174 



THE BLOOD 



type in all other particulars. In other vertebrates, 1 it is elliptical 2 

 and contains a very conspicuous nucleus. It is soft and very elastic, 

 peculiarities which enable it to traverse capillary channels of smaller 

 diameter than its own. In these minute tubules the otherwise circular 

 discs often assume a shape approximating the elliptical. 



The size of the red cell differs greatly in different animals, but 

 varies only very slightly in animals of the same group. In man it 

 measures 7.5/x 3 in diameter (7.1 to 7.8ju) and l.Gju in thickness. Its 

 volume equals 0.000,000,072 c. mm. Variations in size between 6.5 

 and 9.3^1 have been noted even in normal persons. Elliptical cor- 

 puscles have been found in a few individuals. The following compila- 

 tion will show that red corpuscles are in existence which are either 

 very much smaller or larger than the human. 4 



Circular corpuscles 



Musk-deer 2 . 3/z 



Elliptical corpuscles 



Lama 7 . 5 X 4 . 2/u. 



Pigeon 14.7 X 6.5ju 



Frog 23.0 X 16. SM 



Triton 29.5 X 19. 5 M 



Proteus 58.2 X 35. 6 M 



Amphiuma ...77.0 X 58.0/x 



Goat 4.25/t 



Sheep 5 . Oju 



Horse 5 . 5/t 



Pig 6.0/* 



Cat 6.2 M 



Rabbit 7 . IM 



Dog 7.2/x 



Man 7 . 5/* 



Ox 8.0 M 



Elephant 9.4 M 



If observed under the microscope, a single mammalian red corpus- 

 cle possesses a yellowish, or even green- 

 ish color, but if many of them are 

 grouped together, a distinct sensation of 

 red is obtained. In shed blood, these 

 bodies frequently arrange themselves in 

 the form of rolls, but since these rouleaux 

 formations are not found in circulating 

 blood, and rarely in defibrinated blood, 

 it is assumed that their surfaces must 

 first be rendered sticky before this ag- 

 glutination can take place. The agent 

 which produces this change, must be 

 derived from the fibrin or its precursor, 

 because the agglutination may be dimin- 

 ished or prevented altogether by adding normal saline solution, or 

 some other non-destructive medium to the blood. 



1 In lamprey eels the corpuscles are round, biconcave and nucleated. 



2 Not oval, because this term implies that one of the ends is more pointed 

 than the other. 



3 IM (micron) equals 0.001 mm. 



4 Monassein, Dissertation, Berlin, 1872; and Schilling Torgau, Folia hema- 

 tologica, i, 1912. 



FIG. 99. CIRCULAH RED COR- 

 PUSCLES DRAWN TO SCALE. 

 M, musk-deer; G, goat; P, pig; Mi 

 man; 0, ox; E, elephant. 



