189 L] MICROSCOPICAL JOURNAL. 179 



but unless a suitable lodgment is found for the germs, no disease will 

 be produced by them. From the experiments of a distinguished in- 

 vestigator, it has been shown that the human body has enlisted in its 

 service what may be called a microscopical militia, whose duty it is to 

 ward ort' the assaults of the invading microbes. These militiamen are 

 the lymphatic cells, whose function in part is to swallow or annihilate 

 the hostile bacteria before they enter the blood. Where, of two persons 

 exposed to the same contagion, one escapes and the other falls a victim, 

 the explanation lies wholly in the fact that in the one case the sentries 

 are victorious, while in the other they are defeated in their struggle 

 with the invading bacteria. 



In the language of the " germ theory," certain constituents of the 

 system are exhausted by the infectious germs, and until they are re- 

 stored the body is protected from any further attack of the same disease. 

 To exhaust the system of this nidus, a germ less vigorous and dangerous 

 than the disease-producer will sometimes suffice. If, then, after feebler 

 organism has exhausted the system without fatal results, the virulent 

 germ should find its way into the system, it will be harmless. This 

 is the whole secret of vaccination. 



A very interesting and valuable fact has been brought to light by the 

 experiments of a distinguished European writer, who has shown that 

 sometimes "two micro-organisms, either of which singly is harmful 

 to the human body, may be deadly foes to each other. This was 

 found to be true of the microbes of diphtheria and erysipelas. Of a 

 large number of persons afflicted with diphtheria, all those who were 

 inoculated with erysipelas recovered, while those not so inoculated, 

 died. It was noticed that those who recovered from diphtheria had 

 only a very mild form of erysipelas, as if the microbe peculiar to that 

 disease had been exhausted in the conflict with his diphtheria enemy." 



Each group of pathogenic bacteria seems to have its specific organ 

 for attack. Thus the Bacillus tuberculosis generally has its seat in 

 the lungs ; the typhoid bacillus penetrates the mucuous membrane of 

 the intestines and accumulates in the spleen ; and the micrococcus of 

 diphtheria produces extensive layers of false membranes in the fauces. 

 We are, therefore, to assume that each zymotic disease is accompanied 

 by its specific germ ; and that each germ produces only its own kind. 

 The doctrine that '' like produces like" continues eternally true, but 

 there may be a gradual change produced by a change of environment. 

 If we sow wheat only, we do not reap a crop of oats or barley ; but 

 just as wheat springs from wheat, so each zymotic disease has its ac- 

 companying distinctive germ. And so, if we plant only cholera germs 

 in our system, we do not reap a crop of small-pox or measles, but in- 

 variably a crop of cholera. 



Bacteria have the power of elaborating organic poisons, known as 

 Ptomaines, and the question as to whether zymotic diseases are the di- 

 I'ect result of the action of pathogenic bacteria upon certain organs, or 

 the result of Ptomaines elaborated by them, cannot in the present state 

 of knowledge be answered with certainty. In some cases, however, 

 the disease seems to have come from the organic poison. Tyrotoxicon 

 is the poison produced in the fermentation of milk by the agency of 

 bacteria, and it seems to be the cause of much sickness originating 

 from spoiled milk. It produces a complexus of symptoms in the 



