92 PRACTICAL ZOOLOGY. 



higher power, say a quarter-inch objective, and study the 

 little bodies floating in the blood. These are the cor- 

 puscles. 



1. The large, faintly colored oval corpuscles; do they 

 change their shape when pressed, as in turning a cor- 

 ner ? What is the color of these corpuscles ? Mould 

 a bit of clay into the shape of one of these bodies. 



2. The smaller, rounded, paler corpuscles, fewer in num- 

 ber and moving with a slower and more unsteady 

 motion along the sides of the channel ; what must 

 be the shape of these ? Place a drop of frog's blood 

 on a slide, cover with a cover-slip, and examine with 

 a high power. Make careful drawings of the two 

 kinds of corpuscles. (Take a small drop of blood for 

 this, and after covering it, run a little oil around the 

 edge of the cover to prevent drying.) 



THE NERVOUS SYSTEM OF THE FROG. 



The nervous system is better seen in alcoholic speci- 

 mens. Slit the skin along the back from the snout to the 

 anus ; with a sharp knife cautiously cut away the top of 

 the skull, and find : — 



1. Between the eyes, side by side, two elongated white 

 bodies, the two halves, or hemispheres, of the cere- 

 brum. Observe two small pear-shaped bodies, the 

 olfactory lobes, in front of the cerebral hemispheres. 

 These taper forward into nerves running to the nasal 

 region; these are the nerves of smell, or olfactory 

 nerves. 



2. Back of the cerebral hemispheres are the optic lobes, 

 forming the widest part of the brain. Prove that a 



