RED CORPUSCLES OR ERYTHROCYTES 



109 



is no difference between the sexes in the number of red cells per cubic milli- 

 meter, but after menstruation is established a relative anemia develops in 

 women. Welcker's original estimate placed the difference at 500,000 per 

 cubic millimeter, and these figures have been generally accepted, though 

 Leichtenstein asserts that the difference is 1,000,000. 



Menstruation in healthy subjects has practically no effect, as not more 

 than ico-200 cubic centimeters of blood are lost normally in the course of 



FIG. in. The Illustration is Somewhat Altered from a Drawing by Gulliver, in the 

 Proceed. Zool. Society, and exhibits the typical characters of the red blood-cells in the main 

 Divisions of the Vertebrata. The fractions are those of an inch, and represent the average diameter. 

 In the case of the oval cells, only the long diameter is here given. It is remarkable, that although 

 the size of the red blood-cells varies so much in the different classes of the vertebrate kingdom, 

 that of the white corpuscles remains comparatively uniform, and thus they are, in some animals, 

 much greater, in others much less, than the red corpuscle existing side by side with them. 



several days. Under such circumstances the normal diminution of red cells 

 per cubic millimeter is probably less than 150,000, though Sfameni has placed 

 the loss at about 225,000. In fact an increase has been claimed. The 

 leucocytes are slightly increased during menstruation. It is now the general 

 opinion that pregnancy has little or no effect on the number of red cells, and 



