THE BLOOD 55 



There are many kinds of leucocytes, which differ in their size 

 and in the proportion of their protoplasm and nucleus : 



1. Small cells of 4-7^ diameter with little protoplasm and one 

 nucleus; few in number. 



2. Larger cells of 7-1 o/* diameter with much protoplasm and 

 one or more nuclei (large uni-nuclear and poly-nuclear cells); 

 these make up the bulk of the leucocytes. 



3. Granular cells of 8-14^ diameter, with many granules in 

 their protoplasm; these granules stain differently in different cells. 

 Accordingly, we speak of oxyphile (eosinophile), basophile and 

 neutrophile cells, as the granules stain with acid, basic or neutral 

 stains. 



The number of leucocytes is about 10,000 in one cu. mm. 

 (about 500 red to one white), but it varies greatly. The 

 leucocytes contain besides water chiefly proteids (especially 

 nucleins and nucleo-albumin) and in smaller quantities 

 lecithin, cholesterin, and salts. 



The white blood corpuscles are able to pass through the 

 stomata of the walls of the capillaries and thus wander into 

 the tissues, hence they are also called wandering cells. 

 They are of physiological importance because they serve as 

 transports for many undissolved substances (fat, pigment) 

 and because they are able to destroy and remove foreign 

 bodies (e.g. Bacteria). They migrate in large numbers 

 from the vessels to those places where foreign substances 

 causing inflammation are present, and there they form the 

 pus. They are stimulated to activity by chemical action. 

 They originate in the lymph glands and spleen (see Chapter 

 VI). 



Besides the red and white blood corpuscles, there are still other 

 constituents in the blood having a definite form, viz. : 



Blood platelets, colorless, strongly refractive disks having a 

 diameter of or ^ that of the red blood corpuscles. They are 

 apparently the nuclear remains of destroyed leucocytes. 



Elementary granules, i.e. fat granules, which are brought to the 

 blood by the chyle. 



2. THE BLOOD PLASMA 



Pure plasma can be obtained by letting uncoagulated blood 

 stand at low temperature (about o C. ). By this, coagulation is 



