420 MEMOIES OE THE NATIONAL ACADE.AIY OF SCIENCES. 



ill structure; but fur tLe present it seems best to accept the liacteriologist's point of view ni order 

 tliiit dilfereut observers may know wlietlier or not they are dealiiiy- witli the same ori;anisuis, in 

 experiiiieiiting- upon tlie conditions of culture media, temperature, etc., which produce variations in 

 tlie morphology or iu the products. In obtaining "pure cultures" — that is, in obtaining from a 

 sample of water containing' several different kinds of organisms a series of cultures each of wliicli 

 contains but one kind — changes in the nutritive material, in the temperature, iu exposure to light, 

 etc., may pi'oduce quite different results, and hence descriptions based on the results obtained by 

 the older and more simple methods are now found to be quite insufficient for purposes of identifi- 

 cation, and there is a vast amount of work to be done over again. 



In the hope of obtaining a useful contribution to this work, I suggested to Dr. J. H. Wright, 

 on his appointment to a fellowship in connection with the Laboratory of Hygiene of the University 

 of Pennsylvania, nnder my direction, that he should devote special attention to the chemistry and 

 bacteriology of the water supply of the city of Philadelpliia during his term of duty in the labora- 

 tory, and the result of this, covering a period of eigiit months iu 18'J2-03, is herewith presented. 



Dr. Wright found that the water supply of Philadelphia, from both the Delaware and 

 Schuylkill, was impure, which was well known before; but it did not appear to be markedly 

 impure as compared with the water supplies of some other large cities, and in his nnmeious tests 

 he found no distinctly pathogenic organisms, such as the bacillus of typhoid, nor any which 

 indicated excremeutal pollution, such as the bacterium coli. There is no doubt, however, that 

 these organisms were ]}resent, at times at least, in the waters which he examined; but the method 

 which he used of testing a drop or two from a sample would rarely detect these organisms if 

 there were but three or four in half a ])int of the fluid. Iu February and March of 1894 Dr. 

 Olmstead, assistant in bacteriology in the Laboratory of Hygiene, at my re<|uest made a number 

 of examinations of the Schuylkill water by taking 80 cc. in each sample, and after adding 20 cc. 

 of sterilized alkaline sugar bouillon of four times the ordinary strength, placing the mixture 

 immediately iu a thermostat and keeping it at a temperature of 37° C. for twenty-four hours. 

 This kills or prevents the growth of the ordinary water bacteria, and, as a lule, the bouillon thus 

 treated was found to coutaiu a luxuriant growth of but one organism^ — the bacterium coli— so far as 

 could be determined. He also used the fermentation-tube method of Dr. Theobald Smith, with the 

 same results. This colon bacillus is a constant inhabitant of the intestines of man and of domestic 

 animals, where it ordinarily i^roduces no ill effects, and probably aids somewhat in the digestive 

 process by decomposing certain coustituents of the food into more easily absorbable substances. 

 Under certain circumstances, of which we know little, it passes from the intestinal tract into the 

 organs and cavities of the body of the living animal, producing intiammatiou and suppuration, 

 and, after the death of the animal, especially in warm climates, it may invade the tissues and 

 organs, taking part in the complex process known as putrefaction. Either there are several 

 closely allied species or else it varies considerably in the kind of growth it produces in different 

 culture media, in its motility, in its effects as a ferment, and upon the casein of milk, etc. 

 Whether it grows and tiouri.shes to any considerable extent outside the animal body and its 

 discharges is uncertain; but its presence in a water supply is usually considered to indicate f;ecal 

 contamination. It is evident, however, that it does not necessarily indicate human ftecal 

 contamination, since it may come from manured lands and from the excreta of hogs, cows, etc., 

 from which no stream in a cultivated country is free. 



The morphology of the colon bacillus is in many respects similar to that of the typhoid 

 bacillus; the individual rods are about the same shape and size, often varying considerably in 

 length; both are aerobic, facultative anaerobic, and nonliquefying: tlie typhoid bacillus is motile; 

 the colon bacillus is sometimes motile and sometimes not; neither is known to form spores. They 

 grow at ordinary room temperatures, but flourish best at the temperature of the human body, 37c> 

 to 38° C. Attempts to find them by cultures inoculated with water at ordinary temperatures are 

 usually unsuccessful, because many of the water bacteria which flourish at such temperatures 

 liquefy the gelatin and make it impossible to identify the luniliquefying, slower-growing colonies 

 of the typhoid and colon bacilli. 



In this connection attention is invited to a valuable report iqion the waters of the Mohawk, 

 and Hudson rivers, contained in the thirteenth report of the State Board of Health of New York 



