io 6 
Dr, Marcet's Reply 
Reply of Dr . Marcet on the same Subject . 
Russell Square, January 8, i8ii. 
My Dear Sir, 
I am much gratified to find that you have at last been induced 
to communicate to the Royal Society your curious inquiry 
respecting the state of the blood in diabetes. I was anxious that 
the specious hypothesis of the presence of sugar in diabetic 
blood, which had been sanctioned by the authority of Dr. Rollo 
and Mr. Cruickshank, and which I had myself urged in sup- 
port of their theory, fourteen years ago, in an inaugural pub- 
lication, should no longer obtain an undue weight amongst 
physiological inquirers. 
With regard to the experiments which I tried at your re- 
quest some years ago, with a view to ascertain whether prus- 
siat of potash taken into the stomach, and found to exist in the 
urine, could also be detected in other secretions, I find, on 
referring to my memorandums, the following particulars which 
I shall transcribe verbatim. 
“ August 19, 1807. Having heard from Dr. Wollaston, 
that prussiat of potash could be taken into the stomach with 
perfect safety, and that its presence could afterwards be 
discovered in the urine, but not in the serum ; and being 
invited by him to follow up this inquiry, with a view to 
connect it with the theory of diabetes, I tried the following 
experiments. 
