VITAL LIMIT OF EXSICCATION. 33 



body. He used the earthworm Allolobophora foctida and a desic- 

 cator containing calcium chloride. Durig (1901) found that the 

 common European frog would lose 30 to 39 per cent, of the body 

 weight if the drying was slow. Hill (1906) states that if a man 

 loses ten per cent, of his weight in water, he usually dies. Shel- 

 ford (1913) found in studying the reactions of animals to evapo- 

 ration that smaller animals died from loss of water much more 

 rapidly than larger. He also states that when the skins of am- 

 phibians became dry they did not recover when put into water. 



This paper describes the exsiccation of certain animals. Ex- 

 periments were carried on at the University of Wisconsin under 

 the direction of Professor A. S. Pearse to whom the writer is 

 greatly indebted for many suggestions and criticisms. Professor 

 M. F. Guyer has also given numerous helpful suggestions. 

 Thanks are also due to Dr. H. H. T. Jackson for the identifica- 

 tion of the mammals used, and to Drs. J. A. E. Eyster and W. J. 

 Meek for help in the construction of apparatus. 



II. METHOD OF DETERMINATION OF THE VITAL LIMIT. 



Apparatus. 



The apparatus for these experiments consisted of an air-pump, 

 exsiccating jars, filters, and an exsiccating chamber (Fig. i). 



The air-pump was an automatic electric air compressor 1 pro- 

 vided with an air-tank and a pressure gauge. The tank had a 

 capacity of four gallons. A switch controlled the starting and 

 stopping of the motor, whenever the pressure fell to 20 Ibs. or 

 rose to 25 Ibs. A valve constructed on the air-tank allowed 

 whatever flow of air was deemed necessary. The air-pump was 

 always in the same room with the exsiccating chamber and where 

 only fresh air was pumped and used. 



The exsiccating jars (Fig. i, P, S] consisted of four glass jars. 

 The first (Fig. i P) was a 500 cc. \Youlff bottle, full of crushed 

 pumice stone, the pieces ranging from 0.5 mm. to 5 mm. in di- 

 ameter, and about half full of sulfuric acid C.P. The other 

 three jars were the ordinary washing bottles, filled with sulfuric 

 acid C.P. The four jars were connected in series. Air passing 

 i Central Scientific Co. Cat. No. 218, listed as No. 1390. 



