THE COLORLESS CORPUSCLES OR LEUCOCYTES 131 



The Colorless Corpuscles or Leucocytes. In human blood the white 

 corpuscles, leucocytes, are nearly spherical masses of granular protoplasm 

 without cell wall. In all cases one or more nuclei exist in each corpuscle. 

 The corpuscles vary considerably in size, but average IO/JL 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 



FIG. 115. Colored Nucleated Corpuscles, from the Red Marrow of the Guinea-pig. 



(E. A. Schafer.) 



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 lymphoid 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 there are at birth from 14,200 to 27,400 per cubic milli- 

 meter, and after the fourth day from 12,400 to 14,800. 



The colorless corpuscles present a great diversity of form. There are 

 certain constant types found in fairly definite proportions in normal 

 blood, but in pathological bloods a long series of variants have been 

 described and figured by such authors as Wood, Webster, and Simon. In 

 histological and clinical examination the white corpuscles are classified 



