1907.] Substance in Serum which influences Phagocytosis. 405 



Here the calculated value does not exceed 10, whereas the experimental, 

 value was 15. 



Experiments with the Dysentery Bacillus of Shiga. 



In the case of such organisms as the Dysentery bacillus, Typhoid bacillus,, 

 and Cholera vibrio, a difficulty presents itself owing to the occurrence of 

 bacteriolysis. If the full strength of certain fresh normal sera is employed,, 

 an accurate estimation of the phagocytosis by this method of investigation 

 may be impossible on account of the fact that many of the bacilli disappear 

 altogether or are visible only as shadow forms both inside and outside the 

 leucocytes. These phenomena are still more pronounced when one mixes 

 with such a fresh normal serum a heated immune serum of any potency. 

 The intracorpuscular and extracorpuscular bacteriolysis in such an experi- 

 ment may be extreme. By a process of dilution of both the normal and the 

 immune serum it was found possible to overcome this difficulty. For 

 example ; after a number of orientating experiments with dysentery,, 

 cholera, etc., it was found that if a dilution of 1/100 of a particular sample 

 of heated anti-dysenteric serum was employed with a dilution of 1/20 or 

 1/30 of fresh serum, marked phagocytosis occurred with slight intracellular 

 but no obvious extracellular bacteriolysis. When 1 volume of these 

 dilutions is mixed with 1 volume of leucocytes and 1 volume of bacterial 

 emulsion, the ultimate dilutions reached are 1/60 or 1/90 of the fresh normal 

 serum and 1/300 of the heated immune serum. 



The procedure carried out in such an experiment is as follows. Tubes and 

 preparations are made in the usual manner from the following combinations : — 



A. Heated anti-dysentery serum (dilution 1 : 100), 1 volume, + 

 Normal salt solution, 1 volume, + 

 Leucocytes, 1 volume, + 

 Dysentery bacillus (Shiga), 1 volume. 



Average number of 

 bacilli per leucocyte. 



> 4-3 



B. Fresh normal serum (dilution 1 : 30), 1 volume + 

 Normal salt solution, 1 volume, + 

 Leucocytes, 1 volume, + 

 Dysentery bacilli (Shiga), 1 volume. 



I 5-6 



C. Heated anti-dysentery serum (dilution 1 : 100) , 1 volume, + 

 Fresh normal serum (dilution 1 :30), 1 volume, + 

 Leucocytes, 1 volume, + 

 Dysentery bacilli, 1 volume. 



I 16-1 



In Table III are shown the results of four such experiments with anti- 

 dysentery serum and fresh normal sera of different ages, with the mean 

 values obtained. 



