INFECTIOUS DISEASES. 299 



would require far more space than is available at present. It prevails 

 as an endemic disease in all the inhabited parts of Europe, Asia, and 

 America, and the occurrence of epidemic outbreaks depends largely 

 upon an unusual degree of contamination of the water supply of a 

 community by the discharges of those sick with the disease. It 

 may prevail at any season, but as a rule the autumn months afford 

 more cases than occur at other seasons of the year. It is more preva- 

 lent in the temperate zone than in the tropics, but in the Orient it 

 claims many victims in tropical regions, and especially in the densely 

 populated portions of India. 



Extended experience gained in this country and in Europe shows 

 that the relation of this disease to local insanitary conditions is very 

 marked, and that the typhoid mortality rate is a good index of the 

 general hygienic conditions of a town or city, especially as regards 

 purity of water supply and efficiency of sewage disposal. 



Asiatic cholera is a fatal pestilential disease which has its perma- 

 nent habitat in India, and which during the present century has 

 repeatedly invaded the countries of Europe, and has even crossed the 

 Atlantic and prevailed as an epidemic in certain portions of the 

 western hemisphere. In India it has, no doubt, prevailed from a 

 remote period, and its chief endemic seat in that country appears to 

 be in lower Bengal. The deaths from cholera in the various prov- 

 inces of India during the five years from 1871 to 1875 amounted to 

 more than seven hundred and fifty thousand. 



As regards its epidemic extension to the countries of Europe, 

 cholera is a disease of the present century. The first great epidemic 

 dates from the year 1817, and the disease did not disappear from 

 European soil until 1823. A second period of prevalence in Europe 

 lasted from 1826 to 1837, a third from 1846 to 1863, a fourth from 

 1865 to 1875, and the fifth and last from 1892 to the present date. 

 The time at my disposal will not permit me to trace the origin and 

 progress of these epidemics; but the general statement may be 

 made that they had their origin in India, and that the progress of the 

 disease was along routes of travel, showing that its propagation de- 

 pends upon human intercourse. Since the discovery of the cholera 

 spirillum by Koch, in 1884, the method in which the disease is spread 

 has been established in a most satisfactory manner. We now know 

 that the germs of the disease are found in immense numbers in the 

 intestine of cholera patients, and even in individuals who have been 

 exposed to infection, but who manifest no symptoms of the disease 

 other than a slight diarrhoea. Such persons sow cholera seed with 

 the discharges from their bowels, and under favorable conditions 

 rapid multiplication of the germ occurs outside of the body. In- 

 fection usually occurs by the ingestion of water or food contami- 



