HYDROSULPHOCYANIC ACID. 455 



extract of saliva is free from sulphuric acid (for the sulphates are 

 insoluble in alcohol) ; hence Pettenkofer thought that he might 

 make a quantitative determination of the sulphocyanogen in the 

 saliva, by oxidising the alcoholic extract with chlorate of potash 

 and hydrochloric acid, and precipitating the sulphuric acid that was 

 formed by chloride of barium. 



Sulphocyanogen is almost always present in human saliva ; it 

 is, however, occasionally absent, without any apparent physiological 

 or pathological reason. It appears to be wanting in the secretion 

 during salivation from any cause ; at least, I could never detect it 

 during the ptyalism following the use of mercury or iodine, or 

 occurring in the course of typhus or other diseases. 



Sulphocyanogen occurs also in the saliva of the dog and the 

 sheep ; I have examined the saliva of four different horses without 

 detecting any traces of it ; Wright asserts, however, that it occurs 

 in the saliva of that animal. 



Considering the extremely small quantity in which it occurs, 

 and that it is often absent without any apparent bad consequence, 

 it seems hardly probable that the alkaline sulphocyanides take any 

 definite part in the process of digestion. 



I have noticed several healthy, vigorous young men, whose 

 saliva contained no sulphocyanogen, and yet who enjoyed the best 

 digestion. 



It would be very easy to explain, by chemical formulae, how 

 sulphocyanogen might be formed from the histogenetic substances ; 

 but, unfortunately, we as yet possess no facts to confirm us in the 

 establishment of any particular chemical equation ; it is better, 

 therefore, frankly to confess that we know absolutely nothing re- 

 garding the place or the mode in which sulphocyanogen is formed 

 in the animal organism. 



END OF THE FIRST VOLUME. 



^r -^ 



