ANIMAL BIOLOGY. 



[Part I. 



middle division receives on its dorsal side in the male the 

 openings of the ureters, and the vasa deferentia, and in the 

 female those of the ureters and the left oviduct. The posterior 

 chamber has on its dorsal wall, in young birds, the aperture of 

 the Bursa Fabricii. 



5. The Nervous System. In the thoracic region, white threads, 

 the thoracic nerves, pass outwards between the ribs. The 

 anterior thoracic and posterior cervical nerves form a brachial 

 plexus, whence the wing is innervated. In the pelvic region 

 there are two plexuses : one anterior, the lumbar ; the other 

 posterior, the sacral or sciatic. The gangliated sympathetic 

 chain passes up on either side of the vertebral column, and in 

 the neck runs within a canal embraced by bony processes of the 

 vertebrae, and called the vertebrarterial canal. 



The central nervous system must be displayed from the dorsal 

 aspect. Great care must be taken in exposing the brain, which 

 fits closely to the skull, the walls of which must be shaved or 

 scraped away until the brain is exposed, and then carefully 

 broken away piece by piece. The brain and an inch or two of 

 the spinal cord may be removed and placed in strong spirit for 

 future study We may note in passing the large smooth cerebral 

 hemispheres (Fig. 22, c. h.), with the small anterior olfactory lobes 



C.I 



FIG. 22 BRAIN OF PIGEON. 

 A. From above. B. From below. C. In longitudinal section. 



(olf.) constituting the visible parts of the fore-brain ; the ridged 

 cerebellum (cb.\ and underlying medulla oblongata^ constituting the 

 hind-brainy and between the two the rounded optic lobes (op. I.} 

 of the mid-brain. 



