56o MICRO-ORGANISMS AND DISEASE [CHAP. 



of bacillus prodigiosus, or bacillus coli, bacillus typhosus, or 

 cholera vibrio, in its relation to the subcutaneous tissue of 

 the guinea-pig. If a small dose of either of these living 

 microbes (taken from the slanting surface of an Agar cul- 

 ture), say one-fifteenth or one-twentieth of a culture of an 

 ordinary not exceptionally virulent stock distributed in 

 sterile salt solution or sterile bouillon, be injected subcu- 

 taneously into a normal guinea-pig of about 300 grammes, 

 the result is nil, no tumour is noticed, no leucocytosis ; if 

 the dose be larger, say one-tenth to one-eighth of a culture, 

 there is noticed next day a more or less distinct swelling 

 and leucocytosis, with general constitutional disturbance ; 

 the swelling increases for a day or two, then diminishes and 

 becomes firmer, and may ultimately lead to suppuration 

 and ulceration of the skin. While the tumour grows and 

 increases, and even when it has begun to decrease and to 

 become firmer, the microbes injected can be recovered by 

 culture in a living state. If the dose be still more increased, 

 say a quarter to a third of a culture, the result is more 

 pronounced, the tumour and leucocytosis are greater and in 

 some cases in two or three days may be followed by general 

 infection and death. 



So that the capability or incapability of a microbe to per- 

 sist in a tissue, and to maintain its life and multiply therein, 

 stands in no necessary relation to the existence or non- 

 existence of a leucocytosis. 



Moreover, even in the case of a particular microbe, e.g. 

 bacillus anthracis, its introduction into the subcutaneous 

 tissue of an insusceptible animal, say an adult rat or dog, 

 is by no means necessarily followed by leucocytosis, and 

 yet no infection ensues ; this is noticed in the case when 

 a small dose is injected. A further important fact to be 

 mentioned in this connection of leucocytosis preceding 



