ANIMAL FLUIDS AND TISSUES. 653 



The proteins of blood-plasma. There are three important proteins 

 in blood-plasma : serum-albumin, serum -globulin (paraglobulin), and 

 fibrinogen. Of the other proteins described, the nucleo-protein seems 

 to be the best founded. As fibrinogen is directly concerned in the 

 clotting of blood, it will be described in that connection. The albumin 

 and the globulin of the blood are typical members of their respective 

 classes, and possess all the qualifications of these classes and of pro- 

 teins in general. They are found together also in the lymph and in 

 various other fluids of the body. There is some evidence that the 

 albumin is in reality made up of two or three different albumins, 

 while the globulin can be divided into two portions by fractional pre- 

 cipitation. Thus, on adding saturated ammonium sulphate solution 

 to plasma, all the globulin will be precipitated before the sulphate 

 solution amounts to 50 per cent, of the resulting mixture. The 

 so-called euglobulin will precipitate between 28 and 36 per cent, 

 of saturation with ammonium sulphate, and the pseudoglobulin 

 between 36 and 44 per cent. Under these conditions no albu- 

 min will be cast down. If, however, solid ammonium sulphate be 

 now added to the point of saturation, all of the albumin will be 

 precipitated. 



Coagulation. When blood leaves the body and is allowed to stand 

 a while, it will be seen that the entire mass has coagulated /. e., has 

 been converted into a semi-solid, gelatinous material known as the 

 blood-clot, or the placenta sanguinis. Later it will be observed that 

 a small quantity of straw-colored liquid, known as the blood-serum, 

 appears on top of the clot. While the latter shrinks in volume the 

 quantity of serum increases, the clot finally floating in the liquid, 

 which itself ultimately gelatinizes in consequence of the coagulation 

 of the serum-albumin. Clot consists of fibrin holding in its meshes 

 blood-corpuscles, which may be removed by washing the clot in a 

 stream of water. 



The coagulation of blood can be prevented in various ways. After 

 the injection of albumose into a vein of a dog the blood does not coag- 

 ulate on leaving the body. If the blood be drawn directly into a sat- 

 urated solution of magnesium sulphate, in the proportion of 3 to 1, 

 or into a solution of potassium oxalate, so that the mixture contains at 

 least 1 per cent, of oxalate, no coagulation takes place. The plasma 

 obtained from such blood is known as peptone, salt, and oxalate plasma, 

 respectively. 



Coagulation of blood may be retarded by rapidly cooling it. If 

 the blood of a horse, whose blood always coagulates slowly, be re- 



