunk soon divides into a dorsal and a ventral division, each con- sisting of lateralis and general cutaneous fibers. Each division then divides into two rami. c. Ramus buccalis VII, and ramus maxillaris V.—The ventral, or infra-orbital division, forms a ventrally situated ramus consisting solely of lateralis fibers, the buccalis VII, and a more dorsal one of general cutaneous fibers with a few lateralis fibers, the maxillaris V. The few lateral line fibers mixed with the maxillaris are soon given off to certain neuromasts of the infra-orbital series posterior to the eye. The r. buccalis innervates the neuromasts of the infra-orbital series anterior to the eye. Its two main divisions that anastomose with the r. ophthalmicus profundus V have been described. ‘The maxillaris of Amphiuma seems to be distributed chiefly to the skin of the side of the head posterior and a little anterior to the eye, but it does not run as far anteriorly as in most Urodela that have been figured, in the more anterior parts of the head being replaced by branches of the opththalmicus profundus. The term, ramus maxillaris V, is here used with the limitations that CoGHILL gave it. STRONG (1895) called attention to the strik- ing parallelism between trigeminal and lateral line branches in the tadpole of the frog. This is especially noticeable between certain so-called accessory lateral line branches of the ophthal- micus superficialis and the buccalis and so-called accessory trigem- inal twigs. Of these the most striking is the close relationship between the buccalis and the larger of the accessory trigeminal branches. CoGHILL’s contention that the so-called maxillaris in Urodela is the homologue of this larger accessory trigeminal twig of the tadpole seems to me valid. ‘The distribution of the maxil- laris in Amphiuma agrees very closely with the distribution of this accessory twig in the tadpole. The intimate union of maxillaris and buccalis in Amphiuma suggests the parallelism in the tadpole between the buccalis and the accessory trigeminal branch. The distribution of the terminal branches of the ophthalmicus pro- fundus V, palatinus VII and maxillaris V in Amphiuma agrees almost to details with that in Amblystoma. CoGuHILu’s conclu- sions that “there is no distinct maxillaris branch of the trigeminus Norris, Nerves of Amphiuma. 539 in Amblystoma” can be as truly applied to Amphiuma. The smaller accessory general cutaneous and lateralis twigs given off from the combined lateral line and gasserian ganglia in Rana seem to represent possibly a ramus oticus. A determination of their exact terminations would be necessary before coming to any con- clusions in the matter. But it must be noticed that ia both Amphiuma and Amblystoma there occur some minute rudimen- tary nerves given off from the gasserian ganglion. ‘These possibly correspond to the smaller accessory twigs in Rana. d. Ramus ophthalmicus superpicralis VII and ramus oticus.— The supra-orbital division of the “dorsal VII” forms a ventral lateralis ramus and a dorsal portion consisting of both lateralis and general cutaneous fibers. ‘he ventral ramus is the r. opthal- micus superficialis VII, that supplies all the neuromasts of the supra-orbital series except some at the posterior end of the series. Anteriorly in the nasal region it anastomoses with the nasalis internus, as already noted. The dorsal portion of the supra-orbital division, consisting of general cutaneous and lateralis fibers, divides into a number of small branches supplying the skin of the dorsal part of the head posterior to the eye, and the neuromasts that form the posterior end of the supra-orbital series and four or five neuromasts at the posterior dorsal end of the infra-orbital series (fig. 24). In its distribution to neuromasts this dorsal division seems to represent the ramus oticus of fishes. In the latter it supplies the neuromasts of the posterior end of the supra-orbital series and the first few neuromasts of the infra- orbital series. In the r. oticus of fishes are found general cutaneous fibers from the gasserian ganglion associated with the lateralis fibers. In Amphiuma these general cutaneous fibers are dis- tributed to a region which in some other Urodela, as Amblystoma, is innervated by branches of the ophthalmicus profundus. In some specimens of Amphiuma there occurs an anastomosis between the maxillaris and this dorsal general cutaneous division just before the latter breaks up into its smaller branches. We have here the suggestion that these dorsal general cutaneous fibers represent in part the posterior portion of the ophthalmicus super- ficialistrigemini. Both WILDERand StronGare of the opinion that the ophthalmicus profundus in Amphibia “represents the united ophthalmicus profundus and ophthalmicus superficialis trigemin1”’ of fishes. It is certainly true that the distribution of these dorsal 540 ‘fournal of Comparative Neurology and Psychology. general cutaneous branches and of the nasalis internus collectively corresponds to that of the piscine ramus ophthalmicus superficialis V. e. The ventral trunk of the facial nerve.—As the ventral division of the facial nerve leaves the acustico-facialis ganglion complex it consists of lateralis, communis and motor fibers. As above noted, the lateral line fibers are derived from the dorsal and ventral rootlets of the dorsal division of the facial nerve. In this acustico- facial ganglion are three distinct groups of cells: (1) the large lateralis ganglion cells of the lateral line component. ‘These are situated mostly on the anterior and dorsal borders of the complex. (2) Small cells of the geniculate ganglion, situated on the anterior mesal border of the complex. (3) Medium sized acustic cells, situated at the posterior and along the dorsal border of the gan- glionic mass. Of these the cells of the vestibular branch of the VIII nerve are larger and situated anterior to the others. }- Ramus palatinus VII.—Vhere is first given off from the ventral facial trunk the r. palatinus of communis fibers from the geniculate ganglion. The palatine runs anteriorly and shortly after its emergence from the cranium receives an anastomosing branch from the r. pretrematicus IX. This anastomosing branch is JACOBSON’S commissure, of communis fibers. “The anastomo- sis of the r. palatinus with the r. ophthalmicus profundus V has been already noticed. In Amblystoma according to CoGHILL there occurs a ganglion on the r. palatinus at the junction of its lateral division with the lateral division of the trigeminal branch. In Amphiuma there seems to be a ganglion on the palatine nerve shortly before the anastomosis with the trigeminus is reached. From this region (fig. 26) are given off a number of small nerves some of which pass to the roof of the mouth and the median series of teeth. Some of these small nerves contain general cutaneous as well as communis fibers, but the exact composition of all of them was not determined. g. The ramus alveolaris VII.—The second branch given off from the ventral facial trunk is the r. alveolarisof communis fibers. From the r. pretrematicus [X it receives two anastomosing branches (alv. (r) and (2)). Near the angle of the jaw it gives off a small branch (alv. (3)) that passes mesally, ventral to the quadrate carti- lage, to the roof of the mouth. There seem to bez no peculiarities about the distribution of the alveolaris in Amphiuma. It divides Norris, Nerves of Amphiuma. 541 into a number of terminal branch2s, one of which anastomoses with the mandibularis V as already noted. ‘The other branches supply the ventral lateral wall of the anterior floor of the mouth. In this account the alveolaris is assumed to be a pretrematic nerve. h. The rami mentalts externus and internus VII.—¥rom the hyomandibular trunk of the facial nerve there are given off two large lateral line rami, of which the anterior dorsal one supplies the angular and the oral series of neuromasts, and the posterior ventral one the gular series of neuromasts. KINGSLEY designated the first as r. mandibularis externus, and the second as r. hyoman- dibularis accessorius. Each contains lateral line fibers only, and the two evidently correspond to the two nerves which in other Urodela hitherto figured arise by a common trunk from the hyomandibularis, and which in Amblystoma are termed by Coc- HILL r. mentalis externus and r. mentalis internus. FISCHER seems to have overlooked the internal division in Amphiuma. At a point about opposite the articulation of the lower jaw the r. mentalis internus divides into two branches that pass anteriorly parallel to each other. I find no anastomoses between the r. mentalis internus and the r. mandibularis V, such as KINGSLEY reports, much less can I substantiate the statements of DRUNER that numerous anastomoses occur between these nerves. At the point where the r. mentalisexternus leaves the hyomandib- ular trunk there are given off a few small nerves (figured as two in number in the illustrations), partly from the main nerve and partly from the mentalis externus, which supply the post-orbital and jugular series of neuromasts. These small lateralis branches have a very wide distribution for their size. Some of their smaller divisions may be traced through hundreds of sections, yet consist of but two or three fibers each. In their origin and distribution these small lateralis nerves seem to represent opercular branches of fishes. DRUNER reports a small cutaneous branch given off from the mentalis externus and passing to the skin overlying the depressor mandibule muscle. I fail to find such a nerve. More- over the occurrence of general cutaneous fibers in a branch of the seventh nerve before the anastomosis X ad VII is received is improbable. I do find a small branch of lateralis fibers leaving the r. mentalis internus and supplying the posterior neuromasts of the gular series overlying the depressor mandibulz muscle. 542 ‘fournal of Comparative Neurology and Psychology. 1. The ramus jugularis VII.—At about the level of the origin of the r. mentalisinternus there is givenoff from the hyomandibular trunk a small motor branch to the anterior division of the depressor mandibulz muscle. Another motor branch to the same division of the muscle runs along and in the anastomosis X ad VII. At about the place where the hyomandibularis finally breaks up into the larger divisions of the r. jugularis it is joined by the anas- tomosis from the glossopharyngeal-vagal complex carrying general cutaneous fibers. ‘The origin and composition of this commissure will be considered under the subject of the glossopharyngeus and vagus nerves. ‘The r. jugularis is distributed to the interhyoideus (mylohyoideus posterior), depressor mandibulz (digastricus) and sphincter colli (levator maxillz inferioris ascendens of FISCHER, quadrato-pectoralis of DRUNER) muscles, and in addition carries general cutaneous fibers to the skin overlying these muscles. Lat- eral line fibers also occur in the r. jugularis. k. The ramus lateralis VII.—There is one branch of the r. jugularis, if indeed it may be considered as a branch of the latter, that requires especial mention. It was first described by FiscHER as a structure peculiar to Amphiuma, and said to be traced to the hyotrachealis (interbranchialis 4) muscle. KINGSLEY states that it supplies the dorso-trachealis muscle. ‘The writer (1904) gave a brief description of this nerve, showing that it does not end in the dorso-trachealis muscle, but passes posteriorly into the trunk region as far as the pelvis. ‘There was suggested a possible rela- tion to the neuromasts of the trunk, and the nerve was provisionally designated as r. lateralis VII. In the same year (1904) appeared the paper of DRUner in which he described the nerve, calling it nervus lateralis VII and asserting that it supplied in part the median series of neuromasts of the trunk, that is, he considered it a lateral line nerve. In the following year the writer in a second paper withheld the name, r. lateralis VII, believing that the evidence of the presence in the nerve of lateral line fibers was not convincing. ‘The statements of DRUNER as to the composition of the nerve may now be confirmed. It is composed largely, if not entirely, of lateralis fibers; I have not, however, as yet detected any connection between it and the neuromasts of the trunk. Such connection doubtless exists. Most of its fbers come from those branches of the r. jugularis that supply the posterior division (cerato-mandibularis) of the depressor mandibula muscle. In Norris, Nerves of Amphiuma. 543 addition it is reinforced by fibers from the jugularis branch that supplies the sphincter colli muscle. If the nerve contains any general cutaneous fibers they must come from the latter source. The exact mode of origin of this nerve is subject to a great deal of individual variation, and as it leaves the posterior border of the depressor mandibulz muscle it may consist of two or more parallel twigs that run for some distance before uniting (as in fg. 1). In passing the thymus gland the nerve is always in two Be more divisions, “Sémermes 4 small’ branch runs back ito the trunk along with the main nerve (fig. 1). In some individuals a small branch is seen to leave the main nerve in the neighborhood of the thymus gland, and to pass antero-dorsally anastomosing with the r. supratemporalis X. In one instance the anastomosis was also with one of the twigs of the r. lateralis medius X. “The r. lateralis VII seems to be peculiar to Amphiuma among the amphibians. Its origin and distribution suggest a_ possible homology with the r. lateralis recurrens VII of fishes, but in these latter, as shown by Herrick (1899, 1900, 1901) and CLapp (1898) the ramus recurrens, or lateralis accessorius, is primarily a communis nerve, with which a few lateralis or general cutaneous fibers may be associated. As shown above, chev may occur an anastomosis between the lateralis VII and the r. supratemporalis X, suggesting a similar relation in fishes. In the trunk region there occur some peculiar relations between the lateralis VII and the spinal nerves, but further study of this region will be necessary before it will be safe to attempt exact comparisons. KINGSLEY (1902b) in comparing the Czecilians and Amphiuma gives as one of the supposed points of resemblance: ‘The occurrence in both of a ramus lateralis recurrens branch of the facial nerve,’ but he gives no further explanation. All of the branches of the r. jugularis, except those supplying the anterior portion of the depressor mandibulz muscle, may contain lateralis fibers. From the branches of the jugularis that pass back into the posterior division of the depressor mandibulze muscle there are given off two or three small lateralis twigs which after emerging superficially from the muscle run posteriorly just beneath the skin to supply a few of the more posterior of the jugular series of neuromasts. “hese commonly anastomose more or less with the twigs of the lateralis branches that supply most of the neuromasts of this series. The fore-going small lateralis 544 ‘fournal of Comparative Neurology and Psychology. twigs are possibly the “rr. cutanei jugulares’’ mentioned by Drtner. From the descriptions of FiscHER, KinGsLEY and DRUNER, we are led to infer that the two jugularis branches that pass back through the depressor mandibulaw muscle are distinct from each other, but in fact they anastomose. In the dorsal one, the r. lateralis VII which may be double, there are motor fibers associated with the lateralis fibers. The ventral one, primarily motor, may be exclusively motor or it may contain lateral line fibers also. I have not been able to demonstrate general cutaneous fibers in these; in fact in the r. lateralis VII I have been able to demonstrate beyond question that in some individuals no general cutaneous fibers can possibly be present until it receives the branch from the nerve that supplies the sphincter colli muscle. As noted above, it is not impossible that the r. lateralis VII after it has emerged from the muscle may contain general cutaneous fibers. Cross-sections of the main nerve show scattered among the intensely black-stained lateralis fibers that compose the bulk of the nerve some lighter colored ones. It may also contain com- munis fibers, but I have detected no evidence of this. js “THE GLOSSOPHARYNGEAL AND VAGUS NERVES. a. The roots of the IX-X complex.