392 THE BRAIN OF MAMMALS, BY TH. MEYNERT. 



temporal convolutions. At the same time it extends fas is 

 shown in fig. 233) like a clamp forwards in the frontal ex- 

 tremity and the temporal extremity of the primordial arch 

 surrounding the Sylvian fissure. 



The cul de sac of the Sylvian fissure, and the capsule-like vault 

 enclosing it, constitute the form- determining centre of the convexity 

 of the cerebrum, a region that is identical in all Mammalian brains, 

 defined and connected together by the claustrum into one whole. It 

 was therefore not only incontestably the right of Leuret, as the dis- 

 coverer of the normal type of convolution, to supply a terminology, 

 but it was also correct to make this the starting-point for the enu- 

 meration of the convolutions. The industrious Huschke followed 

 him. His classification of the convolutions did not lead to the 

 illogicality of the classification adopted since the time of Wagner, 

 which breaks up the unity of the convolution defined by the claustrum 

 into the terminological patchwork of a third frontal tract with a first 

 temporal tract ; and, on the other hand, since in the animal series the 

 number of the frontal convolutions varies between two and four, 

 assigns a varying number to the so clearly marked lowermost frontal 

 tract. 



The claustrum in frontal transverse sections of the brain (fig. 

 245, Cl), presents the form of an arched cone with its base below. 

 This lower enlargement forms the most compact mass where 

 the claustrum penetrates over the base of the insula into the 

 temporal lobes. Here, constituting the anterior limit of the 

 descending cornu of the lateral ventricle (fig. 233, inf), and 

 formed from the elements of the claustrum, is a rounded mass, 

 the amygdaloid nucleus (fig. 233, A), which by means of a 

 series of transitional masses, that may be regarded as belonging 

 either to it or to the claustrum, is continuous with the base 

 of the latter. The whole fusiform-cell formation, which is ex- 

 panded over the walls of the Sylvian fissure, and terminates 

 below in the amygdala, appears in the form of an unfolded 

 fan, with its rays parallel to the island, and with (in the first 

 primordial convolution) recurved borders, the handle or 

 peduncle of which terminates in a spheroidal body, the 

 amygdaloid nucleus. 



That this formation does not belong, " as the external corpus 

 striatum" (Arnold), to the central ganglia, follows from its 



