THE LIFE-HISTORY OF THE FORMED ELE- 

 MENTS OF THE BLOOD, ESPECIALLY 

 THE RED BLOOD CORPUSCLES. 



W. 11. IIOWEI.L, Ph.D., M.D., 

 Professor of Physiology and Histology, Uniyersity of Michigan. 



I. The Red Blood Corpuscles. 

 The origin and the fate of the mammalian red corpuscles 

 have been the subjects of an extraordinary number of scientific 

 papers from workers in various fields of biological research. 

 Contributions have been made from the side of pathology, of 

 normal histology, and of embryology, so that to discuss the 

 subject in all its aspects becomes a difficult undertaking. The 

 results of investigation along these different lines are not at all 

 in agreement, so that many theories radically different from one 

 another have been proposed. Indeed, the embryologist, the 

 pathologist, or the histologist often works at the subject without 

 any reference to the results made known by the investigations 

 of the other, inasmuch as the journals in which these results 

 appear are likely to be read only by the specialists in whose 

 interest they are published. To one who reads over the liter- 

 ature even incompletely, the conviction comes, I think, with a 

 good deal of force, that the various phenomena which have 

 been observed and described, and which have served as a basis 

 for the divergent theories, might all find a simpler and better 

 explanation under some one theory. One cannot help believ- 

 ing, in other words, that in the mammalia the method of pro- 

 duction of the red corpuscles is essentially the same in disease 

 as in health and in the adult as in the foetus ; and furthermore 

 that the formation of these elements takes place not in a num- 

 ber of different ways, but according to some one scheme of 

 reproduction, as in the development of tissue elements in gen- 

 eral. Many authors, on the contrary, have advanced one theory 

 of the formation of the red corpuscles as the result of their 

 own work, but have admitted at the same time that the differ- 

 ent veiws advocated by others might hold good under certain 



