34 THE BIOLOGY OF THE FROG chap. 



In the fall of the year the body is richly stored with 

 nutriment accumulated during the summer while food is 

 abundant. During the winter this material is employed not 

 only in maintaining the temperature of the body and furnish- 

 ing the energy necessary to carry on the various activities of 

 the organs, but it is drawn upon to contribute to the growth 

 of the reproductive cells. A part of this material is stored 

 in the muscles, which during the winter decrease in weight 

 in relation to the rest of the body. Gaule * found that in 

 female frogs killed in July the gastrocnemius muscle weighed 

 on the average 32.6 mg. for every gram of body weight. In 

 August the ratio rose to 34.8. In December it sank to 26.1. 

 In January it was 26.4, and in June, the laying period, 27.1. 

 In the male the decrease in relative weight of the muscles 

 is not nearly so great, as there is much less material to be 

 employed in the development of the sexual products. 



The liver undergoes marked seasonal changes which will 

 be more fully described in connection with the account of 

 that organ. In the winter it contains a large amount of 

 glycogen, which almost entirely disappears by the end of the 

 breeding season. Until early spring, however, the glycogen 

 suffers comparatively little loss. The color of the liver also 

 varies between winter and summer, owing probably to differ- 

 ences of nutrition. In winter there is an accumulation of 

 pigment which gives the liver a dark appearance. In sum- 

 mer this pigment in most frogs largely disappears and the 

 liver becomes lighter in color. The size of the cells varies, 

 increasing through the summer, reaching its maximum in 

 Rana temporaria in November, then decreasing through the 

 winter and early spring, reaching the minimum in April 

 (Leonard) 2 or May (Funke). 3 The size of the liver in 



1 Gaule, Arch. ges. P/iys., Bd. 81, 1900. 



2 Leonard, Arch. . Inat. it. P/iys., phys. Abth. Suppl., 1881. 



3 Funke, Deuksckr., Wien Akad. math. nat. CI. Bd. 68, 1900. 



