152 VICTOR E. EMMEL 



The technique employed in making the culture was essentially 

 that developed by Harrison, Burrows, and Carrel. Some homo- 

 plastic cultures were made by placing the blood cells of younger 

 embryos in the centrifuged plasma of much older specimens. The 

 best results for the present purpose, however, were obtained from 

 autoplastic cultures and the data to be described is chiefly from 

 the latter kind of preparations. The fact that in the autoplas- 

 tic cultures from these young embryos the culture media does not 

 coagulate appears one of great importance as furnishing the more 

 favorable conditions for the continued normal life and function 

 of the erythrocytes, for it seems evident that the normal environ- 

 ment of these cells in the embryonic circulation, is in marked 

 contrast to that of most other tissue cells, and for which, as em- 

 phasized by Harrison, a coagulated medium appears the more 

 favorable for growth in vitro. Appreciating the great sensitive- 

 ness of the blood cells to surrounding physical, chemical and 

 thermal conditions, especial care was laken in the cleaning and 

 sterilization of all glass ware and apparatus as well as in the 

 maintenance as nearly as possible of a constant normal tempera- 

 ture throughout the experiments. Variations in culture conditions 

 were studied, including a comparison of free hanging drop cultures 

 with others resting upon a glass surface or a film of agar-agar. 

 Cotton fibers were introduced into some cultures, and Ringer's 

 solution into others. Comparisons were also made between dry 

 culture chambers and moist chambers in the bottom of which 

 various quantities of water. Ringer solution and plasma had been 

 placed. Of these various experiments the cviltures in chambers 

 kept moist by a small drop of distilled water proved the most satis- 

 factory. The investigation included over eighty experiments. In 

 each case controls were made consisting of preparations fixed in 

 formalin vapor and stained with Giemsa's mixture. The cultures 

 were always examined in a warm chamber and camera lucida 

 drawings made of the corpuscles under observation. 



Further details concerning the preparation of the cultures, 

 plasma, temperature, normal and degenerative cytological charac- 

 teristics will be more conveniently discussed in the course of the 

 ensuing description. 



