and vegetable origin.

_General Properties._--Blood is an opaque, viscid liquid of bright red
colour possessing a distinct and characteristic odour, especially when
warm. Its opacity is due to the presence of a very large number of solid
particles, the blood corpuscles, having a higher refractive index than
that of the liquid in which they float. The specific gravity in man
averages about 1.055. The specific gravity of the liquid portion, the
plasma (Gr. [Greek: plasma], something formed or moulded, [Greek:
plassein], to mould), is about 1.027, whilst that of the corpuscles
amounts to 1.088. To litmus it reacts as a weak alkali.

_Blood Plasma._--The plasma is a solution in water of a varied number of
substances, and as a solvent it confers on the blood its power of acting
as a carrier of food stuffs and waste products. One important food
substance, oxygen, is, however, only partly carried in solution, being
mainly combined with haemoglobin in the red corpuscles. The food stuffs
carried by the plasma are proteins, carbohydrates, salts and water. The
main waste products dissolved in it are ammonium carbonate, urea,
urates, xanthin bases, creatin and small amounts of other nitrogenous
bodies, carbonic acid as carbonates, other carbon compounds such as
cholesterin, lecithin and a number of other substances. Thus, if we take
mammalian blood as a type, the plasma would have the following
approximate composition:--

In 1000 grms. plasma--
Water 901.51
Substances not vaporizing at 120 deg. C.--
Fibrin 8.06
Other proteins and organic substances 81.92
Inorganic substances--
Chlorine 3.536
Sulphuric acid 0.129
Phosphoric acid 0.145
Potassium 0.314
Sodium 3.410
Calcium 0.298
Magnesium 0.218
Oxygen 0.455
----- 8.505
----- 98.49
-------
1000.00

_Proteins._--The proteins of the blood plasma belong to the two classes
of the albumins and the globulins. The globulins present are named
fibrinogen and serum-globulin; as its n