CHAPTER IV 



CELLULAR STAINING, DEATH, AND ACHROMASIA 



BY far the larger number of cells examined in these 

 researches have been blood-cells taken from the finger. 

 The white blood-corpuscles have offered a very interest- 

 ing study, and since they respond to chemical agents in 

 a way very similar to those observed in several other 

 varieties of cells, and, since they are very easily obtained 

 and can be very carefully watched, it is convenient to 

 describe what w r e have seen with them. These cells 

 play an important role in the phenomenon of healing, 

 and ultimately go to form some of the fixed tissue- 

 cells, especially after an injury has been sustained. 



For the examination of blood-cells in in vitro it is 

 best first to mix the sample of blood (which should be 

 drawn freshly from the finger) with an equal volume of 

 "citrate solution." 1 The citration of the blood not 

 only prevents it coagulating, but it also keeps the cells 

 alive sometimes for as long as seven days. 



The way in which w r e citrate the blood is as follows: 

 One end of a capillary tube, such as has been described 

 (Chapter II.), is dipped into the citrate solution, some of 



1 Three-per-cent sodium citrate, and 1-per-cent sodium chloride. 



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