754 MODE OF SPREAD OF INFECTIVE DISEASES. 



selves may remain for a long time in the body, and thus 

 afford a protection against subsequent invasions. But this 

 disinfecting power of the products of the bacteria, which has 

 been often insisted upon, appears, according to the accurate 

 experiments of Sirotinin, to be in most cases a fable, or at 

 any rate to be much exaggerated; and, on the other hand, 

 such a stubborn retention of minute quantities of this bacterial 

 poison in the living body does not at all correspond to our 

 ordinary physiological ideas. Grawitz sought to explain 

 immunity by supposing that as the result of the battle 

 between the cells of the body and the pathogenic organisms, 

 the vital energy and the assimilating power of the animal 

 cells is increased as compared with that of the parasites ; and 

 that the duration of the immunity is occasioned by the trans- 

 mission of this increased physiological energy from one cell 

 generation to another. But in this case it would be very 

 difficult to understand why it is always only the same or 

 similar infective agents which occasion a sufficient increase 

 of the cell energy. 



Assumption of A better view, and one more in correspondence with 

 alteration^ ^ e views developed in the preceding pages, as to the 

 the seat of mode of entrance of the infective agents, is that put for- 

 ward by Buchner, viz., that that organ which is associated 

 with the development of the specific infective agents 

 undergoes a reactionary alteration of its tissue under the 

 influence of the bacteric development, and that this lasts 

 for a long time, and does not permit a second develop- 

 ment. Wolff berg has put forward a similar hypothesis 

 with regard to the origin of the immunity against small- 

 pox after vaccination. Wolff berg asserts that the altera- 

 tions which lead to the immunity must occur in the skin, 

 as being that organ which forms the first and most im- 

 portant point of attack for the infective agents ; and he 

 tries to point out the probability that the causes of the 

 immunity are chiefly the destruction of the weak cells of 

 the rete, and the retention and development of the more 

 resistant elements. 



On the assumption of a reactionary alteration of the 

 specific seats of invasion, we can understand that it is 

 only the infective agents of the same disease, or of 

 one similar to it (or only weakened agents), which arc 

 able to give immunity against a later attack by the same 