—The IX-X complex in Amphibia is generally described as arising by five roots, but care- ful comparison by determination of components shows that the roots described in one species by one writer do not always corre- spond to the roots of a second species described by another writer. Hence a statement that in general the [X-X complex in Amphibia arises by five roots requires some qualifications. In Amphiuma the IX-X nerves arise from the brain by five roots, or rather groups of rootlets (fig. 1); but these roots do not correspond in detail to those described in Necturus by Kincspury, nor to those in Amblystoma as described by Cocuity. The five roots are those mentioned by Krnestey. The first group of rootlets (figs. I, 10 and 23) is composed of lateralis (X (z)), communis (1X (z)) and motor (1X (2)) fibers. The communis and motor fibers after passing through the ganglion form the glossopharyngeal or first branchial nerve, with the exception of the general cutaneous com- ponent in the latter. The lateralis component supplies all the lateral line fibers of the vagus group. ‘This lateralis component Norris, Nerves of Amphiuma. 545 enters the brain by two rootlets which szem to correspond in origin to the median and ventral rootlets of the lateral line com- ponent of the facial nerve. ‘The second group of rootlets consists of general cutaneous (X (2a)), communis (X (2))) and motor (X(2c)) rootlets. The communis rootlet carries all the communis fibers of the second (X.z.) and third (X.2.) branchial nerves and of the r. intestino-accessorius. [he general cutaneous compo- nent supplies fibers to the glossopharyngeus nerve, to the ramus communicans cum faciali, to the r. auricularis xe and to the second and third branchial nerves. The motor rootlets supply the second jand third branchial nerves and contribute fibers to the r. intestino-accessorius. ‘The third (X (3)), fourth (X (4)), and fifth (X (5)), groups of rootlets are exclusively motor. They may be considered as constituting one root. With some fibers from the second group of rootlets they form the motor component of the r. intestino-accessorius. In some individuals the fifth root ‘is lacking or extremely attenuated on one side (fig. 23). In one specimen there was found a posterior vagal rootlet emerging with the first spinal nerve. A comparison of the [X-X roots in Amphiuma with those in Necturus and Amblystoma is shown in the following table: NeEcTURUS. AMBLYSTOMA AMPHIUMA. (Kincsgury). (Cocuit). mx (re 2) Exe IX X (1a + 1b) Xs XGA XC CareebrEezc) pastas a X23 (approximately) X (3), X (4), X (5) Sed X.4 The [X-X ganglion is elongate in shape, somewhat oval pos- teriorly, and anteriorly flattened wedge-shaped where it passes under the ear capsule. The nerves leaving the ganglion are eight in numb=r. b. The ramus communicans rum faciali.—Of these the ramus communicans cum faciali, or anastomosis X ad VII, will be con- sidered first. It would appear from the different accounts given that this trunk in origin and composition is subject to considerable variation in the amphibians. It is usually described as leaving the ganglion in a common trunk with the glossopharyngeus proper. KINGSLEY and DRUNER both so describe it in Amphiuma, but I 546 ‘fournal of Comparative Neurology and Psychology. have yet to find an instance in Amphiuma where the two do not emerge from the ganglion separate from each other. In Ambly- stoma (CocHILL) he. r. communicans is composed of general cutaneous and communis fibers; in Spelerpes (BOWERS) of general cutaneous fibers only, apparently. DDRUNER assumes that in the Urodela in genera] the anastomosis contains motor fibers. For example, in Amblystoma and Triton he describes (1901 and 1904) a motor component in the anastomosis X ad VII, but CoGHILL (1906) can find no evidence of motor fibers in the anastomosis in these forms. In Amphiuma DRUNER believes the anastomosis to consist solely of motor fibers, but I can find nothing | to support such an opinion. Beyond question DRUNER is correct in hguring the r. communicans as giving off fibers to branches of the jugularis VII, but it is not necessary to draw his conclusion that these are motor fibers. In Amphiuma the r. communicans consists chiefly, if not wholly, of general cutaneous fibers. In serial cross-sections these can be followed with precision from the second [X-X root into the ganglion, thence out into the anastomosis. I have not been able to demonstrate with certainty that no communis fibers pass fromthe first [X-X root into the r.communicans. Such fibers pass very close to the beginning of the latter, and possibly some enter. That none of the coarse deeply staining motor fibers of the first IX-X root enter the anastomosis seems certain. As the anastom- sis approaches th VII nerve it is seen to divide into a dorsal and a ventral branch (figs. 9, ga, 14-16, 18 and 21). ‘These two branches unite with branches of the r. jugularis that innervate the sphincter colli and interhyoideus muscles. ‘The variability in the mode of union is shown in figs. 14-18. In some cases (fig. 17) the r. communicans does not divide on approaching the r. jugularis. FrscHEeR noticed the double nature of the anterior end of the r. communicans and designated the dorsal portion as “Kopftheil des Sympathicus.” DrtNer also describes a dorsal smaller portion that passes ventrally into the r. jugularis. In Amblystoma (Siredon) he recognizes a sensory component in the r. communicans, and suggests the possibility of some of the fibers being sympathetic. In Amphiuma motor branches from the facial nerve commonly run posteriorly into the anterior portion of the depressor mandibulz muscle closely joined with the dorsal branch of the anastomosis. When these branches are finally distributed to the muscle there Norris, Nerves of Amphiuma. 547 is an appearance of fibers being given off from the r. communicans but careful search shows that all of the fibers so given off come from the VII nerve. I can find no indication of motor fibers associated with the posterior part of the anastomosis. DRUNER figures the anastomosis as giving off fibers to the anterior portion of the depressor mandibulz muscle the direction of the fibers being such that the only interpretation that can be given to the figure is that these fibers come from the [X-X complex. I have sought carefully in all my series of sections, the material being so sharply differentially stained that nerves such as figured by DRUNER could not escape detection, and I find not a suggestion of the presence of such fibers. In one series of sections, sagittally cut, with most excellent differentiation of components, the motor fibers from the VII nerve that usually run posteriorly along the smaller dorsal portion of the r. communicans are everywhere distinct from it, and not a single twig is given off from the r. communicans until the r. jugularis is reached (figs. 15 and 21). In a preliminary communication (1908) I stated that the r. communicans contains communis fibers. While I am not yet ready completely to retract that statement, I now regard the pres- ence in the r. communicans of such fibers as highly improbable. We may summarize the foregoing statements regarding the ramus communicans in Amphiuma as follows: (1) DRUNER’s contention that the r. communicans is exclusively motor will not stand. A large general cutaneous component enters the ramus from the second IX-X root. The general cutaneous fibers in the VII nerve can come from no other source. (2) That the r. communicans contributes fibers to the r. jugularis does not indi- cate that these fibers are motor. ‘The branches that receive fibers from the r. communicans are those that contain general cutaneous fibers; they must receive them from that source. (3) DRUNER’S statement and figure showing branches given off from the r. communicans to the anterior divisionof the depressor mandi- bula muscle are incorrect. It has been seen in some instances that this cannot possibly be true; in other cases the fibers so given off do not originate from the [X-X ganglion, but come from the r. hyomandibularis, that is, are not to be considered a part of the r. communicans. (4) That motor fibers enter the r. communi- cans from the [X-X ganglion has not been demonstrated, and is highly improbable. (5) The r. communicans is composed of 548 ‘fournal of Comparative Neurology and Psychology. general cutaneous fibers from the second IX-X root; it may possibly contain other sensory fibers, communis or sympathetic. c. The rami ‘supratemporalis and aurtcularis X.—Passing out from the ganglion with the r. communicans is a small nerve that evidently answers to the r. supratemporalis as described by vari- ous writers. Its course out through the cranial wall is correctly described by Kinestey. It is exclusively lateralis, and, as KinGs- LEY suggests, supplies neuromasts in the occipital region. Anas- tomosing with the terminal divisions of the r. supratemporalis are branches of a second nerve springing dorsally from the LX-X ganglion. It is composed of lateralis and general cutaneous fibers. ‘The general cutaneous component evidently corresponds to the r. auricularis -vagi of the tadpole (STRONG 1895), and to the general cutaneous component of the nerve in Amblystoma termed r. auricularis vagi by CoGHILL. d. The glossopharyngeal nerve-—General cutaneous, commu- nis and motor fibers are contained in the glossopharyngeus, or first branchial nerve, which divides just before or soon after it leaves the ganglion into a r. pretrematicus and a r. posttrematicus. According to DRUNER the r. pretrematicus is larger than the r. posttrematicus and the r. communicans larger than either. Cross sections of the three as they leave the ganglion show that the r posttrematicus is the largest of the three, and the r. communicans the smallest. The manner of branching of the r. pretrematicus is so variable that it is difficult to make statements regarding it at all accurate. Shortly after leaving the ganglion the r. pretre- maticus gives off its principal branches. One small branch goes ventrally to supply the dorsal wall of the pharynx ventral and posterior to the ear capsule. Another branch which may be called the pharyngeal proper (ph. JX.) is given off dorsally. From it there passes a slender nerve anastomosing with the r. palatinus VII, forming Jacopson’s commissure. ‘The fibers of this anas- tomosis on entering the r. palatinus are seen to pass some cen- trally and some peripherally. From the anterior portion of Jacosson’s commissure near where the latter joins the r. palatinus there is givenoffa branch to the roof of the mouth. The pharyn- geal branch sends an anastomosis to the r. alveolaris VII. “The main portion or ramus pretrematicus proper, passes antero-ventrally and mesally until the hyoid arch is reached. Thence, after dividing sooner or later into two branches, it passes anteriorly a little dorsal “ Norris, Nerves of Amphiuma. 549 to the hyoid arch as far as the tip of the latter, supplying the floor of the mouth at the sides. From the pretrematic proper there passes an anastomosis with the r. alveolaris VII. The fibers of the anastomosis on entering the alveolaris pass some centrally and some peripherally. Between the pretrematic proper and the pharyngeal branch there may occur anastomoses (fig. 21). Some- times the pharyngeal anastomosis with the r. alveolaris comes from the main pretrematicus (fig. 1). From the pharyngeal branch there may pass a branch inio the main hyomandibular trunk (fig. 21). Thus there may be formed in the hyoid and mandibular region a plexus between the IX and VII nerves, consisting of communis and possibly sympathetic fibers, all the fibers of which are destined presumably to supply blood vessels and the mucous membrane of the mouth and pharynx. Some of the smaller twigs of this plexus can be traced into the close vicinity of blood vessels of this region. Of isolated ganglia or ganglion cells in this region I find none. | It is the pretrematic division of the IX nerve that KIncsLEY considered the glossopharyngeus proper. He was thereby led into the error of supposing that the LX nerve contains no motor fibers. He failed to discover the actual anastomoses with the seventh nerve. The branch that anastomoses with the palatine he cor- rectly termed the pharyngeal. The main pretrematic branch he designated provisionally the hyoid branch. According to him the r. supratemporalis X is a branch of the glossopharyngeus. I find the former more intimately associated with the r. communicans at its exit from the ganglion. As the posttrematic division of the glossopharyngeus ascends to the level of the dorsal border of the branchial arches it gives off from its ventral border several small pharyngeal twigs, as described by Druner. As the trunk turns to pass laterally between the dorsal ends of the hyoid and first branchial arches it gives off a small motor branch (/ab. 1) to m. levator arcus branchialis 1. A little more laterally a small general cutaneous branch runs obliquely postero-laterally over the first branchial arch to the skin of that region. ‘This general cutaneous component of the glossophar- yngeus is so small that I have as yet detected it in but one individ- ual. Mention of it was omitted in my preliminary paper. DRUNER says that the first branchial nerve sends two branches to the m. lev. arc. br. 1. As he does not mention this general 550 ‘fournal of Comparative Neurology and Psychology. cutaneous branch he possibly mistook it for a motor branch. KincsLeY describes and figures a branch of the first branchial nerve as innervating the posterior portion of the depressor mandi- bula muscle. Such a relation would certainly be anomalous. I do not find such a nerve, but in one specimen I find that the ramus posttrematicus just as it begins to descend along the outer anterior border of the first branchial arch divides into a posterior portion that runs nearly in the usual course, and an anterior por- tion that becomes almost lost among the fibers of the depressor mandibule muscle, rejoining the other division more ventrally. This anterior portion, or possibly a still more aberrant but corre- sponding branch, may be the one mistaken by Krncstey for a division to the muscle. Ventrally the posttrematicus divides into motor branches to the ceratohyoideus internus muscle and com- munis branches to the lateral pharyngeal wall between the hyoid and first branchial arches, the extreme anterior portion being the ramus lingualis of communis fibers to the tongue. e. The second and third branchial nerves.