BACTERIOLOGICAL EXAMINATION OF WATER. 153 



appears probable that the typhoid bacilli get iato the 

 springs directly from the cesspools. Very ofteu too 

 the springs are in a condition which at the least can- 

 not be called clean, and are in addition frequently 

 situated very near to the privy. Small crevices in 

 the soil, holes caused by mice, rats, or even by 

 earthworms, are sufficient to establish a communica- 

 tion, or we may find that the cesspools are too shal- 

 low, or so badly constructed, that they overflow during 

 heavy rains, so that some of the fluid enters into the 

 spring, an accident which unfortunately occurs only 

 too frequently. Under any of these conditions, of 

 course, if typhoid bacilli are present in the cess- 

 pool, they also enter the spring, and thus the one case 

 of the disease can give rise to a number of others. 



It is clear from former statements that the presence 

 of the typhoid bacillus in the water cannot be de- 

 tected in the majority of cases. But the bacteriolo- 

 gical examination of the water enables us to ascertain 

 with some degree of certainty whether such a com- 

 munication as described above has taken place, and 

 hence, whether it is possible for typhoid bacilli to get 

 into the water or not. If there is such a communi- 

 cation, a great number of other kinds of bacteria are 

 to be found in the water^ which have come from the 

 cesspools or privies, and which can be easily recog- 

 nised by their power of decomposing albumen and 

 of energetically liquefying the gelatine of the culture- 



