408 



PliOF. G. ELLIOT SMITH OX THE 



claustrum becomes so diffuse that its extent caiiuot be accurately mapped out. But its 

 distributiou shows clearly that, tlie anterior part of the iusula is freely exposed on the 

 surface of the brain, as it is in the Anthropoid Apes. In the genus Lemur the claustrum 

 is an exceedingly plump and well-defined strueture. It extends back-ward as far as 

 the posterior [inferior] limiting- sulcus (which is the pseudosylvian sulcus), and extends 

 forward slightly beyond th^ fronto-orbital (diagonal) sulcus (fig. 00(0, ;it the same time 

 becomius: somewhat diffuse. 



Fig. 60a 



Fig. (!(). — A scliciuc representing the sulci common to most !Miimm;ili:i. 

 Fig. Wa. — Lemur fuhnts. Horizontal section through the bniin. x 1'. 



This may perhaps seem to throw doubt upon the homology of this sulcus in the 

 Lemurs and the Anthropoid Apes. It is impossible to appreciate the true value of such 

 evidence until we know more than wc do at present of the significance of the claustrum *. 



* This subject lias been studied by T. E. Clark (" Comparative Anatomy of the Insula," .Touru. Comp. Neurology, 

 vol. vi. June L'SiJO, pp. 5'.J-1((],;3.5 figures), and more recently by M. HoU (" Ueber die Insel des Carnivorengchirns,"' 

 Arch. f. Anat. n. Physiol. [.Vnat. .\bth.] '.'> u. 4, pp. 217 ct seq.. lS!j9; '• Ueber die Insel des Uugulatengehirns,'" 

 ■ihidoii, ') u. 0, pp. l'!t.j i1 srq., KM II I J. 



