36 F. G. HALL. 



Plan of Experiments. 



The animals used for these experiments, with the exception of 

 the mice, were kept for several days without food; so that their 

 digestive systems were evacuated. They were kept in cages and 

 supplied constantly with water. The mice were kept in cages, 

 and supplied with food and water. All the animals were weighed 

 separately; the earthworms, leeches, and meal worms were 

 weighed and then placed in small flat glass dishes which were 

 covered with cheese cloth. From one to eight dishes were placed 

 in the exsiccating chamber at a time; the salamanders, frogs, 







snakes, lizards, turtles, and mice were weighed in screen cages 

 and transferred directly to the exsiccating chamber. A screen 

 partition was used to separate the animals when more than one 

 was exsiccated at a time. 



The temperature, air-flow in cubic centimeters per minute, and 

 the time were noted on a record card for each individual. The 

 corn or oats fed the mice was weighed and the amount eaten 

 noted each day. The relative humidity was found to vary con- 

 siderably while animals were in the chamber. With an air-flow 

 of 1,000 cubic centimeters per minute the relative humidity varied 

 from o to 10 per cent. 1 The supply of sulfuric acid in the ex- 

 siccating jars was renewed whenever there was indication that it 

 had been weakened much by the absorption of water. 



After removal from the exsiccating chamber the animals were 

 placed in as normal an environment as could be obtained. The 

 invertebrates were placed on moist filter paper at normal room 

 temperatures. Some individuals were placed in a refrigerator 

 where recovery from exsiccation was more easily accomplished. 



The limit of exsiccation was determined by the maximum per- 

 centage of water that could be removed from an animal without 

 the loss of vitality. Water was removed from an animal by sub- 

 jecting it to dry air in an exsiccating chamber (Fig. I, C). The 

 loss of weight was the means used for the determination of the 



i By means of absorption tubes containing H 2 SO,, c. p. connected at the 

 outlet of the exsiccating chamber (Fig. i, C), not a trace of water was found 

 to pass for a period of 25 hours, providing there was no animal in the exsic- 

 cating chamber. 



