20 On the Non-existence of Sugar in the Blood. 



probable conjecture respecting the presence or absence of 

 sugar in the serum of diabetic persons. 



This method, it is evident, is liable to a two-fold objec- 

 tion : first, that an excess of other ingredients beside sugar 

 will cause an increase of the quantity of oxalic acid formed; 

 and secondly, that slight variations in the process for form- 

 ing oxalic acid will unavoidably occasion difl'erences in the 

 result. 



'I'he method which I employed appears to me capable of 

 detecting much smaller quantities of such an ingredient ; 

 for though it might not enable us to distinguish exactly the 

 nature of any small quantity that may be discovered, still 

 the mere question of absence or presence admits of deter- 

 mination with great precision. 



For this purpose I investigated, in the first place, how 

 the albuminous part of healthy serum could be most com- 

 pletely coagulated, and by what appearances the presence 

 of sugar that had been added to it would be most easily 

 discerned. 



When heat alone had been employed for the coagulation 

 of serum, to which water had been added, that which ex- 

 suded from it war^ still found to contain a portion of albu- 

 men dissolved in it ; and if this were allowed to remain, any 

 saccharine matter which might be present would be dis- 

 guised, and could not with certainty be delected. 



I found, however, that this residuum of coagulable matter 

 might be altogether prevented by the addition of a small 

 quantity of dilute acid to the serum before coagulation*; 

 To six drachms of serum [ added half a drachm of muriatic 

 acid previously diluted with one drachm and a half of water, 

 and immersed the phial containing them in boiling water 

 during four minutes, 'ihe coagulation was thus rendered 

 complete. In the course of a few hours a drachm or more 

 of water exsudes ironi seruin that has been so coagulated. 

 If a drip of this water be evaporated, the salts which it 

 contains are found to crystallize, so that the form of the 

 crystals may be easily distintiuished ; they are principally 

 common salt. 



If any portion of saccharine matter has been added to 

 the seruin previous to coaiiulation, the crystallization of 

 rhe salts is impeded, or wholly prevented, according to the 

 quantity of sugar present. 



If the quantity added ddes not exceed two grains and a 



* I presumed that this portion of aHniincn was retained in solution by the 

 alkali redundant in serum, and added the acid tor the i>ur^jyse of neutraliz- 

 ing it. 



half 



