44 



ANIMAL BIOLOGY. 



[Part I. 



mater) lines the skull and spinal canal, while a delicate membrane 

 (pia mater) covers the brain and myelon. Between the two is a 

 third (arachnoid) membrane. (These membranes also exist in 



el,. 



B. 



FIG. 19. BRAIN OF RABBIT. 

 A. From below. B. In longitudinal section. 



our other types.) The brain should be carefully removed, 

 together with about an inch of the spinal cord. A number of 

 nerves which proceed from the brain will have to be carefully 

 severed. Before putting it into strong spirit for future study 

 its chief parts may be noted as seen from the dorsal aspect. 

 Posteriorly is a part which looks like an enlargement of the 

 spinal cord (medulla oblong ata, Fig. 19, m. o.). Over it hangs a 

 convoluted ridged mass, with a median and two lateral portions 

 (cerebellum, cb.). The medulla oblongata and cerebellum are 

 parts of the hind-brain. In front of this is a smooth, somewhat 

 pear-shaped portion, divided in the middle line. The two divi- 

 sions constitute the cerebral hemispheres (c. h.). Anterior to these 

 are two club-like prolongations, the olfactory lobes (olf.). The 

 cerebral hemispheres and olfactory lobes are parts of the fore- 

 brain. The mid-brain is hidden from view. But on lifting the 

 posterior edges of the cerebral hemispheres, four rounded promin- 

 ences (optic lobes, na. and te.), answering to the two we saw in the 

 frog and the fish, will be seen. They are parts of the mid-brain. 



