August 2, 1889.] 



SCIENCE. 



73 



of this address, to discuss the details of such questions as house 

 disinfection ; but I may be permitted to say that the methods for 

 •disinfecting apartments have been worked out on a satisfactory ex- 

 perimental basis, and should be known, at least, by all public- 

 health officers. Whether it be pertinent to this occasion or not, I 

 cannot forbear to add my protest to that of others against placing 

 reliance upon any method hitherto employed of disinfecting houses 

 or apartments by fumigation ; and I would furthermore call atten- 

 tion to the lack, in most cities of this country, of public disinfecting 

 establishments, such as are in use with excellent results in most 

 •cities of Europe, and which are indispensable for the thorough and 

 convenient disinfection of clothing, bedding, carpets, curtains, etc. 



After this short digression, let us pass from the consideration of 

 the air as a carrier of infection to another important external source 

 of infection ; namely, the ground. That the prevalence of many 

 infectious diseases depends upon conditions pertaining to the soil 

 cannot be questioned ; but the nature and the extent of this in- 

 fluence have been and are the subjects of lively discussion. The 

 •epidemiological school led by Pettenkofer assigns, as is well known, 

 to the ground the chief, and even a specific and indispensable, in- 

 fluence in the spread of many epidemic diseases, particularly 

 cholera and typhoid-fever. The statistics, studies, and specula- 

 tions of epidemiologists relating to this subject probably surpass in 

 number and extent those concerning any other epidemiological 

 factor. The exclusive ground-hypothesis has become an ingenious 

 and carefully elaborated doctrine with those who believe that such 

 diseases as cholera and typhoid-fever can never be transmitted by 

 contagion. These authorities cling to this doctrine with a tenacity 

 which indicates that on it depends the survival of the exclusively 

 localistic dogma for these diseases. 



To all who have not held aloof from modern bacteriological in- 

 vestigations it must be clear that views which have widely pre- 

 vailed concerning the relations of many infectious germs to the 

 soil require revision. The question is still a difficult and perplex- 

 ing one ; but on some hitherto obscure or misunderstood points 

 these investigations have shed light, and from the same source we 

 may expect further important contributions to a comprehension 

 of the relations of the ground to the development of infectious dis- 

 eases. 



The ground, unlike the air, is the resting or the breeding place 

 of a vast number of species of micro-organisms, including some 

 which are pathogenic. Instead of a few bacteria or fungi in a 

 litre, as with the air, we find in most specimens of earth thousands, 

 and often hundreds of thousands, of micro-organisms in a cubic 

 centimetre. Fraenkel found the virgin soil almost as rich in bac- 

 teria and fungi as that around human habitations. This vast rich- 

 ness in micro-organisms belongs, however, only to the superficial 

 layers of the earth. Where the ground has not been greatly dis- 

 turbed by human hands, there is, as a rule, about three to five feet 

 below the surface an abrupt diminution in the number of living 

 ■organisms ; and at the depth where the subsoil water usually lies, 

 bacteria and fungi have nearly or entirely disappeared. Fraenkel, 

 who first observed this sudden diminution in the number of micro- 

 organisms at a certain level beneath the surface, explains this 

 singular fact by the formation at this level of that sticky accumu- 

 lation of fine particles, consisting largely of bacteria, which forms 

 •the efficient layer in large sand-filters for water. Of course, the 

 number of bacteria, and the depth to which they penetrate, will 

 vary somewhat with the character, especially the porosity, of the 

 soil, and its treatment ; but the important fact that all, or nearly all, 

 of the bacteria and fungi are retained in the ground above the 

 level of the subsoil water, will doubtless hold true for most situa- 

 tions. 



The conditions are not favorable for the multiplication of bac- 

 teria in the depth of the ground, as is shown by the fact that in 

 specimens of earth brought to the surface from a depth of a few 

 feet the bacteria which are at first present rapidly multiply. What 

 all of the conditions are which prevent the reproduction of bacteria 

 in the deep soil has not been ascertained, but the fact necessitates 

 similar precautions in the bacteriological examination of the soil as 

 in that of water. 



