16 Dr. A. Leared on the presence of Sulpha cyanides [Jane 17, 



XIII. " On the presence of Sulphocyanides in the Blood and Urine." 

 By Arthur Leared, M.D., M.R.I. A., &c. Communicated by 

 C. Handfield Jones, M.B. Cantab. Received June 17, 1869. 



In the course of some investigations into the composition and uses of 

 saliva, I was led to study one of its components, sulphocyanide of potas- 

 sium, in relation to its presence and action in the system, in a way that 

 has not hitherto been done. 



Treviranus, in 1814, discovered that saliva became reddened by a per- 

 salt of iron in solution ; and the reaction was afterwards stated by Tiede- 

 mann and Gmelin to be due to the presence of sulphocyanide of potas- 

 sium*. A strange difference of opinion has nevertheless prevailed on the 

 subject. Thus the reaction has been supposed to be caused by a taint of 

 the saliva from carious teeth ; whilst Bernard states that he found it took 

 place only in the saliva of tobacco-smokers. 



It is unnecessary to produce here the arguments on both sides of the 

 question ; the weight of authority is altogether in favour of the existence 

 of the salt in saliva. By some of those, however, who have admitted that 

 it is an ingredient of the secretion it has been regarded as a curiosity 

 rather than as playing any part in the economy. 



I have made numerous experiments for the purpose of satisfying myself 

 as to the constancy with which a sulphocyanide exists in human saliva. 

 For this end a solution containing twenty grains of perchloride of iron in an 

 ounce of distilled water was employed. Such a solution is of a light- 

 yellow colour, but it acts better than the paler solution of the persulphate 

 of iron. The mode of procedure was very simple. The saliva to be tested 

 was ejected on a surface of white porcelain, or upon a piece of white 

 paper, and a drop of the test-solution added. The colour which the saliva 

 assumed was compared with a scale of four shades of red on paper, re- 

 sembling those produced by the sulphocyanide of iron. These shades 

 were labelled " very marked," "marked," "faint," "a trace," and cor- 

 responded approximately with the colours struck by iron in solutions of 

 sulphocyanide of potassium of the relative strength of y 1 ^, ^ TT4> t^F °^ 

 a grain to the ounce of distilled water. 



Such a scale is appended herewith. An examination of the saliva of 

 fifty persons taken consecutively, half being males and half females, and of 

 ages ranging from under one year to Go years, gave the following results : — 



Very marked. Marked. Faint. A trace. None. 



25 Males .... 0 17 4 3 1 



25 Females 1 10 8 2 4 



As regards the influence of age and other practical points, the numbers 



* Recherches experimentales, Physiologiques et Chimiques sur la Digestion. Paris, 

 1827. 



