Origin and Death of the Red Blood-Corpuscle. 299 



opinions, prejudices which are not easily allayed are excited. 

 Differences in the interpretation of facts are to be expected and 

 hoped for ; final conclusions should be determined by their 

 reasonableness and their fitness to the phenomena they explain. 



THE ORIGIN AND DEATH OF THE RED BLOOD- 

 . CORPUSCLE. 



BY PROF. C. H. ST DWELL. 



{Received J Nue 26th, iSyg.) 



At the early period of embryonic life, when the foetus is 

 little more than 2"""- in length, the blood becomes red. The 

 red elements are much larger than those found in the adult, 

 varying in size from 9.75 ' " to 15.0 ' " in transverse diameter. In 

 shape they are circular, oval, or globular. Nearly all have a nucleus 

 readily seen without the aid of reagents. 



What is the origin of these primary red corpuscles of the 

 embryo ? 



Early in the history of the embryo the rudimentary heart con- 

 sists of a mass of epithelial cells, and radiating from it are two or 

 more tracts — generally one on each side — which, by their subse- 

 quent subdivision, form the vascular area. 



These cells are nucleated and vary in shape according to the 

 pressure to which they have been subjected. In size they agree 

 with the early red corpuscles described above. 



At a certain time some of these nucleated cells in the interior 

 of the mass composing the rudimentary heart, become loosened 

 from their fellows. The exact time of this occurrence and its cause 

 are not known. There are certain normal functions of the body 

 performed in a regular way, the cause or causes of the regularity 

 remaining in obscurity. We only know that these particular cells 

 are separated from the rest to serve a special purpose as carriers 

 of oxygen. 



The remaining cells become transformed into the tissue com- 

 posing the walls of the vessel, which, by twisting upon itself, finally 

 becomes the heart. There is reason to believe that throughout 

 the vascular area, cells in the interior of the blood-tracts become 

 loosened from their fellows, while the remaining ones are meta- 

 morphosed into the walls of the vessels. These loosened cells may 



