702 



ACUTE INFECTIOUS DISEASES. 



When cholera has been introduced into a place, it sometimes hap- 

 pens that only those persons are attacked who live in the same house, 

 or use the same privy. It has even been observed that, in certain 

 cities where cholera has been repeatedly introduced, it has always 

 been limited to these house epidemics. But, in other cases, the dis- 

 ease spreads from the house where it was introduced, to neighboring 

 streets, large portions of the city, or even over the whole vicinity. 

 This may either happen every time the cholera visits the place, or only 

 in certain epidemics, while in others this extension does not occur. 

 We are indebted to Pettenkofer for the discovery that porosity of the 

 soil, enabling the contents of the privies and cess-pools containing the 

 cholera germs to freely permeate and soak the ground for some dis- 

 tance around with this dangerous mixture, favors the rapid extension 

 of the disease, while the opposite quality to some extent protects from 

 such an extension. We are also indebted to Pettenkofer for the dis- 

 covery that the occasional predisposition of a place to an extension of 

 cholera depends on the excrements containing the germs, and per- 

 meating the soil, being exposed to circumstances favorable to decom- 

 position. As we have already shown, when speaking of the etiology 

 of typhus, moisture of the soil plays a very important part among 

 these circumstances, but it is not the only one. There is no doubt 

 that the conditions for decomposition may be peculiarly favorable 

 when a very moist soil suddenly dries to a certain extent ; and it can- 

 not be denied that the sudden fall of the water of the soil may prove 

 very dangerous for the spread of cholera. The opposing facts, which 

 have also been proved, show that the number of cholera cases may in- 

 crease independently of the sudden fall of the water in the soil, and 

 that it is one-sided to regard the fall of the water as the sole cause for 

 favoring decomposition of the excretory matters, mingled with cholera 

 germs, which have soaked through the soil. 



The cholera poison is rarely taken into the system by drinking 

 water containing it. As a rule, it undoubtedly enters the nose and 

 mouth with the air, and is swallowed with the saliva. Using infected 

 privies is so dangerous, because they are the favorite lurking-places 

 for cholera germs, and the gases arising always contain dust-like par- 

 ticles. The poison passes from the privy into the atmosphere of the 

 house, and we must agree with Jliermer in considering the dwellings 

 as more liable than the inhabitants to infect. Next to the soaking of 

 tne infecting substance through the soil, the disease appears to spread 

 from one house to another, chiefly through the gutters and drains. 



The susceptibility to cholera pcison is very extensive. No age, 

 Bex, or constitution, escapes it. When the cholera poison spreads over 

 the whole city, almost every one suffers from it ; even those not af 



