xxxiv THE BLOOD. 



state, is calculated at I 1 088. They consist, as already stated, of an 

 insoluble, colourless tegumentary substance (envelope) and an included red 

 matter which is soluble and separable by water. The former doubtless 

 belongs to the group of albuminoids or protein-bodies, and some have 

 regarded it as a species of fibrin, but in truth it cannot be specifically 

 characterised. In numerical statements of blood-analysis it is reckoned 

 along with the globulin. The soluble coloured ingredient, for which it is 

 convenient to retain the old name of m*or, is separable into two sub- 

 stances, one named globulin, of itself colourless, and very nearly allied to 

 albumen in its nature ; the other a colouring principle, named h<jematin or 

 lic&matosin, which imparts redness to the first ; and hence the cruor is often 

 also designated as hwmato-globulin. These may be separated by the following 

 process. 



Blood deprived of fibrin by stirring is mixed with at least four times its bulk of 

 saturated solution of sulphate of soda, and thrown upon a filter; a few of the corpuscles 

 pass through with the liquid, but the greater part remain on the filter in form of a 

 moist red mass. This is boiled with alcohol slightly acidulated with sulphuric acid ; 

 the hsematin is thereby dissolved, while the colourless globulin remains behind. 

 Carbonate of ammonia is then added to the acid solution of haematin while it is yet 

 hot, to remove sulphuric acid, and, after being cleared by filtration from sulphate of 

 ammonia, and a little globulin which is precipitated, the liquor is evaporated to a 

 twelfth of its bulk ; it then deposits the haematin in form of a dark brown or almost 

 black powder, from which a minute proportion of fat may be extracted by means of 

 ether. 



Hcematin thus obtained appears to be altered by the process of separa- 

 tion, for it is no longer soluble in water. It is insoluble also in alcohol 

 and ether ; but it readily dissolves in any of these liquids after being 

 mixed with potash, soda, or ammonia, forming deep red solutions. It 

 likewise dissolves in alcohol to which an acid has been added, but its acid 

 combinations are insoluble in water. When burned, it yields nearly ten 

 per cent, of peroxide of iron, representing nearly seven per cent, of iron. 

 The quantity of iron is estimated by Schmidt as 1 to 230 parts of red cor- 

 puscles. According to Mulder, hsematin is composed of carbon 6 5 '8 4, 

 hydrogen 5 '37, nitrogen 10*40, oxygen 11'75, and iron 6*64 ; or C 44 , H 22 , 

 N 8 , 6 , Fe. 



That haematin is an altered product is further shown by an observation of Hoppe, 

 confirmed by Stokes, both of whom have found that the solution of cruor (obtained by 

 diffusing the red clot in water) is speedily decomposed by acids, and that the coloured 

 product of decomposition, which has all the characters of haematin, agrees with 

 haematin in its effects on the prismatic spectrum, but differs in this respect from the 

 natural or unaltered colouring matter of the cruor, which Mr. Stokes distinguishes by 

 the name of cruorin* 



There has been much question as to the condition in which the iron exists in 

 haematin, and especially whether it be in the state of oxide and in special combination 

 with some part of the constituent oxygen, or associated in an elementary form with 

 the organic matter, as sulphur is in albumen. The latter view seems to be the more 

 probable, for the whole of the iron may be removed from haematin, without abstracting 

 oxygen or disturbing the relative proportions of the other elements. When thus 



* For an account of the examination of the colouring matter of the blood by the prism, 

 and of the differences in its absorptive effect on light, according to its oxidated or 

 deoxidated condition, the reader is referred to an important paper by Professor Gr. G. 

 Stokes, in the Proceedings of the Royal Society for June 16, 1864, vol. xiii. p. 355. 



