298 Professor J. Burdon Sanderson [May 15, 



dies, proceeds pari passu with the development of the disease-pro- 

 ducing organism x ; for in the hours, be they few or many, which 

 intervene between the sowing of the seed in the body of a living 

 animal and the maturation of the harvest — that is, between inocula- 

 tion and death — the whole of the living body of the affected animal 

 becomes so thoroughly infested that in many instances no fragment 

 of tissue, no single drop of circulating blood, can be found which 

 does not contain thousands and tens of thousands of the character- 

 istic rods (or bacilli), each of which individually is capable of com- 

 municating the disease if sown into the body of a healthy animal. 

 So also in another well-investigated instance, that of relapsing fever, 

 we have evidence that the multiplication of x takes place in the cir- 

 culation, and that the presence there of the characteristic spirilla is 

 so associated with the appearance of the fever itself, that the one 

 never manifests itself without the other having preceded it. 



But as regards cholera, nothing of the kind can be observed. As 

 yet no one has been able to find the organism, either in the blood 

 or in any living tissue, notwithstanding that the research has been 

 conducted with every possible care. Nor has it been found either 

 that the bodies of persons affected with cholera, or that any part of 

 them, possessed the power of infecting other healthy persons. Con- 

 sequently the opinion first arrived at and formulated by Professor 

 Pettenkofer has come to be very generally adopted — that in cholera 

 the multiplication of x takes place, not in the tissues of the sick 

 person, but in his environment. Let us examine a little more closely 

 what this means. 



Under the term environment is included everything which is in 

 relation with the external surface of the body, including the air we 

 breathe and the water and other material which we use as food. 

 And inasmuch as no multiplication can take place otherwise than in 

 a suitable soil consisting of organic matter, and no such soil exists in 

 the air, we may limit the possible seats of multiplication to tbe 

 moist organic substances of various kinds which exist at or near the 

 surface of the earth. Putting this into plainer language, it means 

 that when the cholera x invades a previously uninfected locality in 

 which it is about to become epidemic, the first thing it does is not to 

 find a home for itself (as the x of smallpox, of cattle-plague, or of 

 splenic fever w^ould do) in the body of some healthy j)erson, but to 

 sow itself in ivliatever material at or near the surface is Jit for its 

 reception and vegetation. 



Now, in our study of the laws of diffusion of cholera we have seen 

 that, although cholera may be repeatedly introduced by personal 

 intercourse into an uninfected locality without result, it finally, after 

 a shorter or longer latency, bears fruit ; and this we exjslain on the 

 hypothesis that, of the two conditions which are essential to the 

 fructification of the germ — namely, the presence of the organism 

 itself, and the presence of a soil suitable for its growth, the latter is 

 of more importance than the former ; that, in short, the reason why 



