332 THE BLOOD. 



regarded as one of the characteristic features of the globulins. In 

 dilute saline solution they are all soluble with comparative readi- 

 ness, but on standing the substance gradually becomes insoluble. 



From their solutions the globulins are precipitated by half-satura- 

 tion with ammonium sulphate, or by complete saturation with 

 magnesium sulphate. Sodium chloride causes only an incomplete 

 separation when added to saturation, and with half-saturation no 

 effect at all is produced. It is thus an easy matter to isolate 

 serum-globulin, even though fibrinogen be present at the same time. 

 An incomplete precipitation occurs when its neutral or feebly acid 

 solutions (using acetic acid) are diluted from 10 to 20 times with dis- 

 tilled water, or on passing a stream of carbon dioxide through such 

 dilute solutions. In the presence of 5 to 10 per cent, of sodium 

 chloride the globulin fraction coagulates at 75 C. 



Elementary analysis of the entire fraction, as may be expected, 

 has not given rise to constant results. An analysis by Hammarsten 

 gave the following figures : C = 52.71 ; H = 7.01 ; N = 15.85 ; 

 S = 1.11 ;O = 23.32. 



Isolation. Serum-globulin is most conveniently obtained from 

 blood-serum by half-saturation with ammonium sulphate i. e. y by 

 treating a given volume of the serum with the same amount of a 

 saturated solution of the salt. Saturation with magnesium sulphate 

 in substance may also be employed. In either case the precipitated 

 serum-globulin is filtered off, washed with the corresponding salt 

 solution, dried at 115 C., then washed with boiling water to remove 

 the remaining salts, extracted with alcohol, then with ether, and 

 finally dried and weighed. In any case the original solution should 

 be nearly neutral in reaction. 



Serum-albumin. Serum-albumin is found in the plasma, the 

 serum, the lymph, in exudates and transudates, and under certain 

 pathological conditions also in the urine, where it usually occurs in 

 association with serum-globulin. 



In the dry state serum-albumin is a transparent, gum-like, brittle, 

 hygroscopic mass, or a white powder, which can be heated to 100 C. 

 without undergoing decomposition. Solutions of the pure substance 

 in distilled water coagulate at 50 C., while in the presence of salts 

 a higher temperature is necessary. This varies with the amount of 

 salt present, as also with the concentration of the albumin. A 1 

 to 2 per cent, solution containing 5 per cent, of sodium chloride 

 coagulates between 75 and 90 C. From its salt solutions serum- 

 albumin may be obtained in crystalline form. Its specific rotation 

 in distilled water varies between 62.6 and 64.6. 



One of the most remarkable properties of serum-albumin is its 

 pronounced tendency to form a sulphate. It is manifestly capable 

 of abstracting sulphuric acid (not sulphates) from the sulphates 

 used in its isolation, and this sulphur cannot be removed by wash- 

 ing with water (Morner). 



According to Halliburton, the serum-albumin of mammalian 



