50 COMPOSITION OF PLASMA AND SERUM. 



alkaline at the same time. The amount is about 3 - 4 p. c. (Fredericq). 

 If sodium chloride be cautiously added to serum, the coagulating 

 temperature may be lowered to 50C. It has a rotatory power of 56. 

 It is changed into syntonin or acid-albumin by the action of dilute 

 HC1, and by dilute alkalies into alkali-albuminate. 



[Although serum-albumin is closely related to egg-albumin they differ : 

 (a.) as regards their action upon polarised light ; (6.) the precipitate produced by 

 adding HC1 or HN0 3 is readily soluble in 4 c.c.m. of the reagent in the case of 

 serum-albumin, while the precipitate in egg-albumin is dissolved with very great 

 difficulty ; (c. ) egg-albumin, injected into the veins, is excreted in the urine as a 

 foreign body, while serum-albumin is not (Stockvis). 



Serum-albumin has never been obtained free from salts, even when it is dialysed 

 for a very long time, as was maintained by Aronstein, whose results have not been 

 confirmed by Heynsius, Haas, Huizinga, Salkowski, and others.] 



After all the para-globulin (serum-globulin) in serum is precipitated by 

 magnesium sulphate, serum-albumin still remains in solution. If this solution 

 be heated to 40 or 50C. a copious precipitate of non -coagulated serum-albumin is 

 obtained, which is soluble in water. If the serum-albumin be filtered from the 

 fluid, and if the clear fluid be heated to over 60C., Fred6ricq found that it becomes 

 turbid from the precipitation of other proteids; the amount of these other bodies, 

 however, is small. 



II. Fats (O'l to 0'2 per cent.). Neutral fats (tristearin, tripalmitin, 

 triolein) occur in the blood in the form of small microscopic granules, 

 which, after a meal rich in fat (or milk), render the serum quite 

 milky. 



The amount of fat in the serum of fasting animals is about 0'2 per 

 cent.; during digestion 0'4 to 0*6 per cent.; and in dogs fed on a diet' 

 rich in fat it may be 1'25 per cent. There are also minute traces of 

 fatty acids (succinic). Eohrig showed that soluble soaps i.e., alkaline- 

 salts of the fatty acids cannot exist in the blood. [Cholestcrin may 

 be considered along with the fats. It occurs in considerable amount- 

 in nerve-tissues, and, like fats, is extracted by ether from the dry 

 residue of blood-serum. Hoppe-Seyler found 0'019 to 0*314 per cent, 

 in the serum of the blood of fattened geese. There is no fat in the red 

 blood-corpuscles (Hoppe-Seyler). Lecithin (and protagon) occur in 

 serum and also in the blood-corpuscles.] 



III. Traces of Grape Sugar (0*05 per cent.) occur normally in 

 blood and serum, and also a trace of glycogen. 



The amount of grape sugar in the blood increases with the absorption of sugar 

 from the intestine, and this increase is most obvious in the blood of the portal 

 and hepatic veins; there is also a slight increase in the arterial blood, but there it 

 is rapidly changed. The presence of sugar is ascertained by coagulating blood by 

 boiling it with sodium sulphate, pressing out the fluid and testing it for sugar 

 with Fehling's solution (Cl. Bernard). Pavy coagulates the blood with alcohol. 



IV. Extractives. Kreatin, urea (O'Ol to 0'085 per cent, in the 



