PART I.J His Belief that the Cholera-germ Develops in the Soil. 43 



Again, heavy falls of rain on distant hills may affect the level of the water in the 

 plains, should an impermeable stratum extend from the one to the other, over which 

 water might flow. These and many other such facts connected with the geology and 

 the topography of a place must be carefully considered before any opinion can be 

 formed of the correctness of the views advanced by this distinguished professor. 



It will be seen from the foregoing that the poison is considered not to develop 

 in water, which is contrary to the commonly received opinion, nor does it 

 multiply to an appreciable extent in the intestinal canal, the human body being 

 merely the stage upon which this actor plays its part. The poison requires a special 

 nidus in which to multiply and to develop into infecting matter. This Pettenkofer 

 traces to the soil, especially to alluvial soil, which, being so exceedingly porous, 

 allows free interchange between the air in its interstices and the air above, as well 

 as being subject to a great variation in the amount of water which it contains. 



Whilst marking out on a map the places suffering from cholera, he was 

 particularly struck with the predisposition it semed to manifest for following the 

 natural water-courses of the country, rather than the usual routes of traffic. In the 

 former, the places of attack were pretty regularly situated, whilst along the roads 

 for intercommunication, the affected places show great irregularity, cholera spreading 

 only in those parts in which the soil was of an alluvial nature, although quite as 

 many opportunities existed for the dissemination of the poison by means of intercourse 

 in the places never attacked as in the less fortunate localities. 



The cholera-germ, as described by Pettenkofer, may be defined as a specific 

 leaven, requiring earth, consisting of organic matter and salts, with a certain amount 

 of water for its development to infectious matter, just as other ferments require certain 

 special substrata and moisture before it manifests its action. If ordinary leaven be 

 added to sand no action takes place ; if it be added to dry flour, it does not spread 

 beyond the immediate vicinity in which it was placed ; but if the flour be moistened 

 ' the little leaven leaveneth the whole." 



The question naturally occurs — By what means does it get into the human body 

 after being thus developed in the earth? To this Pettenkofer replies: There are 

 two ways by which substances may arise from the ground, even from a great 

 depth : — 



By means of (1) the water, and by means of (2) the air contained in its 

 interstices. 



Numerous illustrations may be produced of the possibility of substances, perceptible 

 to the olfactory nerve, making their way upwards from considerable depths, such as 

 when a sewer bursts, or an escape occurs in a gaspipe. Frequently this fact is not 

 observed where the mischief has taken place, but in' a house, perhaps, some distance 

 from it, the warmth of which, should it not stand on an impervious layer, attracts 

 the disengaged matter like a chimney, and the house acts as an escape-pipe for a 

 noxious gas. Were it ever conclusively shown that cholera depended upon some 



