206 Profs. P. F. Frankland and Marshall Ward. 



the kind of water, the temperature and other external conditions 

 remaining the same. 



He gives examples showing that the increase is most rapid, as a 

 rnle, during the first thirty-six hoars, and then a diminution sets in, 

 day after day, ending in the water containing a smaller number than 

 at first. 



This gradual diminution was not due to mere precipitation, but 

 was, perhaps, in part to be accounted for by the coherence of the 

 germs in clamps, and in part to actual death. 



He then isolated and described sixteen of the commonest species, 

 which were shown to actually grow and multiply in ordinary drinking 

 waters. 



Two of these forms were shown to be capable of easy multiplication 

 in such waters, and that quite independently of the chemical con- 

 stitution of the waters. He found that they flourished in the purest 

 distilled water he could obtain, as well as in "bad" water, and assumes 

 that this is because the very small amount of organic nutriment they 

 demand* is never absent. 



Bolton concluded from his experiments that variations of tem- 

 perature, and in the amount of oxygen dissolved in the water, were 

 far more important factors than the chemicals dissolved in ordinary 

 waters. In this conclusion, however, he is neither supported by his 

 own nor the previous experiments of Leone, for it was found by both 

 that the multiplication was almost equally rapid if a stream of 

 hydrogen or a stream of air was passed through the water. 



He further inferred that, in practice, the accumulation of bacteria 

 in pipe waters is due to the multiplication of forms (carried in by 

 surface drainage in the first instance) in the standing water as the 

 temperature rises. 



He then tried the effects of (1) distilled water, (2) common drink- 

 ing waters, and (3) badly contaminated waters, on specific pathogenic 

 and other bacteria, obtained from pure cultures and added to the 

 waters with as little traces of the culture medium as possible. In 

 many of his experiments, however, he has apparently failed to secure 

 this last-named condition, as in most cases the number of organisms 

 introduced into the particular waters is recorded as " un-countable," 

 thus clearly pointing to insufficient dilution before inoculation. To 

 save repetition it must be mentioned that all of Bolton's experiments 

 were made with waters previously sterilised by heat. 



* It is, however, much to be regretted that in not a single instance is the 

 chemical composition of any of these waters recorded by the author. 



It may be observed here that we cannot accept, without reserve, general statements 

 to the effect that pure water is capable of supporting the life of bacteria. Miquel 

 shows how such water, which may be obtained in quantity by simple condensation 

 (' Analyse Bact. des Eaux,' p. 156), is incapable of supporting bacterial life 

 (pp. 157—158). 