—The second and third branchial nerves (X.r. and X.2.) sometimes leave the gan- glion as a common trunk that soon divides; sometimes they origi- nate separately, but close together. “They have the same general arrangement of parts. [hey send branches to mm. levatores arcuum branchialium 2 et 3 respectively. Each divides into a ramus posttrematicus and a ramus pharyngeus. From the latter ramus in each there runs anteriorly a small branch just dorsal to the extreme dorso-lateral angle of the pharynx as far as the preced- ing branchial arch and thence along the inner border of the latter, supplying the ventro-lateral wall of the pharynx. This answers to a pretrematic ramus in its distribution. DRUNER’s failure to find a distinct pretrematic branch on either of these two nerves is probably due to the fact that in adults, such as he examined, it has become much attenuated. The main portion of the r. phar- yngeus is distributed to the dorsal wall of the pharynx. ‘The r. posttrematicus after giving off a branch or branches to its corre- sponding m. levator arcus branchialis turns ventrally and send- ing off one or two small general cutaneous branches to the skin, passes antero-ventrally along the outer border of its respective branchial arch. The second branchial posttrematic sends branches to mm. subarcuales recti I, 2 et 3 (m. constrictor arcuum branchiarum Norris, Nerves of Amphiuma. 551 inferior), and to m. subarcualis obliquus (m. constrictor arcuum branchiarum superior), and continues anteriorly to innervate the m. ceratohyoideus internus. It also sends communis branches to the ventral wall of the pharynx. The third branchial posttre- matic according to DRUNER has no motor fibers in its ventral portion, although in describing the mm. subarcuales he says they receive branches from the second and third branchial nerves. | find that the greater part of the ventral portion of the third branchial posttrematic is of communis fibers distributed, as DRUNER says, to the ventral pharynx wall at the sides of the larynx; but I also find a small motor branch given off to m. sub- arcualis rectus 3, and in one instance | have traced fibers to the m. subarcualis obliquus. Between the posttrematic divisions of the second and third branchial nerves and the ramus intestinalis recurrens X there occur anastomoses such that it is difficult to distinguish the source of some of the fibers innervating the subar- cual muscles. }- The rami laterales X.—From the posterior end of the [X-X ganglion there pass out two large nerve trunks. The dorsal of these is composed solely of lateralis fibers, and soon divides form- ing a smaller dorsal r. lateralis dorsalis supplying the neuromasts of the dorsal series of the trunk of the body, and a larger ventral r. lateralis medius supplying the median series of neuromasts of the trunk. The remaining lateralis component of the vagal group will be described in the following section. g. The ramus intestino-accessorius X.—The second great trunk passing posteriorly from the [X-X ganglion is the r. intestino- accessorius, compose d of lateralis, communis and motor fibers. The communis and motor fibers have a very diverse distribution. A short distance posterior to the ganglion there leaves the main trunk a small nerve of communis and motor fibers, that in part represents fourth and fifth branchial nerves. It sends motor fibers to mm. levator arcus branchialis 4, trapezius and dorso- laryngeus. ‘The branches to the trapezius and dorso-laryngeus muscles may arise separately from the main int.-acc. trunk. After giving off fibers to the m. lev. arc. br. 4, the nerve, now of communis fibers only, passes near the dorsal ends of the third and fourth branchial arches and there divides, one branch running along the anterior median border of the third branchial arch, and evidently forming a fourth ramus pretrematicus (prt. X. 3), 552 Fournal of Comparative Neurology and Psychology. and a second branch running similarly along the fourth branchial arch and constituting a fifth ramus pretrematicus (prt. X. 4). “The main intestino-accessorius trunk finally divides (figs. 1 and 12) into a r. lateralis ventralis supplying the ventral series of neuro- masts of the trunk; three rr. intestinales that pass posteriorly, one dorsal to the cesophagus and the other two latero-ventral to the same; and a r. intestinalis recurrens that turns anteriorly to sup- ply m. interbranchialis 4 (m. hyotrachealis) and mm. subarcuales. From one of the intestinal branches there turns anteriorly a r. laryngeus recurrens that innervates muscles of the larynx, mm. dorso-laryngeus, constrictor laryngei, etc., and also supplies com- munis fibers to the pharyngeal wall in the same region. Com- munis fibers are also given off to the pharyngeal wall from the r. intestinalis recurrens in the laryngeal region. ‘The rr. intestinales were traced posteriorly as far as the heart only and nothing can be stated precisely of their destination. 8. THE FIRST AND SECOND SPINAL NERVES. The first spinal nerve in its early stages, as described by Kr1ncs- LEY, arises by four roots, two dorsal and two ventral, and is thus in origin clearly double (fig. 19). “The common trunk formed by these roots passes out through a foramen in the first vertebra. In individuals of 120 mm. length I have found the first spinal nerve to possess two very rudimentary dorsal roots, two large ventral roots, and a small ganglion (fig. 19). In individuals of 140 mm. length the dorsal roots have disappeared, but the ganglion remains. In individuals of 175 mm. length the ganglion has disappeared. In older individuals the nerve appears to arise by four ventral roots in two groups. According to DRUNER the hypobranchialis (hypoglossus) nerve is derived from the first and second spinal nerves. Careful search through my preparations fails to show any anastomosing between these two nerves. I have found no instance where they come intocontact even. The nearest approach to contact is between a general cutaneous division of the second spinal nerve and the main hypoglossal trunk of the first spinal nerve. The hypoglossus nerve is formed solely from the first spinal nerve, and contains only motor fibers. The main ventral portion of the first spinal nerve soon after it emerges from the spinal canal passes posteriorly and after giving off a few small Norris, Nerves of Amphiuma. 553 branches runs back to the region where the r. int.-acc. divides into its several branches (figs. 1 and 12). Here the hypoglossus comes into intimate relations with the r. lateralis ventralis and the r. intestinalis recurrens X, but there is no fusing between them such as KiNncsLey describes and figures. In some cases there may be a temporary mingling of fibers, but in other instances the distinction between hypoglossal and other nerves is absolutely clear throughout, so that we may confidently deny the occurrence of any anastomosing between the hypoglossal and vagal nerves. From the point of the branching of the r. int. acc. trunk the hypo- glossal nerve runs antero-ventrally, giving off no branches until it reaches the anterior section of the sternohyoid muscle. This it innervates and then runs along in the geniohyoid muscle supply- ing it, to end anteriorly in the genioglossal muscle. The main ventral branch of the second spinal nerve passes posteriorly in a direction nearly parallel with that of the hypoglossal trunk. A short distance posterior to the place of branching of the r. int.-acc. it turns sharply about and running antero-ventrally comes into close relations with the r. intestinalis recurrens X. It receives a general cutaneous branch from the third spinal nerve and then divides into a general cutaneous and a motor division. The general cutaneous branch supplies the latero-ventral skin in the anterior post-branchial region; the motor branch divides into a nerve that runs anteriorly to innervate the anterior segment of the sternohyoid muscle, and a second branch that runs ventrally to supply other sections of the same muscle, after anastomosing with a motor branch of the third spinal nerve. The brachial plexus is formed from branches of the third and fourth spinal nerves. [he ramus lateralis ventralis X becomes very intimately associated with portions of the brachial plexus, but it is very clearly seen that no anastomosing occurs, such as Bowers describes (doubtless incorrectly) in Spelerpes. Q. CONCLUDING STATEMENTS. It is evident that the arrangement of the cranial nerves of Amphiuma gives support to the view that this species represents In many respects a primitive amphibian type. The group of nerves here designated as ramus oticus; the nasalis internus V; the clear differentiation of pretrematic, posttrematic and pharyn- 554 fournal of Comparative Neurology and Psychology. geal rami in the branchial nerves; possibly also the ramus lateralis VII; the lateral line lobe; all these have distinctly fish-like charac- teristics. Although the nerves connected with the eyes are degen- erate, this cannot be said of the other cranial nerves. As com- pared with other Urodela, Amphiuma shows in the arrangement of its cranial nerves a tendency towards great diffuseness and individual variability. A nerve trunk in one individual may break up into a number of divisions later to become consolidated into a main trunk again. In another specimen the same nerve may show no such tendency to diffuse subdivsion. General con- clusions based upon one or two specimens, in Amphiuma at least, are likely to be much in error. The resemblances between the cranial nerves of Amphiuma and those of Amblystoma are very striking. When the com- ponents of the cranial nerves of Cryptobranchus, Necturus, Siren, and one or two more of the Salamandride have been carefully: worked out, we shall be in a position to define the urodele type of cranial nerves, and in the opinion of the writer, not until then. The distribution of the lateral line organs of Amphiuma has been carefully mapped out and described by Kincspury (1895b). The innervation of these organs on the head has been worked out by the writer with precision, corroborating the description of KinGsBuRY, except in some details. A detailed account of the innervation of these organs in Amphiuma is withheld from this paper because of the uncertainty as to the exact distribution of the ramus lateralis VII on the trunk of the body. Iowa College, June 20, 1908. LITERATURE CITED: Bowers, Mary A. 1900. The peripheral distribution of the cranial nerves of Spelerpes bilineatus. Proc. Amer. Acad. Arts and Sci., vol. 36. Crapp, Cornea M. 1898. The lateral line system of Batrachus tau. ‘four. Morph., vol. 15. Cocuitt, G. E. 1902. The cranial nerves of Amblystoma tigrinum. our. Comp. Neurol., vol. 12. 1906. The cranial nerves of Triton teniatus. Jour. Comp. Neurol. and Psych., vol. 16. Drier, L. 1go1. Studien zurAnatomie der Zungenbein-, Kiemenbogen-,und Kehlkopfmuskeln der Urodelen. I Theil. Zool. fahrb., Bd. 15. 1904. Studien zur Anatomie der Zungenbein-, Kiemenbogen-, und Kehlkopfmuskeln der. Urodelen. II Theil. Zool. Fahrb., Bd. 19. Fiscuer, J. G. 1864. Anatomische Abhandlungen tiber die Perennibranchiaten und Derotremen. Hamburg Norris, Nerves of Amphiuma. 555 Herrick, C. Jupson. 1899. The cranial and first spinal nerves of Menidia. Four. Comp. Neurol., vol. 9. 1goo. A contribution upon the cranial nerves of the codfish. Four. Comp. Neurol., vol. 10. 1901. The cranial nerves and cutaneous sense-organs of the North American siluroid fishes. Four. Comp. Neurol., vol. 11. Jounston, J. B. 1906. The nervous system of vertebrates. Philadelphia. Kincsgury, B. F. 1895a. On the brain of Necturus maculatus. Four. Comp. Neurol., vol. 5. 1895b. The lateral system of sense organs in some American Amphibia, and comparisons with Dipnoans. Proc. Amer. Micr. Soc., vol. 17. Kinestey, J. S. 1goza. The cranial nerves of Amphiuma. Tufts College Studies, no. 7. 1gozb. The systematic position of the Cecilians. Tufts College Studies, no. 7. Norris, H. W. 1904. The so-called dorsotrachealis branch of ae seventh cranial nerve in Amphiuma. Proc. Towa Acad. Sci., vol. 10. 1905. The so-called dorsotrachealis branch of the seventh cranial nervein Amphiuma. Anat. Anz. Bd. 27. 1908. The cranial nerve components in Amphiuma. Scvence, n. s., vol. 27, no. 702. Osgorn, H. F. 1888. A contribution to the internal structure of the amphibian brain. ‘four. Morph., vol. 2. STRONG, O. S. 1895. ‘The cranial nerves of Amphibia, ‘four. Morph., vol. 10. Wiper, H. H. 1892. Die Nasengegend von Menopoma alleghaniense und Amphiuma tridactylum. Zool. Fahrb., Bd. s. 550 ace. ags. alv. alv.(1). alv.(2). alv.(3). alv.(4). am. ao. aur. bhy. bplx. Ibr.,2br.,3br. buc buen gece): ch. chi. chi.X.1. chy. gVI-VII. g.1TX-X. h. hgl. hhy. hm. hy. ib.4. th. im. int. int.-acc. int.rec. 10. ies je-(a). Fournal of Comparative Neurology and Psychology. EXPLANATION OF THE PLATES. REFERENCE LETTERS. branch of the X nerve supplying the anterior part of the trapezius muscle. angulo-splenial bone. r. alveolaris VII. first anastomosing branch between r. alveolaris VII and r. pretrematicus IX. second anastomosing branch between r. alveolaris VII and r. pretrematicus IX. branch of r. alveolaris VII that supplies roof of mouth. branch of r. alveolaris VII that anastomoses with r. mandibularis V. muscles of the arm. antorbital cartilage. cartilage of the ear capsule. ossifications of the ear capsule. r. auricularis X. basihyal cartilage. branches of the brachial plexus. first, second and third branchial arches. r. buccalis VII. branches of the r. buccalis VII that anastomose with the r. oph. prof. V. cerebral hemisphere. m. ceratohyoideus internus and branches of IX nerve innervating it. branch of the second branchial nerve innervating m. ceratohyoideus internus. ceratohyal. coracoid cartilage. dentary bone. diencephalon. m. dorsolaryngeus. branches of the X nerve innervating the dorsolaryngeus muscle. m. depressor mandibule. anterior division of m. depressor mandibule and the nerve innervating it. posterior division of m. depressor mandibule and nerve innervating it. fasciculus communis. fasciculus longitudinalis medius. frontal bone. ganglion acusticum. ganglion geniculatum. ganglion Gasseri. m. geniohyoideus. first spinal ganglion. ganglion on ‘‘dorsal VII.” lateral line ganglion fused with ganglion acusticum. acustico-facial ganglion. ganglion common to IX and X nerves. humerus. n. hypoglossus. hypohyal cartilage. tr. hyomandibularis VII. hyoid arch. m. interbranchialis 4 = m. hyotrachealis. m. interhyoideus and branches of r. jugularis VII innervating it = m. mylohyoideus posterior. m. intermandibularis = m. mylohyoideus anterior. rr. intestinales X. r. intestino-accessorius X. r. intestinalis recurrens X. m. obliquus inferior. Jacogpson’s commissure. branch of Jacopson’s commissure innervating the roof of the mouth. ]2- lab.1,2,3, and 4. lag. md.