INTRODUCTORY LECTURE. 
659 
were, with an accurate balance-sheet, showing th.e food taken 
into the system and the final products coming out, and has 
shown us that the supply can be identified and accounted 
for in the expenditure, we are still but imperfectly informed 
of the inte'rmediate changes which the nutrient matters 
undergo in the blood and in the tissues before they are 
brought to their finally excreted condition. Among the 
actual data which afford a basis for this inquiry, and which 
may eventually lead to the solution of the question, I refer 
to the several compounds which have been obtained from 
muscle, and which are probably the immediate products of 
the metamorphosis of that tissue; but especially to the 
brilliant discovery by Bernard of the production in the 
animal economy of a substance analogous to starch. This 
amyloid substance, gl^mogen, shown by Bernard to be largely 
generated in the liver, and, according to subsequent experi¬ 
menters, also in the muscle and other tissues, is supposed to 
be converted into sugar and finally oxidated; although Dr. 
Pavy, led by his ingenious and laborious researches, has 
thrown doubt on its actual conversion into sugar during life. 
However this may be, it is plain that in the production of 
glycogen we see the actual formation of a hydrocarbonous 
product in the animal body; and, as its production goes on 
wdien hydrocarbonous food, and, indeed, every kind of food, 
is withheld, it probably represents one of the transitional 
conditions through which hydrocarbonous matter, w-hether 
proceeding- directly from the food, or derived from the meta¬ 
morphosis of the albumenoid tissues, passes before final 
oxidation. As bearing on these larger questions, I would 
also refer to the advances made in the chemical examination 
of the tissues and fluids, especially to the blood j the experi¬ 
ment of Harley and Lothar Mayer showing, in opposition 
to Magnus, that the oxygen is not merely retained in the 
fluid by physical absorption, but held by chemical affinity; 
also the recognition of ammonia in the blood, and the well- 
known discovery of our distinguished associate. Dr, Richard¬ 
son, of its efficacy in maintaining fluidity. 
It is worthy of note that, in the course of such inquiries, 
particular facts are sometimes elicited which afford hints of 
fresh discovery and suggest important practical applications. 
The unlooked-for contrast between the saline constituents of 
the blood-plasma and corpuscles, the one containing chiefly 
soda and the other potash, and the predominance of potash 
in muscle, taken in connection with the well-known impair¬ 
ment of muscular strength and impoverishment of the blood 
in scurvy, led Dr. Garrod to suspect that the disease might 
