January 6, 1888.] 



SCIENCE. 



Subsequent to i860, I have fourteen series, ranging in length 

 from ten to twenty-four years, with an aggregate of two hundred 

 years. The results, presented below, show that the rainfall in the 

 two halves of these series was identical. 



Amherst 



New Haven... 



Boston 



Fort Trumbull 

 Middletown. . . , 



Lawrence 



Lunenburgh. .. 

 New Bedford.. 



Providence 



Albany , 



Flatbush 



New York 



West Point 



Gardiner 



Aggregate Rainfall. 



33S 



+14 



265 



—14 



343 



+30 



348 



+48 



393 



+16 



30s 



—23 



237 



+3 



38= 



+^ 



2og 



—37 



With these results in view, it seems idle to discuss further the 

 influence of forests upon rainfall from the economic point of view, 

 as it is evidently too slight to be of the least practical importance. 

 Man has not yet invented a method of controlling rainfall. 



Henry Gannett 



THE GERM THEORY AS A SUBJECT OF EDUCATION. 



The time is past when it is necessary to discuss the probability 

 of the ' germ theory 'as explaining infectious diseases. This is no 

 longer a theory, but as fully demonstrated as most of the other 

 universally accepted conclusions of science. No one to-day who is 

 competent to form a judgment from a knowledge of the facts, will 

 doubt that many infectious diseases are caused by the growth of 

 microscopic organisms in the body. Of course, no general proof 

 of the parasitic nature of all infectious diseases has been adduced, 

 nor is such general proof possible ; but when the causal connection 

 between certain specific bacteria and definite infectious diseases has 

 in many cases been proved by a demonstration so conclusive as to be 

 beyond question, and when such causal connection has been rendered 

 extremely probable in many other cases, indeed in almost every in- 

 fectious disease, it is only ignorance of the facts that can explain 

 any doubt as to the very general applicability of the theory. It is true 

 that many, perhaps a majority, of practising physicians do not have 

 much sympathy with the conception of the parasitic nature of in- 

 fection, sometimes indeed treating the whole subject with ridicule. 

 Some are incapable of forming correct judgments, but most of 

 them have not found the time or inclination to study the subject 

 enough to know what facts have been established. At the time 

 when most of the physicians who are nov^^ practising were pursuing 

 their studies, the germ theory of disease was scarcely entertained 

 as a theory, and nowhere accepted. Only three or four years ago 

 some of our better medical schools taught their students that the 

 theory was a wild hypothesis, and destined to be exploded like 

 any other visionary speculation. It is not surprising, therefore, that 

 they should still refuse to accept a theory which so revolutionizes 

 the conceptions of disease. But our leading physicians, including 

 professors in better medical schools, are now convinced of the truth 

 of the theory and the great importance of the subject, and medical 

 papers throughout the country are giving more and more space to 

 the subject of bacteriology. The inevitable result of this will be 

 that the next generation of doctors will accept the germ theory as 

 the basis of practice. 



This discovery of the parasitic nature of infectious diseases is of 

 more than scientific interest : it is of vast practical value. It has 

 not yet, perhaps, contributed very materially to the methods of 

 treating disease directly, although we may confidently expect great 

 results in the future along this line. There is nothing to prevent 

 direct experiments with germicides upon living bacteria in the lab- 

 oratory, and we may hope in this way to get a more scientific 

 method of curing infectious diseases, after the theory of their para- 

 sitic nature becomes more truly the property of doctors as well as 

 of scientists. Thus far, however, the value of the theory has been 

 rather as the foundation of the science of preventive medicine. 

 Here its importance cannot be overrated, and is only beginning to 

 become reaUzed. 



We need do no more than mention the advances made in surgery 

 in the last twenty years, which are due almost solely to the knowl- 

 edge of septic bacteria. It needs no words to enforce the value of 

 discoveries in this line. Every one appreciates this inatter ; and 

 the value of antiseptic dressing, which alone makes the difficult 

 operations possible, is almost everywhere recognized, and its use 

 taught in all medical schools. 



In other lines than surgery the value of the germ theory is even 

 greater, though at first sight not quite so apparent, since the matter 

 is yet in its infancy. The great advantage which we are to acquire 

 through this theory is not in curing infectious diseases, but in pre- 

 venting them. Professor Koch, in a recent address to a class of 

 medical students, voiced this fact: " Gentlemen," he said, "you 

 have been hitherto taught only how to cure disease, in the future 

 you will be taught how to prevent disease." We can see in this 

 direction great practical results arising along at least two different 

 lines. The first is by preparing the body to resist the disease, the 

 method of inoculation. The most widespread instance of this 

 method of treatment is of course vaccination for small-pox. Vac- 

 cination was discovered, it is true, empirically, and entirely inde- 

 pendent of the germ theory; but it finally received its rationale 

 through the brilliant work and generalizations of Pasteur. Work- 

 ing in accordance with the same idea of preventing a severe form 

 of a disease by giving the individual previously a mild form, Pasteur 

 has successfully treated splenic-fever and hydrophobia. Others, 

 following in his lead, claim success in a similar treatment of yellow- 

 fever and cholera, although these claims certainly need further 

 verification. But only a beginning has been made in this direction, 

 and it does not seem improbable that we may see a time when 

 many of our most severe epidemics may be as thoroughly subdued 

 by inoculation as small-pox has been by vaccination. 



But of much more importance than inoculation is the more 

 natural method of avoiding the diseases. We are now learning to 

 keep the bacteria away from our bodies, either by directly destroying 

 them or by keeping away from the contaminating material. When 

 we know the exact nature of an infectious disease, — what are the 

 habits of the organism which produces it ; where they are most likely 

 to be found lurking during epidemics, whether in water, food, 

 clothing, drains, in the air, in the excreta or scales from the skin of 

 the patient ; in what conditions they will grow, and what will kill 

 them ; how they make their way into the healthy body, whether by 

 food, drink, by breathing, or by contact of infected material with 

 the skin, — in short, when we understand the natural history of an 

 infectious disease, it is usually easy to avoid it. If the disease is 

 taken in drinking-water, it may be avoided or rendered harmless ; if 

 in food, the food may be cooked ; if from excreta or clothing, they 

 may be easily disinfected by some of the effective germicides ; if by 

 contact with the skin, care in handling the infected material, and dis- 

 infecting the skin afterward, will usually suffice. As yet we have 

 discovered no way of avoiding contagion which comes to us in the 

 air, but we are just beginning to find out the extremely important 

 fact that the air does not become contaminated with bacteria unless 

 they are allowed to dry. Recent investigations have shown a smaller 

 number of bacteria in the air of a well-kept sewer than in that of a 

 poorly ventilated schoolroom. It is a valuable discovery that this 

 means of infection by breathing — a means which we cannot 

 guard against — is uncommon. The air is not the ordinary mode 

 of transferrence of germs, and would be scarcely at all, if proper 

 precautions were taken to prevent infectious material from drying. 

 Here we immediately get suggestions as to the management of the 



