CHANGES IN WEIGHT OF CENTRAL NERVOUS SYSTEM 679 
TABLE 8 
The percentage changes in the value of C in each of the three lots of frogs. The March 
value used as the standard is underlined 
CHICAGO LOT MINNESOTA LOT BRANDYWINE LOT 
o a | Sr _|| a Cai ae mS | 8 
5 | 28 | s | 28 5 | 68 
DATE Ng A in| DATE a | 2% DATE Balhae z 
5 | gs S| Be 5 | 28 
2 a ° < g° < a? 
> m& | > 0) > iv 
= — It ————— —- —__— — 
| | | February 4 23.7 |-1.0 
| | | February 22 | 23.8 |—0.8 
March 28 | 24.7| 0 || March 26 | 28.1 0 March 23 | 24.0) 0 
April 9/25.8| 4.8] | | April Dal 247 Se 353 
May 427 ON 9 3. | | May 20 | 26.8 | 11.6 
June D206) 7 June 107) 31.1) 10.7 || June 19 | 26.3 | 9.6 
June 29 | | | | 
July 27 | 28.5 | 15.4 | | August 13 | 26:1} 8.7 
August 24 | 28.3 | 14.6 | | September 8 27.2 | 13.3 
September 22) 27.9 | 13.0 | | | September 24 | 25.2) 5.0 
| October 29 | 28.2 | 0.3 | October 19 | 24.5| 2.1 
| | | 0.4 
| . 
November 16 23.9 — 
0.4 | | | 
| | | 
| 
January 30 | 24.8 
The percentage change in the value of C as indicated by the 
observations when the late March value is taken as the standard, 
is given for all three lots in table 8. 
When thé data on these tables are put in the form of a chart 
(chart 4) and then an ideal symmetrical curve is drawn a number 
of interesting relations come into view. 
In the first place the maximum of this curve in July is 13 per 
cent above the initial value of C. Second, during the month from 
the end of March to the end of April, C increases about 7 per cent; 
during the month from the end of April to the end of May, about 
4 per cent, and from the end of May to the end of June, about 2 
per cent. During July little change occurs and then the converse 
changes follow during the three months from August first to the 
end of October. During hibernation, November first to the end 
of March, the value of C is nearly constant. 
These values are admittedly only approximations, but when so 
understood, they serve to show the general course of the seasonal 
changes. 
