THE PRESENCE OF GLYCOGEN IN THE 



CELLS OF EMBRYOS OF FUNDULUS 



HETEROCLITUS STUDIED IN 



TISSUE CULTURES. 



MARGARET REED LEWIS, 



CARNEGIE INSTITUTION OF WASHINGTON, 

 JOHNS HOPKINS MEDICAL SCHOOL. 



At the present time it is practically impossible to demonstrate 

 the various chemical substances of the living cell, owing to the 

 fact that most means of analysis cause the death of the cell. A 

 few of the differential stains, such as Sudan III. and Nile blue, 

 have been applied to studies of living tissues, but these do not 

 behave in the same manner in the living cell as in dead material 

 (Lewis and Lewis, 1915; M. R. Lewis, 1918). In most cases 

 the chemical nature of cytoplasm has been discussed from the 

 standpoint of results obtained from dead cells, and it is doubtful 

 whether such conclusions can be applied directly to the living. 

 This is true in regard to the experiments given herein; for, while 

 the substance described reacts as does glycogen to the tests 

 usually employed to demonstrate glycogen, these results were 

 not obtained until after the cells had begun to be affected by 

 the iodine. 



Bernard (1859) demonstrated the presence of glycogen in 

 many kinds of tissues and since that time several methods for 

 showing this substance in the cell have been reported. The 

 methods most frequently used for histological purposes are those 

 of Best (1909), Gage (1917). Neither of these was used in the 

 experiments given below. Instead, the living cells were exposed 

 to iodine vapor in such a manner that they could be followed 

 throughout the experiment, i.e., when living, while dying, and 

 after death had occurred. 



TECHNIQUE. 



Small pieces of fundulus embryos (just before hatching) were 



explanted into hanging drops of the following solution: 80 c.c. 



241 



