Apbii, 8, 1910] 



SCIENCE 



549 



if its presence is noted either on the plates or on 

 the agar streaks, this is recorded. 



Interpretation. — Tests of a single shellfish from 

 any location have little diagnostic value. When 

 a suiBcient number of shellfish have been tested, 

 the absence of B. eoli, or of positive fermentations 

 followed by an overgrowth of sewage streptococ- 

 cus in 80 per cent, of the samples tested, indicates 

 that the location is reasonably free from pollu- 

 tion. If 50 per cent, or more of shellfish from a 

 location show B. coli, or fermentation overgrown 

 by sewage streptococcus, the location is danger- 

 ously polluted. Between these limits, the inter- 

 pretation is a question of degree of pollution, 

 based on individual judgment, into which analyses 

 of the sea water from the same source, and a 

 sanitary inspection of the source must enter. 



Some Peculiarities in the Counts of Ba^iteria at 

 20° C. and at 40° C. from Waters Treated loith 

 Disinfectants: Stephen DeM. Gage, Massachu- 

 setts State Board of Health, Experiment Sta- 

 tion, Lawrence, Mass. 



For some years we have been making counts of 

 the bacteria at 40° C. in addition to the usual 

 count at 20° C, and have found that with natural 

 waters and the effluents from good water filters 

 there is an approximately constant ratio between 

 the counts at the two temperatures. For example, 

 eflluents from good water filters, and surface and 

 ground waters used as public water supplies in 

 Massachusetts, usually contain less than 100 bac- 

 teria per cubic centimeter according to the 20° C, 

 less than 10 per cubic centimeter, as shown by the 

 40° count, and about half of the latter will pro- 

 duce red colonies on litmus lactose agar. 



When dealing with waters, etc., which have been 

 treated with certain disinfectants such as bleach- 

 ing powder, whose efiiciency is produced by oxida- 

 tion, we have frequently found that while the 

 numbers of bacteria determined at 20° C. might 

 be reduced to less than 100 per cubic centimeter 

 by a small amount of disinfectant, frequently 

 there would be no corresponding decrease in the 

 40° count, and that considerably more disinfectant 

 must be used to make the 40° count conform to 

 the standard of the good waters, as previously 

 stated. 



Furthermore, in a great many instances the 

 40° count on disinfected waters was as high or 

 higher than the 20° count. This phenomenon has 

 occasionally been observed with natural waters 

 and sewages, but an analysis of the records of 

 many thousand samples shows that the percentage 

 of such samples is not over five per cent. On the 



other hand, 20 to 25 per cent, of samples of water 

 and 50 to 70 per cent, of samples of sewage and 

 effluents from contact and trickling filters, after 

 treatment with bleaching powder, showed higher 

 counts at 40° than at 20° C. This abnormally 

 high 40° count is seldom found when the 20° 

 count is high, but when the latter count is below 

 100, these peculiar results are frequent. 



These abnormal ratios with disinfected waters 

 are not peculiar to Massachusetts, but have also 

 been noticed elsewhere where bleach disinfection 

 has been tried. In many instances, however, such 

 results appeared to be so erratic that they were 

 considered to be abnormal and were thrown out, 

 and we so considered them at first. When we 

 found that they occurred with a frequency of 20 

 to 70 per cent., however, we did not feel justified 

 in calling them abnormal or in throwing them out. 

 It can be stated definitely that this phenomenon 

 of abnormal ratios is not due to spores. A care- 

 ful study of this point has been made, and the 

 ratio between total colonies and spore formers at 

 both 20° and 40° has been proved to be practically 

 the same before and after disinfection. 

 Diphtheria Bacillus Carriers in the Puilio 

 Schools: F. H. Slack, B. L. Aems, E. M. Wade 

 and W. S. Blanchabd, of the Bacteriological 

 Laboratory of the Boston Board of Health. 

 This paper presents the details and results of 

 an experiment undertaken at the beginning of the 

 school year in the Brighton District of Boston, 

 Mass. 



The pupils in this district number over 4,000 

 and two cultures were taken from each during 

 two successive weeks. All microscopic examina- 

 tions were made in the bacteriological laboratory 

 of the Boston Board of Health by the regular 

 corps of workers. 



Positive results were reported only on those 

 cultures showing the A, C or D types of organ- 

 isms (Wesbrook). 



On the first day, 1,287 cultures were examined; 

 the second, 1,131; the third, 1,029; the fourth, 

 699— a total of 4,146, and of these 55 or 1.33 per 

 cent, were positive. 



These cases were for the most part removed 

 from school. 



The second round the following week gave 1,275 

 cultures the first day; 1,113 the second; 1,029 

 the third, and 670 the fourth — a total of 4,081, 

 of which 38, or .93 per cent., were positive. 



Details concerning these cases and a five-year 

 chart of clinical cases in the district are given. 

 The following conclusions are reached: 



