CHEMISTRY. 



143 



5. Oxide of manganese. 



6. Phosphate of lime. 



7. Carbonate of lime, very scanty. 



8. Silica. 



9. Sulphur. 



The colouring matter of hair appears from Vauque- 

 lin's experiments to be an oil. The oil is blackish green 

 in black hair, red in red hair, and white in white hair. 

 Vauquelin supposes that sulphureted iron contributes to 

 the colour of dark hair ; and ascribes to the presence of 

 an excess of sulphur the property which white and red 

 hair have of becoming black with the oxides of the white 

 metals. The sudden change of colour in hair from grief, 

 he thinks, is owing to the evolution of an acid. 



2. Feathers seem to possess nearly the same proper- 

 ties with hair. Mr Hatchett has ascertained that the 

 quill is composed chiefly of coagulated albumen. Though 

 feathers were boiled for a long time in water, Mr Hat- 

 chett could observe no traces of gelatine. 



Having given the preceding account of the solids 

 which compose animal bodies, we proceed next to the 

 fluid which circulates through living bodies, namely 

 Hood ; and to the various secretions formed from the 

 blood, either in order to answer some important purpose 

 to the animal, or to be evacuated as useless, that the 

 blood thus purified may be more proper for answering 

 the ends for which it was destined. Many of these sub- 

 stances have been examined with more care by chemists 

 than the animal solids. 



SECT. IX. Of Blood. 



Blood is a well known fluid, which circulates in the 

 veins and arteries of the more perfect animals. It is of 

 a red colour, has a considerable degree of consistency, 

 and an unctuous feel, as if it contained a quantity of 

 soap. Its taste is slightly saline, and it has a peculiar 

 smell. 



The specific gravity of human blood is, at a medium, 

 1.0527. 



When blood, after being drawn from an animal, is al- 

 lowed to remain for some time at rest, it very soon coa- 

 gulates into a solid mass of the consistence of curdled 

 milk. This mass gradually separates into two parts ; 

 one of which is fluid, and is calk-d serum ; the other, the 

 coagulum, has been called cnior, because it alone retains 

 the red colour which distinguishes blood. This separa- 

 tion is very similar to the separation of curdled milk in- 

 to curds and whey. 



1. The serum is of a light greenish yellow colour; 

 it has the taste, smell, and feel of the blood, but its con- 

 sistence is not so great. Its mean specific gravity is 

 about 1.0287. It converts syrup of violets to a green, 

 and therefore contains an alkali. On examination, Rouelle 

 found that it owes this property to a portion of soda. 

 When heated to the temperature of 156, the serum 

 coagulates, as Harvey first discovered. It coagulates 

 also when boiling water is mixed with it ; but if serum 

 be mixed with six parts of cold water, it does not coa- 

 gulate by heat. When thus coagulated, it has a greyish 

 white colour, and is not unlike the boiled white of an 

 egg. If the coagulum be cut into small piect-8, a mud- 

 dy fluid may be squeezed from it, which has been term- 

 ed the lernsily. After the separation of this fluid, if 

 the residuum be carefully washed in boiling water and 

 examined, it will be found to possess all the properties 

 of coagulated albumen. The serum, then-fore, contains 

 a considerable proportion of albumen. Hence its coa- 



gulation by heat, and the other phenomena which albu- Chemical 

 men usually exhibits. 



If the coagulated serum be heated in a silver vessel, 

 the surface of the silver becomes black, being converted 

 into a sulphuret. Hence it is evident, that it contains 

 sulphur ; and Proust has ascertained, that it is combined 

 with ammonia in the state of a hydrosulphuret. 



If serum be mixed with twice its weight of water, and, 

 after coagulation by heat, the albumen be separated by 

 filtration, and the liquid be slowly evaporated till it is 

 considerably concentrated, a number of crystals are de- 

 posited when the liquid is left standing in a cool place. 

 These crystals, first examined by Rouelle, consist of 

 carbonate of soda, muriate of soda, besides phosphate 

 of soda and phosphate of lime. The soda exists in the 

 blood in a caustic state, and seems to be combined with 

 the gelatine and albumen. The carbonic acid combines 

 with it during evaporation. 



2. The cruor, or clot as it is sometimes called, is of Cruor. 

 a red colour, and possesses considerable consistence. Its 

 mean specific gravity is about 1.245. If this cruor be 

 washed carefully, by letting a small jet of water fall up. 

 on it till the water runs off colourless, it is partly dis- 

 solved, and partly remains upon the scarce. Thus it is 

 separated into two portions: namely, 1. A white, solid, 

 elastic substance, which has all the properties of Ji'urin ; 

 2. The portion held in solution by the water, which 

 consists of the colouring matter, not however in a state 

 of purity, for it is impossible to separate the cruor com- 

 pletely from the serum. 



Bucquet proved that this watery solution contained 

 albumen and iron. Mcnghini had ascertained, that if 

 blood be evaporated to dryness by a gentle heat, a quan- 

 tity of iron may be separated from it by the magnet. 

 The quantity which he obtained was considerable : ac- 

 cording to him, the blood of a healthy man contains 

 above two ounces of it. Now, as neither the serum nor 

 the fibrin extracted from the cruor contains iron, it fol- 

 lows of course, that the water holding the colouring 

 matter in solution must contain the whole of that metal. 



This watery solution gives a green colour to syrup of 

 violets. When exposed to the air, it gradually depo- 

 sites flakes, which have the properties of albumen. 

 When heated, a brown-coloured scum gathers on its 

 surface. If it be evaporated to dryness, and then mix- 

 ed with alcohol, a portion is dissolved, and the alcoholic 

 solution yields by evaporation a residuum, which lathers 

 like soap in water, and tinges vegetable blues green ; 

 the acids occasion a precipitate from its solution. This 

 substance is a compound of albumen and soda. Thus 

 we see that the watery solution contains albumen, iron, 

 and soda. 



Fourcroy and Vauquelin have ascertained, that the 

 iron is combined with phosphoric acid, and in the state 

 of subphosphate of iron ; thus confirming an opinion 

 which had been maintained by Sage, and announced as a 

 fact by Gren. 



Brande has lately shown, that the colouring matter of 

 the blood is of an animal nature. He has proved, that 

 it may be advantageously used as a dye-stuff. 



Such are the properties of blood, as far as they have 

 been hitherto ascertained by experiment. We have seen 

 that it contains the following ingredients : 



1. Water. 



'2. Fibrin. 



3. Albumen. 



4. Hydrosulph. of ammo- 



5. Soda. 



6. Subphosphate of iron. 



7. Muriate of soda. 



8. Phosphate of soda. 



9. Phosphate of lime. 



Besides benzole acid, which has been detected by Proust. 



