322 NERVOUS SYSTEM. 



and is deeply reddened and higlily vascular within; but I have 

 not remarked that it contains earthy matter, as is the case so 

 frequently with that of the human brain. 



Nates and Testes. — Above the third ventricle, behind the pi- 

 neal gland, and immediately over the iter a tertio ad quartuin 

 ventriculum, are four considerable eminences, the tubercula qua- 

 drigemina — or rather bigemina, since they are divided into the 

 TWO nates and two testes. The 7iates, the foremost and by 

 much the largest of these bodies, separated by a groove from the 

 testes, and by a deep perpendicular fissure from each other, pre- 

 sent semi-oval exteriors, of a mixed composition, cineritious and 

 medullary, and are in intimate union with each other and with 

 the testes. The testes, much smaller than the nates, are also 

 ovoid in figure, but their long diameters are placed contrariwise 

 — transversely. In their composition they are alike also, as well 

 as in their connexions, both being jonied to the crura cerebri, by 

 which they are supported. 



Cerebellum. 



In order to guard against a common misconception of the rela- 

 tive position of this part, I shall repeat here what I took occasion 

 to lay some stress upon in a former place — that the three divisions 

 of the horse's brain are similarly lodged, in regard to their cra^ 

 nial case, to what the correspondent parts in man are; but that 

 when we view them as the animals naturally stand, their relative 

 situation is altogether altered. The cerebellum (as in man) occu- 

 pies that compartment in the basis of the cranium which is 

 formed, above and behind, by the anterior occipital bones ; late- 

 rally, by the petrous portions of the temporal bones ; and supe- 

 riorly and anteriorly, by the tentorium : that septum being defi- 

 cient inferiorly and anteriorly, to give passage to the crura cerebri 

 to form a junction with the cerebellum; while the vacuity admits 

 also of the projection of the anterior vermiform process, which 

 is the only portion of the latter that does not rest upon the ten- 

 torium. 



Peculiarities. — In volume, figure, and aspect, the cerebellum 

 is at once distinguishable from the cerebrum. It is only one- 

 sixth of the volume of the cerebrum. Its figure is irregular — it 

 has two oval ends, placed transversely, united in the middle by a 

 broad and prominent vermiform belt, its lateral dimension ex- 

 ceeding its longitudinal. Its aspect is lobular or convoluted : 

 but, in addition, it is everywhere so striated with deej) transverse 

 fissures, that its appearance is altogether different from any other 

 part of the brain. 



