1869.] 



in the Blood and Urine. 



17 



are insufficient for the deduction of trustworthy results. Some points, 

 however, which it is unnecessary to prove by tabulation, were well borne 

 out, and these are sufficient for the present purpose. 



It was established that in the saliva of the great majority of persons a 

 red colour is struck with perchloride of iron. 



It was ascertained that the existence of carious teeth is not requisite 

 for the production of this reaction, because it occurred in many instances 

 in which all the teeth were sound. 



It was further ascertained that tobacco-smoking was not indispensable, 

 because the colour was produced in many cases in which the individual 

 never used tobacco. 



It was also remarked that in all the cases in which the absence of the 

 sulpho-cyanide was noted, although no definite disease was apparent, the 

 health was feeble, and that, on the other hand, a marked reaction with 

 iron usually corresponded with the ordinary indications of sound health. 

 To this subject I shall afterwards have occasion to return. It is probable 

 that, by means of evaporation, a sulphocyanide would in every instance 

 have been detected in the saliva. But for practical purposes it is assumed 

 that when not discovered by the means described, it is not present. 



The particular base combined with the sulphocyanic acid in human saliva 

 is a matter of little importance. It has lately been stated that it is not 

 potassium, but sodium, which was long ago mentioned by Tiedemann and 

 Gmelin as taking the place of potassium in the saliva of sheep. 



The soluble sulphocyanide which exists in the saliva cannot be 

 regarded as an excretion, because it passes with the saliva into the 

 stomach. "Whatever its use or its ultimate destination, it seemed probable 

 that a salt of so stable a nature was not decomposed in its passage through 

 the system. This suggested that I should look for it in the urine. 



Iron, as is well known, yields a very characteristic test of the presence 

 of sulphocyanides. One compound only which it forms, namely, that 

 with meconic acid, is at all likely to be confounded with the sulpho- 

 cyanide of iron. The great sensitiveness of this test also makes it pecu- 

 liarly adapted for quantitative analysis, by means of colour. 



I found in my first experiments that when the urine of a person in 

 whose saliva a sulphocyanide was abundant, was concentrated by evapora- 

 tion, a reddish-brown colour was caused by the addition of perchloride of 

 iron. But owing to the dark colour assumed by the concentrated urine, 

 and the mode in which precipitation occurred, no reliance could be placed 

 on this as a proof of the presence of a sulphocyanide in the urine. The 

 step which then suggested itself was to decolorize the urine by means of 

 animal charcoal. But it turned out, when this was effected, that the 

 colourless liquid gave no reaction with the persalt of iron. The following 

 experiment was then tried : — 



A solution of one grain of sulphocyanide of potassium in an ounce of 



VOL. XVIII. c 



