8o 



SCIENCE. 



[Vol. XIV. No. 339 



ever, be little doubt that this significance of the variations in sub- 

 soil-water is apparent only for certain localities, and has been 

 considerably exaggerated and often misunderstood. It is not, 

 however, pertinent to my theme to discuss this or other purely 

 epidemiological observations concerning the relations of the ground 

 to the spread of epidemic diseases, interesting and important as 

 are many of these observations. 



Before leaving the subject of the ground as a source of infection, 

 permit me to indicate briefly some conclusions which may be 

 drawn from what has been said, as to the principles which should 

 guide us in preventing infection, directly or indirectly, from the 

 ground. 



First in importance is to keep infectious substances as far as 

 possible from the ground. This implies the early disinfection or 

 destruction of such substances as typhoid and cholera excreta and 

 tuberculous sputum. 



Second, the ground should be rendered, so far as practicable, 

 unsuitable for the continued existence of infectious germs. This, 

 at least for some diseases, is accomplished by a proper system of 

 drainage ; which, moreover, for other reasons', possesses hygienic 

 importance. 



Third, means should be provided to prevent waste products from 

 getting into the ground around human habitations, or from gaining 

 access to water used for drinking or domestic purposes. In cities 

 this can be accomplished only by a properly constructed system of 

 sewers. The system of storing waste products in cesspools, 

 whence they are to be occasionally removed, cannot be approved 

 on hygienic grounds. There are conditions in which the disposal 

 of waste products in deep wells only used for this purpose, and 

 whence these products can filter into the deep layers of the ground, 

 may be permissible ; but this can never be considered an ideal 

 method of getting rid of e.xcrementitious substances, and is wholly 

 wrong in regions where wells are used for drinking-water. But I 

 am trespassing with these remarks upon a province which does not 

 belong to me, but rather to practical sanitarians and engineers. I 

 shall only add that the advantage gained by preventing organic 

 waste from soaking into the ground is not so much that the ground 

 is thereby rendered better adapted for the existence of infectious 

 micro-organisms, but is due rather to the fact that this waste is 

 likely to contain infectious germs. 



Finally, in cities, good pavements, absence of unnecessary dis- 

 turbance of the soil, cleanliness of the streets, and laying of dust 

 by sprinkling, are not only conducive to comfort, but are some- 

 times hygienically important in preventing infection from the ground 

 and dust. 



In passing from the consideration of the ground to that of water, 

 one feels that he now has to do with a possible source of infection 

 against which, in this country and in England, he is at liberty to 

 make any accusation he chooses without fear of contradiction. 

 There is reason to believe that such accusation has been repeatedlv 

 made, without any proof of misdemeanor on the part of the water. 

 It is not, therefore, with any desire to awaken further the medical 

 or the public conscience that I wish to say a few words concerning 

 the behavior of bacteria in water, and the dangers of infection from 

 this source. That such dangers are very real must be apparent 

 when we consider the universal employment of water, and its ex- 

 posure to contamination from all kinds of sources. 



Ordinary water, as is well known, contains bacteria in large 

 number. Not a few species of bacteria can multiply rapidly, and 

 to a large amount, even in distilled water. These are the so- 

 called water bacteria, and, like most of the micro-organisms found 

 in ordinary drinking-water, are perfectly harmless saprophytes. 

 What we wish to know is, how pathogenic micro-organisms con- 

 duct themselves in water. Can they grow, or be preserved for any 

 length of time in a living condition, in water .' As regards the 

 multiplication of pathogenic bacteria in water, the results of differ- 

 ent experimenters do not altogether agree. Whereas Bolton failed 

 to find any growth, but rather a progressive diminution, in number 

 of pathogenic bacteria planted in sterilized water, Wolffhiigel and 

 Riedel observed a limited reproduction of such bacteria, including 

 those of typhoid-fever and of cholera. This difference is due 

 probably to the methods of experimentation employed. According 

 to Kraus, these latter bacteria diminish rapidly in number in 



unsterilized spring or well water kept at a low temperature. These 

 experiments indicate that water, even when contaminated with 

 more organic impurities than are likely ever to be present in drink- 

 ing-water, is not a favorable breeding-place for pathogenic bacteria. 

