Dr. Wollaston on the Non-existence, &c. 97 
logical, relating to the natural course of circulating fluids, and 
more especially so much of the investigation as is conducted 
by chemical means, is within the range of those pursuits which 
are generally interesting to the Royal Society, I will endea- 
vour to give you as distinct an account as I am able of the 
progress of my own experiments, requesting that you will in 
return state, more fully than you have hitherto done, the re- 
sult of that further 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 part 
of his inquiry by the well known talents of Mr. Cruickshank, 
it appears that they “ had not been so fortunate as to obtain 
“ a sufficient quantity of serum for chemical experiment;”* 
and were unable fully to satisfy themselves by the taste or by 
other means which they could employ, concerning the exist- 
ence or non-existence of sugar in the blood of persons labour- 
ing under diabetes ; but nevertheless they were persuaded of 
its presence. 
For the purpose of forming some judgment on this ques- 
tion, Mr. Cruickshank made trial of the quantities of oxalic 
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 differ- 
ence perceptible in these trials, he formed a probable conjec- 
ture respecting the presence or absence of sugar in the serum 
of diabetic persons. 
This method, it is evident, is liable to a two-fold objection : 
first, that an excess of other ingredients beside sugar will 
* Ror . lo on Diabetes, p. 408. 
o 
MDCCCXI. 