(3b). md.(4).,md.(5). mes. mplx. mtl.ext. mil.int. mx. na. nas. nas.int. ne. ngm. nio. nio.(a). op.(3). op.(4) and (5). op-pal. op.-pal.d. op.-pal.l. op.-pal.m. op.-pal.mn. op.-pal.ph. op.-pal.pn. Os. osph. ot. pa. Norris, Nerves of Amphiuma. 557 r. jugularis VII. JAcogson’s organ. mm. levatores arcuum branchialium and the nerves innervating them. lagena and branch of the VIII nerve innervating it. r. laryngeus recurrens X. r. lateralis dorsalis X. r. lateralis medius X. r. lateralis ventralis X. r. lateralis VII. communis branch of r. posttrematicus IX to the tongue. lobus linez lateralis. m. levator bulbi. m. masseter. r. maxillaris V. branch of r. mandibularis V innervating the retractor and levator bulbi muscles. Mecxet’s cartilage. r. mandibularis V. branch of r. mand. V innervating skin of side of head. branch of r. mand. V running just above and in the mandible. branch of preceding innervating skin near tip of lower jaw at the side. mandibular branch anastomosing with r. alveolaris VII. branches of r. mand. V innervating m. intermandibularis and overlying skin. mesencephalon. metaplexus. r. mentalis externus VII. r. mentalis internus VII. maxilla. neuromasts of the angular series. nasal bone. rm. nasalis internus, first terminal division of r. profundus V. nasal cartilage. median nasal gland = Jacopson’s gland (?). neuromasts of the infra-orbital series. neuromasts of the infra-orbital series innervated by the r. oticus. neuromasts of the supra-orbital series. neuromasts of the supra-orbital series innervated by the r. oticus. r. ophthalmicus profundus V. first terminal division of the r. oph. prof. V. = rm. nasalis internus. branch of the preceding that passes into a canal in the edge of the frontal bone = ethmoideus caudalis of Kincstry. branch of op. (1) innervating the skin of dorsum posterior and dorsal to eyeball. second terminal division of r. oph. prof. V =r. glandularis II of Wiper. third terminal division of r. oph. prof. V, anastomosing with r. palatinus VII. Fourth and fifth terminal divisions of r. oph. prof. V, anastomosing with the two main divisions of r. buccalis VII. anastomosis of the third terminal division of r. oph. prof. V with r. palatinus VII. branch or branches from the oph-pal. anastomosis passing antero-dorsally inner- vating the dorsal lateral nasal epithelium and JAcopson’s organ. branches from the oph.-pal. anastomosis supplying the lateral (maxillary), series of teeth and roof of mouth. branch from the oph.-pal. anastomosis supplying the median (vomero-palatine) series of teeth and the roof of the mouth. branch from the oph.-pal. anastomosis supplying the median nasal epithelium. small branches from the oph.-pal. anastomosis passing chiefly to the roof of the mouth at the posterior border of the nasal capsule. branch from oph.-pal. anastomosis supplying the posterior nasal epithelium. r. ophthalmicus superficialis VII. orbitosphenoid bone and cartilage. Tr. oticus. parietal bone. 558 rtb. Sar.I,2,3. yes SO. se. Isp. Isp.d.. Isp.rd. Isp.rv. Isp.v. 2sp. 3p. spV. sp. VIII, sphe. spt. Sq. SSC. sthy. stp. th. thr. tm. tma. tmn. imp. tmpt. ae tra. trap. trapa. trb. irc. Fournal of Comparative Neurology and Psychology. r. palatinus VII. prefrontal bone. r. pharyngeus IX. r. pharyngeus of the second branchial nerve. r. pharyngeus of the third branchial nerve. premaxilla. postnares (edge of wall). prosoplexus. r. pretrematicus IX. r. pretrematicus of the second branchial nerve. r. pretrematicus of the third branchial nerve. branch of the r. intestino-accessorius X, representing a pretrematic ramus of a fourth branchial nerve. a nerve associated with the preceding and representing a pretrematic ramus of a fifth branchial nerve. parasphenoid bone. Tr. post-trematicus [X. Ir. post-trematicus of the second branchial nerve. r. post-trematicus of the third branchial nerve. m. pterygoideus. pterygoid cartilage. nerve innervating m. pterygoideus. pterygoid bone. m. rectus externus. m. rectus inferior. m. rectus internus. m. rectus superior. m. retractor bulbi. mm. subarcuales recti 1, 2 scapula. m. obliquus superior. saccus endolymphaticus. first spinal nerve. dorsal branch of first spinal nerve. dorsal roots of first spinal nerve. ventral roots of first spinal nerve. ventral branch of first spinal nerve. second spinal nerve. third spinal nerve. tractus spinalis trigemini. tractus spinalis acusticus. m. sphincter colli and the nerve innervating it. r. supratemporalis X. squamosal bone. suprascapula. m. sternohyoideus. stapes. thymus gland. thyroid gland. m. temporalis. anterior division of m. temporalis. branch of the r. mandibularis V innervating m. temporalis. posterior division of m. temporalis. tendon of the posterior division of m. temporalis. trachea. “tractus a’ of Kincspury. m. trapezius, posterior division. m. trapezius, anterior division. “tractus b” of Kincsrpury. tracheal cartilages. and 3, constrictor arcuum branchiarum inferior. VIla+VIIbb. VIIb. VIIb(1+2+ 3) V IIba. VIIbb. VIlIbat+V. VIIl. VIIIap. VI Ilag. VIIImn. VIII pb. VIIIs. VITIv. VIII(1). VIII(2). VIII(3). VIII(4). EX): IX(a2). X.I. X.2. X.3+4. X(z). X(2) X(3),X(4),X (5). X.adV II. X.adV II.d. X.adVII.v. Norris, Nerves of Amphiuma. 559 muscles of the trunk. vomero-palatine bone. n. olfactorius. branch of n. olfactorius innervating Jacopson’s organ. roots of n. olfactorius. n. opticus. n. oculomotorius. n. trochlearis. motor root of the V nerve. n. abducens. the ventral roots of the facial nerve, communis and motor components. the communis portion of the preceding. the motor root of the facial nerve. the ventral or main trunk of the facial nerve. the lateral line portion of the facial nerve. the three rootlets of the preceding. the ‘‘dorsal VII.” that portion of the lateral line component of the facial nerve that passes ventrally and joins VIIa. the trunk formed by the union of general cutaneous fibers from the gasserian gan- glion with the ‘‘dorsal VII.” n. acusticus. branch of VIII nerve to the posterior ampulla. branch of VIII nerve to the lagena. branch of the VIII nerve to the macula neglecta. branch of the VIII nerve to the pars basilaris. branches of the VIII nerve to the sacculus. vestibular branch of the VIII nerve. fibers of the VIII nerve that pass into the tractus spinalis VIII. fibers of the VIII nerve that pass anteriorly into the acusticum. fibers of the VIII nerve that enter “‘tract b.” coarse fibers that enter the sp. VIII tract distinct from VIII (1). communis root of the [X nerve. motor root of the IX nerve. second branchial nerve. third branchial nerve. branch of r. int.-acc. representing the fourth and fifth branchial nerves. first or lateral line root of the X nerve. second root (group of rootlets) of the X nerve. third, fourth and fifth roots of the X nerve. r. communicans between the X and VII nerves. dorsal division of r. communicans. ventral division of r. communicans. 560 Fournal of Comparative Neurology and Psychology. : EXPLANATION OF PLATE IV. ae Fic. 1. A projection upon the sagittal plane of the V, VII, VIII, IX and X cranial n with portions of the first and second spinal nerves, of Amphiuma means. The roots an slightly schematic for the sake of clearness. In only a few cases have the positions of nerve tru been slightly changed. The scale above the figure indicates the serial numbers of the tr tions employed in the reconstruction, the sections being 10 micra thick X 32. ; i a LN 'e Wits re > = - : ¢ . ae « es a t an" > m + ‘y Bea hal 4 yin ; - eae ’ ; Senne hae i. eal et A ‘ a Z § Journal of Comparative Neurology and Psychology. Vol. XVIII. = Sh Le ae _——— I= Tr TE a ip en at r YR a a (PR a a) aa) (I a a ge ee ae | 2a Oe a es 1240 1200 1100 1000 900 800 700 600 500 400 300 200 100 tmn. lab, 3 pst. X.1 b.2 General Cutaneous Systera Lateral Line System Communis System Visceral Motor System Somatic Motor System Plate IV. cS y! rh'S = 4 me's ‘ie Ke ; 7 oh Misr, AeTk Aas i a ‘sy : « ns = ger se fe : oa sel oka ae Wie iV. as 7 ef ee ke be oar a 4 i i ae coals om 8 562 ‘fournal of Comparative Neurology and Psychology. EXPLANATION OF PLATE V. Fics. 2 to 10. Cross-sections of the left half of the head at different levels. The outlines were drawn with a camera lucida; the details are schematic. These were made from a different series of sections than that from which fig. 1 was plotted. After the description of each figure is given the num- ber of the section in fig. 1 which corresponds approximately to the section described. Fic. 2. Cross-section through the nasal capsule at the level where the branch of the olfactory nerve that innervates Jacopson’s organ is passing around to the dorsal side of the latter structure. Section 200. X 30. Fic. 3. Cross-section through the nasal capsule at the point where the olfactory nerve trunk breaks up into its terminal divisions and enters the capsule. Section 260. X 30. Fic. 4. Cross-section cutting through the posterior portion of the eyeball. To show the retractor and levator bulbi muscles and their insertion on the antorbital cartilage. Section 350. X 20. Fic. 5. Cross-section at the level where the r. mandibularis V enters the lower jaw. Section 460. X 20. Fic. 6. Cross-section through the origin of the r. mandibularis V. The abducens nerve is seen separating from the gasserian ganglion. Section 560. X 30. Fic. 7. Composite cross-section through the roots of the VII and VIII nerves. Sections 675- 680. xX 30. Fic. 8. Cross-section through the roots of the lateral line component of the VII nerve. Section 685. X 30. Fic. 9. Cross-section slightly posterior to that of fig. 8. X 20. Fic. 9a. An enlargement of a part of the preceding, showing the r. communicans. Fic. 10. Cross-section at the level where the roots of the lateral line components of the X nerve enter the brain. Section 710. X 30. —— v Journal of Comparative Neurology 0) | op-pal. m. psph. and Psychology. 3 LAVIN. Bb. gma 189: x ad, Vil. WN iY iN Op-pal. d. op. (5). op. (4) -- bue, (2) \ ~-\buc, (1) ARAN = NY yy Vol. XVIII. 8 ving Ne , Vile, (Qe VII. b, (S)ERSSps tp Vill. ie VIN. (D-2Bhegs Plate V. i d Gee - © : a ge oa @ ' « = ; MARAT IN te Bie sl aw fp Rs Wg | On, he mA rice y 564 ‘fournal of Comparative Neurology and Psychology. EXPLANATION OF PLATE VI. Fic. 11. Cross-section through the gill-cleft. Section 960. X 19. Fic. 12. Cross-section at the level where the r. intestino-accessorius breaks up into its branches. Section 1090. X 19. Fic. 13. A projection upon the sagittal plane to show chiefly the olfactory, optic and eye-muscle nerves. The outlines of the acustico-facial, gasserian and dorsal lateral line ganglia are drawn in their correct relations. Fics. 14 to 18. Projectionsupon the sagittal plane of the r. hyomandibularis VII in the region where it divides into its chief branches. These are from four different individuals. Figs. 14 and 15 are from the same individual. All are represented as seen from the right side. These sections are to show primarily the variable mode of fusion between the anastomosis X ad VII and the r. jugularis VII. Vol. XVIII. Plate VI. Journal of Neurology and Psychology. g. Vil. ba. Mee] ee wm » IK.) \ 9. Vil+ VIN IX. (2) : X ad. Vil..g Jat vii, dmp. I X. ad. Vil. ait iesne hae eed 566 = =“Fournal of Comparative Neurology and Psychology. EXPLANATION OF PLATE VII. Fic. 19. A projection upon the sagittal plane of the origin of the first spinal nerve, in an individual of 120 mm. length, seen from the right side. Fic. 20. A projection upon the sagittal plane of the olfactory nerve, its roots and principal branches. Fic. 21. A projection upon the sagittal plane of the IX-X, and Y-VII-VIII ganglionic com- plexes, and the plexus developed between the IX -X, and VII nerves. The roots of the ganglia are omitted. In the individual from which the plotting was made Jacogson’s commissure is double; from the r. pharyngeus IX there passes an anastomosis to the tr. hyomandibularis VI. The V-VII-VIII ganglionic mass is much more compact than in younger individuals, such as shown in figs. 1, 13 and 24. Fic. 22. Composite sagittal section through the insertion of the retractor and levator bulbi muscles upon the antorbital cartilage, as seen from the left side. The eyeball and the greater portion of the eye-muscles are situated lateral to the section and are represented in dotted outlines. For the sake of clearness the branches of the r. ophthalmicus profundus V and of r. ophthalmicus superficialis VII are omitted. The outlines of the section were drawn with a camera lucida. Journal of Comparative Neurology and Psychology. Vol. XVIII. Plate VII. g. VIL+VINL, Vill. ss, VIII mn. 9. IKK, ‘aur. Vill. ap... vim ad. Vil. VIII. p af a ie a es “ - (ek See mtl. int: aly ) dmp.+sphe.+ th.’ 3 a prt. IX, lat. m, et d. d nt. acc. || ss Pe “aly. (2) “ “ye 3 4 Roe a Po. ‘ ae ~ > be } + - u's MJ - ae = = ‘ r bl ty . : <> Fah ‘ c = . r « ' 2 ae of > i au i 7 — = - « . % 4, i Si " ' ng = » 5 er. = F ia - de Ls Vaid bot eal i ad " A Sy ‘ mn ‘ FL o > . - = : ‘ i A r : ' 1 cans 7 4 > ni ” ev i - u be ae yd = 7 } ov a as ef ae a: ae) f iv = = Ler" 5.5 oe Se 3 - —— SSeS es —— 33 han \ am a A a! aE Bs Rr a ce aaa ethane orn hea ee : ‘ - E : oy ie. | , Sy Soo ae aaa ; ; Z aie De : ~ | ita he a CST A a > J f ae ieee | = - — ; ; * ap k + Piel een! inert f " bi wah, ne Lhe iG S ey i iene i 568 fournal of Comparative Neurology and Psychology. EXPLANATION OF PLATE VIII. Fic. 23. A projection upon the horizontal plane of the roots, ganglia and principal trunks of the V, VII, VIII, IX and X nerves. Fic. 23a. The roots of the VIII nerve. Fic. 24. A projection upon the sagittal plane of the ramus oticus and its branches, together with the neuromasts which it innervates. Fic. 25. A projection upon the sagittal plane of the anastomoses between ther. oph. prof. V and the r. buc. VII. The condition here is more complicated than in fig. 1. Fic. 26. A projection upon the sagittal plane of the anastomosis between the r. oph. prof. V and the r. pal. VII. The exact composition of a few of the smaller branches is uncertain; hence they are only partly colored. Journal of Comparative Neurology and Psychology. Vol XVII wPiES VIN: 24 --Op, ga. K_)) Vil. ba.» V ac Z iE ! Vila Vil. bb, g. VIL. ba. VII ab... ri Nilpaarell Vo Nill. reese“ IX.) ae IX, (2) >= : Villa) Vill, (243) prt. IX. x. ad. Vil. X. (3) .