IMMUNITY AGAINST MICEOBES. 417 



Immunity against Microbes. 

 By 



m* Armand Ruffer, m.il., ]9I.I>.(Oxoii.). 



With Plates XXXII and XXXIII. 



Part II. 



The first part of this paper, with few exceptions, was taken 

 up with the struggle taking place in the healthy body between 

 micro-organisms and amoeboid cells. It is now time to study 

 what happens where micro-organisms have found their way 

 into the tissues of animals. 



Very little consideration, however, shows that the problem 

 to be solved is a most difficult one, on account of the many 

 factors which influence the clinical course and pathological 

 appearances of a disease. 



In the first place, the clinical aspect and the pathological 

 appearances will vary according to the number of micro- 

 organisms introduced into the system. This fact was formerly 

 denied by competent bacteriologists ; for it was difficult to 

 imagine that the number of micro-organisms could be of 

 importance, when it was shown that 1,000,000,000,000th part 

 of a drop of blood from an animal dead of septicaemia injected 

 into another animal reproduced the same disease. Lately, 

 however, overwhelming evidence has been brought together 

 proving the influence of numbers. Thus 250,000,000 staphy- 

 lococci injected into a rabbit will produce an abscess in this 

 animal,^ but 1,000,000,000 of the same parasites will cause 



' Davaine. 



VOL. XXXII, PART IV. — NEW SEE. p p 



