SCIENTIFIC PROCEEDINGS. 
GARDEN, 
Abstracts of the Communications. 
Forty third meeting. 
The Laboratory for Hygiene, University of Pennsylvania. April 
10, i on. President Morgan in the chair. 
50 (575) 
On the regular seasonal changes in the relative weight of the 
central nervous system of the leopard frog (R. pipiens). 
By HENRY H. DONALDSON. 
[From the Wistar Institute of Anatomy and Biology.] 
The relative weight of the central nervous system of the frog, 
Rana pipiens, changes during the active season, and such a change 
is probably characteristic for other species of frogs with like 
habits. 
The relative weight of the central nervous system is low at the 
time of emergence, high in the midsummer (July) and low again 
at the time of hibernation. During hibernation it remains nearly 
constant. In the formula 1 used to express the weight of the 
central nervous system, the absolute value of C is characteristic 
for the station from which the frogs come. 
The range from minimum to maximum in the value of C is 
about 13 per cent., rising 7 per cent, from the end of March to the 
end of April, 4 per cent, more from the end of April to the end of 
May, and 2 per cent, more from the end of May to the first of July, 
remaining stationary in July and then falling month by month 
at a similar rate to the end of October. 
This variation in the relative weight according to season is 
due to lack of coincidence between the growth of the central 
nervous system and the growth of the entire body. 
1 This formula is as follows : Weight of C. N. S. = (log. wSl L.) C indicating 
that the weight of the central nervous system is equal to the log. W., body weight 
in grams, by ^ of the total length L, in mm., this product to be multiplied by C, a 
^ constant. 
