HUXLEY ON THE EELATIONS OF MAN TO THE LOWER ANIMALS. 75 



tailless catarrhine apes of the old world, the cerebral hemispheres project 

 for back beyond the cerebellum, though the latter is very well developed 

 —in fact, as the cerebral hemispheres project nearly a centimetre behind 

 the cerebellum, while the whole brain is only 5J centimetres long, the 

 backward projection of the third lobe is, in this monkey, relatively 

 greater than in man. 



The "Transactions of the Koyal Netherlands Institute at Amster- 

 dam for 1849" contain one of the most valuable memoirs on the cerebral 

 organization of the higher apes that has yet been written, entitled, "An 

 Anatomical Investigation of the Brain of the Chimpanzee," by Schroeder 

 van der Kolk and Yrolik. In their two plates they represent the brains 

 of a chimpanzee, an orang, and a new-born child, and, in all, the letter 

 c is applied to the same part — the posterior or third lobe, which they 

 term " achterhoofds-kwab," " occipital lobe," in the explanation of the 

 plates, or frequently in the text, "achter-kwab," "posterior lobe" ; nor 

 among the heads of their careful enumeration of the differences between 

 the brain of man and the higher apes does any one of the three differ- 

 ential characters whose existence I have denied find a place. 



Finally, in the preface to the most elaborate special memoir that has 

 yet appeared upon the conformation of the brain in the higher Mam- 

 malia — the " Memoire sur les plis Cerebraux de 1' Homme et des Pri- 

 mates," by M. P. Gratiolet, — I find the following passage (p. 2) : — 



''The convoluted brain of man and the smooth brain of the marmoset resemble one 

 another in the fourfold character of a rudimentary olfactory lobe, a posterior lobe, which 

 completely covers the cerebellum, a well-marked fissure of Sylvius, and lastly, a posterior 

 cornu to the lateral ventricle. These characters are met with in combination only in 

 man and in the apes." 



M. Gratiolet' s beautiful original figures of the brain of the chimpan- 

 zee (PL vi), and of the orang (PL vii), show quite clearly that the 

 hinder margin of the cerebral lobes in these animals; when the brain is 

 in its natural condition, overlaps the hinder margin of the cerebel- 

 lum. 



Many months ago, having learned that my friend Dr. Allen Thomson 

 had at one time occupied himself with the dissection of the brain of the 

 chimpanzee, I applied to him for information, and he has very kindly 

 allowed me to print the following extracts from his letters. Of the first 

 brain he examined — that of a young female chimpanzee, seven or eight 

 months old, — this eminently careful anatomist and physiologist says 

 (under date of May 24, I860) : — 



"There is, very clearly, a posterior lobe, separated from the middle one by as deep a 

 groove between the convolutions on the inner side of the hemispheres, as in man, and 

 equally well marked off on the other side. I should be inclined to say, that the posterior 

 lobe is little inferior to that of man, excepting, perhaps, in vertical depth. The cerebral 

 hemispheres completely covered the cerebellum, as seen from above. I took pains to 

 observe this while the brain was still within the cranium, looking down upon it at right 

 angles to the longtitudinal axis of the cranial cavity, and I found the posterior extremity 

 of the cerebral hemispheres projected a little beyond the vertical Hue, passing the back 

 of the cerebellum." 