- X. (4+ 5). op. (2) op. (3) SS i int. ace. X.2 lat. m, etd. —dp-pal, ph. Fy oR ¥ - i” = ADDITIONAL NOTES ON THE CRANIAL NERVES OF PETROMYZONTSs2 BY J. B. JOHNSTON. University of Minnesota. Wiru Tuirty-one Ficures. In the year 1897 I prepared by the Gorci method a number of series of sections of the head of Lampetra wilderi. These were used for the study of the brain (1902) and were reviewed in con- nection with the study of the components of the cranial nerves in Petromyzon dorsatus (1905). Owing to the fact that certain fibers are impregnated and others not, the GoLci preparations are not in themselves suitable for a complete study of cranial nerve components and such differences were found between the two species that it was thought best not to incorporate any of the facts from the Lampetra series in the description of the nerves of P. dorsatus. ‘The Gouci preparations were therefore laid aside with the hope that they could be supplemented by new preparations and the cranial nerves thoroughly gone over by this method. The time for making these new preparations now seems more remote than ever and I have decided to publish certain results which are entirely clear from the preparations in hand. The animals used were adults. All were taken on their nests just after spawning. The general relations of the cranial nerves may first be reviewed by means of figs. 1 to 11. These are camera sketches from a series of horizontal sections. The anterior part of the right half of the head is shown, including the first two gill sacs. The figures are not schematized at all except that detail had to be omitted, and in figs. 3 and 8 a little is added from the sections adjacent to those drawn and fig. 11 is a reconstruction from several sections. The left half of this hgure represents sections farther ventrad than those drawn on the right., “The entire series consists of 109 sections and the section drawn is indicated beneath each figure. In all ! Neurological Studies, University of Minnesota, no. 2. 570 ‘fournal of Comparative Neurology and Psychology. the figures cartilage is shaded with oblique lines and the larger muscles are indicated by light lines running in the direction of the muscle fibers. The following letters are used in addition to Fic. 1. Section 39. Fic. 2. Section 36. Fics. 1 to 11. A series of horizontal sections of the right half of the head to show the general arrangement of the nerves. Explanation in the text. Magnification, 8.5 diameters. those indicating the nerves, which will be explained below: a.o., aortic arches: au, auditory capsule; m.c., mouth cavity; e, eye- ball or orbit; mch., notochord; 0, cesophagus; r.t., respiratory tube; v., blood vessels; th., thyroid gland. Jounston, Nerves of Petromyzonts. 571 In fig. 1 appear the ganglia and roots of the V and [X nerves, the root of the VII nerve within the auditory capsule, the VII-X connective of lateral line fibers (//) on the outer surface of the auditory capsule, the combined roots of the 1 and 2 ventral spinal nerves (1-2) just behind the glossopharyngeus, and a segment of the epibranchial trunk (¢r.ep.) with the stump of the first bran- Fic. 3. Section 43. Fic. 4. Section 48. chial nerve going off from it. Within the brain case appears the root of the third nerve and also two fine fibers which are appar- ently related to the meninges. The section from which fig. 2 was drawn passes through the optic chiasma (ch.). A part of the root of the trigeminus 1s still present and in its ganglion appear the cells and fibers of the velar nerve to be described below. The fibers which cross the root and 572 ‘fournal of Comparative Neurology and Psychology. ganglion at right angles are the fibers coming from the lateral line VII ganglion and going to join the ophthalmicus profundus V (1905, p. 152). Within the auditory capsule are the roots of the VII and VIII nerves and behind the capsule the nerves spinal ventral 1 and 2, LX and X whose relations will be readily under- stood. Along the dorso-mesal surface of the second gill sac runs the trunk of the sympathetic (sym). WA NY AXS =) x he states, “‘the lower brain lobes are united by the ventral commissures, se parated by a very short distance, till close up to the massive ventral com- missure that has been hitherto regarded as the only ventral com- missure between the brain lobes. The thin commissures just described are, however, not directly connected with the fibrous core of the brain lobes, which is on the contrary directly continued into the massive inferior commissure, but they seem to derive their fibers from the outer cellular coating of these lobes. “They pass underneath the two vagus stems, where these spring from the lower brain lobes, and where these are in their turn in front of the mouth united by transverse commissures.”” The brain of Dre- panophorus lankesteri (pl. ix, fig. 10) has a series of ladder com- missures between the lateral nerves. BURGER (1895, taf. 10, fig. 8) figures the brain of Cerebratulus marginatus, in which only the dorsal and the broad ventral com- missure are shown. In the text, however, he describes three com- Tuompeson, Brains of Cerebratulus. 643 missures between the cesophageal nerves; the first of these 1s slender and thin, the second is also slender, but the third is thick and surrounded by ganglion cells. On p. 320, BURGER states “An der namlichen Stelle” (Abgangstelle der Schlundnerven) “befindet sich die erste Durchbrechung der senkrechten Querwand der Gehirnkapsel, durch welche ein Faseraustausch zwischen den Faserkernen der beiden ventralen Ganglien stattfindet.”’ ‘This “‘Faseraustausch”’ is figured on taf. 25, fig. 5, and evidently repre- sents a delicate additional commissure, although BURGER does not describe it as such. MontTcoMErY (1897) describes in the brain of Cerebratulus lacteus a second commissure between the ventral brain lobes, posterior to the broad first ventral commissure, and of much smaller size, and also three between the cesophageal nerves, mak- ing a total of five ventral commissures. In Lineus sp. Monrt- GOMERY finds, posterior to the great first ventral commissure, a second and a third slender commissure between the ventral lobes, and four between the cesophageal nerves, giving a total of seven ventral commissures for this closely related genus. Cor (1895, pl. x, fig. 8) figures the dorsal, the first ventral, and a single cesophageal commissure in the brain of Cerebratulus lacteus. b. The commissures of Cerebratulus lacteus—My observations agree with those of the above mentioned workers in the general features of the brain anatomy, but differ from them in the number and the character of the ventral commissures, which must be taken to include those between the ventral brain lobes, whether originating in the cellular sheath or in the fibrous core, and those between the cesophageal nerves. Fig. 1 is a reconstruction from camera drawings of successive sections, and represents the brain as seen in horizontal optical section. [he dorsal brain lobes, D L, are formed by the union of numerous small branches which originate in the tip of the head, on each side of the rhynchodeum. ‘The arched dorsal commissure D Cy, unites the two dorsal lobes, and gives off from its median anterior surface a delicate nerve that runs forward to the tip of the head. A similar delicate nerve, the median dorsal nerve, m dn, arises on the median posterior surface of the dorsal commissure and runs backward. Just posterior to the dorsal commissure the ventral brain lobes, VY L, are differentiated trom the dorsal 644 “fournal of Comparative Neurology and Psychology. lobes, and almost immediately unite in the broad stout band known as the first ventral commissure, V,; they then extend backward, and with a decrease in size become the lateral cords of the body. The two proboscis nerves, pr n, originate on the anterior surface of the first ventral commissure and pass forward and upward into the proboscis at its attachment. From the lateral surfaces of both dorsal and ventral lobes, nerves, not shown in this figure, are given off at irregular intervals, and are not paired with those of the opposite side. The dorsal lobes end posteriorly in the cerebral sense organs, not shown in this figure, which in their turn termin- ate just in front of the anteriorendof the mouth. ‘The cesophageal nerves, EN, arise within the fibrous core of the ventral lobes as follows: A small portion on the medial surface of each brain lobe is constricted off from the rest by a delicate septum, the nerve sheath. ‘These separated portions are the two cesophageal nerves, which, for a short distance, lie within the fibrous sheath of the brain, but farther back pierce the sheath and assume a more medial position. Behind the broad first ventral commissure comes a series of commissures, 2 to 14, giving a ladder-like appearance to the brain. Closer investigation reveals thirteen of these commissures, some of which, coming only from the cellular sheath of the brain, may. represent the metameric commissures described by HuBREcHT, but others of which, having their roots in the fibrous core of the brain, are commissures that have not been previously described. According to their origin the commissures are of three different kinds: (1) those running from ventral lobe to ventral lobe, whether from the fibrous core or from the cellular sheath, brain commis- sures; (2) those running from ventral lobe to ventral lobe and traversing the substance of the cesophageal nerves, brain-esoph- ageal commissures; (3) those running between the cesophageal nerves only, esophageal commissures. As many of the commissures are figured here for the first time, they will be described with considerable detail. Their clearness and distinctness are evidently due to the size and the extension of the very favorable material. The following table 1s a summary of the position, thickness and character of the commissures. TuHompson, Brains of Cerebratulus. 645 TABLE OF COMMISSURES. | inci) b ORIGIN OF COMMISSURE. s Brg 5 pear) oniee Bike he ee ee cen Sig NAME OF ies 5 | ates | jo 2 ° So COMMISSURE. eae fen) Ss teh) gece eras Mae 4 a) @ Region in brain. ica g os i Gt ean Owe le 4 Ba | (2) dorsal brain fibrous core 10 | 7oft Ist ventral brain fibrous core. 15 | 18 | ré6op 2d ventral | brain cellular sheath. 33 2 Iif 3d ventral | brain cellular sheath and fibrous core Gi a) 248 4th ventral | brain cellular sheath 8 3 424 sth ventral | brain fibrous core 4 I Soy 6th ventral oesophageal I 3 53 7th ventral | brain fibrous core, |. root; cellular sheath, r. root,, 4 2 42 8th ventral | oesophageal 2 2) oy gth ventral brain cellular sheath and fibrous core I 4 524 roth ventral | brain-cesophageal | cellular sheath and fibrous core 4 4 424 11th ventral brain-cesophageal | cellular sheath 2 2 21 12th ventral | brain-cesophageal | 1. root, cellular sheath 4 2 42 13th ventral | brain-cesophageal | fibrous core ec 4 42fe 14th ventral | brain-cesophageal | fibrous core [Papa Io. || 85pe Dorsal Commissure.—The dorsal commissure, fig. 1, D C, curves forward and also upward, encircling the proboscis at its point of attachment, but the latter curve is not represented in fig. 1, which is approximately in one horizontal plane. From its most anterior point to its posterior ending in the dorsal lobes the dorsal commissure is present in ten sections, and the dorso-ventral mea- surement is 704. Upon the surface of the commissure ganglion cells of type I are very abundant, and a few are found within, between the fibers. First ventral commissure.—The first ventral commissure, fig. 1, V,, is the stoutest commissure in the brain, measuring 160” dorso- ventrally, and eighteen sections in thickness. Its surface is closely invested with a layer of ganglion cells of type I, and great clusters of cells of types II and LII are present in the outer part of the cellular sheath, especially on the ventral side. Second ee ial commissure.—lThe second ventral commissure, fig. I, 2, is situated thirty-three sections posterior to the first. “The thickness is two sections, and the dorso-ventral measurement is 646 Fournal of Comparative Neurology and Psychology. tin. This is a brain commissure, as the roots come from the cellular sheath of the brain lobes, and it is clear and distinct, though delicate. As the central part is at a more ventral level than the roots, a wide V is formed, which gives the commissure a very distinctive appearance. A few cells of type I are scattered along the surface, but there is no continuous layer. “This commis- sure is intermediate in position to the first two pairs of neurocord cells, and evidently corresponds to the second ventral commissure described by Montcomery (1897) for Cerebratulus and Lineus. T hird ventral commissure.—The third ventral commissure, fig. I, 3, Is seven sections posterior to the second, and extends through three sections. It is a well defined brazm commissure, as the roots may be traced into the cellular sheath of the brain lobes. On the right side, fig. 3, two roots are clearly distinguishable, passing toward the brain, one dorsal and one ventral to the right cesopha- geal nerve, the latter entering the fibrous core. On the left side, ay one root is seen, ventral to the cesophageal nerve. Like the second, this commissure also forms a broad V. The central part lies at a more ventral level and is considerably broader than the roots, measuring 24 dorso-ventrally in the broadest part. The anterior border is thickly beset with ganglion cells of type I. This commissure is here described for the first time in Cerebratulus but seems to correspond, except in its distance from the second, with the third ventral commissure described by MonrcoMERY in Lineus sp. Fourth ventral commissure.—TVhe fourth ventral commissure, fig. 1, 4, is situated eight sections posterior to the third. It 1s three sections thick and has a dorso-ventral measurement of 424. The fibers of this commissure are derived from the cellular sheaths of the brain lobes and run from side to side in nearly a straight line at the level of the ventral surface of the cesophageal nerves. A few cells oftype I are scattered along the surface of the commissure. Fifth ventral commissure.—The fifth ventral commissure, fig. 5, comes from the fibrous core of the brain, and lies four sections behind the fourth. The central mass is one section thick and has a dorso-ventral measurement of 50. ‘This is the only commissure about which there is any doubt; the roots are clear and distinct, and extend through several sections, fig. 5, 5, the right root measur- ing in width 214, the left slightly less, and there is a short central mass in one scction, fig. 6, 5c, but the connections between this Tuompson, Brains of Cerebratulus. 