1891.] on Infectious Diseases, 289 



in which they can live and exist — for a time, at any rate — these cells 

 offering to them more favourable conditions of existence. 



In the case of the normal frog, this is also only of a temporary 

 nature, since the substance of the lymph-cells suspended in the lymph 

 or in the blood-plasma becomes likewise permeated with the germicidal 

 influence of the fluid lymph and the fluid plasma, and hence the 

 bacilli soon die, even in the substance of the cells. This explanation 

 is in perfect harmony with the large number of carefully conducted 

 experiments of a host of workers (ITodor, Nutall, Buchner, Petruschki, 

 Lubarsch, and others), according to whom the refractory condition of 

 an animal to a particular infectious disease is due to a chemical 

 germicidal action of the tissue-juices, the lymph, or blood plasma, and 

 independent of any cellular elements. The more pronounced this 

 germicidal action of the juices is, the more refractory the animal. 



Hence we find that, for instance, when in an animal even a very 

 small number of bacteria introduced are sufficient to produce disease, 

 the germicidal action of the living blood fluid is very small indeed ; 

 but when a considerable number of bacilli are required to produce 

 infection, as in animals possessing only a slight refractory power, 

 this germicidal action of the blood and tissue fluid is greater, and it 

 is greatest of all in those bodies in which not even a large number 

 of bacilli can produce infection, as is the case in animals possessed of 

 immunity. As stated just now, this part of the subject, as to the 

 germicidal action of the fluid of the tissues and the blood, has been 

 worked out very carefully, and it has been shown that, as regards the 

 destruction of bacteria, the leucocytes of the lymph and blood, or 

 other similar cells, might just as well be absent altogether. Quite 

 recently the whole argument has been clenched by showing* that if 

 an animal susceptible to a particular disease be first infected with the 

 bacilli causing this disease, and then into such an infected animal the 

 cell-free serum or plasma of the blood of an animal refractory to that 

 disease be injected, the development of the disease in the former 

 animal is stopped or prevented. Thus mice are very susceptible to 

 anthrax ; if they are infected with anthrax bacilli they die of virulent 

 anthrax within thirty-six to forty-eight hours ; but if simultaneously 

 with, or soon after, the introduction of the virulent anthrax bacilli, 

 blood of frog or blood of dog (both animals very refractory to 

 anthrax) be injected into these mice, no fatal anthrax follows. 

 Guinea-pigs, very susceptible to diphtheria, when infected with 

 virulent culture of the diphtheria bacilli, die in the course of a day 

 or two, but rats are little or not at all susceptible to the diphtheria 

 bacilli ; and therefore if the guinea-pigs, after infection with the 

 diphtheria bacilli, are injected with rat's blood they recover, this 

 blood being a powerful destroyer of the diphtheria bacilli. Tetanus 

 is easily communicable to mice, in which it produces fatal tetanus in 



* Ogata and Tasuhara, 'Mitth. der Med. Faculfat d. Kais. Japan Uni- 

 versitat,' Tokio. 



