September 19, 1913] 



SCIENCE 



411 



initial medium, and Endo's agar was used for 

 isolating the members of the B. coli group in pure 

 culture, nearly 100 per cent, successful isolations 

 having been obtained by the use of this medium, 

 whereas the frequent encountering of spreaders on 

 litmus agar and the fact that many of the acid- 

 forming colonies proved not to be members of the 

 colon group seriously impaired the efficiency of 

 this latter medium. No attempt was made until 

 in the last two or three months to differentiate the 

 four members of the colon group; but this is now 

 being done with the use of duleit, in addition to 

 the usual sugars, and morphological examinations, 

 and the results seem to show a greater vulnera- 

 bility of the two B. coli organisms than of B. 

 aerogenes and B. aoidi lactici. The results ob- 

 tained by the use of the 20° temperature show 

 much greater reduction in the bacterial count than 

 those obtained with the 37° temperature, and we 

 believe that counts should be made at the higher 

 temperature in addition to those made at 20°. The 

 effects of the treatment of this water supply have 

 been a very good reduction in the bacterial count 

 of the water as it enters the first storage reser- 

 voir, and almost entire elimination of the members 

 of the B. coli group, the treated water during 

 three months showing none of these organisms at 

 any time in 100 c.c. The reduction in the number 

 of eases of typhoid fever occurring in Baltimore 

 during 1912 is 31 per cent., compared with an 

 average of the number of cases occurring during 

 the years from 1906 to 1910, and 24 per cent., 

 compared with the number of eases occurring dur- 

 ing 1911, in the last six months of which the 

 water supply was treated. We wish to acknowl- 

 edge indebtedness to Mr. Ezra B. Whitman, water 

 engineer, and to Mr. Emory Sudler, engineer in 

 charge of the improvement of the water supply, 

 for an interest unusual with the engineers not 

 directly acquainted with the details of the labora- 

 tory work. 



Experimental Disinfection of Water with Calcium 

 Eypochlorite (preliminary note) : F. W. Hach- 

 TEL, MS)., and Eaymond Freas, A.B., Bac- 

 teriological Laboratory of the State and City 

 Boards of Health, Baltimore, Md. 

 The following brief report is made upon cer- 

 tain experiments that were begun in the midsum- 

 mer of 1911 and which have for their object the 

 determination of the amount of available chlorine 

 necessary to eliminate the B. coli from 10 c.c. of 

 water under varying conditions of turbidity. They 

 were instituted because, although the quantity of 



available chlorine added to the Baltimore drinking 

 water had gradually been increased from 0.4 to 

 0.75 parts to the million gallons, the colon bacillus 

 still persisted with too great frequency in 1 and 

 10 c.c. of water collected at the storage reservoirs 

 and as drawn from the taps. The first series of 

 experiments had to be done in a hurry, as heavy 

 rains on the watershed were markedly increasing 

 the turbidity. At this time, therefore, only pre- 

 sumptive tests in lactose bile were done. This, 

 however, is not a guide to the sanitary condition 

 of water treated with hypochlorite of calcium as 

 shown by some work carried on in the laboratory 

 on samples collected from the taps and storage 

 reservoirs after treatment. As a result of these 

 we found that although they would not infre- 

 quently produce gas in lactose bile, we were un- 

 able to obtain the colon bacillus in pure culture 

 even after repeated platings in lactose-litmus-agar. 

 A number of these were then plated out anaerobie- 

 ally and in a considerable percentage of cases we 

 obtained B. welchii or the B. sporogenes or both. 

 This, therefore, led us to repeat our work, and the 

 results may be summarized as follows: With a 

 turbidity of 32 we have found that 0.75 and 1 

 part of available chlorine to the million gallons 

 caused a bacterial reduction of about 80 and 90 

 per cent., respectively, in six hours. During the 

 same period the bacterial content of the untreated 

 water was doubled. At the end of twenty-four 

 hours, although the untreated water showed a 

 count of 300 times as great as when the experi- 

 ment was started, the two treated waters gave 

 counts of only 0.3 per cent., as great as that of 

 the raw water at the beginning. Again, the water 

 before treatment contained the colon bacillus in 

 1 c.c. but not in 0.1 c.c; at the end of one hour 

 after the addition of calcium hypochlorite in the 

 aforementioned quantities 1 c.c. of the treated 

 water failed to ferment. In addition, although 

 there was gas formation in all the lactose-bile 

 tubes inoculated with 10 c.c. for the first six 

 hours after treatment, nevertheless the colon ba- 

 cillus was not isolated from any of these, though 

 they were plated out on three consecutive days. 

 On the other hand, we were able to obtain B. 

 welchii or B. sporogenes from almost all of them. 

 Four, five, six and twenty-four hours after the 

 addition of hypochlorite 50 c.c. of each of the 

 treated waters were inoculated into large tubes of 

 lactose-bile and although fermentation occurred in 

 all save one, B. coli was not obtained from any 

 of these in spite of repeated attempts. In every 



