24 • On the Non-existence of Svgnr in the Blood. 



salt, and to repeat it everv hour to the third time. The urine 

 being examined every haifhoiir, was found in two hours to 

 be tinged, and toafFord a deep blue at the end of four hours. 

 Blood was then taken from the arm, and the coagiikim, 

 aflerit had formed, was allowed to contract, so that the se- 

 rum might be iully separated. The presence of the priissiate 

 \yas then endeavoured to be discovered by means of a solu- 

 tion of iron, !)nt without effect; and as f thought that the 

 redundant alkali (which had been ascertained (o prevail in 

 this serum) might tend lo prevent the appearance of the 

 precipitate, I added n small quantity of dilute acid; but still 

 I could not discern that any degree of blueness was occa- 

 sioned by it. 



This experiment having been repealed a second time with 

 ihe same result, seemed to me nearly conclusive with re- 

 spect to ihe existence of some passage, by which substances 

 certainly known to be in the stomach I'nav find their way 

 to the bladder without being mixed wiih the general mass 

 of circulating fluids. 



Being desirous of ascertaining whefher the prussiate could 

 be discovered in any other secretions, I have rtpeatedlv cxa- 

 jnincd my saliva, at limes when ihe urine has maivfestcd a 

 very strong blue, by adding solution of iron, but I could at 

 jio time perceive ihc saliva'to be tinred. 



I have also, during a severe cold, accompanied with pro- 

 fuse running of water from the nose, made a similar exa- 

 mination of this discharge, but have not been able to per- 

 ceive any (race of the prussic acid. 



Jt was nearly in this state that I left the inquiry at the 

 period I have mentioned, and I do not remember lo have 

 made any other experiments, when I requested your assist- 

 ance in making :rial of the scrum that is secreted in conse- 

 quence of the application of a blister. Your report upon 

 the result of your experiments, in addition to those which 

 T have above related, nearly satisfied mc as to the existence 

 of some unknown channel of conveyance by which sub- 

 stances may reach the bladder. 



With respect to Dr. Darwin's conception of a retrograde 

 action of the al)S(irbcnis, it is so strongly opposed by the. 

 known structure of that system of vessels, (hat I believe 

 few persons will admit it to 'be in aiiy degree probable. 



Since we have becouie acquainted with the surprising 

 chemical effects of the lowest states of electricity, I have 

 been inclined (o hope that we might from th;U source de- 

 ji^^e some explanation of such phsenomena. liut though 



1 havj 



