1 88 GENERAL BIOLOGY OF MICRO-ORGANISMS 



no pathogenic bacteria are found, cannot be taken as proof that 

 the water-supply under examination may not be contaminated 

 at times. Flugge 1 has shown that the chemical examination 

 of itself also permits of no definite conclusion 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 exami- 

 nations of water unaccompanied by a sanitary inspection. In 

 fact, many of those who have made disinterested study of the 

 subject are inclined to question the value of the ordinary chemical 

 and bacteriological water analysis in toto, and in view of the 

 arbitrary and mechanical 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 intelligent consideration of all the conditions 

 entering into the case, but no hard and fast rules can be 

 applied. 



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, Sedgwick 

 and Winslow have stated that when typhoid bacilli are frozen 

 in water the majority of them are destroyed. 3 Nevertheless, 

 it is as necessary to have the source from which ice is taken as 

 carefully scrutinized as that of the water-supply, especially in 

 view of the universal habit of cooling water in the summer time 

 by adding ice directly to the water. It is better to cool water 

 and articles of food by surrounding with ice the vessels containing 

 them. 



1 Flugge: Zeitschrift fur Hygiene, Bd. XXII, 1896, pp. 445 et seq : 



2 Bolton: Sanitary Water Supplies for Dairy Farms. Public Health and 

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



3 Clark. Bacterial Purification of matter by Freezing. Reports American 

 Public Health Association, Vol. XXVII. See also Hutchings and Wheeler: Ameri- 

 can Journal Medical Sciences, Vol. CXXVI, p. 680. 