 Still it is to be remembered that these laboratory experiments do 

 not reproduce exactly all of the conditions in nature ; and it may 

 happen that in some nook or cranny, or vegetable deposit at the 

 side of a well or stream, some pathogenic bacteria may find suit- 

 able conditions for their multiplication. 



But, as has been repeatedly emphasized in this address, it is not 

 necessary that pathogenic bacteria should actually multiply in a 

 medium in order to render it infectious. It is sufficient if their 

 life and virulence are not destroyed in a very short time. As to 

 this important point, Bolton found that in sterilized water typhoid 

 bacilli may preserve their vitality for over three months, and cholera 

 bacteria for eight to fourteen days, while Wolffhiigel and Riedel 

 preserved the latter in water for about eighty days. Under natural 

 conditions, however, these organisms are exposed to the over- 

 growth of the water bacteria ; so that Kraus found in unsterilized 

 water kept at a temperature of 10.5° C. the typhoid bacilli no longer 

 demonstrable after seven days, and the cholera bacteria after two 

 days. The conditions in Kraus's experiments were as unfavorable 

 as possible for the continued existence of these pathogenic bacteria, 

 more unfavorable than those often present at the season of prev- 

 alence of cholera and typhoid-fever ; nevertheless I do not see 

 that they justify the conclusions of Kraus as to the slight proba- 

 bility of drinking-water ever conveying infection with the germs of 

 typhoid-fever and of cholera. To render such a conclusion proba- 

 ble, it would be necessary to demonstrate a much shorter pres- 

 ervation than even Kraus himself found. In judging this question, 

 it should not be overlooked that infection of drinking-water with 

 the typhoid or the cholera germs is not so often the result of throw- 

 ing typhoid or cholera stools directly into the source of water-supply 

 as it is the consequence of leaky drains, cesspools, privy-vaults, or 

 infected soil ; so that there may be continued or repeated acces- 

 sions of infected material to the water. 



In view of the facts presented, there is no sufficient reason, there- 

 fore, from a bacteriological point of view, for rejecting the trans- 

 missibility of typhoid-fever and cholera by the medium of the 

 drinking-water. This conclusion seems irresistible when we call 

 to mind that Koch once found the cholera bacteria in large num- 

 bers in the water of a tank of India, and that the typhoid bacilli 

 had been repeatedly found in drinking-water of localities where 

 typhoid-fever existed. Nor do I see how it is possible to interpret 

 certain epidemiological facts in any other way than by assuming 

 that these diseases can be contracted from infected drinking-water, 

 although I know that there are still high authorities who obsti- 

 nately refuse to accept this interpretation of the facts. 



In this connection it may be mentioned that pathogenic bacteria 

 may preserve their vitality longer in ice than in unsterilized drink- 

 ing-water. Thus Prudden found typhoid bacilli still alive which 

 had been contained in ice for one hundred and three days. 



When we come to consider the ways in which water may be- 

 come infected with pathogenic micro-organisms, we recognize at 

 once a distinction in this respect between surface-water and sub- 

 soil-water. Whereas the subsoil-water may be regarded under 

 ordinary circumstances and in most places as germ-free, the sur- 

 face-water, such as that in rivers and streams, is exposed to all 

 manner of infection from the ground, the air, and the direct admis- 

 sion of waste substances. Unfortunately, in the ordinary way of 

 obtaining subsoil-water for drinking purposes by means of dug 

 wells, this distinction is obliterated ; for the water which enters 

 these wells free from bacteria is converted into a surface-water 

 often exposed, by the situation of the well, to more dangerous 

 contamination than other surface-waters used for drinking pur- 

 poses. 



Now let us turn our attention, as we have done with other 

 sources of infection, to a brief outline of certain general prin- 

 ciples which may help us in avoiding infection from the water. 



We shall, in the first place, avoid, so far as possible, the use of 

 water suspected of infection, especially with the germs of such 

 diseases as typhoid-fever and cholera. When it is necessary to 

 use this suspected water, it should be boiled. 



