The Nervous System. 



179 



and defends it; and the pythoness broods her eggs. Yet most reptiles 

 leave their young to hatch and take care of themselves. 



The encephalon of fishes and reptiles is represented by a small 

 amount of cerebral neurine. Four or five pairs of ganglia are distinct 

 in the neural chain. Olfactory nodules are present, yet the sense of 

 smell is feeble or altogether lacking. The optic lobes are prominent; 

 the cerebellum is distinctly represented, as well as the swellings of the 

 medulla oblongata, but the cerebral hemispheres are insignificant in 

 size. The brain of a crocodile is not as big as that of a parrot or a 

 goose. The great saurian knows little except to capture and drown 

 prey. 



Birds have a large cerebrum as compared with the weight of their 

 bodies. The canary has comparatively more than twice as much brain 

 as man. Yet the little thing is chiefly noted for song. The blue jay, 

 a member of the crow famil}-, is about as wise as an} 7 bird that lives; 

 and, like the parrot, can mimic many voices. Some birds, to call atten- 

 tion from their nests, will feign lameness and inability to fly, as if 

 wounded. The woodcock, having its first nest, will feign as well as a 

 bird that has practised the stratagem a half dozen different years, 

 therefore the execution is purely instinctive and inherited. Several 

 kinds of small birds will combine an attack upon a discovered owl. 

 Each assailant feels that a common enemy is to be punished and 

 driven out. And what is more, the small birds assault timidly while 

 the owl is in the dark retreat of a thicket, yet boldly when the night 

 prowler is driven into the light of day where its sight is blinded. 



The spinal cord in vertebrates is the basis of the nervous system, 

 although there is a lisceral combination of nerves and ganglia which 

 is highly important to the carrying on of the digestive and secretory 

 functions. This splanchnic system is not wholly independent of the 

 crebro-spinal combination, yet it is wholly beyond volition. The in- 

 testines vermiculate, and the glands secrete, though the brain be 

 thoroughly anaesthetized. 



The lowest vertebrate, the lancelet, or amphioxus, has simply a 

 spinal cord ; no brain is developed on its cephalic extremity. The 

 frog has appreciable cerebral hemispheres, } r et a small amount of 

 vesicular neurine in them. The} r seem to represent the beginning of 

 that bulging on the anterior extremity of the spinal cord, which is 

 thrown into convolutions in the higher vertebrates. 



The ridged or convoluted state of the surface of the cerebral hemis- 

 pheres is not seen in rats, squirrels, and the lower mammalia. The 

 cerebrum is composed largely of " grey" neurine; and its functions are 



