124 ORIENTAL PLAGUE chap. 



ment, for I have not found any marked attenuation taking 

 place of the really virulent B. pestis — e.g. type 1 — when 

 this is transferred from an animal such as the mouse dead 

 of typical acute plague to an animal of a different species, 

 e.g. the rat or the guinea-pig. Experiments which I have 

 made in this direction (and as to which I need not enter 

 into details) with virulent B. pestis (Cardiff bubo) show 

 that no such general rule obtains as is implied in Calmette's 

 statement; that, indeed, general experience is to the 

 contrary. 



On the other hand, attenuation of B. pestis once 

 having become as it were fixed, I have not been able to 

 notably modify it. For instance, I have not found that, 

 starting with attenuated B. pestis, passage of it through a 

 succession of guinea-pigs causes any enhancement of its 

 virulence. 



As I have already pointed out, inoculation of a guinea- 

 pig cutaneously with plague from whatever source (virulent 

 or less virulent) results invariably in a subacute disease, 

 fatal after six, seven, and more days ; the animal showing 

 post mortem necrotic bubo and small necrotic white 

 nodules in the spleen, liver, and often also the lung. This 

 is, as I have said, invariably the result of inoculating the 

 animal by rubbing in the infective material into cutaneous 

 abrasions or superficial incisions. Also I have shown that 

 in the case of subcutaneous injection with ordinary small 

 dose of virulent material the disease is fatal in from forty- 

 eight to seventy-two hours, but without necrotic changes 

 being found in the bubo, spleen, liver, or lung. And further, 

 I have shown that in the case of attenuated virus (or of 

 very small doses of more virulent material) even sub- 

 cutaneous injection will cause the subacute disease with 



