88 
AMPHIBIANS 
At the anterior end of each kidney in both the male and 
female frog is to be seen an irregular mass, the fat body, 
which contains stored energy that the frog uses as it begins 
to grow eggs or sperms in the early spring before there is 
plenty of food. 
77. Nervous System. — The nervous system of the frog is 
more highly developed than that of the crayfish. It consists 
of a central part en¬ 
closed in the backbone 
and cranium (braincase). 
This central nervous sys¬ 
tem in all vertebrates is 
always found above the 
digestive tube, and is di¬ 
vided into the brain and 
the spinal cord, from which 
numerous nerves arise and 
extend to all parts of the 
body. 
The parts of the brain 
are the same as in man 
and much easier to study. 
Beginning at the front 
(anterior) end of the brain 
the parts are as follows: 
(1) small olfactory (ol-fac'- 
t6-ry) lobes, which are not 
sharply marked off from 
the rest of the brain, and, 
as shown in Figure 74, 
connect with (2) the cerebral (ser'e-bral) hemispheres, which 
are oval in outline. (3) A short mid-brain region, partly 
covered by the back part of the cerebral hemispheres, con¬ 
nects the front and back part of the brain. (4) Two large 
optic lobes, the widest part of the brain, are just back of 
Figure 74. — Central Nervous System 
of Frog. 
