THE BLOOD 255 



in Proteus and Amphiuma the long diameter attains an average length of 

 0.058 mm. and 0.07 7 mm. respectively. In fish the corpuscles are smaller, 

 oval, and nucleated, with the exception of the lamprey eels, in which they 

 are circular, biconcave, and nucleated, though the nucleus is generally con- 

 cealed in the peripheral portion of the corpuscle. As in these animals the 

 corpuscles are almost twice the size of the human red corpuscles, they can, 

 notwithstanding the similarity of shape, be readily distinguished from them. 



The Function of the Red Corpuscles. The red corpuscles, by virtue 

 of the capacity of their contained hemoglobin for oxygen absorption, may be 

 regarded as carriers of oxygen from the lungs to the tissues, and therefore 

 important factors in the general respiratory process. The size as well as the 

 number of the corpuscles in different classes of animals appears to be directly 

 related to the activity of the respiratory process. In those animals in which 

 the corpuscles are small and numerous and the total superficial area large, 

 respiration is active, the quantity of oxygen absorbed is large, and the 

 energy liberated through oxidation is correspondingly large. In those, 

 animals, on the contrary, in which the corpuscles are large and relatively 

 few in number, the reverse conditions obtain. This is in accordance with 

 the fact that the superficial area of any given volume of substance is increased 

 in proportion to the extent to which it is subdivided. 



The superficial area of a single human red corpuscle has been estimated 

 at 0.000128 sq. mm. If the number of corpuscles in i cubic millimeter of 

 blood averages 5,000,000, the superficial area would amount to 640 square 

 millimeters; and if the amount of blood in the body of a man weighing 70 

 kilos is taken as one-nineteenth of this weight that is, 3864 grams (3659 c.c.) 

 the total area of the corpuscular surface will amount to 2341 square meters. 



HISTOLOGY OF THE WHITE CORPUSCLES OR LEUKOCYTES 



The presence of white corpuscles in the blood can be readily observed 

 under the same conditions as the red corpuscles are observed. Thus when 

 the mesentery of the frog or the guinea-pig is examined with the microscope 

 the white corpuscles are seen adhering to the walls of the blood-vessels; in 

 a drop of freshly drawn blood they are found in the spaces between red 

 corpuscles (Fig. 91). A careful examination of the blood by the employ- 

 ment of appropriate methods has revealed the presence of several varieties of 

 white corpuscles, to which reference will be made in a subsequent paragraph. 



Shape and Size. In the resting condition, whether seen in the vessel 

 or on the stage of the microscope, the white corpuscle, as its name implies, is 

 grayish in color, round or globular in form, though often presenting a more 

 or less irregular surface. Its diameter varies from 0.004 to 0.013 mm., 

 though the average is about o.ou mm. or about 3 5*00 inch. 



Structure. A typical white corpuscle consists of a ground-substance 

 uniformly transparent and apparently homogeneous, in which are embedded 

 a number of granules of varying size, some of which are very fine, while 

 others are large. By various reagents it has been demonstrated that the 

 granules are fatty, protein, and carbohydrate (glycogen) in character. In 

 the fresh cells the existence of a nucleus is difficult of detection, though its 

 presence can be demonstrated by the addition of acetic acid, which renders 

 the perinuclear cytoplasm more transparent and makes the nucleus con- 



