THE BLOOD 253 



tions, there must be a constant renewal of corpuscles from day to day The 

 evidence of destruction of red corpuscles is furnished by the presence in the 

 blood, in various situations of the body, of a pigment containing iron and the 

 presence of pigments in the bile and urine, all of which are believed to be 

 derivatives of effete hemoglobin. The blood-pigment (hematin), which 

 contains the iron of the hemoglobin, is found in the capillaries of the liver, 

 in the cells of the splenic pulp, and in the marrow of the bones. Whether 

 the presence of the pigment in these organs is a proof that the corpuscles are 

 destroyed here, or whether they are to be regarded merely as agents con- 

 cerned in the further reduction and elimination of the hematin, is uncertain. 

 The genetic relationship between bile-pigment and hemoglobin is shown by 

 the fact that any artificial destruction of hemoglobin or its injection into the 

 blood is attended by an increase in the quantity of bile-pigment eliminated. 

 It appears also from chemic considerations that the hemoglobin will undergo 

 cleavage into a globulin body and hematin, which by the loss of its iron is 

 readily converted into the bile-pigment, bilirubin. The amount of this 

 latter pigment may therefore be taken as an index of the extent of corpuscular 

 destruction. 



There is some evidence for the view that the iron set free by the reduc- 

 tion of the hematin, eventually reaches the blood-making organs and is 

 utilized by the developing corpuscles in the formation of the necessary 

 hemoglobin. 



This gradual decay of corpuscles as well as the losses occasioned by 

 hemorrhages necessitate a continuous formation of new corpuscles, so that 

 the normal number may be maintained. The rapidity with which corpuscles 

 may be renewed, in the woman at least, is shown by a computation of Mr. 

 Charles L. Mix. A woman loses during a menstrual period 150 c.c. of 

 blood. At the end of twenty-eight or thirty days this volume is restored, so 

 that in one day 5 c.c., or 5000 c.mm., of blood must be formed, or 208 

 c.mm. per hour and 3^ c.mm. per minute. That is, during a certain num- 

 ber of years 15,750,000 corpuscles must be formed every minute, and this 

 independent of the daily loss due to functional activity. 



At the present time there is a general agreement among histologists that 

 in adult life the red corpuscles are derived from embryonic forms, the so- 

 called erythroblasts, cells of a large size with distinctly reticulated nuclei, 

 which are found chiefly in the red marrow of the long bones. 1 In this 

 situation both arterial and venous capillaries are relatively large and the 

 blood is separated from the surrounding marrow by extremely thin walls. 

 In the passages of this capillary network the erythroblasts make their appear- 

 ance most probably by a transformation of pre-existing marrow cells which 

 cross the capillary wall from without. At first they are large, homogeneous, 

 colorless, perhaps slightly tinged with hemoglobin and distinctly nucleated. 

 They increase in number by karyokinesis and at the same time increase in 

 their hemoglobin content. In the course of their development the nucleus 

 becomes smaller and denser, when the cells are known as normoblasts. 

 Subsequently the nucleus is extruded, carrying with it a portion of the peri- 

 nuclear cytoplasm, after which the remainder of the corpuscle assumes 



1 For an admirable resume" of the various views regarding the origin and formation of red 

 corpuscles see the paper of Mr. Charles L. Mix, Boston Med. and Surg. Journal, 1892, Nos. 

 ii and 12; also paper by Prof. W. H. Howell, Journal of Morphology, vol. iv, 1892. 



