1905.] On Spontaneous and other Phagocytosis. 215 



abolished by the heating of even a normal serum. The residual phagocytosis 

 registered in the protocols must, as reflection will show, be either 

 spontaneous phagocytosis, meaning by this phagocytosis occurring apart 

 from any co-operation of the serum, or phagocytosis dependent upon the 

 chemical activity of an element which has resisted the destructive action 

 of heat.* 



When face to face with the consideration that the elimination of all 

 spontaneous phagocytosis must be a necessary preliminary to the proper 

 investigation of every question which has reference to the presence of an 

 incitor element in heated serum, a suggestion from our fellow worker 

 Captain Stewart E. Douglas, I.M.S., led us to inquire whether the phagocytic 

 activity of the leucocyte might not be affected in a conspicuous manner by 

 the salt content of its fluid environment. Captain Douglas's suggestion was 

 a happy one. For, as will appear in the next section, we found that in 

 certain concentrations of salt the leucocytes display considerable spontaneous 

 phagocytosis with respect to the tubercle bacillus, while again in other salt 

 concentrations spontaneous phagocytosis with respect to these micro- 

 organisms is entirely suppressed. 



Investigation of the Influence of the Salt Content of the Fluid Environment of 

 the Leucocyte upon Spontaneoiis Phagocytosis. 



The general results of our experiments conducted with tubercle bacilli 

 will be best submitted in the form of the subjoined graphic curves. 



In Curve 1 we show the phagocytic counts obtained in an experiment 

 conducted without any admixture of serum. In these experiments one 

 volume of washed blood corpuscles, suspended in - 85 per cent. NaCl 

 solution, was mixed in each case with an equal volume of suspension of 

 tubercle bacilli in distilled water, and with one volume of a graduated 

 solution of salt. It will be observed that the spontaneous phagocytosis 

 which is here in question is greatest where the phagocytic mixture contains 

 - 6 per cent, of NaCl, and that the count falls off in a gradual manner, 

 and finally reaches a figure which does not differ sensibly from zero when a 

 concentration of 1*2 per cent. NaCl is arrived at. 



* In favour of the former of these two alternative explanations of the residual phago- 

 cytosis is,Jirst, the difficulty of conceiving in connection with the experiments conducted 

 with carmine and Indian ink particles that these were chemically acted upon by the 

 serum ; secondly, the difficulty of explaining, otherwise than as a result of individual 

 differences in phagocytic activity as between leucocyte and leucocyte, the fact that in 

 preparations made with heated normal serum and tubercle bacilli suspended in physio- 

 logical salt solution, the phagocytosis is generally restricted to a very small percentage of 

 the leucocytes instead of coming into evidence, as in the case of experiments conducted 

 with unheated and active serum, in association with practically all the mature leucocytes. 



Q 2 



