NONEXISTENCE OF SUGAR IN DIABETIC BLOOD. 185 



Society, I will endeavour to give you as distinct an account 

 as lam able of the progress of my own experiments; request- 

 iDtr that you will in return state, more fully than you have 

 hitherto done, the result of that farther step in the inquiry, 

 which you took at my suggestion ; and if it is agreeable to 

 you, we will without delay make a joint communication of 

 our researches to the Society. 



Although Dr. Rollo had been assisted in the chemical Dr. Rollo and 

 part of his inquiry by the well known talents of Mr. Cruick- ^^[-^^ JJ'^'J ^^ 

 shank, it appears, that they " had not been so fortunate as opportunity of 

 «* to obtain a sufficient quantity of serum for chemical ex- ^^l^!^^l% 

 •' periment*;"and were unable fully to satisfy themselves by rectly, 

 the taste, or by other means which they could employ, con- 

 cerning the exist»»nce or nonexistence of sugar in the blood of 

 persons labouring under diabetes ; but nevertheless they 

 were persuaded of its presence. 



For the purpose of forming some judgment on this ques- but attempted 

 tion, Mr. Cruickshank made trial of the quantities of oxalic '' indirectly. 

 acid, that could be formed from serum or from blood in 

 their natural state, and from the same serum or blood after 

 the addition of a certain proportion of sugar; and from 

 the difference perceptible in these trials, he formed a pro- 

 bable conjecture respecting the presence or absence of su- 

 gar in the serum of diabetic persons. 



This method, it is evident, is liable to a twofold objec- Their method 

 tion; first, that an excess of other ingredients beside su- °^j««^'°"*^^«* 

 gar will cause an increase of the quantity of oxalic acid 

 formed ; and secondly, that slight variations in the process 

 for forming oxalic acid will unavoidably occasion differences 

 in the result. 



The method which I employed appears to me capable of ^^^^Jj'^^^^Jj^^ 

 detecting much smaller quantities of such an ingredient ; l^^^^,^ ^ 

 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 

 determination with great precision. 



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

 the albuminous part of healthy serum could be most com- 



* Rollo on Diabetes, p, 408. 



pletely 



