66 4 



BIKDS. 



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 fchird 

 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 fills the cranial cavity The cerebral hemispheres 





FIG. 368. Brain of pigeon (I. dorsal, II. ventral, III. lateral aspects). 



OLF.L., Olfactory lobes ; C.ff., cerebral hemispheres ; PB., pineal body ; 

 OL.y optic lobes; CB., cerebellum; FL., flocculus or lateral exten- 

 sion of cerebellum; M.O., medulla oblongata ; PIT., pituitary body 

 at end of infundibulum (INF.)\ O.N., optic nerves crossing in. the 

 chiasma, 



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. deficient 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 large cerebellum is ridged transversely and divided 

 into a median lobe and two small lateral flocculi. The 



