174 PEACTICAL BOTANY 



159. Watercourses as means of distribution of bacteria of 

 disease. As may be expected, water courses are means of dis- 

 tribution of some kinds of bacteria. To what extent tliis is 

 true for all kinds is not known, but in case of the typhoid 

 bacteria there has been mucli conclusive investigation. The 

 following illustration is one of a number that might be cited. 

 The southern part of New Hampshire and the northern part 

 of Massachusetts are drained by the Merrimac River. In the 

 region thus drained are many industrial cities and towns. In 

 1890—1891 there occurred in this region a great epidemic of 

 typhoid fever. The water of the Merrimac River and its trib- 

 utaries was the means of carrying away the sewage for the 

 entire region, and the cities of Lowell and Lawrence, which 

 took their water supply from this river, took sewage-polluted 

 water. The cities of Concord, Nashua, and Haverhill did not 

 get their water from the Merrimac. The epidemic began ia 

 Lowell, and this was soon followed by a more severe epidemic 

 in the city of Lawrence, situated downstream from Lowell. 

 There is a small stream, Stony Brook, which flows through a 

 suburb of Lowell and empties into the Merrimac three miles 

 above the point at which the Lowell water supply was taken. 

 The first cases of typhoid were along Stony Brook, and these 

 cases polluted the water, thus in turn polluting the supply for 

 the main part of Lowell. Furthermore, the Lowell sewers 

 entered the Merrimac nine miles above the water intake for 

 Lawrence, and thus polluted the water supply so that typhoid 

 fever was well distributed throughout those parts of Lawrence 

 where this water was used. 



The other cities in this same valley had very little typhoid 

 fever, while Lowell and Lawrence suffered many deaths, 

 reaching in twelve months (1890) 187 per 10,000 population 

 in Lawrence and 195.4 per 10,000 population m Lowell. 

 There are many such cases showing the effect of typhoid- 

 polluted water. 



160. Tuberculosis : the great white plague. The disease 

 commonly known as tuberculosis is so generally distributed 



