BLOOD AND H^MOPOIETIC ORGANS 87 



stood. It cannot be doubted that the coarse granules 

 which they contain must be intimately concerned in 

 some way with the functional activity of the cell, and 

 if we knew the nature of these granules we might be 

 nearer to a comprehension of the work of the cell as 

 a whole. But, unfortunately, we do not know the nature 

 of the granules. They have been variously supposed* 

 to consist of (1) fat, (2) protein, (3) haemoglobin or a 

 derivative of it, (4) nucleo-albumin, (5) defensive secretory 

 granules. Some people have asserted that the granules 

 are rich in phosphorus and iron; others have denied 

 that they can find any evidence of iron in them at all. 

 Nor is any light thrown upon their functions by the fact 

 that their number in the blood is increased in such 

 diverse conditions as asthma, some skin diseases, and 

 helminthiasis. If we know little of the eosinophils, we 

 know nothing of the basophils at all. They are so 

 extremely scanty in normal blood that one cannot 

 attribute to them any important function. 



The total number of white cells in the adult blood 

 varies between 10,000 and 7,000 per cubic millimetre, 

 and is by no means the same in every one. 



Assuming the total number of leucocytes in a cubic 

 millimetre of blood to be 7,500, the proportion of this 

 made up by the different varieties is as follows : 



Polymorphonuclears ... ... 5,000 



Lymphocytes ... ... ... 2,000 



Large mononuclears ... ... 350 



Eosinophils ... ... ... 150 



* See Howard and Perkins, Johns Hopkins Hospital Reports, 

 1902, x. 249. 



