SCIENCE. 



[N. S. Vol. XX. No. 496. 



Upon to determine by tests the normal or 

 pathological character of some body fluid 

 or excretion about which the physician 

 must have information before he can make 

 a correct diagnosis. This work is, of 

 course, extremely important, but, as ordi- 

 narily applied, it calls, perhaps, for the 

 lowest order of chemical knowledge and rep- 

 resents the lowest requirement which can be 

 made in the chemical education of the med- 

 ical student. In the hands of the medical 

 practitioner chemical analysis degenerates 

 usually into a routine performance in 

 which a few very simple and accurate tests 

 are carried out in a marvelously inaccurate 

 manner. Medicine is as yet very far from 

 availing itself of the great aid which an- 

 alysis is ready to offer in the solution of its 

 practical problems in every-day experience, 

 and this is largely due to the fact that in 

 most of our medical schools instruction in 

 chemistry stops before the student has be- 

 come sufficiently familiar with the real sci- 

 ence to feel at home in its applications. 

 All medical students learn something about 

 sugar and albumen and they usually are 

 able to apply their laboratory acquisitions 

 in later practise. But the same can not be 

 said of their experience with acetone or 

 indicah or the aromatic sulphates, for ex- 

 ample. These, too, certainly have a mean- 

 ing, and the student has probably learned 

 the tests for them in his laboratory work. 

 But, unfortunately, their relations to dis- 

 ease are less tangible; their bearings do 

 not become clear without a greater mental 

 effort, and hence the once acquired facility 

 is allowed to slip away, or to degenerate 

 into a valueless routine, in which an as- 

 sumed accuracy may be wholly illusory. 



Supposing, however, that the medical 

 man's knowledge of analytical chemistry is 

 full enough and satisfactory for the pur- 

 pose, and that he continues to practise and 

 even improve upon the tests which he has 

 learned, something more is still desirable 



or necessary. Much that should be possible 

 in diagnosis is often lost because of the dif- 

 ficulty in connecting that which is shown 

 by analysis with what it indicates or de- 

 pends upon. The value of analytical chem- 

 istry in medicine soon reaches a limit un- 

 less it is accompanied by a very much fuller 

 knowledge of general physiological chem- 

 istry than is usually acquired. And, more- 

 over, while routine analytical work may be 

 extremely important, in many cases really 

 essential to diagnosis, it is far from repre- 

 senting the major service which chemistry 

 may render to medicine. By analytical 

 tests we are able to measure some of the 

 effects of certain reactions taking place 

 within the body, but the causes of the re- 

 actions and the relations of the things re- 

 acting involve ordinarily much deeper 

 problems than those of simple analysis. 

 An illustration may be given. Some years 

 ago Ehrlich introduced a valuable test in 

 the examination of uz'ine which is com- 

 monly known as the diazo test, and which 

 depends on the formation of an azo color 

 when a certain reagent is added to the 

 urine. To complete the reaction some aro- 

 matic product must be furnished by the 

 secretion, and the presence of this was sup- 

 posed at one time to be indicative of a 

 definite pathological condition. Later, 

 through more extended clinical observa- 

 tions, it seemed possible to connect it with 

 still other conditions, and then a long dis- 

 cussion arose as to the limits and useful- 

 ness of the reaction. Among the many 

 papers published in the discussion some 

 have been good and some bad, even ab- 

 surdly bad, because they overlooked wholly 

 the essential conditions of the reaction con- 

 sidered from the chemical standpoint. It 

 is evident that many of the writers on the 

 subject were unfamiliar with the chemistry 

 involved in the diazo combination and were, 

 therefore, led to absurd expressions. To 

 fairly comprehend a problem of this kind 



