148 MANUAL OF JBACTERIOLOGY. 



at times.* Fliiggef has shown that the chemical examination 

 also permits of no conclusion of itself as to the potability of water 

 It would seem that those best suited by training and experience 

 and who are capable of forming disinterested opinion attach 

 but limited importance to the result of laboratory examinations 

 of water unaccompanied by a sanitary inspection. Opinions 

 based upon analyses of water shipped to a chemical or bacterio- 

 logical laboratory should be taken with reserve. In fact, many 

 of those who have made disinterested study of the subject are 

 inclined to question the value of chemical and bacteriological 

 water analysis in toto, and in view of the arbitrary and mechani- 

 cal manner in which the results of these analyses- are sometimes 

 interpreted, this attitude is justified. It would seem, however, 

 that after the establishment of normal, standards for a given 

 locality, such analyses are useful if they are checked by intelli- 

 gent consideration of all the conditions entering into the case, 

 but no hard and fast rules can be applied. J 



Ice. — The bacteriological examination of ice differs in no 

 respect from that of water. Although development may be 

 arrested, the vitality of bacteria is not necessarily impaired by 

 freezing. Prudden found the bacillus of typhoid fever alive 

 in ice after more than one hundred days. However, Sedg- 

 wick and Winslow have stated that when typhoid bacilli are 

 frozen in water the majority of them are destroyed. § Never- 

 theless, it is as necessary to have the source from which ice is 

 taken as carefully scrutinized as that of the water-supply, es- 

 pecially in view of the universal habit of cooling water in the 

 summer time by adding ice directly to the water. It is better 



*Gunther loc. cit. 283. 



jFlugge. Zeitschrift jiir Hygiene. Bd. 22, 1896, pp. 445 et seq 



J Bolton. Sanitary Water Supplies for Dairy Farms. Public Health and 

 Manne Hospital Service. Bulletin 41, February, 1908, p. 534. 



§Clark. Bacterial Purification of mater by Freezing. Reoorts AmenVan 

 Public Health Association. Vol. XXVH. See also Hutchingrand Wheder " 

 American Journal Medical Sciences. Vol. CXXVI., p. 6S0 



