ICO 
Dr. Wollaston on the Non-existence 
As a further test of the absence or presence of sugar, I 
found it convenient to add a little nitric acid to the salts that 
remained after crystallization of the drop. If the serum has 
been successfully coagulated without any addition of sugar, 
the addition of nitric acid merely converts the muriatic salts 
into nitrates, and nitrate of soda is seen to crystallize without 
foam or blackness. But when sugar has been added, a white 
foam rises round the margin of the drop, and if further heat 
be applied, it becomes black in proportion to the quantity of 
sugar present. 
Such are the appearances when the proportions have been 
duly adjusted, and the proper heat for coagulation applied. I 
must own, however, that I could not always succeed to my 
satisfaction at the time when these experiments were con- 
ducted, and I am inclined to ascribe occasional failures to hav- 
ing used more muriatic acid than was really necessary, which 
by excess of heat might redissolve a part of the coagulated 
albumen, and thence occasion appearances, which, without 
careful discrimination, might be ascribed to sugar. 
After having, by this course of experiment, satisfied myself 
as to the phenomena exhibited by serum in its natural state, 
and the effects of any small additions of sugar, I then pro- 
ceeded to the examination of such specimens of diabetic blood 
or of serum, as I was able to procure. 
The first which I examined was a portion of blood that had 
been taken from a person whose urine had been analysed, and 
found to contain sugar. This blood had been dried, when 
fresh, by a gentle heat, so as not to coagulate the serum. 
After being reduced to powder, it was mixed with water, in 
order that every thing which remained soluble might be ex~ 
