CHEMISTRY IN ITS RELATIONS TO MEDICINE. 221 



what he is on a warm and murky day. The quantity of ozone in the 

 air also varies. Perhaps our moods, our " spirits," are dependent upon 

 ozone. Give us ozone enough, and the world will be happier and 

 healthier. These are some of the ideas which have been advanced. 

 Possibly there is some connection between these two very unlike 

 things. Certainly much more accurate experiments than any which 

 have thus far been made, are called for to prove the connection. 



In the light of many experiments it appears exceedingly probable 

 that one of the most important constituents of the air is aqueous vapor, 

 and that variations in its quantity beyond certain limits are productive 

 of serious results. The influence of carbonic acid, carbonic oxide, or 

 ozone, upon the value of air is almost nothing as compared with the 

 influence exerted by the moisture. This is a point that does not or- 

 dinarily receive the amount of attention which it deserves. A reliable 

 hygrometer should be as frequently used in a dwelling as a reliable 

 thermometer. It is undoubtedly a very difficult thing to regulate the 

 amount of moisture in the atmosphere of dwellings, but more could be 

 done than is done. The methods now adopted for this purpose are 

 mostly exceedingly imperfect. Further, the importance of doing every- 

 thing to regulate the amount is not sufficiently recognized, at least by 

 the people at large. 



As regards the water we drink, every one knows that cases are very 

 common in which it becomes polluted in one way or another, and that 

 disease results from its use. Innumerable chemical examinations of 

 drinking-water have been made, and large numbers of methods pro- 

 posed for the analysis. Some of the methods have been shown to be 

 utterly unreliable; others to be questionable; very few indeed to give 

 results which can be regarded as at all valuable. It is about as diffi- 

 cult at the present day to say what pure water is as it is to say what 

 pure air is. Papers upon papers are written on the subject of water 

 analysis. Some of these are based upon experiments performed; some 

 are simply critical. Out of the mass of literature we gather some 

 truths. One that stands out prominently is this, that the presence of 

 chlorine, of organic matters, of ammonia, and of so-called " albumi- 

 noid ammonia," indicates that the water containing them is very prob- 

 ably contaminated through sewage, cesspool, privy, or barnyard ref- 

 use. By the later methods of analysis, the estimations of the quanti- 

 ties of the substances mentioned have become comparatively simple 

 processes, so that now it is undoubtedly possible to pass a fairly reli- 

 able judgment upon the value of a given specimen of water. It is, 

 however, still quite impossible to determine by chemical methods 

 whether the typhoid-poison is present in water or not, just as it is still 

 impossible to determine whether in the air there is present that indefi- 

 nite something known as " malaria." There is still a great deal to be 

 done in order that a close connection between disease and the condition 

 of drinking water may be established. The open questions are to a con 



