BLOOD. 



479 



2. The White Blood-Corpuscles. — The white blood-cells are nucle- 

 ated masses of free protoplasm destitute of any membrane, granular in 

 appearance, and of the same nature as lymph and pus, or connective- 

 tissue corpuscles. When in globular form these cells have a diameter 

 of about 0.01 millimeter ; like other forms of free protoplasm, such as 

 the amoeba, they are capable of assuming the most diverse shapes. Even 

 after being drawn from the body, if a drop of blood is kept at the body 

 temperature on a warm stage under the microscope, the white blood- 



Fig. 178.— Human Leucocytes showing Amceboid Movements. (Landois.) 



cells may be seen to change their shape and position, and even take fine 

 granules, such as carmine, into their interior. In other words, they 

 behave precisely like the amoeba (Pig. 178). 



The white blood-cells are found in much smaller numbers in the 

 blood than the red cells ; their relative proportions vary according to the 

 nutritive condition of the animal, the locality from which the blood is 

 taken, and various other circumstances. As an average, it may be stated 

 that there are about three hundred to three hundred and fifty times as 

 many red cells as white. 



