OBSERVATIONS ON THE POST-MORTEM ARSORB- 



TION OF WATER BY THE SPINAL CORD OF 



THE FROG (RANA VIRESCENS). 



By Henry H. Donaldson and Daniel M. Schoemaker. 



{From The N^eurological Laboratory of the University of Chicago.) 



In some previous investigations on the weight of the spinal 

 cord of the frog (i, 2), it was found that if the cord were left 

 in a frog for 24 hours or so after death, it had a weight much 

 greater than that of the cord removed from a frog of the same 

 size, immediately after it had been killed. It was assumed at 

 the time that this post-mortem increase in weight was due to 

 the absorbtion of water. To test this assumption and to ob- 

 tain more extended data on this reaction, the present investiga- 

 tion was undertaken. 



Introduction. 



In studying the absorbtion of water by the spinal cord of 

 the frog after death, we have had in view the collection of in- 

 formation which would serve to control errors which might arise 

 when determining the weight and size of the spinal cord in this 

 animal, and also be of use in interpreting the histological pic- 

 tures to be obtained from the spinal cords taken from frogs at 

 different periods after death. In the course of this work we 

 have found several interesting sources of error. 



On collating our various observations previous to this in- 

 vestigation, we are impressed by the fact that the living frog in 

 this region is an animal continually changing from month to 

 month, utilizing the brief period between April and October, 

 first for reproduction, next for growth and active feeding, and 

 finally, for a somewhat prolonged preparation for its final disap- 

 pearance in "the mud during the winter sleep. 



