302 



Professor J. Burclon Sanderson 



[May 15, 



favour its development. Hitherto the investigation of the latter has 

 been by far the most successful. But it would be a great mistake 

 to allow the apparent failure of such researches as those of Dr. Koch 

 in Egypt and in India to discourage the efforts which are now being 

 made everywhere by earnest and devoted workers to accomplish 

 what has baffled so able an investigator. Whenever the discovery is 

 made, it will not only serve as a key to the understanding of 

 cholera as a disease, and thereby tend to render its treatment a little 

 less hopeless than it is at present, but it will serve as the necessary 

 completion of the knowledge we have gained from the combined 

 experience of the medical profession in India, in Europe, and in 

 America, with reference to the behaviour of cholera as an epidemic 

 disease. To make this clear, all that is necessary is to summarise 

 statements which have been already placed before the reader in the 

 course of this article. What we have learned is that the liability of 

 a locality to cholera depends, first, on the physical characters of the 

 soil; and secondly, on certain changes which it undergoes in the 

 course of the seasons. The peculiarity of the soil which favours 

 cholera is unquestionably want of natural or artificial drainage, con- 

 bined with the presence in the liquid with which it is soaked of such 

 organised material, derived from the tissues of plants or animals, as 

 render it a fit soil for the development and vegetation of microphytes. 

 The seasonal change w^hich favours cholera is that which expresses 

 itself in the drying of such a soil under the influence of summer 

 temperature. In Europe this takes place in July, August, and* 

 September, in which last month, as the following table * strikingly 

 shows, cholera attains its maximum of destructiveness : — 



But be it ever remembered that these two liabilities of time and 

 place do not explain everything. No combination of soil and season, 

 however favourable, will produce a harvest unless the seed has been 

 sown. It holds as true now as it ever did, that " if we possessed 

 the requisite knowledge, the disease could always be traced back in 

 lineal descent to its origin in some poor Hindoo on the banks of the 

 Ganges, as certainly as the pedigree of a horse or dog can be fol- 

 lowed to his remote ancestors." 



* The numbers express the mortality from cholera in Prussia during the 

 thirteen years, 1848-1860. 



