130 THE BLOOD 



corpuscle. The corpuscles vary considerably in size, but average lo/u in 

 diameter. 



The number of leucocytes in a cubic millimeter of blood is estimated 

 at 7,500 to 8,000. The proportion of white corpuscles to red, therefore, is 

 about one of the former to 700 of the latter. This proportion is not very 

 constant in health and great variations occur under the influence of disease, 

 especially in certain infectious diseases in which the number of white cor- 

 puscles is markedly increased. 



After a full meal the white cells in a healthy adult are increased in number 

 about one-third, the increase beginning within an hour, attaining a maxi- 

 mum in three or four hours, and then gradually falling to normal. This 

 process is frequently modified by the character of the food, the greatest 

 increase occurring with an exclusively meat diet, while a purely vegetarian 

 diet has usually no effect. The increase is also more marked in children, 

 and especially in infants. The essential factor is probably the absorption 

 of albuminous matter in considerable quantities. This causes proliferation 

 of leucocytes in the adenoid tissue of the gastro-intestinal tract. 



In pregnancy there is often a moderate increase in the number of white 

 cells during the later months. This does not begin until after the third 

 month, and is most marked and constant in primiparae. After parturition 

 the leucocytes gradually diminish under normal conditions, and usually 

 reach the normal within a fortnight. The essential factor is probably the 

 general stimulation in the maternal organism. It is well established that the 

 white cells are very numerous in the new-born, though different observers 

 have made very conflicting estimates. Still all agree that there is a very 

 rapid decrease in their numbers during the first few days, and that this is 

 followed by a less marked increase, which continues for many months. 

 According to Rieder, who is perhaps the most reliable, there are at birth 

 from 14,200 to 27,400 per cubic millimeter, and after the fourth day from 

 12,400 to 14,800. 



Varieties of Leucocytes. The colorless corpuscles present greater diver- 

 sities of form than the red ones, Plate II. They are usually classified ac- 

 cording to their reaction to staining agents or to the presence or absence of 

 granules in their cytoplasm. Kanthack and Hardy offer the following classi- 

 fication, based upon both phenomena: 



Leucocytes. 



A. Oxyphile (staining with acid dyes) . . . . \ *' Finely granular. 



( 2. Coarsely granular eosmophile 



B. Basophile (staining with basic dyes) ... i. Finely granular. 



f i. Small lymphocyte. 



C. Hyaline 4 



( 2. Large myelocyte. 



The finely granular oxyphile constitutes 75 per cent, of all leucocytes. 

 It has an average diameter of 10/1, and possesses phagocytic action to a 



