242 TEXT-BOOK OF PHYSIOLOGY. 



respiration is active, the quantity of oxygen absorbed is large, and the energy 

 evolved through oxidation great. In those animals, on the contrary, in 

 which the corpuscles are large and relatively few in number, the reverse 

 conditions obtain. This is in accordance with the fact that the superficial 

 area of any given volume of substance is increased in proportion to the 

 extent to which it is subdivided. 



The superficial area of a single human red corpuscle has been estimated 

 at 0.000128 sq. mm. If the number of corpuscles in i cubic millimeter of 

 blood averages 5,000,000, the superficial area would amount to 640 square 

 millimeters; and if the amount of blood in the body of a man weighing 70 

 kilos is taken as one-nineteenth of this weight that is, 3864 grams (3659 c.c.) 

 the total area of the corpuscular surface will amount to 2341 square meters. 



Life-history of Red Corpuscles. In the performance of their functions 

 the red corpuscles undergo more or less disintegration and finally destruction; 

 but as the average number is maintained under normal physiologic condi- 

 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. 



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 menstral 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 



1 For an admirable re'sume' 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. 



