ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 455 



favourable. Cholera bacilli in unsterilized water were found to disappear in 

 a few days, but in sterilized water an initial diminution was followed by a 

 copious increase. The authors also noted that typhoid and cholera bacilli 

 were capable of luxuriant growth in milk. 



The method adopted was more minute and fractional than that of Bolton. 

 Inoculations were at first made with platinum wire, and afterwards by means 

 of a capillary pipette, divided into 1/500 cc. If after using 1/500 cc. too 

 many germs appeared on the plate, 5/500 cc. of the infected water was 

 diluted with 200 cc. of sterilized distilled water, and then 5/500 cc. of this 

 fluid used, so that only 5/100,000 cc. of the germ water were sown. 



Bacteriological Examinatioii of Water.* — ^Dr. O. Katz examined the 

 tap-water of Sydney by means of Koch's gelatin plate method. Tbe five 

 forms noted are described as Bacterium A, B, C, D, and E. The appearance 

 of the colonies on gelatin plate, in test-tube of gelatin, and on oblique 

 surface of agar-agar, is described and figured. The author notes the 

 greater number of bacteria in the water after rain. 



Bacteria in Ice.f — Dr. T. M. Prudden in a series of thirty-two analyses 

 of Croton water found the lowest number of living bacteria to be 57 per 

 cm., the highest 1950 ; the average 243. His experiments to test the effects 

 of freezing on bacteria, showed that after prolonged freezing a considerable 

 number of the typhoid bacilli remained alive. His method was as follows. 

 Into sterilized test-tubes was put sterilized water mixed with a small quantity 

 of a pure cultivation, the number of bacteria in one cubic centimetre of water 

 having been previously determined. The tubes were then heated to from 

 14°-30° F. Six species of bacteria were experimented on. (1) Bacillus 

 prodigiosus ; (2) a short bacillus found in Hudson river water ; (3) a 

 slender bacillus common in Croton water; (4) Staphylococcus pyogenes 

 aureus ; (5) a short bacillus from ice, which is called " a fluorescent bacil 

 lus " from its appearance in gelatin ; (6) typhoid bacillus. In the case of 

 JS. prodigiosus, 6300 in a c.cm. before freezing diminished in four days after 

 freezing to 2970 ; in 37 days to 22, and in 51 days to none. Staphylococcus, 

 which were countless before, diminished after freezing for 18 days to 

 224,598, to 49,280 in 66 days. The number of typhoid bacilli, countless 

 before freezing, was 1,019,403 after 11 days, 336,457 in 27 days, 89,796 in 

 42, and 7348 in 103 days. 



The general conclusions at which Dr. Prudden arrived, are that analysis 

 of water and ice gives evidence of bacteria, many of which are the origina- 

 tors of disease, but the study is too much in its infancy for a definite 

 opinion to be given as to whether the ice or water be suitable or not for 

 drinking purposes, &c. ; that the freezing process only partially purifies, the 

 grosser impurities only being removed, and the bacteria remaining to a con- 

 siderable extent unaffected ; that the different species of bacteria show dif- 

 ferent degrees of vulnerability to cold, the bacilli of enteric fever and the 

 bacteria of suppuration being capable of standing prolonged exposure to a 

 low temperature ; that in natural waters there may be a purification up to 

 90 per cent. ; that while filtration destroys noxious and harmless bacteria 

 to an equal extent, the freezing process is more destructive to innocuous 

 than to pathogenic organisms ; that there is a much greater number of 

 bacteria in snow-ice and in bubbly ice than in transparent ice, which if 

 taken from certain lakes and ponds is very pure ; that the average number of 

 bacteria in ice from all sources is much greater than the standard for 

 ordinary water. 



* Proc. Lirni. Soc. N. S. Wales, i. (1886) pp. 907-23 (2 pis.), 

 t Med. Eecord, 1887, March 26 and April 2, 61 pp. 



