BLOOD AND LYMPH 207 



afterwards see that it is derived from the liver, and that it 

 is excreted in the urine by the kidneys. 



Creatin (p. 40), with uric acid (p. 427), and some allied bodies 

 appear to be normally present in traces, and their amount 

 may be increased in diseased conditions. 



Of the inorganic constituents of the serum the most abund- 

 ant is chloride of sodium, but in addition sodium carbonate 

 and alkaline sodium phosphate are also present. Calcium, 

 potassium, and magnesium occur in very small amounts. 



III. Cells of Blood. 



1. Leucocytes White Cells. These are much less numerous 

 than the red cells, and their number varies enormously in 

 normal conditions. On an average there is one to every 400 

 or 500 red cells. 



They are soft, extensile, elastic, and sticky, and each con- 

 tains a nucleus and a well-developed double centrosome. In 

 size they vary considerably, some being much larger than the 

 red cells, some slightly smaller. The character of the nucleus 

 varies greatly, and from this and from variations in the proto- 

 plasm, they may be divided into four classes. 



1st. Lymphocytes. Cells with a clear protoplasm and a more 

 or less circular nucleus. Some are very small, while others 

 are larger. They constitute about 20 to 25 per cent, of the 

 leucocytes (fig. 102, b and c). 



2nd. Polymorpho-nuclear leucocytes, with a much-distorted and 

 lobated irregular nucleus and a finely granular protoplasm, 

 whose granules stain with acid and neutral stains. These 

 constitute about 70 to 75 per cent, of the leucocytes. 



3rd. Eosinophil or oxyphil leucocytes, with a lobated nucleus 

 like the last, but with large granules in the protoplasm which 

 stain deeply with acid stains. From 1 to 4 per cent, of the 

 leucocytes are of this variety. 



4th. Basophil leucocytes, practically absent from normal 

 blood, with a lobated nucleus and granules in the protoplasm, 

 staining with basic stains. 



Myelocytes are large leucocytes with a large circular or 

 oval nucleus and a finely granular protoplasm. They are 

 not normal constituents of the blood, but appear when the 



