308 THE BLOOD. 



also shown the presence of amylase (diastase), catalase, nudease and per- 

 oxidase in the poly nuclear leucocytes. 



The blood-plates (BrzzozEKo), hsematoblasts (HAYEM), whose nature, 

 preformed occurrence, and physiological importance have been much 

 questioned, are pale, colorless, gummy disks, round or somewhat oval 

 in shape, generally with a diameter one-half or one-third that of the 

 blood-corpuscles. In mammalia their number, according to AYNAUD, 

 is on an average 500,000 in 1 c.mm. They change their shape readily, 

 attack foreign bodies and agglutinate under conditions which AYNAUD 

 has carefully studied. Human blood-plates consist, according to DEETJEN/ 

 of a nucleus and a hyaline protoplasm. They are very sensitive toward 

 alkalies and much more so than the plates from other mammalia. They 

 are destroyed in a concentration of hydroxyl ions, Con = lXlO" 5 and 

 in a concentration of H ions, CH = 2X10~ 4 . 



According to the researches of KOSSEL and of LILIENFELD 2 the blood- 

 plates consist of a chemical combination between protein and nuclein, 

 and hence they are also called nuclein-plates by LILIENFELD, and are 

 considered as derivatives of the cell nucleus. It seems certain that the 

 blood-plates have some connection with the coagulation of blood. The 

 views on this question, especially in regard to the manner in which these 

 plates act in coagulation, are unfortunately very divergent. 



HI. THE BLOOD AS A MIXTURE OF PLASMA AND BLOOD-CORPUSCLES. 



The blood in itself is a thick, sticky, light or dark red liquid, opaque 

 even in thin layers, having a salty taste and a faint odor differing in 

 different kinds of animals. On the addition of sulphuric acid to the 

 blood the odor is more pronounced. In adult human beings the specific 

 gravity ranges between 1.045 and 1.075. It has an average of 1.058 

 for grown men and a little less for women. LLOYD JONES found that the 

 specific gravity is highest at birth and lowest in children until about 

 two years old, and in pregnant women. The determinations of LLOYD 

 JONES, HAMMERSCHLAG, 3 and others show that the variation of the specific 

 gravity, dependent upon age and sex, corresponds to the variation in 

 the quantity of haemoglobin. 



The determination of the specific gravity is accurately obtained 



1 Aynaud, Maly's Jahresb., 39; Deetjen, Zeitschr. f. physiol. Chem., 63. 



2 In regard to the literature of the blood-plates, see Lilienfeld, Arch. f. (Anat. u.) 

 Physiol., 1892, and "Leukocyten und Blutgerrinnung," Verhandl. d. physiol. Gesellsch. 

 zu Berlin, 1892; and also Mosen, Arch. f. (Anat. u.) Physiol., 1893, and Maly's Jahres- 

 ber., 30 and 31. 



3 Lloyd Jones, Journ. of Physiol., 8; Hammerschlag, Wien. klin. Wochenschrift, 

 1890, and Zeitschr. f. klin. Med., 20. 



