CH. XXVI.] THE WHITE CORPUSCLES 421 



Electricity causes the red blood-corpuscles to become crenated, and at 

 length mulberry-like. Finally they recover their round form and become quite 

 pale. 



The Colourless Corpuscles. In human blood the white or 

 colourless corpuscles or leucocytes (when at rest) are nearly spherical 

 masses of granular protoplasm. In all cases one or more nuclei exist 

 in each corpuscle. The size of the corpuscles varies considerably, 

 but averages ^innr f an i nc ^ (IfyO i n diameter. 



In health, the proportion of white to red corpuscles, which, taking 

 an average, is about 1 to 500 or 600, varies considerably even in the 

 course of the same day. The variations appear to depend chiefly on 

 the amount and probably also on the kind of food taken ; the number 

 of leucocytes is generally increased by a meal, and diminished by 

 fasting. Also in young persons, during pregnancy, and after great 

 loss of blood, there is a larger proportion of colourless blood-cor- 

 puscles. In old age, on the other hand, their proportion is diminished. 



There are four principal varieties of colourless corpuscles found 

 in human blood : 



1. Poly -morpho -nuclear cells. These contain several nuclei united 

 by fine threads of chromatin. Their protoplasm is filled with fine 

 granules, which are termed oxyphile on account of their affinity for 

 acid dyes like eosin. These are the most important leucocytes, con- 

 stituting from 60 to 70 per cent, of the total. 



2 Eosinophile cells. These are not so actively amoeboid as the 

 first variety. Their nucleus is simple or lobed. Their protoplasmic 

 granules are large, and are much more deeply stained by eosin than 

 the fine granules of the first variety. They comprise about 5 per 

 cent, of the total leucocytes. 



3. Lymphocytes. These have a large spherical nucleus and a 

 limited amount of clear protoplasm around it. Transitional forms 

 between them and the next variety are also found. They constitute 

 from 15 to 30 per cent, of the total. 



4. Hyaline cells. These differ from the last by having more proto- 

 plasm around the nucleus. The protoplasm is amoeboid, and is clear. 

 It, however, stains slightly with methylene blue, and this is perhaps 

 due to the presence of fine basophile granules. 



The nuclei of all these varieties are basophile, i.e., they have a 

 strong affinity for basic aniline dyes like methylene blue. Cells, with 

 large basophile granules, are very rare in healthy human blood. 



Amoeboid Movement. The remarkable property of the colour- 

 less corpuscles of spontaneously changing their shape was first demon- 

 strated by Wharton Jones in the blood of the skate. If a drop of 

 blood is examined with a high power of the microscope, under condi- 

 tions by which loss of moisture is prevented, and at the same time 

 the temperature is maintained by a warm stage at about that of the 



