INFECTIOUS DISEASES AND MICROBES, ETC. 191 



incubation has been seven days, when injected intra- 

 cranially into a dog, develops rabies in the latter 

 animal in about twelve days. The nervous matter 

 of this dog, inoculated back by the same process 

 into rabbits, at once reproduces the malady after an 

 incubation of seven days, and thus the series is 

 recovered/ 



Pasteur's treatment is prophylactic and not cura- 

 tive, for it is powerless against the disease when the 

 first symptoms have once made their appearance. 

 Hence the necessity of early treatment. 



The mode of action of the Pasteurian inoculations 

 has been explained by the two following theories : 

 (1) Metschnikoff 1 states that the white blood- 

 corpuscles (phagocytes) absorb and digest the living 

 microbes, and their power of absorption for microbes 

 is trained and increased by the progressively stronger 

 inoculations, so that finally the virus deposited by 

 the rabid animal can also be absorbed and destroyed. 

 The whole process is carried out, therefore, in the 

 lymphatic system. (2) Woodhead and Wood be- 

 lieve that the treatment consists essentially in caus- 

 ing the tissues to acquire a tolerance before the 

 microbe has had time to develop. ' The tissue cells 

 are acted upon by increasingly active virus, each 

 step of which acclimatises the cells for the next 

 stronger virus, until at length when the virus formed 

 by the microbes introduced at the time of the bite 

 comes to exert its action, the tissues have been so 

 far altered or acclimatised that they can continue 

 their work undisturbed in its presence, and, treating 



1 Fortschrift der Medicin, 1885. 



