130 THE MICHIGAN ACADEMY OF SCIENCE. 



It may be said, however, that the greater part of them fall into either 

 the proteus or the colon group. 



The bacterial count of the sewage showed that approximately 56,000 

 organisms per cubic centimeter developed at room temperature, and 

 about 36,000 per cubic centimeter at thirty-seven degrees C. It will 

 thus be seen that about 20,000 bacteria per cubic centimeter could not 

 withstand the temperature of body heat. 



Experiment II. (a) Cultures made from heart's blood of the guinea- 

 pig which died within eighteen hours after an intraperitoneal injection 

 of a beef-tea culture of the uncontaminated sewage. The organisms 

 recovered belong either to the proteus or colon groups. None resem- 

 bling the typhoid bacillus were detected. 



(&) Cultures made from the heart's blood of the guinea-pig which 

 received the injection of experimental sewage. Organisms were recov- 

 ered morphologically, resembling and having cultural properties indica- 

 tive of the typhoid bacillus. 



Experiment III. Experimental sewage diluted 1 : 20 and subjected 

 to aeration. Samples taken at intervals of two hours, etc. Organisms 

 morphologically and culturally resembling typhoid were obtained from 

 most of the samples, particularly after twelve, twenty-seven and thirty- 

 three hours. 



Experiment IV. Undiluted experimental sewage aerated. Eesults 

 similar to the preceding experiment were obtained. 



Experiment V. Experimental sewage exposed to sunlight. Germs 

 having morphological and cultural properties similar to those of the 

 typhoid bacillus were obtained after an exposure of ten days. It should 

 be stated, however, that these experiments were conducted during the 

 month of March when the actinic properties of the sun's rays are not 

 nearly so active as they are when the sun is higher in the heavens, or 

 during summer months. This undoubtedly explains the long survival of 

 the typhoid organisms in this experiment. 



Conclusions. The results of this study, thus far, indicate that the 

 typhoid bacilli are not totally destroyed in sewage, (1) by sunlight for 

 several days, at those periods of the year when the rays are not so 

 chemically active, (2) or by dilution, (3) or aeration, (4) or by the 

 combination of these factors up to thirty-three hours. It is probable, 

 however, that they are lessened in numbers, as the work of other investi- 

 gators has shown. To ascertain if this be true, and to what extent, 

 the writer has under way a series of experiments. 

 John Ralston Williams^ M. D., 



From Hygienic Laboratory, University of Michigan, 

 Ann Arbor, Mich. 



