CHEMISTRY IN ITS RELATIONS TO MEDICINE. 219 



a heated tube, and then passed into alcohol for the purpose of retaining 

 the products formed by heating the organic substances. The alcohol 

 gradually changed its color and became dark brown. This experiment, 

 though exceedingly imperfect, at present points, I think, to the possi- 

 bility of estimating the purity of air by a direct determination of the 

 quantities of those constituents which probably are the really injurious 

 ones; while, at present, for the want of a more reliable method, we 

 are obliged to be satisfied with determining the quantity of carbonic 

 acid, and then drawing conclusions with reference to the amount of 

 the organic matters present. 



Various attempts have been made to simplify the determination of 

 the amount of carbonic acid in air, so that even those who are not 

 skilled in chemical manipulation might have a ready means for pro- 

 nouncing upon the quality of air. The simplest of the methods proposed 

 is the minimetric process of Lunge, which has been used to some extent 

 in this as well as other countries. To show you, however, in what 

 an unsatisfactory state this matter of air analysis still is, I will simply 

 say that experiments undertaken, within a few months, by Hesse,* 

 have shown that Lunge's minimetric process does not give reliable 

 results, and hence conclusions reached from determinations made by 

 this method are not to be regarded as final. 



Another point still in dispute concerns the presence of carbonic 

 oxide in the air. This lower oxide of carbon is undoubtedly poisonous, 

 and can not be taken into the lungs without serious effects. The pres- 

 ence of only a small proportion of this gas will suffice to produce death. 

 Now, if it could be shown that there are certain causes at work which 

 apparently tend to introduce the gas into our dwellings and other 

 buildings, alarm would naturally follow. Some years ago St. Claire- 

 Deville, the French chemist, discovered that certain metals, when 

 heated to red-heat, are porous for certain gases. This he found to be 

 true of cast iron with reference to carbonic oxide. It is well known 

 that in our coal-fires there is always formed a large quantity of car- 

 bonic oxide; and, further, that stoves and furnaces not uncommonly 

 become red-hot. Putting these facts together, men became alarmed. 

 Stoves and furnaces were regarded with horror. In the eyes of many 

 they were looked upon as poison-generators of a very dangerous kind. 

 Active diseases were, in some cases, believed to have their origin in 

 the presence of carbonic oxide in the air ; and, in cases in which ac- 

 tive disease did not show itself, lassitude, headache, and other similar 

 symptoms were supposed to be caused by the gas. There was a fashion, 

 in some places, and particularly among those who prided themselves 

 on " keeping up with the times," of referring every bodily affection to 

 carbonic oxide when no other cause could be thought of, very much as, 

 in days gone by, every disease which was not understood was classed 

 under the general head " trouble with the liver." 



* " Zeitschrift fur Biologie," Bd. xiii., 395. 



