PROTEIDS OF PLASMA. 163 
Albumins of blood plasma. — The albumins of plasma are also found 
in the serum after coagulation of blood, and hence they have been 
termed serum albumins. They remain in plasma or serum after half- 
saturating it with ammonium sulphate, i.e. by mixing it with an equal 
amount of saturated ammonium sulphate solution, or after entirely 
saturating it with magnesium sulphate. 
The precipitated globulins and nucleo-proteid are removed by filtra- 
tion, and the filtrate dialysed to remove the salts. The solution which 
remains contains only the albumins; they can be precipitated from it by 
saturation with ammonium sulphate or by sodio-magnesium sulphate. 
According to Gnrber, they can be obtained in a crystalline form by 
adding ammonium sulphate just sufficient to produce precipitation and 
allowing the fluid to stand exposed to the air. 1 
The material obtained in these ways constitutes what has usually 
been called serum albumin (serine), but, as Halliburton has shown, 2 it is 
really a mixture of three separate albumins, which he has termed 
respectively a, /3, y- These differ from one another in their temperature 
of heat coagulation ; a-albumin coagulates at 72°-75° C. : (S-albumin at 
77-78° C. ; and y-albumin at 83°-86° C. In the plasma of horse, ox, 
and sheep blood, a-albumin is absent, but the other two are present ; in 
man, and all other mammals and birds investigated by Halliburton, all 
three were present ; but in reptiles, amphibia, and fishes investigated, 
a-albumin was usually the only one found. 3 
The crystals of serum albumin which were obtained by Giirber from the 
serum of horse's blood were hexagonal prisms with one pyramidal end, 
and were doubly refracting ; some of them were as much as 1 cm. long. 
Their elementary composition was C, 53T ; H, 7T ; N, 15*9; S, 1*9, 
- 22 ; and ash, 0*22 per cent. Dissolved in water and the excess of 
ammonium sulphate removed by dialysis, the solution had a heat coagulation 
temperature of 51° to 53°, and a specific rotation for yellow light of -61°. 4 
The globulins of blood plasma. — The globulins of blood plasma con- 
sist of serum globulin and fibrinogen. Serum globulin (paraglobulin, 
Kiihne ; fibrino-plastic substance, A. Schmidt) has a heat coagulation 
temperature of 75° C, which is almost constant in all animals in 
which it has been examined. The amount to which it is contained 
in plasma is represented by the figures in the second column of the 
table on p. 162. It will be seen from this, that in man it constitutes about 
three parts per cent, of the total serum. It is precipitated from serum by 
half-saturation with ammonium sulphate, 5 and also by complete saturation 
with magnesium sulphate, sodium chloride, and some other neutral salts 
which do not precipitate the albumins ; also, but less completely, by dilut- 
ing the serum with water (fifteen times) and passing OCX through it, or by 
1 Sitzungsb. d. phys.-med. Gesellsch. zu Wiirzburg, 1894, S. 143. 
2 Jour a. Physiol., Cambridge and London, vol. v. p. 152. 
3 In the slider terrapin (Howell, John Hopkins Univ. Stud. biol. lab., Baltimore, vol. 
iii. p. 49) the albumin present is apparently of the £ variety, coagulating at 77° to 80°, 
and in the eel and dog-fish this variety was also found by Halliburton (Journ. Physiol., 
Cambridge and London, vol. vii. p. 320). 
4 Michel (with Giirber), Vcrhandl. d. phys.-med. Gesellsch. zu TFiirzburg, 1895, N. F., 
Bd. xxix. No. 3. 
3 Kauder (Arch. f. exper. Path. u. Pharmakol., Leipzig, 1886, Bd. xx. S. 411) found 
that solutions of ammonium sulphate stronger than 24 per cent, completely precipitated 
serum globulin ; above 33 '5 per cent, some of the serum albumin also conies down. A 
half-saturated solution contains about 26 per cent. 
