ON THE REGULAR SEASONAL CHANGES IN THE 
RELATIVE WEIGHT OF THE CENTRAL NERVOUS 
SYSTEM OF THE LEOPARD FROG 
HENRY H. DONALDSON 
The Wistar Institute of Anatomy and Biology 
FIVE CHARTS 
The bearing of this investigation can best be understood by a 
short account of the steps leading up to it. In some earlier stud- 
ies on the innervation of the muscles and skin of the leg of the 
bullfrog and of the leopard frog (Donaldson ’98) (Donaldson and 
Schoemaker ’00)! the weights of the brain and of the spinal cord 
of the frogs were taken, and the percentage of water in these two 
portions of the central nervous system determined. 
When the records thus obtained were assembled, the arrange- 
ment of them as they appeared on the chart suggested that the 
increase 1h the weight of the central nervous system might run 
parallel to a logarithmic curve, based on the weight of the entire 
body. The curve based on this datum alone was however found 
to fall away from the observed values as the body weight increased 
and hence a second factor, the value of which increased gradually 
but at a diminishing rate, was necessary to make the calculated 
values correspond to those observed. This second factor was 
found in the total length of the frog, the fourth root of which in- 
creased at such a rate that when the logarithm of the body weight 
is multiplied by the fourth root of the total length, the values 
obtained are an almost constant fraction of those observed. It 
remained then merely to multiply the number thus found by a 
constant to approximate the observed values. 
‘In the paper cited above and in several other publications from my labora- 
tory, the leopard frog has been designated R. virescens brachycephala Cope. 
Since 1908 the name Rana pipiens has been used (see Donaldson, Science, vol. 
26, p. 655, 1907). 
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