BACTERIA IN WATER. 647 



present in a living condition on the second day, but no colonies de- 

 veloped after the third day ; the typhoid bacillus died out between 

 the fifth and seventh days ; the cholera spirillum was no longer found 

 on the second day. In the meantime the common water bacteria 

 had increased in numbers enormously. Similar results have been 

 reported by Hochstetter and others. Hueppe, in ten experiments in 

 which the typhoid bacillus was added to well water of a bad quality, 

 found that in two no development of this bacillus occurred after the 

 fifth day, while a few colonies developed in the other experiments as 

 late as the tenth day. In these experiments the temperature was 

 comparatively low (10.5 0.). At a higher temperature the experi- 

 ments of Wolffhugel and Biedel show that an increase may take 

 place. At the room temperature (about 20 C. ) the typhoid bacillus 

 added to distilled water, to well water, and to Berlin hydrant water 

 was still present, in some instances, at the end of thirty-two days. 

 And it was found that in some cases a decrease in the number 

 occurred, then a notable increase, and finally a second diminution. 



Koch found the cholera spirillum in a water tank at Calcutta 

 during a period of fourteen days, and in his experiments showed that 

 it preserved its vitality in well water for thirty days, in Berlin sewer 

 water for six to seven days, and in the same mixed with faeces for 

 twenty-seven hours only. In the experiments of Nicati and Rietsch 

 the cholera spirillum preserved its vitality in distilled water for 

 twenty days, in sewer water (of Marseilles) thirty-eight days, in 

 water of the harbor for eighty-one days. The numerous experiments 

 recorded by the observers named, and by Bolton, Hueppe, Hoch- 

 stetter, Maschek, Kraus, and others, show that while the cholera 

 spirillum may sometimes quickly die out in distilled water, in , other 

 experiments it preserves its vitality for several weeks (Maschek), and 

 that it lives still longer in water of bad quality, such as is found in 

 sewers, harbors, etc. Bolton found that for its multiplication a 

 water should contain at least 40 parts in 100,000 of organic material, 

 while the typhoid bacillus grew when the proportion was considerably 

 less than this 6.7 parts in 100,000. 



Russell (1891) has studied the bacterial flora of the Gulf of 

 Naples, and of the mud at the bottom of this gulf, collected at 

 various depths up to eleven hundred metres. His investigations 

 show that sea water does not contain as many bacteria as an 

 equal volume of fresh water; that bacteria are found in about 

 equal numbers in water from the surface and in that from various 

 depths ; that the mud at the bottom constantly contains large num- 

 bers of bacteria ; that some of the species isolated grow best in a 

 culture medium containing sea water. 



At a depth of 50 metres the water contained 121 bacteria per cubic 



