238 TEXT-BOOK OF PHYSIOLOGY 



from the tissues, they seldom accumulate beyond a small amount, since 

 they are constantly being eliminated from the blood by the various ex- 

 cretory organs. 



Inorganic Salts. The inorganic salts of the plasma are chiefly sodium 

 and potassium chlorids, sulphates, and phosphates, together with calcium 

 and magnesium phosphates. Of the salts, sodium chlorid is the most 

 abundant, amounting to 0.56 part per hundred. Calcium phosphate is 

 present in small quantity, 0.2 part per 100. This salt is not present to 

 the same extent in serum for the reason that it became a constituent of 

 fibrin at the time of coagulation. In other respects serum differs but 

 slightly from plasma in the proportions of its saline constituents. 



HISTOLOGY OF THE RED CORPUSCLES OR ERYTHROCYTES 



The histologic features of the red corpuscles are readily observed in a 

 drop of freshly drawn blood when examined microscopically. The field of 

 the microscope will be seen to be crowded with red corpuscles floating in a 

 clear transparent fluid the plasma. Here and there will also be seen a white 

 corpuscle, round or irregular in shape; and granular in appearance. Within 

 a short time a characteristic phenomenon takes place: viz., the arranging of 

 the corpuscles in the form of columns of varying lengths, resembling rolls of 



coins. These rolls interlace with 

 each other at all angles and form a 

 network in the meshes of which lie 

 individual red and white corpuscles. 

 (See Fig. 91.) The cause of this 

 tendency of the corpuscles to adhere 

 to one another is not definitely 

 known. Since it does not take place 

 in circulating blood, and since it is to 

 a great extent prevented by defibrin- 

 ating the blood, it has been supposed 

 to be dependent on the formation of 

 some adhesive substance connected 

 with the formation of fibrin. 



Color. When viewed by trans- 

 mitted light, a single corpuscle is 

 FIG. 91. CORPUSCLES FROM HUMAN SUB- slightly yellow or greenish in color; 

 JECT. A few colorless corpuscles are seen but when a number are grouped to- 



among the colored discs, many of which are ^pfUp- tu p W rWrPnc nnrl tV.A re- 

 arranged in rouleaux. (Funke.) gether, the color deepens and the cor- 

 puscles appear red. In either case 



the color is due to the presence in the corpuscle of a specific coloring- matter, 

 hemoglobin. 



Shape. The red corpuscle is a circular, flattened disc with rounded 

 edges. Each surface is perfectly smooth and presents a shallow depression 

 in its center, so that it is also biconcave. A longitudinal section of a cor- 

 puscle would present, when viewed edgewise, an outline similar to that of 

 Fig. 92. This difference in the thickness of the peripheral and central 

 portions of the corpuscle gives rise to differences in optical appearances 

 when examined microscopically. At a certain distance of the object-glass 



