Vital Staining 



367 



The staining of the living cells depends on many physical 

 conditions. Such a small variation between 0.6 per cent, and 

 0.65 per cent, of NaCl in Ringer's solution makes a great differ- 

 ence in the vital staining process. The temperature is also im- 

 portant for it seems that each color, to give the best results, 

 must be used at a particular temperature, for instance Cresyl 

 Violet gives best results at the low temperature of 20°C, Diazin 

 Green and Janus Green at 26°C, Natural Red at 32° to 35°C. 



177 (2137) 



Some changes in the dying cell. 

 By ROBERT CHAMBERS. 



[From the Department of Anatomy, Cornell University Medical 

 College, New York City.] 



By ordinary transmitted light the nucleus of the living cell 

 is an optically homogenous body lying in a cytoplasm which is 

 more or less granular. The optical difference between the 

 nucleus and the cytoplasm is more strikingly shown by dark 

 field illumination where the nucleus appear optically empty, 

 whereas the cytoplasm scintillates with bright spots. The cyto- 

 plasm has, therefore, been considered to be distinctly hetero- 

 geneous in contrast to the optically homogenous nucleus. That 

 this is not true may be seen in the following experiment : 



By means of the centrifuge the cytoplasmic granules of the 

 sea urchin egg can be driven to one side of the egg. On cutting 

 away this part one may obtain an egg fragment consisting of 

 protoplasm which is transparent and optically empty, even when 

 viewed with dark field illumination. This fragment is fully 

 capable of developing. We must, therefore, conclude that the 

 cytoplasm may be as optically structureless as the nucleus. When 

 the cell dies, however, a difference in structure with the dark 

 field illumination becomes at once apparent. Coagulating 

 agents, which are not violent in their reaction, such as gentle 

 heat or weak formalin, make the cytoplasm diffusely milky in 

 appearance, owing to the formation of closely packed and uni- 

 formly sized spherules. In the sea urchin egg these globules 



