NEK VO US S YSTEM. 639 



complex sacral region, of ischia sloping backwards, and of 

 pubes running parallel to the ischia. The incomplete 

 ossification of the acetabulum and the absence of ventral 

 symphyses are noteworthy. 



The hind-limb consists of a short stout femur, a tibia to 

 which the proximal tarsals (astragalus and os calcis) are 

 fused (forming a tibio-tarsus), an incomplete fibula joined 

 to the tibia, three metatarsals fused to one another and to 

 the distal tarsals (forming the tarso-metatarsus), a free first 

 metatarsal, and, finally, the four toes. The first, turned 

 backwards, has two phalanges, the second three, the third 

 four, and the fourth five. 



Nervous system. In contrast to the brain of crocodiles 

 and other Reptiles, the brain of the pigeon and other Birds 







Iscli. .^^ I 



ML 



FIG. 316. Side view of pelvis of cassowary. 

 //., Ilium; fsc/i., ischiuin ; 7V'., pubis ; Ac., acetabulum. 



fills the cranial cavity. The cerebral hemispheres are large 

 and smooth. Their roof is thin, their main mass consists 

 of the large corpora striata which bulge into the ventricles. 

 They meet the cerebellum and throw the solid optic lobes 

 to the sides. The olfactory lobes are very small (cf. de- 

 ficient sense of smell). Between the cerebral hemispheres 

 and the cerebellum, the pineal body rises to the surface, 

 and a slight posterior separation of the hemispheres will 

 disclose the region of the optic thalami. The cerebellum 

 is ridged transversely and divided into a median lobe and 

 two small lateral flocculi. The curvature of the brain is 

 well marked in the adult, thus the medulla is quite hidden 

 by, and descends almost vertically from, the cerebellum. 



There are as usual twelve cranial nerves. 



In connection with the spinal cord, the brachial plexus of nerves 



