■i2C) PROF. G. ELLIOT S.AIlTIi OX THE 



the cerebellum of many mammals in the current terminoloo-y ; and that even in the case 

 of those Avhich conld be so described, the account would be altogether unnatural and 

 hopelessly cumbrous. The chief reason for this is that the cerebellar fissure (fissura 

 horizontalis magna), ^^liich is regarded in Human Anatomy of such fundamental 

 importance as to be invariably taken as the starting-point in the primary subdivision, is 

 a most insignificant cleft of quite secondary importance in most mammals, and is even 

 absent jiltogether in others. 



It therefore became necessary to seek some more stable line of demarcation between 

 the various cerebellar regions. Accordingly I proposed a tentative scheme of subdivision 

 based uj)on the recognition of the fissure called " preclival " as the primary natural line 

 of separation of the mesial parts of the organ. My reason for adopting this fissure was 

 the fact that it is present in all mammals, without exception, and is, moreover, the 

 deepest fissure crossing the mesial plane. Ample confirmation of the justice and 

 jiaturalness of this selection was afforded by the fact that two other investigators 

 had independently come to the same conclusion — Stroud, as the result of a study of the 

 development of the organ in the Cat and in Man, and Kuithan from embryological 

 studies on the Sheep. 



Fig.ez. 



cgp. 



^'^P- p. Cr. py. Ca. 



I'arsios s/jcclriim. 



Left lateral aspect of the brain-stem and cerebellum, exposed bj- cutting through the thalmo-striate 



junction and removing the cerebral liemisphere. x 4. 



When I examined the cerebellum in Tarsias, JlicroceljHS, Galago, Lemur, JS^/fcdcebus, 

 and CJiii-Oiiii/s, it was not sur25risiag to find that it conformed to the plan wliicii has 

 ])reviously been shown to prevail among such divergent groups of mammals as the 

 Ungulata, Edentata, and Carnivora. Yet I was not j)repared to find within the Primates 

 a form of cerebellum such as that of Tarsixs, which so nearly approaches the most 

 generalized mammalian type met with in the Insectivora, Marsupialia, the Dasypodidse, 

 and some Rodentia. 



In the one Order we find therefore every gradation of cerebellar form, from the 

 simplest and most generalized mammalian type to the most complex, though not 

 the largest, example of cerebellar architecture. The undoubtedly close affinity of the 

 different Primate genera enables us to speak with greater certainty of the appareiit 



