nd coagulates at 64 deg. C.

_Carbohydrates._--Three several carbohydrates are described as occurring
in plasma, viz. glycogen, animal gum and dextrose. If glycogen is
present in solution in the plasma it is there in very small quantities
only, and has probably arisen from the destruction of the white blood
corpuscles, since some leucocytes undoubtedly contain glycogen. A small
amount of carbohydrate having the formula for starch and yielding a
reducing sugar on hydrolysis with acid has also been described. The
constant carbohydrate constituent of plasma, however, is dextrose. This
is present to the approximate amount of 0.15% in arterial blood. The
amount may be much greater in the blood of the portal vein during
carbohydrate absorption, and according to some observers there is less
in venous than in arterial blood, but the difference is small and falls
within the error of observation. The statement that when no absorption
is taking place the blood of the hepatic vein is richer in dextrose than
that of the portal vein (Bernard) is denied by Pavy.

_Fats._--Plasma or serum is as a rule quite clear, but after a meal rich
in fats it may become quite milky owing to the presence of neutral fats
in a very fine state of subdivision. This suspended fat rapidly
disappears from the blood after fat absorption has ceased. To some
extent it varies in composition with that of the fat absorbed, but
usually consists of the glycerides of the common fatty acids--palmitic,
stearic and oleic. In addition, there is a small amount of fatty acid in
solution in the plasma. As to the form in which this occurs there is
some uncertainty. It is possibly present as a soap or even as a neutral
fat, since a little can be dissolved in plasma, the solvent substance
being probably protein or cholesterin. Fatty acids also appear to be
present to some extent combined with cholesterin forming cholesterin
esters (about 0.06%).

_Other Organic Compounds._--In addition to the substances above
described, belonging to the three main classes of food stuffs, there are
still other organic bodies present in plasma in small amounts, which for
convenience we may classify as non-nitrogenous and nitrogenous. Among
the former may be mentioned lactic acid, glycerin, a lipochrome, and
probably many other substances of a similar type whose separation has
not yet been effected.

The non-protein nitrogenous constituents consist of the following:
ammonia as carbonate or