Report on the Bacteriology of Water. 



187 



long period of time, in some cases several months, whilst other forms, 

 especially in the absence of spores, are very rapidly destroyed. In 

 some instances actual multiplication, although but rarely on any very 

 extensive scale, has been observed in the case of some pathogenic 

 forms in potable water, and more frequently in badly contaminated 

 waters and in sewage. In those cases in which pathogenic forms have 

 been introduced into waters in their natural condition, the destruction 

 of these forms has almost invariably been more rapid, and in some 

 cases very much more rapid, than when the same forms were introduced 

 into the same waters after the latter had been previously sterilised. 

 This more rapid disappearance of the pathogenic forms in the un- 

 sterilised water is generally accounted for by assuming that they have 

 perished in the struggle for existence with the other microbes present 

 in the water, and which by their nature and previous history are more 

 fitted for this aquatic existence. "We are of opinion that these 

 results with unsterilised water must be accepted with considerable 

 caution, as the experimental difficulties involved are very great 

 indeed, and the possibility of the comparatively few pathogenic forms 

 being undiscovered amidst the countless swarms of water organisms 

 must be borne in mind. 



Having thus given a general survey of the present position of our 

 knowledge concerning the bacteriology of water, we shall now 

 proceed to enter into each of the questions involved in more detail, 

 giving special attention to the existing literature on the several parts 

 of our subject. 



In view 'of the fact that the introduction of Koch's methods, in 

 1881, thus revolutionised the subject of hygiene, we naturally com- 

 mence our review of the literature at the period just previous to and 

 after the above date. There are, in fact, practically no investigations 

 on the more special part of our subject anterior to this date. 



Most of the more systematic work has been done on the Continent, 

 and, at first, especially in the public laboratories of Germany, where 

 the new methods were at once applied industriously to the examina- 

 tion of the bacteria in the air, the soil, food stuffs, water, &c. 



A number of French enquirers also arose, though it is significant that 

 Koch's gelatine-plate method to this day has not found much favour 

 in one of the oldest and best of the French stations, the Observatoire 

 de Montsouris, whence excellent work has come* England, Italy, 

 America, and other countries soon followed ; but, although a number 

 of exceedingly valuable memoirs on special questions relating to the 

 general subject were published at an early date in this country and 

 in France, it is still noticeable that most of the prolonged and sys- 

 tematic investigations of the bacterial life to be found in the waters 



* See ' Annuaire de 1' Observatoire de Montsouris,' 1877 to 1891, and Miquel, 

 1 Manuel Pratique d' Analyse Eacteriologique des Eaux,' Paris, 1891. 



