384 



H. M. Vernon 



Thiis it drives off a good deal of the dissolved gases, but also removes 

 some of the ammonia present. For instance, the water used in Exp. 102 

 coDtained 36^ less free, and 1% less organic ammonia, than the 

 normal water. 



These results lead one to conclude either that a temperature of 

 50° is almost as fatal to those bacteria in the water which exert 

 an injurious action on larvai growth as a temperature of 100° or 

 that the favourable eflfect produced by heating the water is due 

 rather to the removal of the small amouut of animai and higher 

 vegetable life present, to which, rather than to the bacteria, the 

 harmful effects are accountable. As to the actual germicidal eflfects 

 of heating the water, the observations of Miquel>, made of course 

 with fresh water bacteria, may be cited. Thus in one case, after 

 heating to 50" for about half an hour, there were killed some 84^ 

 of the germs: after heating to 80° ^1 % , and to 100°, 99.4^. 



Bacteriological examination of the water used in Expts. 102, 103 

 and 104, gave the follo wing results. 



From this table we see that, previous to the introduction of the 

 fertilised ova, the water heated to 100° already contained more 

 bacteria than the normal, whilst the specimens heated to 76° and 

 50° contained considerably less. This unexpected result must bave 

 been due to the rapid multiplication of the bacteria in the water 

 during the 24 hours previous to the introduction of the ova. Thus 

 the jars into which the water was poured after heating were un- 

 sterilised, and had recently been washed out with sea-water, whence 

 the rapidly multiplying bacteria may bave arisen. Doubtless also 

 some of them came from the spores and bacteria unharmed by the 

 heating. After the fertilised ova had been developing two days, the 

 water heated to 76° was found to contain considerably more bacteria 



1 La Semaine Medicale, 31 Juillet, 1884. 



