On the Non-existence of Siigar in the Blood. £? 



To the remaining quantity of the scrum I had added 

 twice the formfr proportion of the urine, and found tliat 

 this quanliiv did not wholly prevent the crystallization of 

 th« salts during the evaporation of the drop. 



The result of these trials was such as to satisfy nie that 

 the serum in this instance contained no perceptible quantity 

 of sucar, or at least that the water separable from the coagu- 

 lated serum did not contain one-thirticih part of that pro- 

 portion which 1 had found in the urine of the same person. 



In order to account for the presence of sugar in the urine, 

 we must consequeuily either suppose a power in the kid- 

 neys of forming tliis new product by secretion, which does 

 not seem to accord with the proper office of tnat organ ; or, 

 if we suppose the sugar to be formed in the stomach by a 

 process of imperfect assimilation, we must then admit the 

 existence of some channel of conveyance from the stomach 

 to the bladder, without passing through the general system 

 of blood-vessels. That some such channel does exist, Dr. 

 Darwin* endeavoured to ascertain, by giving large doses 

 of nitre, which he could perceive to p;^s with the urine, 

 but could not detect in its passage through the blood ; and 

 he imagined the channel by which it was conveyed to be 

 the absorbent system, upon the supposition that they might 

 admit of a retrograde motion of their contents. 



Without adopting the theory of Dr. Darwin, it did ap- 

 pear to me that the fact deserved to be ascertained by some 

 test more decisive than nitre ; and I conceived thai if prus- 

 siate of potash could be taken with safety, its presence 

 would be discerned by means of a solution of iron in as 

 small proportion as almost any known chemical test. Upon 

 trial of this salt, I found that a solution of it might he taken 

 without the least inconvenience, and that in less than one 

 hour and a half the urine became perceptibly impregnated, 

 and continued so to the fifth or sixth hour, although the 

 (juantily taken had not amounted to more than three grains 

 of the salt. 



After a few previous trials of the period when the prin- 

 cipal impregnation of the urine might be expected, and 

 when the presence of the prussiate (if it existed in the blood) 

 might with most reason be presumed to occur, a healthy 

 person about thirty-four years of age was induced to take a 

 dose corresponding to three grains and a half of the dry 



* Account of the retrograde Motion of the absorbent Vessel*, by Charles 

 l);irwin. 



C 4 S^lt, 



