4 8 F. G. HALL. 



ance that inhibits evaporation beyond a certain limit. Obviously, 

 a mouse got some water from the corn eaten. The corn was 

 tested and was found to contain less than eight per cent, water. 

 Thus the amount of water obtained from the small amount of 

 corn eaten would be too small to supply the daily loss. Probably 

 metabolic water plays a part in replacing that evaporated. 



DISCUSSION. 



The chief functions of water in animals are: (i) to dissolve 

 nutrients, (2) to serve as a medium for their distribution, (3) to 

 aid excretion by removing waste products from cells, and (4) to 

 control the body temperature. Water is the most abundant con- 

 stituent of the living organism and is essential to all life. The 

 relative amount of water contained in animals depends upon the 

 kind of organism, the period of growth, and the nature of food, 

 environment, and activities. 



In these experiments an attempt has been made to determine the 

 effect of a dry environment upon the amount of water present in 

 organisms, and the effect of exsiccation upon the vital activities. 

 There is need of more complete knowledge of the effects of ex- 

 siccation and though the present paper does not settle all prob- 

 lems relating to the loss of water by animals, it adds certain facts 

 that may be of general interest. The different types of animals 

 were subjected to comparable conditions. 



It is apparent that the water content of different species varies 

 greatly. The relative amount of water that may be lost and the 

 relative length of time that animals can endure exsiccation also 

 varies considerably. The important factors which limit such va- 

 riations are : the kind of animal, the size of the animal, the integu- 

 ment, the general metabolism, and the elimination of body wastes. 



The results of the writer's experiments apparently support the 

 statements of Babcock (1912), that the need for water is much 

 less for animals that excrete uric acid than those that excrete 

 urea, since uric acid, being practically insoluble in the body fluids, 

 is not as poisonous as urea, and is excreted in solid form with the 

 loss of very little water. Weese (1912) has shown that the ex- 

 cretions of horned " toads " are largely uric acid. This is prob- 

 ably true for many insects. 