64.7 central part and the roots are not distinguishable. At first it seemed possible that the roots might be merely entering fibers from large cells in the cellular sheath, and this view was supported by the presence of a group of cells of type III, just medial to each of the brain lobes. A further study of succeeding sections showed, however, that the fiber bundles, or roots, may be traced paride the cellular sheath and slightly beyond the medial side of the cesophageal nerves. ‘The question then arises, whether the central part may not be merely the anterior part of the sixth commissure, - which begins in the following section. My final conclusion, based upon the careful study of successive sections with the immersion lens, is that the fiber bundles in question are either the roots of a separate, very delicate brain commissure, the fifth, which immedi- ately adjoins the sixth, or the roots of a compound brain-cesopha- geal commissure, the fifth and the sixth, the anterior fibers of which come from the brain, the posterior fibers from the cesopha- geal nerves. Since further study of the sections makes the former view slightly more probable, the fifth commissure 1s represented, fig. 1, as separate from the sixth. ete ital consind oie Moca havea commissure, fig. 1, 6, is found one section posterior to the central part of the fifth, and is the first esophageal commissure, running only between the cesophageal nerves. ‘This commissure is three sections thick; in the first two sections the dorso-ventral measurement 1s 53, but is much less in the last section. It 1s a very clear and well defined commissure, and the passing out of the fibers from the cesophageal nerves is distinctly seen in several sections, as the nerve sheaths are wide open on their medio-ventral surfaces owing to the breadth of the bands of fibers. As the left root originates a few sections posterior to the right, the entire commissure is not in the same frontal plane. Seventh ventral commissure.—Vhe seventh ventral commissure, hg. 1, 7, is found four sections posterior to the central part of the sixth; its central mass is present in two sections, with a dorso- ventral measurement of 424. The left root is a sharply defined, rather broad band of fibers, and may be traced beneath the left cesophageal nerve through the cellular sheath into the fibrous core of the brain. ‘The right root is delicate and rather indistinct and can be traced only as far as the cellular sheath of the right ventral lobe.. Some of the more ventral fibers of the left root seem also 648 “fFournal of Comparative Neurology and Psychology. to originate in the cellular sheath of the left ventral lobe, hence this commissure may be designated as a brain commissure, derived on the left side from both fibrous core and cellular sheath, but on the right side from the cellular sheath only. Eighth ventral commissure.—The eighth ventral, fig. 1, 8, is the second commissure between the cesophageal nerves. It lies two sections behind the seventh; the central part is two sections thick, with a dorso-ventral measurement of 504. Owing to the opening of the roots into the oesophageal nerves three or four sections posterior to the central part, the commissure has the form of a broad curve. ; Ninth ventral commissure.—TYhe ninth ventral. commissure, fig. 1, g, is only one section posterior to the eighth. The central part is present in four sections, and measures dorso-ventrally 52. Its most median portion is considerably thicker in an antero- posterior direction than the lateral parts near the nerves. Like the eighth, this commissure forms a broad curve, owing to the posterior position of the roots. The fibers pass beneath the cesophageal nerves and may be traced in part into the fibrous core, in part into the cellular sheath of the ventral brain lobes. ‘There is an intimate relation between the fibers of the roots of this com- missure and those of the tenth, which will be described below. Tenth ventral commissure.—The central part of the tenth com- missure, fig. I, 70, lies four sections posterior to that of the ninth; it is present in four sections, and has a dorso-ventral measurement of 42. The anterior surface of the commissure is a straight line, the posterior, a curve, owing to the greater antero-posterior dimension of the median part. The roots come from the fibrous core of the brain lobes, and their fibers then run into and through the cesophageal nerves, making a commissure that may be termed brain-esophageal. he relation between the fibers of the roots of commissures nine and ten will now be described. Leaving the central part of the ninth commissure, the fibers run outward beneath the cesophageal nerves and then slant upward toward the brain lobes, making an oblique fiber band along the lateral surface of each cesophageal nerve. In the following sections the band becomes broader, and the more dorsal fibers, which are from the roots of the tenth commissure, enter the cesophageal nerves on their lateral, and pass out again from their medial surfaces to form the central, cesophageal, part of the tenth commissure. Tuompson, Brains of Cerebratulus. 649 Eleventh ventral commissure.—The central part of the eleventh commissure, fig. 1, //, and figs. 7 to 8, //, is situated two sections posterior to the tenth; it is two sections thick, and has a dorso- ventral measurement of 214. ‘This is the second brain-eesophageal commissure. ‘The fibers of the central part, figs. 7 to 12, pass above the cesophageal nerves, and are reinforced, especially on the right side, by fibers that issue from the dorsal surface of the nerves. The left root is slender and delicate but may be traced almost to the cellular sheath of the left brain lobe. ‘The right root 1s stout and runs obliquely backward, through eight sections into the cellular sheath of the right brain lobe, figs. 7 to 12. Twelfth ventral commissure.—The central part of the twelfth commissure, fig. I, 12, lies four sections posterior to theeleventh; it 1S present in two sections, and measures dorso-ventrally 42). This commissure, figs. 9 to 10, may be traced from the cellular sheath of the left brain lobe across to and into the right cesophageal nerve, but no fibers are distinguishable between the right cesopha- geal nerve and the right brain lobe. ‘The fibers pass above the left cesophageal nerve, and as the nerve sheath is absent at this point there is probably a mingling of nerve substance. In the next two sections, figs. II to 12, a very stout bundle of fibers enters the left cesophageal nerve on its lateral surface, and may represent a second root of the same commissure. Fig. 10 is of- interest since it contains parts of three commissures, namely, the eleventh, the twelfth and the thirteenth. The fibers at the more dorsal level, 72, belong to the twelfth, the ventral ones, 13,tothe thirteenth and the root to the right, rz, to the eleventh. From this it is seen that the twelfth and “dhe thirteenth commissures are jn contact with each other, the ventral surface of the former adjoining the dorsal surface of the latter. Thirteenth ventral commissure.—Vhe anterior part of the thir- teenth ventral commissure is in the same section with the posterior part of the twelfth, but ventral to it, fig. 10. At its widest part the dorso-ventral measurement 1s 604. ‘This commissure is pres- ent in four sections, and in the last two sections, figs. 12 to 13, the beginnings of the fibers of the fourteenth commissure are seen ventral to the fibers of the thirteenth. The stout distinct roots are several sections posterior to the central part, fig. 1, and may be ._ traced into the fibrous core of the ventral lobes. “The fibers from the brain sweep beneath the cesophageal nerves and then upward, 650 fournal of Comparative Neurology and Psychology. forming a broad central loop between. ‘The sheath is absent from the ventral surfaces of the nerves, and an interchange of fibers takes place. Fourteenth ventral commissure.—Before the loop of the thir- teenth commissure has quite disappeared, figs. 12 to 13, other fibers are seen ventral to it which extend across the space between the cesophageal nerves. ‘These fibers may be traced through the ventral part of the cesophageal nerves, and toward the brain lobes, and represent the slender anterior part of the fourteenth and last ventral commissure, which extends altogether through ten sec- tions. It gradually becomes broader until it measures 85 dorso- ventrally, and in thickness is the second of the ventral commis- sures. [he cesophageal nerves are no longer distinguishable as separate structures but have become a part of the commissure, which is now very wide from side to side and extends from one ventral brain lobe to the other. The very broad roots arise on the dorsal surface of the commissure, and run upward to the brain lobes, entering each fibrous core as a large bundle of fibers several sections posterior to the termination of the central part of the commissure, fig. 1. The cesophageal nerves reappear, and continue backward to the mouth, which begins fifteen sections farther back. ‘This commissure evidently corresponds with the large, third and last, commissure between the cesophageal nerves described by Husprecut, BURGER and Montcomery. 4. NEUROCORD CELLS. a. Historical review.—BURGER (1894) was the first to distinguish the fourth type of ganglion cells, the giant cells which he terms neurocord cells. He states (1899, p. 105), ‘‘Neurochordzellen fand ich bei allen von mir untersuchten Cerebratulen, ferner bei Langia formosa. Das Gehirn besitzt stets nur ein einziges Paar von Neurochordzellen, welches an der medialen Flache der ven- tralen Ganglien dort gelagert ist, wo die Schlundnerven ent- springen. Zahlreiche Neurochordzellen be finden sich indessen im Ganglienzellbelag der Seitenstamme * * * ” ‘The statements of BURGER (1895) in regard to the presence of neurocord cells in the Heteronemerteans may be summarized as follows. In several genera a single pair of neurocord cells is found on the medial sides of the ventral brain lobes in the region of the origin of the cesopha- Tuompson, Brains of Cerebratulus. 651 geal nerves, and numbers of neurocord cells are irregularly dis- tributed along the lateral cords. In the Metanemerteans, Dre pa- nophorus and Prosadenophorus, BURGER found that a single pair of neurocord cells occurs in the brain, but that these cells are entirely absent from the lateral cords. BURGER (1895) p. 320 states “Bei C. marginatus sieht man auf einem Querschnitt, welcher die ventralen Ganglien an der Abgang- stelle der Schlundnerven getroffen hat, zwei Ganglienzellen von ungewohnlicher Grosse einander gegentiber liegen, welche um so mehr auftallen, als in diesem Abschnitt des Gesammthirnes nur die kleineren Formenherrschen * * * ” He gives the measure- ments of neurocord cells in two different genera. In Cerebratulus marginatus the diameter across is 20y, the length 404, in Langia formosa the diameter across is 124, the length 4op. Montcomery (1897) finds in Cerebratulus lacteus three pairs of neurocord cells in the ventral brain lobes, and, like BURGER, a large number at unequal intervals along the lateral cords. Montcome_ry states that the first pair of cells lies in the same sec- tion with the beginning of the cesophageal nerves. The third pair lies six sections behind the first, and the cells that compose the second pair, which are not in the same frontal plane, lie between the first and the third pairs. On pp. 402 to 403 the structure of these cells is described. “The structure of the giant ganglion cells IV of Cerebratulus (figs. 27 to 29, 32) has much resemblance to that of cells III of the same species, though there are certain differences which may usually serve to distinguish them. “The nucleus (fig. 31, a-e) may be nearly spherical but is more frequently spherico-oval. It usually has a proximal position within the cell, close to the cell membrane, is seldom central and never distal in position. In it small masses or granules of chro- matin (chr.) of adequal size are arranged peripherally on the inner surface of the well-marked nuclear membrane; and these do not form a continuous layer, as is frequently the case in the nucleus of III, but are placed at more or less regular distances apart. * * * A thin mass of chromatin envelops the nucleus (7). ‘The latter is never absent, is of large size, and almost always peripherally situated; it has thus the same position in the nucleus as the latter hase mathe cela at Ss ‘heicelly(fes42,7 1020) 31) sis unusually of a shortened pyriform shape, occasionally nearly spherical, or again elongated (this is the case with the first pair 652 ‘fournal of Comparative Neurology and Psychology. im the Drain), 014 er As a rule, though not always, these cells are much larger than III. “The cytoplasm is, especially distally, coarsely vacuolar, more so than in any other ganglion cell; this gives the cell much the same appearance as a slime-producing gland cell.” Cor (1895) does not find cells of the fourth type in Cerebratulus lacteus. The writer (Tompson 1901) has found in the brain of Zygeu- polia litoralis one pair of neurocord cells, and a pair also in the brain of Micrura ceca. b. The neurocord cells of Cerebratulus lacteus——The present investigation differs in one particular from those of the workers quoted above, namely: in the number of the neurocord cells of the brain. Here for the first time are described six pairs of cells and one unpaired cell that in position, in size, and in structure are undoubtedly neurocord cells. Structure.—For all thirteen cells the general form of the cell body is broad and pear shaped, and the cytoplasm in most cells stains but slightly and contains large vacuoles, although in a few instances the cytoplasm is dark and densely granular. ‘The nucleus is either spherical or slightly flattened, and is always found at the broad end of the cell. Both chromatin and nucleolus are situated at the margin of the nucleus, the latter closely pressed against the nuclear membrane. The following table gives the size and position of each neurocord cell. TABLE OF NEUROCORD CELLS. | No. oF SECTIONS BEHIND | VA | - WiptH. | No. oF SECTIONS THICK. | severe eee Left cell. | Right cell. | Left cell. | Right cell. Left cell. Right cell. ; | | Sty Palle tesi- eis) e = 27 | 30/4 A55 | 4+ 2d pair........ 25 | 21 | I I 5 | 5 Rdipaitie eee er 23/4 | 21pl | 2 2 4 | 3 Athepainedaee oe 234 264 | ta | War 3 3 oddicell teea-c is 25 lL | 2 4 Cte palin sien: 2644 25u 2 2+ | 3 ae Gthupains nee UL |e thy | I | I | 10 10 Size and position. First pair.—The first pair of neurocord cells is found in the region in which the cesophageal nerves originate Tuompson, Brains of Cerebratulus. 653 from the fibrous core of the ventral brain lobes, fig. 1, 7,, and it therefore agrees in position with the single pair of BURGER, and the first pair of Montcomery. The cells of the first pair, fig. 2, In, rny, are not symmetrically placed, nor are they exactly equal in size. The right hand cell begins two sections anterior to the left, and extends through four sections, with traces in a fifth; the left cell is present in three sections, with traces in afourth. ‘The width of the right cell is 30” and that of the left 274. The right cell is very conspicuous on account of its great size and its unusual "position, on the ventral surface of the right ventral brain lobe, slightly laterad of the median line of the lobe, and just onthe border of the cellular sheath. That the width of this cell seems, in fig. 2, greater than the length may be accounted for by the plane of the section, which has evidently cut the cell at an angle of about 40° to its long axis. The tubule runs obliquely but directly upward into the fibrous core of the brain lobe. The left cell is situated on the medio-ventral surface of the left ventral brain lobe, within the cellular sheath, and its tubule may be traced directly into the fibrous core. Second pair.