Donaldson AND ScHOEM \KER, Absorption of Water. 187 



specimens similar in body weight and length were selected and 

 killed with chloroform. After death each was examined alone 

 in the followino- manner: It was weighed in a closed box to a 

 centigram ; the weight ot the ovaries when containing devel- 

 oped o\a, being deducted from the body weight. The contents 

 of the stomach were also removed when necessary. The length of 

 the vertical line from the tip of the nose to the lip of the longest 

 toe was taken in millimeters — the frog being suspended from its 

 lip. From this point on, the tieatment <if the two frogs was 

 different. The first Irog, in future to be spoken of as the ''con- 

 trol frog," was at once eviscerated. 'I'he >pinal cord was ex- 

 posed ; the length of the cord between the tip of the calamus 

 scri|)t<)rius and the origin of the dorsal roots of the Xth (last) 

 spinal nerve was determined under a dissecting microscope ; 

 then the cord was removed be i ween these limits, the nerve 

 roots being cut away at their superficial origin. The cord was 

 put in a closed weighing bottle, examined for parasites with a 

 hand lens, and if normal, weighed to the tenth of a milligram. 

 Immediately after the determination of the body-weight the 

 second frog, in future to be known as the "absorbing frog, " 

 was put belly down at the bottom of a litre glass jar. There it 

 rested on a layer of shot which had been put in the jar to sink 

 to within a couple of centimeters of the surface of the water in 

 which the jar floated. The surrounding water was held in a 

 large aquarium and kept constantly flowing, so that the temper- 

 ature within the jar containing the frog was very close to that 

 of the tap water flowing through the aquarium. The jar was 

 closed at the top by dense wire gauze, through which a ther- 

 mometer was inserted, the bulb being at the le\'el of the fiog. 

 There is of course some evaporation and hence loss in weight 

 in the absorbing frog. This has been determined under the 

 conditions here used to be less than 4^^ of the bod)' weight 

 and the error due to it has been neglected. So fir as it goes, 

 it tends to diminish the gain in weight exhibited by the cord of 

 the absorbing frog. At the end of the time chosen, the "ab- 

 sorbing frog" was taken from the jar and the cord removed, 

 measured and weighed, according to the method used for the 