We have but meagre information as to the kinds of bacteria 

 present in the ground in comparison with their vast number. 



Many of those which have been, isolated and studied in pure cul- 

 ture possess but little interest for us, so far as we know. To some 

 of the micro-organisms in the soil appears to be assigned the role 

 of reducing or of oxidizing highly organized substances to the 

 simple forms required for the nutrition of plants. We are in the 

 habit of considering so much the injurious bacteria, that it is pleas- 

 ant to contemplate this beneficent function so essential to the 

 preservation of life on this globe. 



Among the pathogenic bacteria which have their natural home 

 in the soil, the most widely distributed are the bacilli of malignant 

 oedema and those of tetanus. I have found some garden-earth in 

 Baltimore extremely rich in tetanus bacilli, so that the inoculation 

 of animals in the laboratory with small bits of this earth rarely fails 

 to produce tetanus. In infected localities the anthrax bacillus, and 

 in two instances the typhoid bacillus, so far as it was possible to 

 identify it, have been discovered in the earth. There is reason to 

 believe that other germs infectious to human beings may have their 

 abiding-place in the ground ; certainly no one doubts that the 

 malarial germ lives there. As the malarial germ has been shown 

 to be an organism entirely different from the bacteria and the fungi, 

 we cannot apply directly to its behavior in the soil, and its trans- 

 portation by the air, facts which have been ascertained only for 

 the latter species of micro-organisms ; and the same precautions 

 must be observed for other diseases with whose agents of infection 

 we are not acquainted, as, for instance, yellow-fever. 



In view of the facility with which infectious germs derived from 

 human beings or animals may gain access to the soil, it becomes a 

 matter of great importance to determine how far such germs find 

 in the soil conditions favorable for their preservation or their 

 growth. We have, as is well known, a number of epidemiological 

 observations bearing upon this subject ; but, with few exceptions, 

 these can be variously interpreted, and it is not my purpose to dis- 

 cuss them. The more exact bacteriological methods can, of course, 

 be applied only to the comparatively small number of infectious 

 diseases, the causative germs of which have been isolated and 

 cultivated ; and these methods hitherto have been applied to this 

 question only imperfectly. We cannot regard the soil as a definite 

 and unvarying substance in its chemical, physical, and biological 

 properties. What has been found true of one kind of soil may not 

 be so of another. Moreover, we cannot in our experiments bring 

 together all of the conditions in nature which may have a bearing 

 on the behavior of specific micro-organisms in the soil. We must 

 therefore be cautious in coming to positive conclusions on this 

 point on the basis of experiments, especially those with negative 

 result. With these cautions kept constantly in mind, the question, 

 however, is one eminently open to experimental study. 



The experiments which have thus far been made to determine 

 the behavior of infectious micro-organisms in the ground have re- 

 lated especially to the bacilli of anthrax, of typhoid-fever, and of 

 cholera ; and, fortunately, these are the diseases about whose re- 

 lations to the ground there has been the most discussion, and con- 

 cerning which we are most eager to acquire definite information. 



(Canti: 



'■ P- 78.) 



NOTES AND NEWS. 



According to the Calcutta correspondent of the London Times, 

 a herd of loo wild elephants has been captured in Mysore by 

 Superintendent Sanderson. The same correspondent states that 

 there were 6,000 deaths by snake-bites in the North-West Provinces 

 last year. In Mad'-as, 10,096 cattle were killed by wild animals, 

 and the loss of human life by snakes and wild animals was 1,642. 



— The United States Bureau of Education has issued as circular 

 of information No. 7, 1S8S, in the series of contributions to Ameri- 

 can education'al history, edited by Herbert B. Adams, " A History 

 of Education in Florida," by George Gary Bush, Ph.D. 



— ■ The preparations for the Niagara Falls electrical convention, 

 Aug. 6, 7, and 8, have been completed. The convention will be wel- 

 comed to Niagara Falls by the Hon. W. C. Ely, who, in his saluta- 

 tory address, will touch upon the utilization of water-power for 

 electric-light purposes. President E. R. Weeks will open the con- 

 vention with an address, including among other things a statistical 



