224. The serum, the fluid portion of the blood, when obtained perfectly pure, is of a light straw colour, tinged with green. Its taste is saline, and its consistence adhesive. It is composed principally of water holding in solution animal and saline matter. The animal matter gives it its adhesive consistence, and the saline its peculiar salt taste. The chief animal matter contained in it is the proximate principle termed albumen, which may be separated from the water that holds it in solution by the application of heat and by certain chemical agents. Heat being applied, when the temperature reaches 160°, fluid serum is converted into a white opaque solid substance of firm consistence. This is found to be albumen, which may be also separated from the watery portion by the application of spirits of wine, acids, oxymuriate of mercury, and several other chemical substances. The quantity of albumen contained in 1000 parts of serum varies from about 78, the maximum, to 58, the minimum. 225. If the albumen yielded by the serum be subjected to pressure, or be cut into small pieces, there flows from it a watery fluid which is termed the serosity. In meat dressed for the table, the serum of the blood contained in the blood-vessels is converted by the heat into solid albumen, from which, when cut, the serosity flows in the form of gravy. 226. Besides albumen, serum holds in solution both a fatty and an oily matter, in the proportion of about one part of each to 1000 parts of serum. The proportion of its saline substances is about ten in 1000 parts. According to M. le Canu, who has made the most recent chemical analysis of serum, 1000 parts contain, of Water 906·00 Albumen 78·00 Animal matter, soluble in water and alcohol 1·69 Albumen combined with soda 2·10 Crystallizable fatty matter 1·20 Oily matter 1·00 Hydrochlorate of soda and potash 6·00 Subcarbonate and phosphate of soda, and sulphate of potash 2·10 Phosphate of lime, magnesia, and iron, with subcarbonate of lime and magnesia ·91 Loss 1·00 227. All the animal and saline matter held in solution in the serum being removed, the fluid that remains is water, the proportion of which in 1000 parts varies from 853, the maximum, to 779, the minimum.