—The cells of the second pair, fig. 1, lie in the same section, five sections behind the ending of the first pair, and are only one section thick. In width the left cell measures 25, the right cell 214. The position of the cells is on the medio-ventral surface of the cesophageal nerves, near the periphery of the cellular sheath of the ventral lobes, and between the second and third ventral commissures. , Third pair.—Vhe neurocord cells of the third pair are not in the same frontal plane, fig. 1, fig. 3, /n,. The right cell begins three sections, the left cell four sections behind the second pair. Each cell is two sections thick. ‘Their position is near the third ventral commissure on the median side of the cesophageal nerves, the right cell slightly more dorsal than the left and nearer the dorsal blood vessel. In fig. 3 only the left cell is shown, as the right cell ended in the preceding section. ‘The third pair is one of the smaller pairs of neurocord cells, the right cell measuring in width only 21», the left cell 234; but, in spite of the size, the structure is particularly clear, so that there is no doubt that these cells are of the fourth type. Fourth pair and the unpaired right hand cell.—Vhe cells of the fourth pair, fig. 1, fig. 4, rm, are found in the same section, three 654 “fournal of Comparative Neurology and Psychology. sections behind the ending of the third pair. The cells are one section thick, with merely traces in the next, and measure in width, the right cell 26y, the left 234. The fourth pair lies between the third and fourth ventral commissures, but the position in the section of the two cells is not quite the same: the left cell is on the periphery of the left brain lobe medio-ventral to the left cesopha- geal nerve, the right cell is medio-dorsal to the right cesophageal nerve and just beneath the dorsal blood vessel. A second large cell, 25 wide, fig. 4, wc, presumably of the fourth type, lies along- side of the right hand cell of this pair, and extends through two sections with traces in a third. ‘The tubule of this second cell, together with that of the nght hand cell of the pair, may be traced downward through the right cesophageal nerve into the right brain lobe. ‘The line D V, fig. 4 indicates the dorso-ventral axis of the cesophageal nerve. Fifth pair.—The cells of the fifth pair, fig. 1, are not quite in the same frontal plane, the left cell beginning three sections, the right cell four sections behind the fourth pair. This is the second largest pair of neurocord cells; the left cell is two sections thick, and has a width of 26, the right cell is two sections thick, with a trace in a third section, and is 25 wide. ‘This pair is found just anterior to the fourth ventral commissure, and the position in the section of the two cells is similar, both lying on the medial side of the ventral brain lobes, and medio-ventral to the cesophageal nerves. Sixth pair.—The cells of the sixth and last pair are in the same section, ten sections behind the ending of the fifth pair. This 1s the smallest pair, as each cell is present in but one section and has a width of only 214. They are situated posterior to the sixth ventral commissure, fig. 1, but their position in the section 1s asymmetrical, the right cell being onthe lateral surface of the right cesophageal nerve, between the nerve and the right brain lobe, the left cell on the medial surface of the left cesophageal nerve. ‘The structure of both cells conforms to that of the ganglion cells of the fourth type. CONCLUSIONS AND SUMMARY. The present investigation has shown that the ladder-like brain of Cerebratulus lacteus is, in the number of its commissures and neurocord cells, a more complex structure than was heretofore supposed. Tuompson, Brains of Cerebratulus. 655 If we examine the brain of the Metanemertean, Dre panophorus lankesteri, figured by Huprecut (1887, plate ix, fig. 10) we find, posterior to the dorsal and the thick first ventral commissure, a series of thin ventral commissures between the lateral nerves. The commissures occur at fairly regular intervals, and the adja- cent ones are occasionally connected by irregular fiber bundles. In the Turbellaria, in the brain of Planocera grafhi, figured by Lanc (1884, taf. 31, figs. 3 to 4) posterior to the brain are two stout, and many delicate irregular commissures between the lateral nerves, making an intricate network of fibers, but with a generally ladder-like appearance. Again, in the brain of Cestoplana (taf. 31, fig. 2) there is a continuous crossing and interlacing of fibers between the lateral nerves, as far back as the beginning of the proboscis. ‘The nervous system of Gunda segmentata (Lane 1881, tats Xil; fig. 1) is well known on account of the metameric series of commissures between the cesophageal nerves throughout the length of the body. The comparison of the brains mentioned above with that of Cerebratulus lacteus as described in this paper leads to the con- clusion that the brain of Cerebratulus, though complex, is probably of a less specialized and more primitive type than has been sup- posed. The greater number of neurocord cells tesihne ask & greater part of the brain is probably also a primitive character. It is known that they are irregularly placed along the lateral cords, and, the more primitive the brain, the closer is the resemblance in structure of the lateral cords and brain lobes proper. The presence of the unpaired neurocord cell adjacent to the fourth pair leads me to believe that the number of neurocord cells in the brain is not fixed but variable, and may differ in every individual. ‘The fact that Monrcomery found only three pairs of neurocord cells in this same species is additional evidence. It is probably also true that the number of the ventral com- missures varies somewhat with the individual. ‘The stouter com- missures, especially those originating in the fibrous core of the brain, would vary least, but the delicate ones, and those derived from the cellular sheath, would be most capable of variation. 1. Thirteen ventral commissures, posterior to the broad, first ventral commissure, are found in the brain of a large well extended individual of Cerebratulus lacteus. 656 “fournal of Comparative Neurology and Psychology. 2. Of these, six are brain commissures, running from ventral lobe to ventral lobe; two are wsophageal commissures, running between the cesophageal nerves; five are brain-wsophageal com- missures, running from ventral lobe to ventral lobe and through the cesophageal nerves. 3. Of the brain commissures, some originate in the fibrous core, some in the cellular sheath of the brain. 4. Six pairs of neurocord cells and one unpaired neurocord cell are found in the ventral lobes of the brain. 5. The brain, though complex in the number of commissures and neurocord cells, is probably of a primitive type, related to that of the Turbellaria. 6. There is probably individual variation in the number of both commissures and neurocord cells. Wellesley College, Wellesley, Mass. - BIBLIOGRAPHY. Biircer, O. 1894. Studien zu einer Revision der Entwicklungsgeschichte der Nemertinen. Ber. d. Nat. Ges. Freiburg, Bd. 8. 1895. Die Nemertinen des Golfes von Neapel. Fauna u. Flora des Golfes von Neapel, xxii. Monographie. 1897-99. Nemertini. Bronn’s Klassen u. Ordnungen, Bd. 4, Suppl. Cor, W. R. . 1895. On the anatomy of a species of Nemertean (Cerebratulus lacteus Verrill) with remarks on certain other species. Trans. Connect. Acad., vol. 9. Husprecnt, A. A. W. 1887. Report on the Nemertea collected by H. M. S. Challenger during the years 1873-1876. Challenger Report, vol. 19. Lane, A. 1881. Der Bau von Gunda segmentata u. d. Verwandtschaft der Platyhelminthen mit Ccelen- teraten u. Hirudineen, Mitth. aus d. Zool. Station zu Neapel, Bd. iii, Heft 1-2. 1884. Polycladen. Fauna u. Flora des Golfes von Neapel, xi. Monographie. Monrtcomery, T. H. 1897. Studies on the elements of the central nervous system of the Heteronemertini, Fourn. Mor ph., vol. 13. Tuompson, C. B. 1901. Zygeupolia litoralis, a new Heteronemertean. Prec. Acad. Nat. Sci., Philadelphia. Tuompson, Brains of Cerebratulus. 657 Fig. 1 All figures refer to Cerebratulus lacteus, and are drawn at the level of the stage with the Zeiss camera lucida, and with Zeiss lenses, the combinations of which are given with each figure. The plates have been reduced to about two-thirds of the original size. Fic. 1. A reconstruction of the brain from a series of transverse sections. Obj. AA, oc. 2, tube length 160mm. mdn, median dorsal nerve; prn, proboscis nerve; DL, dorsal lobe; VL, ventral lobe;n1, neurocord cell of the first pair; EN, esophageal nerve; DC, dorsal commissure; V1, first ventral com- Missure; 2-14, 2d to 14th ventral commissures; cs, cellular sheath. 658 fournal of Comparative Neurology and Psychology. Fic. 2. A transverse section through the ventral lobes in the region of the origin of the esophageal nerves, and showing the first pair of neurocord cells. Obj. AA, oc. 4, tube length 170 mm. rm, right neurocord cell of the first pair; /m, left neurocord cell of the first pair; en, esophageal nerve; fc, fibrous core; cs, cellular sheath. Fic. 3. A transverse section through the ventral lobes and the third ventral commissure, showing also the left neurocord cell of the third pair. Obj. AA, oc. 4, tube length 170 mm. Z/ng left neurocord cell of the third pair; 3, third ventral commissure, with two roots on the right side. Fic. 4. Part of a transverse section, showing the right neurocord cell of the fourth pair, and the unpaired neurocord cell. Obj. homog. immers. ’5, oc. 2, tube length 160 mm. rn,, right neurocord cell of the fourth pair; uc, unpaired neurocord cell; ren, outline of right esophageal nerve; fc, fibrous core of the right brain lobe; DV, dorso-ventral axis of the right cesophageal nerve. Fics. 5 and 6. Parts of two consecutive sections through the ventral lobes, showing the fifth ven- tral commissure. Obj. AA, oc. 4, tube length 160 mm. 5, fifth ventral commissure: 5c, central part of fifth ventral commissure. 659 Tuompson, Brains of Cerebratulus. 660 ‘fournal of Comparative Neurology and Psychology. Fic. 7. Part of a transverse section through the ventral lobes, showing the eleventh ventral com- missure. Obj. AA, oc. 4, tube length 160 mm. cs, cellular sheath; fc, fibrous core; Jen, left cesophageal nerve; ren, right cesophageal nerve; 7, eleventh ventral commissure. Fic. 8. Part of a transverse section, two sections posterior to that shown in Fig. 7, showing some of the central portion and the right root of the eleventh commissure. Obj. AA, oc. 4, tube length 160 mm, Fic. 9. Part of a transverse section, two sections posterior to that shown in Fig. 8. Obj. AA, oc. 4, tube length 160 mm. 12, twelfth ventral commissure; 17, root of the eleventh ventral commissure. Fic. 10. Part of a transverse section, one section posterior to that shown in Fig. 9, showing parts of three commissures. Obj. AA, oc. 4, tube length160 mm. 17, eleventh ventral commissure}; 12, twelfth ventral commissure; 73, thirteenth ventral commissure. Fic. 11. Part of a transverse section, one section posterior to that shown in Fig. 10. Obj. AA, oc. 4, tube length 160 mm. Fic. 12. Part of a transverse section, one section posterior to that shown in Fig. 11, showing the broadest part of the thirteenth commissure, the left root of the twelfth, and the beginning of the four- teenth commissure. Obj. AA, oc. 4, tube length 160 mm. ; Fic. 13. Part of a transverse section, one section posterior to that shown in Fig. 12, showing the thin posterior part of the thirteenth commissure. Obj. AA, oc. 4, tube length 160mm. 13, thirteenth ventral commissure, 14, fourteenth ventral commissure, rc, root of the thirteenth commissure. Tuompson, Brains of Cerebratulus. 661 EDITORIAL. TWO RECENT TENDENCIES IN CEREBRAL MORPHOLOGY. Many diverse lines of current biological research are putting emphasis on the functional unity of the living animal body. Nor- mal growth, regulation, codrdination of reactions and the mani- fold phases of adptation all point the same way. ‘The degree of perfection of the integrative function of the nervous system in higher vertebrates is determined not only by the complexity of the central internuncial or associational conduction paths, but quite as much by the extent and character of the differentiation of the receptors and effectors, 1.e., the nature of the correspondence (in the Spencerian sense) between the organism and the environment. The central nervous system cannot therefore be studied com- paratively to the best advantage by itself, but only in relation with the peripheral nervous system and indeed with the body as a whole. Recent students of the phylogeny of the vertebrate nervous system, recognizing this principle, have adapted thems elves to it in two very different ways. [he anatomists of one group have made an especial study of the mechanical factors in cerebral archi- tecture, such as the effects on the brain of ontogenetic or phylo- genetic changes in the form of the cranium, position of peripheral organs, vascular supply, arrangements of the non-nervous parts of the brain, etc. The anatomists of the other school have placed more stress upon the conduction paths and have devoted them- selves.to the exposition of the architectural effects of variations in the physiological importance of the several functional systems of neurones of which the nervous system is composed. Differences in the functional patterns or action systems of animals involve parallel differences in the architecture of the nervous system and the solution of many problems is sought in a comparative study of functional systems of neurones, correlating the variations in anatomical structure with differences in physiological value or behavior. 