SCIENCE. 



25 



SATURDAY, JULY 17. 1880. 



A REMARKABLE PECULIARITY OF AN AN- 

 THROPOID BRAIN. 



BY E. C. SPITZKA, M. D. 



Among the features of the cerebral surface, on 

 whose presence or absence the differential characters 

 of the human brain as compared with that of the an- 

 thropoid apes, have been established by anatomists, 

 the so-called transition convolutions occupy a promi- 

 nent place. As is well known, the occipital and pa- 

 rietal lobes 'of the human brain are connected with 

 each other by means of short gyri, which bridge over 

 those fissures, which if uninterrupted would separate 

 these lobes like a chasm. First described by Gratio- 

 let as plis de passage, and known among English 

 writers as annectant or transition gyri ; it is the one 

 among them which borders on the great longitudinal 

 fissure that has been most closely studied. 



With exceptions to be noted, writers on the human 

 and anthropoid brain agree in stating that the brain 

 of the Chimpanzee differs from the human brain, in 

 failing to exhibit this, the so-called first transition con- 

 volution, inasmuch as it is always concealed by the 

 junction of the internal with the external perpendicu- 

 lar occipital fissures. 



The same authorities also observe that while there 

 is this sharp demarcation between the brain of the 

 Chimpanzee and that of man, that another anthropoid 

 resembles the human being in this very respect, namely 

 the Orang, in which animal this fissure is present and 

 superficial. 



The decease of a large number of anthropoid apes 

 which have been on exhibition at various times during 

 the past few years at the New York Aquarium, and 

 whose bodies were kindly placed at my disposal by 

 the managers of that institution, has enabled me to 

 extend the observations made on the brains of the 

 Chimpanzee and Orang by previous writers. 



The first Chimpanzee's brain obtained by myself, 

 differed in no noteworthy respect from those described 

 by Marshall, Gratiolet, Pansch and others, and was 

 utilized for microscopical study.* The second, that 

 of a very large animal, one which had reached the age 

 of puberty, and weighing 389.86 grammes, presented 

 the interesting anomaly I am about to describe, and 

 whose demonstrable existence adds another proof to 

 the many which have been accumulating, that there is 

 no absolute and impassable line of demarcation be- 

 tween the human and simian brain. In the first place, 

 as shown in the subjoined outline diagram, the occipi- 

 tal lobes of this brain are unsymmetrical. 



On the right side the internal perpendicular occipital 

 fissure does not coalesce with the external, while on 

 the left side it does. The result is that on the right side, 

 we have an excellently developed first transition gyrus 

 [G, G] evident and superficial, as in the human being, 

 while on the left side it is concealed as in the ordinary 

 Chimpanzee type. That is, the right side of the brain 



*The peduncular tracts of the anthropoid apes. Journal of Ner- 

 vous and Mental Diseases. July, 1879. 



Outline diagram of o;cipita! end of cerebrum, dorsal view, x%. 



shows a higher grade of development than the left. 

 In so far as the left side is usually the better developed 

 one this asymmetry is anomalous. Yet it shows that 

 the old line of demarcation is not a correct one. 

 Though the transition gyrus is concealed on the left 

 side, yet a portion of it is visible, showing that on the 

 whole this brain exhibits a tendency to a more human- 

 like relation. 



If we now proceed to compare the transition gyri 

 of an Orang's brain with those of this Chimpanzee's 

 right hemisphere, and of Man, we are struck by the 

 observation that its disposition and proportions are 

 more human-like in the Chimpanzee than in the 

 Orang. And this applies to the Orang in my posses- 

 sion as well as to those figured by Tiedemann, Gra- 

 tiolet and Bischoff. Taking the occipital lobe of the 

 Orang as a whole, its physiognomy, if I may so term 

 it, is lower and less human like, than that of the Chim- 

 panzee. 



The fact that the arrangement of the gyri and fis- 

 sures bordering on the occipital fissures is thus shown 

 to be inconstant, and that as Vogt has humorously 

 shown, some of the South American monkeys resem- 

 ble the human being more strongly in this respect 

 than the average Chimpanzee and Gorilla (Pansch), 

 should make us careful in basing fundamental charac- 

 terization on such slight morphological factors. 



I should state that Marshall and Bischoff while fail- 

 ing to ever find the gyrus under consideration appear- 

 ing at the surface, yet have identified it as concealed 

 in the depths of the perpendicular fissure. 



In the occipital lobe of an imbecile recently 

 executed for murder at St. Louis, and whose' brain 

 was referred to me for examination, I have found the 

 external occipital fissure perfect as in the embryo, 

 though intersected by collateral fisssures, and exhibit- 

 ing a bevel, repeating to some extent its disposition 

 in the anthropoid apes. 



THE Albert Medal of the Society of Arts for 1879, 

 was presented to Sir W. Thomson for his electrical re- 

 searches, especially those relating to the transmission of 

 telegraphic messages over ocean cables, last week, at a 

 meeting of the council, held at Marlborough House. At 

 the same time the Albert Medal for the current year was 

 presented to James Prescott Joule, F. R. S., for the re- 

 searches by which he established the true relation be- 

 tween heat, electricity, and mechanical work. The con- 

 versazione of the Society was also held last week, when 

 Mr. Donald Currie, M.P., was presented with the Fother- 

 gill Gold Medal, the award of which we recently an- 

 nounced. 



