172 THE BLOOD 



with ammonium sulphate. They may also be gotten by dialysis with 

 distilled water. As globulin is insoluble in distilled water, it is pre- 

 cipitated. The latter method yields a smaller quantity than the for- 

 mer, and hence, two types of globulins have really been isolated, 

 namely euglobulin, and pseudoglobulin. The latter is the one that is 

 thrown down during half-saturation with ammonium sulphate. 



Serum-albumin is found in plasma, serum, lymph, transudates, 

 exudates, and other animal fluids. It remains in the serum after 

 half-saturation with ammonium sulphate, but is precipitated by com- 

 plete saturation. It may also be prepared in crystalline form by the 

 method of Gtirber. From neutral or acid solutions it is isolated by 

 heating to 70°-75° C; in fact, it has been stated that three heat pre- 

 cipitations occur, namely one at 73°, one at 77° and one at 84°C. 

 This fact has been thought to prove that serum-albumin is a mixture 

 of three proteins. However that may be, it may be assumed for the 

 present that two protein bodies enter into its formation. According 

 to Michel,! its composition is: C 53.08, H 7.10, N 15.93, S 1.90, 

 O 21.96, and its molecular composition, as represented by Schmiede- 

 berg:^ C78Hi22N2oS024- The amount of this body ordinarily found in 

 the blood of the horse equals 3.67 per cent, and in human blood 4.52 

 per cent. 



Thromhogen, or inactive thrombin, is prepared by adding an excess 

 of alcohol to serurn. A precipitation of the proteins and thrombin 

 results; the latter, however, is not so easily coagulated by alcohol 

 as the proteins. 



The extractives embrace nitrogenous and non-nitrogenous material. 

 The former consists of urea and small quantities of uric acid, creatin, 

 creatinin, xanthin, hypoxanthin, and amino acids. The latter com- 

 prises fats, soaps, cholesterin, and sugar. 



CHAPTER XVI 



THE RED BLOOD CORPUSCLES 

 A. PHYSICAL CHARACTERISTICS 



Shape, Size and Color. — With the exception of the camelidse, the 

 mammalian red corpuscle,^ when placed flat upon the slide, possesses 

 the shape of a circular platelet, and, when turned on edge, that of a 



1 Verh. der phys. med. Gesellsch. zu Wiirzburg, xxix. No. 3. 



2 Archiv ftir Exp. Path, und Pharm., xxxix, 1897, 1. 



2 The red corpuscles of the frog were first observed by Swammerdam in 1658 

 and those of the mammal by Malpighi in 1661. They were first described by 

 van Loewenboek in 1673. 



