224 



COMPARATIVE ANATOMY 



poorly developed. 1 The distal enlarged end of the pineal body 

 extends as far as the dura mater, and the structure of the internal 



B 



H PO vim 



FIG. 171. BRAIN OF DOG (POINTER). A, dorsal; B, ventral; and C, 



lateral view. 



Bo, Bo 1 , arcuate fissures ; B.ol, olfactory bulb ; Cr.ee, crura cerebri ; Fi.p, pallial 

 fissure ; FS, Sylvian fissure ; HH, lateral lobe, and HH 1 , flocculus of cere- 

 bellum ; Hyp, hypophysis ; LH, hippocampal lobe ; Med, spinal cord ; XH, 

 medulla oblongata ; Po, pons Varolii ; fiF, rhinal fissure; 8c, sulcus cruci- 

 atus ; TO, olfactory tract ; VH, cerebral hemisplieres ; Wu, superior vermis ; 

 I-XII, cerebral nerves. 



part of the organ resembles that of a tubular gland, penetrated by 

 fibrous tissue and blood-vessels. There is no trace of a parietal 

 organ. 



1 The toothed Birds of the Cretaceous period, with Hesperornis at their 

 head, possessed a very lowly organised, reptilian form of brain, with small 

 hemispheres and large olfactory lobes. 



