370 LOUIS MAX HICKERNELL. 



A further confirmation of the fact that the changes in cell- 

 structure take place early in the desiccation process is found by 

 comparing sections of animals which were dried and kept in the 

 open air with those of animals kept days or weeks in an evacuated 

 desiccator. The essential features of cell structure and arrange- 

 ment are the same in both cases. This certainly seems to indi- 

 cate that the extent of the adaptive, structural response to the 

 new condition is not directly proportional to the intensity of 

 the stimulus. 



The nuclear membrane undergoes no disintegration or other 

 visible change in structure during the drying process. It might 

 be supposed, from a consideration of the movements of the 

 chromatic material into the cytoplasm, that the membrane 

 would break up during the process. Such is not the case. Not 

 only does it remain intact during the drying but it actually 

 thickens. This thickening is of course due to the migration of 

 chromatic material which normally occupies the middle of the 

 nucleus. The chromatin proper cannot be distinguished from 

 the nuclear membrane, however, since both react alike to stains. 

 The nuclear membrane, then, is a persistent cell organ and does 

 not atrophy as a result of the abnormal conditions. 



It is interesting to speculate whether the material which the 

 nucleus imbibes upon recovery from desiccation is the same as 

 that which passed through the nuclear membrane at the time of 

 drying. I have not been able to make any of the finer micro- 

 chemical tests upon this substance but it would seem that the 

 material which passes from nucleus to cytoplasm takes part in 

 the oxidations discussed in a later section. The chromatin 

 remaining in the nucleus probably manufactures new nuclear 

 material from elements imbibed from the cytoplasm upon addi- 

 tion of water. 



The conditions described in the last paragraph show that 

 there are probably two kinds of chromatic material present in 

 the nucleus, one of which is able to pass out into the cytoplasm 

 and one which is not able to do so. Judging from the varying 

 amounts of chromatic material which are present in different 

 cells of the same kind when subjected to similar conditions it 

 seems that the non-diffusable chromatin may, when conditions 



