CHEMICAL COMPOSITION. 25 



CHEMICAL COMPOSITION OF THE BLCOD. 



The blood is slightly alkaline in reaction. Carbonic acid, oxygen, 

 and nitrogen gases may be extracted from it by exhaustion by means 

 of the Torricellian vacuum aided by gentle ■warmth. Carbonic acid 

 is yielded in largest proportion, oxygen next, and nitrogen least. The 

 nitrogen is simply retained by absorption, i.e., in the same proportion 

 as by water at the same pressure and temperature. The oxygen is held 

 by the coloured matter of the red corpuscles ; it may be completely ex- 

 pelled from this combination by means of carbonic oxide gas (Bernard). 

 The carbonic acid, which is obtained in larger proportion from serum 

 than from blood, is in great part combined with carbonate of soda in a 

 bicarbonate ; from this combination it is set loose in vacuo if the colour- 

 ing matter of the blood is present. Arterial blood yields more oxj'gen 

 and less carbonic acid than venous blood. 



On being evaporated, 1000 parts of blood yieid on an average, about 

 790 of water and 210 of solid residue. This residue has nearly the 

 same ultimate composition as flesh. A comparative examination of 

 dried ox-blood and dried flesh (beef), by Playfair and Boeckmann gave 

 the following mean result : — 



FlcsJi. Blood. 



Carbon .ol'SG 51-96 



Hydrogen ........ T'oS 7'2.5 



Nitrogen l.j-0;5 1.5-07 



Oxygen 21-30 21-30 



Ashes •1-23 4-12 



Red Corp-uscies. — The specific gravity of the red corpuscles in a 

 moist state is calculated at 1-088. They consist, as already stated, of 

 an insoluble colourless stroma, and a diffused red matter, which is 

 soluble and separable by water. 



The stroma consists of various substances, chief among which are 

 paragJohulin, cholesferin, and a phosphuretted fat Avhich was named by 

 0. Liebreich jn-ofar/oii, but which, as Hoppe-Seyler has shown, itself 

 consists of two distinct substances — lecithin and neurin. 



If blood be shaken up with ether, the fatty matters of the stroma 

 are dissolved, and the colouring matter is in this way set free (Her- 

 mann). 



Paraglobnlin will be most conveniently described with the serum of 

 the blood, in which it also occurs, and from which it is more readily 

 obtainable ; and, for a similar reason, the consideration of the other 

 two substances will be deferred until the nervous system has been 

 treated of." 



The soluble coloured ingredient of the corpuscles has been named 

 haemoglobin (cruorin of Stokes). This substance, although crystal- 

 lizable, is inditfnsible, and, according to Hoppe-Seyler, contains, when 

 ]uire, in 100 parts 5-4-2 of carbon, 21'5 of oxygen, 16-0 of nitrogen, 

 7 '2 7 of hydrogen, 0*7 of sulphur, and 0'42 of iron ; orC^2oo,Hggo, 



* The nucleus of tlie nucleated red corpuscle consists chiefly of mucin (Kiiline, L. 

 Bruuton). 



