Scientific Proceedings (120). 



serum in narrow agglutination tubes and add 0.02 c.c. of antigen 

 to each tube. Incubate in water bath and read as in the case of 

 the regular quantities described in the preceding paper. Although 

 the total quantity employed in this test is only about 1/10 of the 

 original one, the precipitates can nevertheless be seen with the 

 naked eye. We would, however, recommend this test only in 

 cases where it is extremely difficult or impossible to obtain larger 

 quantities of serum. 



85 (1832) 



Contribution to the chemico-pharmacodynamic relationship of 

 atropine and homatropine. 



By DAVID I. MACHT. 



[From the Pharmacological Laboratory, Johns Hopkins 

 University, Baltimore, Md.] 



The classical researches of Ladenburg on the structure of 

 atropine and the synthesis of various tropeins led almost imme- 

 diately to a wide therapeutic application of homatropine as a 

 mydriatic. Inasmuch as the mydriatic action of atropine is known 

 to be through the parasympathetic nerve-mechanism of the eye, 

 namely, the paralysis of the parasympathetic endings of the 

 oculomotor nerve, it has been generally assumed that the mydri- 

 atic action of homatropine or tropin -mandelate was of exactly the 

 same nature. An examination of experimental data on the sub- 

 ject, however, gives no proof to support this assumption. In the 

 present investigation, the author became interested in the phar- 

 macology of homatropine in connection with a study of mandelic 

 acid. This acid is closely related to benzaldehyde and indeed can 

 be readily prepared from the latter by treatment with hydrocyanic 

 acid and water. Inasmuch as the author has already shown that 

 benzaldehyde possesses the antispasmodic or relaxant properties 

 on smooth muscle which arc exhibited by benzyl alcohol and 

 certain benzyl esters, it was thought possible that the action of 

 homatropine may be exerted, at least partially, directly on smooth 

 muscle itself. A series of expeiiments tended to corroborate his 

 view. In the first place, the action of homatropine on other 

 parasympathetic nerve endings, such as the vagus teiminals in 

 the heart, is very much weaker than that of atropine. Whereas 



