1813.] Chemical Properties of Animal Fluids. 205 



homogenous, and of another which is only suspended and 

 spontaneously separates when at rest. 



2. The liquid part is a solution of much albumen and a little 

 fibrin, both combined with soda. It also contains some other 

 saline and animal substances, but in very small quantity. 



3. The portion which is suspended is the colouring matter. 

 It differs from the albumen chiefly in its colour, and its insolu- 

 bility in serum. The colour seems to be owing to iron, of which 

 it contains J- per cent, of its weight, but which cannot be sepa- 

 rated from it as long as it continues to be colouring matter. This 

 separation can only be affected by combustion, or by the con- 

 centrated acids, both of which agents entirely decompose the 

 substance with which the metal was combined. The colouring 

 matter cannot be artificially produced by uniting albumen with 

 red subphosphate of iron. 



4. Fibrin, albumen, and colouring matter, resemble each 

 other so closely, that they may be considered as modifications of 

 one and the same substance.* I shall in future call them albu- 

 minous contents of the blood, when speaking of them collec- 

 tively. These three substances produce when decomposed, but 

 do nut contain, earthy phosphates and carbonate of lime ; and, 

 indeed, the entire blood contains in solution no earthy phos- 

 phate, except perhaps in too small a quantity to be detected. 



5. The albuminous contents of the blood will unite with acids, 

 and produce compounds, that may be termed saline ; these, 

 when neutralized, will dissolve in water, but separate on addino- 

 an excess of acid. The acetous and phosphoric acids, however, 

 must be excepted, as an excess of either of these forms a com- 

 pound soluble in water. Nitric acid, digested with the albu- 

 minous contents, forms an insoluble compound consisting of the 

 albumen in an altered state, and of the nitric and the malic 

 acids. This property of combining with acids is retained in some 

 instances by the albumen after it has undergone the changes 

 produced in the secretory organs; as for instance in the peculiar 

 matter of the bile, the curd of milk, &c. 



0". The blood contains no gelatine, f 



» One of the most striking points of difference exists in the property which 

 ■ olouring mattet hai of absorbing oxygen, and thereby experiencing a very 

 remarkable change ut colour. Serum absorbs very little oxygen, and only in 

 proportion as it is decomposed. Can the iron in the colouring matter give it 

 this property J Thfl is probable; but we shall never arrive at any accurate 

 knowledge of these phenomena, without first analyzing these elements of the 

 annual kingdom wiih the most scrdpuloui exactness. It is then, and not till 

 mat nrc may form conjectures; at present they are useless. 

 Ii gives me great pleasure to rind that an English chemist, Dr. liostnek, 

 ha* arrived at the same conclusion, without any previous knowledge of my 

 «cjik and (owing to a delay in the publication) prior to its appearance. See 

 Dr. Bottoek't experiments, published in the Brit volume of the Medii o-Chirnr- 

 £M al l ran ai tium. 



