CHEMICAL COMPOSITIOX. 31 



oxygen through the liquid. Its precipitate is distinguished from that 

 of other albuminoids by being always in form of fine granules or 

 molecules. But the most important and distinctive character of para- 

 globulin is its fibrino-plastic property, already referred to, by which it 

 co-operates with fibrinogen in producing solid fibrin ; this property is 

 destroyed by exposure of the solution to a boiling heat. 



Paraglobulin is almost identical in chemical natiu-e and composition -with the 

 substance which composes the ciystalline lens, and which was named by Berzelius 

 f/lobuUn. The latter substance, however, besides exhibiting minor differences, does 

 not possess tlie fibrino-plastic power ; they have therefore been separately distin- 

 guished by Kiihne. Like hajmoglobin. paraglobulin is diffusible tlu-ough animal 

 membranes, not through vegetable parchment. Fibrinogen, on the other hand, 

 is totally indiffusible. Both paraglobulin and fibrinogen may be precipitated 

 from their solutions by the addition of common salt to saturation. 



A substance similar to mi/oshi has also been, described as occurring in blood- 

 serum (Heynsius). 



Fatty Compounds. — A small amount of fat is contained in the 

 serum, partly dissolved, and partly diffused in the liquid. It may be 

 separated by gently agitating the serum with about a third of its bulk 

 of ether, or by evaporating the serum and digesting the dry residue 

 in ether, or in boiling alcohol. The turbid milky aspect which serum 

 often exhibits, is in most cases due to a redundance of fat, and may 

 accordingly be removed by agitation with ether. 



Extractive Matters. — AVhen the scrum has been freed from albu- 

 minous matter by coagulation, and from fat by ether, and is evaporated 

 to dryness, a yellowish or brown mass remains, consisting of organic 

 matters mixed with salts ; the former belonging principally to the ill- 

 defined class of substances denominated " extractive matters." These 

 have now been more carefully sifted, and have yielded several definite 

 and recognisable bodies, generated in the natural process of decomposi- 

 tion of the tissues, or residual matters of nutrition formed in the blood 

 itself, and on their way to be excreted by the kidneys. Several of the 

 substances to be next mentioned belong to this class, and as they are 

 obviously excrementitial and transitory ingredients, they are not allowed 

 to gather in any notable quantity in the healthy state of the economy. 



Great in and Creafinin. — Products of the natural ''wear" of the 

 muscles, or derived from fleshy food. These com]30unds, which are 

 found in muscular sulistances and in the urine, together with lujpox- 

 antliin (also named sarJcin), obtainable from the same sources, have been 

 stated to exist in excessively small quantities in the blood. 



Urea. — This substance, which accumulates in the blood of animals 

 after extirpation of the kidneys or ligature of the renal arteries, as well 

 as in certain diseases, has been found in very minute quantity in the 

 healthy blood of the ox and of the calf, by Marchaud and Simon, and 

 in that of man, by Lehmann, Garrod, and others. It is, however, in 

 such excessively small quantity, that its estimation is attended with 

 great difficulty. 



Uric Acid has been shown to exist in healthy blood by Grarrod, and in 

 that of persons suffering from gout it is in such considerable quantity 

 as to be readily detected. In health its proportion is extremely small. 



Hippuric Acid is found in the blood of herbivora, and, according to 

 some observers, in that of man. There is, however, much doubt upon 

 this point. 



