DEVELOPMENT OF THE RED BLOOD CORPUSCLES 127 



authorities claiming an increase and others a decrease. In childhood there 

 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 1 00-200 cubic centimeters of blood are lost normally in the course of 

 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 

 that any anemia must be due to abnormal conditions. Post-partum anemia 

 should not last longer than two weeks. 



The red corpuscles are not all alike. In almost every specimen of blood a 

 certain number of corpuscles smaller than the rest may be observed. They 

 are termed microcytes, or hematoblasts, and are probably immature 

 corpuscles. 



A peculiar property of the red corpuscles, which is exaggerated in in- 

 flammatory blood, may be here again noticed, i. e., their great tendency to 

 adhere together in rolls or columns (rouleaux), like piles of coins. These 

 rolls quickly fasten together by their ends, and cluster; so that, when the 

 blood is spread out thinly on a glass, they form a kind of irregular network, 

 with crowds of corpuscles at the several points corresponding with the knots 

 of the net, figure 109. Hence the clot formed in such a thin layer of blood 

 looks mottled with blotches of pink upon a white ground. 



The red corpuscles are constantly undergoing disintegration in different 

 parts of the circulatory system, particularly in the spleen. The liberated 

 hemoglobin contributes to the formation of the bile pigments in the liver. 



Development of the Red Blood Corpuscles. The first formed 

 blood corpuscles of the human embryo differ much in their general characters 

 from those which belong to the later periods of intra-uterine, and to all 

 periods of extra-uterine life. Their manner of origin is at first very simple. 



Surrounding the early embryo is a circular area, called the vascular area, 

 in which the first rudiments of the blood vessels and blood corpuscles are 

 developed. Here the nucleated embryonal cells of the mesoblast, from 

 which the blood vessels and corpuscles are to be formed, send out processes 

 in various directions, and these, joining together, form an irregular mesh- 

 work. The nuclei increase in number, and collect chiefly in the larger masses 

 of protoplasm, but partly also in the processes. It appears that hemo- 

 globin then makes its appearance in certain of these nucleated embryonal 

 cells, which thus become the earliest red blood corpuscles. The proto- 



