Page:Proceedings of the Royal Society of London Vol 1.djvu/437

Rh mately separates into two parts, as blood does, exhibiting a ﬁrm coagulum surrounded by a transparent colourless ﬂuid. The former has more the properties of cheese obtained from milk, than of the ﬁbrine of the blood; while the serous part also is like whey, and contains a species of sugar which at least very nearly resembles the sugar of milk.

The next subject which Mr. Brande undertakes to examine, is the lymph found in the thoracic dust of animals deprived of food for twenty-four hours before death. This is rendered slightly turbid by alcohol, but is not coagulated either by heat or by acids. It produces no change in vegetable blue colours till evaporated nearly to dryness. After incineration, it is found to contain a small portion of common salt, but no indications of iron.

The serum of blood has been so frequently examined, that Mr. Brande does not enter into any detailed analysis of it. He however relates some experiments made to satisfy himself, that when serum has been coagulated by heat, after the addition of an acid, or by voltaic electricity, the serosity that remains contains no gelatine. He examines also what quantity of iron might be present, by evaporating a pint of serum to dryness. and then incinerating the residuum. When the ash thus obtained had been dissolved in nitro-muriatic acid, a copious precipitation of phosphate of lime took place on the addition of ammonia, but only a slight trace of oxide of iron.

By similar examination of the crassamentum of blood. the quantity of iron contained in it was also found to be extremely small, and not perceptibly different, by previously washing the crassamentum, so as to free it from its red particles. And in conformity to this experiment, when a quantity of colouring matter had been allowed to sub- side from serum, through which it was diffused, and then examined separately by evaporation, incineration, and re-agents, as before, the traces of iron, even in the red part, were found to be as indistinct as in the rest of the blood.

In order to procure colouring matter for experiment, Mr. Brande generally employed venous blood, from which the ﬁbrine was separated by stirring during its coagulation, and the red globules were then allowed to subside from the serum. through which they thus remain diffused.

The effect of water upon these globules is to dissolve their colouring matter, and leave them colourless. If the solution be heated to near 200°, the colouring matter is rendered insoluble, and falls to the bottom of a brown colour. It is also coagulated by alcohol or by sulphuric acid.

Muriatic acid, poured upon the colouring matter, renders a portion of it insoluble, but dissolves a part, forming a solution, which appears crimson by reﬂected light, but green by transmitted light.

The colour of this solution is turned brown-red by supersaturation with caustic. potash, but rather improved by soda or by ammonia. A portion of the muriatic solution, being evaporated in a water-bath,