THE PHAGOCYTOSIS OF SOLID PARTICLES. 

 11. Carbon. 



By WALLACE O. FENN. 



{From the Laboratory of Applied Physiology, Harvard Medical School, Boston.) 



(Received for publication, January 15, 192L) 



In a former paper (1) some determinations were reported of the 

 rates of ingestion of three different sizes of quartz particles by leuco- 

 cytes of the rat. It was shown that the rate of phagocytosis depends 

 upon the chances of collision between a leucocyte and a particle of 

 quartz. In this paper similar experiments on the phagocytosis of 

 carbon particles of two sizes are reported. 



Carbon Suspensions. 



The method of preparing the carbon suspensions was essentially 

 the same as that already described for quartz. The carbon used 

 was one of the charcoals prepared from coal during the war by the 

 Chemical Warfare Service and activated by treatment with super- 

 heated steam. It was washed repeatedly in distilled water during 

 the process of removing, by means of the centrifuge, the particles too 

 small to use, and was washed once each time before using. It may, 

 therefore, be considered free from easily soluble material. 



The carbon suspensions were considerably more sensitive to agglu- 

 tination than the quartz. It was, for example, impossible to resus- 

 pend a suspension of carbon, after it had settled out either by gravity 

 or centrifugal force, without getting some agglutination. The sus- 

 pensions were agglutinated at once by the addition of tap water 

 and they were somewhat more stable in slightly alkaline than in 

 slightly acid solutions. Non-sterile suspensions agglutinate more 

 readily than sterile ones. Acacia must be added to a suspension to 

 keep it uniform and stable for more than a few hours. Fortunately 



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