THE BLOOD. 153 



coagulate at different temperatures, a at 73 C., /? at 77 C., and f at 84 

 C. The serine is coagulated by the addition of strong acids, such as 

 nitric and hydrochloric; by long contact with alcohol it is precipitated. 

 It is not precipitated on addition of ether, and so differs from the other 

 native albumin, viz., ^-albumin. When dried at 40 0. (104 F.) 

 serum-albumin is a brittle, yellowish substance, soluble in water, pos- 

 sessing a leevorotary power of 56. It is with great difficulty freed 

 from its salts. It is precipitated by solutions of metallic salts, e.g., of 

 mercuric chloride, copper sulphate, lead acetate, sodium tungstate, etc. 

 If dried at a temperature over 75 C. (167 F.), the chief part of the 

 residue is insoluble in water, having been changed into coagulated pro- 

 teid. Serum-albumin may be precipitated from serum, from which the 

 serum-globulin has been previously separated by saturation with mag- 

 nesium sulphate, by further saturation with sodium sulphate, sodium 

 nitrate, or iodide of potassium. 



/?. Serum-globulin can be obtained as a white precipitate from cold 

 serum by adding a considerable excess of water over ten times its bulk, 

 and passing through the mixture a current of carbonic acid gas or by 

 the cautious addition of dilute acetic acid. It can also be obtained by 

 saturating serum with either crystallized magnesium sulphate, or sodium 

 ohloride, nitrate, acetate, or carbonate. When obtained in the latter 

 way, precipitation seems to be much more complete than by means of 

 the former method. Serum-globulin coagulates at 75 C. (167 F.). 

 There seems to be more globulin in the serum than in the corresponding 

 plasma, and supposing Halliburton is correct in believing the fibrin fer- 

 ment to belong to the globulin class, its presence arising from the dis- 

 integration of the colorless corpuscles (cell-globulin) would account for 

 part of the increase, while possibly another part might be due, as sug- 

 gested by Hammersten, to the fact that fibrinogen splits up into fibrin, 

 leaving a globulin residue which appears in the serum. 



c. The salts of sodium predominate in serum as in plasma, and of 

 these the chloride generally forms by far the largest proportion. 



d. Fats are quite constantly present in a free state (i.e., aspalmitin, 

 stearin, and olein), though usually in very small quantities. Gumprecht, 

 however, asserts that they may be present in such quantities as to give 

 the blood a milky hue. Fatty acids have been found by some observers 

 in pathological conditions, but on the other hand it is claimed that this 

 is merely the result of faulty technique. The amount of fatty matter 

 varies according to the time after, and the ingredients of, a meal. 



e. Grape sugar is found principally in the blood of the hepatic vein, 

 to the extent of about two parts in a thousand. 



f. The extractives vary from time to time; sometimes hippuric acid 

 is found in addition to urea, uric acid, creatin and creatinin, xanthin, 

 hypoxanthin, and cholesterin. Urea exists in proportion from .02 to 

 .04 per cent. 