664 “fournal of Comparative Neurology and Psychology. The first group of anatomists works from the standpoint of developmental mechanics, the nervous masses being considered as shaped more or less passively by surrounding growth forces or by internal pressures and strains due to irregularities in the growth of the masses themselves. ‘The second group lays the emphasis rather upon the functional nervous tissue itself as the determining factor in cerebral morphology. An excellent illustration of the methods of the mechanical school is furnished by some of the embryological papers of the late Pro- fessor His, particularly his figures showing very clever mechanical models of the invagination of the neural. plate, formation of the neural tube, etc. As applied to comparative neurology this standpoint received its clearest exposition and most graphic illustration at the hands of Professor RupoLtr BuRCKHARDT, whose untimely death last winter interrupted in the midst dn exceedingly valuable series of researches. In a personal letter written last January a very few weeks before his death he outlined the motives of his work in these words: “The principal point—besides the fact that never such large materials have been examined before—is for me that all our views of the central nervous system are still dominated by practical, psychological, physiological, traditions, and that the simple stand- point of vertebrate phylogeny has never been thoroughly kept, as by observing such objects as growing epithelia which are changed by influences of head-formation, and the central need of sensory organs (the latter has been urged most by JoHNsToN). Second, that brain phylogeny must be studied according to phylogeny as it issues from palzontological researches. You will perhaps miss that I do not enter into description of fiber courses, but only into their quantity as a mechanical factor; that I treat the nerve cells as such as of secondary value for the knowledge of brain genesis and the type of the brain, and that on the other side I attribute such a high value to neuroglia. But you will also see that I wanted to regard the brain as a part of the head, and the real head, not the hypothetical of primary metamerism, which for the brain has not much more value than for the skin. ‘There is, in my opinion, a great field for work, particularly for zodlogists, 1 His, Wm. Ueber mechanische Grundvorginge thierischer Formenbildung. Arch. f. Anat. [u. Physiol.]. 1894. Editorial. 665 in applying knowledge from our side to those of the physiologist and pathologist.” These points will be found elaborated and fully illustrated in the extensive series of papers which has come from Professor BuRCKHARDT’S pen, particularly in the introduction to the last of his papers, on the central nervous system of the selachians asa basis for a phylogeny of the vertebrate brain? the first part of which appeared last year. In the letter from which the above extract was taken he wrote that he was at that time engaged upon the final revision of the second and third parts of this paper, and it is to be hoped that the work was sufficiently far advanced at the time of his death as to permit the speedy publication of these two parts. The most valuable of the concrete résults of BURCKHARDT’S work so far as published is the demonstration of the conservative character of the non-nervous parts of the brain and the consequent worth of the membranous and ependymal tissues in the study of phylogenetic relationships. ‘This is brought out most graphically in the paper published 1 in 1895, entitled Der Bauplan des Wirbel- tiergehirns* which is accompanied by a large plate showing dia- grammatic sagittal sections of all important types of vertebrate brains with the corresponding regions colored the same way throughout the series. The resemblance of these median and largely membranous parts in the series from Petromyzon to man is very striking. An important series of neurological researches which in some ways resemble those of BURCKHARDT has been published by Dr. G. SteRz1I of Padua. The most recent of about a dozen papers relating to the meninges and vascular supply of the central nervous system is the first volume of a comprehensive treatise on the cen- tral nervous system of vertebrates.‘ It is announced that the work will be completed in six volumes, of which this first one is devoted to the cyclostomes, and the others are to be upon the fishes, am- phibians, reptiles, birds and mammals, respectively. The present volume is divided into two books devoted to the petromyzonts ? Das Zentral-Nervensystem der Selachier als Grundlage fiir eine Phylogenie des Vertebratenhirns. I. Teil. Einleitung und Scymnus lichia. With 5 plates and 64 text-figures. Nova Acta, Abh. kais. Leop.-Carol. Akad. d. Naturforscher, Halle, Bd. 73, no. 2, pp. 238-449, 1907. 3 Morph. Arbeiten (Schwalbe), Bd. 4, no. 2. 1895. 4Srerz1, G. II sistema nervoso centrale dei Vertebrati. Ricerche anatomiche ed embriologiche. Vol.1. Ciclostomi. 732 pp. and 194 figs. Padua, A. Draghi, Editore. 1907. Price, Lire 35. 666 ‘fournal of Comparative Neurology and Psychology. and the myxinoids respectively. “The chief topics of considera- tion in each book are, the morphology of the vertebral canal and cranium, the meninges and the blood vessels and lymphatics, the sheaths of the nerves, and the central nervous system, par- ticularly its hypophysis and membranous parts. In short, the non-nervous parts of the brain receive especial attention, with particular reference to the factors of nutrition, metabolism and mechanical support. All of these subjects are treated from the embryological point of view and the developmental stages are fully figured. The form relations of the brain are studied em- bryologically and their comparative morphology considered, but the volume contains no other descriptions of internal architec- ture. Neither the fiber tracts nor the cellular masses are con- sidered. These researches and many others along the same lines have drawn attention to some very important types of relation between the nervous and the other organs of the body, chiefly mechanical and nutritive. But after all, the principal avenues of relation of the nervous system are the nerves themselves. The sense organs and the organs of response are the immediate instruments of almost all animal activities and the central nervous system reflects every change in peripheral relations. ‘This reflection, however, is not a transient and passive return of the nervous impulse from the receptive to the effective periphery as a light beam rebounds from a mirror; it involves an active process of coordination during the process, and—what is far more important from our present stand- point—a permanent structural change in the coordinating mech- anism itself. The cerebral architecture of every animal species has unques- tionably been shaped by its peripheral nervous organs. As animals gradually change their mode of life and different sets of environmental forces impinge on the sensorium, the receptive and effective peripheral organs gradually undergo parallel changes adapted to render the animal more fit to meet the changed environ- mental conditions. And the central correlation apparatus of these peripheral organs must change its form at the same time or the whole process of the selection of adaptive variations would be abortive. The structure of the central nervous system is in fact very sensitive to changes in environment or mode of life. The eyes of cave animals atrophy; so also do the visual centers of the Editorial. 667 brain. The acuity of every sense in the action systems of differ- ent animals can be measured by the comparative anatomist in terms of the size and structural complexity of the corresponding primary cerebral sensory centers. The habitual type of motor response is no less accurately registered in the permanent organ- ization of the motor cerebral centers. Furthermore, an action system of the rigidly stereotyped sort will be served by a nervous system with the primary reflex centers highly elaborated per- haps, but with the association centers small, while the more plastic types of action system as found in the more intelligent animals are characterized by highly complex association centers and tracts. Studies in cerebral architecture carried on from the point of view of the analysis of functional systems of neurones, each of which is both a physiological and an anatomical unit, are as far removed as possible from the older descriptive neurology which seemed to aim at mere enumerations of tracts and cell masses with little effective correlation. The best recent work on cere- bral architecture aims more or less directly at the analysis of con- duction paths and their correlation into~ definite functional sys- tems. A great impetus was given to such studies in the comparative field by the analysis of the peripheral nerves into their components and the rearrangement of these components into functional sys- tems, thus facilitating the integration of the more diffuse sensory systems, like the tactile and gustatory, and permitting the study of their central reflex pathways with almost as great precision as the concentrated systems, like the optic. The analysis of the cutaneous nerves of man into their components by the researches of Henry Heap and others by a combination of physiological, path- ological and anatomical methods promises still more important advances in this direction. The four-root theory of GasKELL and His has been the point of departure, not only for the study of the components of the periph- eral nerves, but also for the study of the functional zones of the central nervous system. The progress which has been made in the functional analysis of the brain and the illuminating value of a knowledge of peripheral nerve components in this study (par- ticularly in the medulla oblongata) are illustrated in a striking way by a comparison of the second volume of the sixth edition of 668 “‘fournal of Comparative Neurology and Psychology. EDINGER’S lectures on the Central Nervous System, published in 1904, and the seventh edition, published in 1908.5 Dr. EpinceEr has, either personally or with the help of other members of his staff, worked over a large part of the field covered by the voluminous literature of comparative neurology of the past decade. He has therefore been able to make this edition of his text-book, like its predecessors, very largely a record of his own observations. ‘This is at the same time a source of great strength and of considerable weakness in his work—of strength because all of the old facts presented come with the added weight of EpINGER’sS confirmation; of weakness because many equally important facts or theoretical conclusions which do not chance to fall within the scope of the author’s personal observation are alto- gether omitted. The older literature on the comparative anatomy of the medulla oblongata is a confusing mass of contradictory detail, dominated largely by misleading metameric schemata. The recognition of functional units within the oblongata, each of which stands in relation with a definite component of the peripheral nerves and each of which is integrated in a characteristic manner and has Its own special type of secondary reflex pathways—this has made possible a far more simple and comprehensive exposition of the structure of this part of the brain than we have had before. While much remains to be explained in the comparative anatomy of the medulla oblongata, the underlying morphological pattern has been exposed and is found to be surprisingly constant in all vertebrates. This constancy of type grows out of the fact that this part of the brain uniformly serves the simpler vital functions, such as feeding, respiration, etc., whose peripheral mechanisms are broadly similar in vertebrates. Such variations in feeding habits as do occur are, however, accompanied by changes in the details of cerebral structure; as, for example, the development of the enormous vagal lobes of the carp correlated with the peculiar palatal organ of this fish, and the modifications in the sensory termini of the facialis nerve correlated with the peripheral distribution of cutaneous taste buds in Ameiurus and Gadus respectively. Another illus- tration is furnished by the development of large eyes and optic 5 Epincer, L. Vorlesungen iiber den Bau der Nervésen Zentralorgane des Menschen und der Tiere. Bd. 2. Verlgeichende Anatomie des Gehirns. Seventh Edition. Lespzig, F. C. W. Vogel. 1908. Editortal. 669 lobes in predacious species which capture moving prey by the sense of sight. The change from aquatic to aérial respiration in the Amphibia involves changes in the medulla oblongata parallel with the atrophy or change of function of the branchial muscles which are as yet imperfectly understood and which can be learned only by a closely correlated examination of the central and periph- eral organs of a selected series of forms. Now returning to Dr. EpINGER’s manual, the changes wrought in this edition are quite revolutionary. ‘The first chapter opens with an analysis of the peripheral nerves based on the work of the recent students of nerve components. In later chapters the me- dulla oblongata is subdivided in accordance with the same criteria along lines which follow in a general way those laid down by the American school of comparative neurologists, though with an entirely new series of illustrative figures and with many differences of interpretation. Most of these differences take the direction of conservatism toward the newer morphological ideas and the result is many cases of confusion, sometimes amounting to actual contradiction, growing out of the imperfect assimilation of the old data and the new morphology. But in the broad view there has been during the past decade a rapid rapprochement between the German and American comparative neurologists, particularly in the interpretation of the peripheral nerves and the brain stem, which is very gratifying to those who have painful recollections of the recent (and still all too prevalent) chaos in the morphological interpretaiton of the medulla oblongata and its nerves. In the midbrain and thalamus there is as yet no such gratifying harmony of interpretation as in the medulla oblongata. In fact, the best course at present open to us in considering the morphology of these regions is a serious application to anatomical study to the end that we may acquire a more precise and comprehensive knowl- edge of the facts before we attempt to complete our morphological interpretation. In the chapters of Dr. Ep1NGER’s work devoted to the forebrain we find the most original and the most important of his own con- tributions to the comparative morphology of the brain. ‘The inter- pretation of the primordial pallium as a center of correlation for all of the sénse organs of the snout (smell, tactile and somesthetic sensations of the lips, tongue, etc.) is an exceedingly fruitful sug- gestion which promises spd point of departure for the ulti- 670 =“fournal of Comparative Neurology and Psychology. mate interpretation of the evolution of the cerebral cortex. This point and many other illustrations of the importance of studying the brain in close functional relation with its peripheral end organs are elaborated in Dr. EDINGER’s address printed in the last issue of this ‘fournal.® C Jen 6 The relations of comparative anatomy to comparative psychology. This Fournal, vol. 18, no. 5. 1908. re if ic - > * * ‘+ * a ee ee) ‘eee > v ae ee * rn = oh ee --- vo. > es > + oe ee ones + Rast st £5'8, pt ots S,'4 t selgit =) . eee oe Se ane atm —* 5% + * a } * 1a ae T9493) ts aS, aie tate x