MORPHOLOGY OF THE BLOOD CORPUSCLES.* 



By Charles-Sedgwick Minot. 



If one goes tlirough the very extensive literature dealing with blood 

 corpuscles one finds the most divergent views defended, and can hardly 

 reach clear ideas, for the conceptions do not agree among themselves, 

 either as to their structure or as to the development of the corpuscles. 

 According to some the red corpuscles arise from the white; according 

 to others the white corpuscles arise from the red ; and according to still 

 others both kinds arise from indifferent cells. In regard to one point 

 only is the majority of investigators united, namely, in the silent 

 assumption that all blood corpuscles are of one and the same kind in 

 spite of the absence of the nucleus in mammalian corpuscles. It is just 

 this assumption that has caused endless confusion, and the morphology 

 of the blood corpuscles can be cleared up only by starting with the 

 recognition of the fundamental difference between nucleated and non- 

 nucleated corpuscles. Further, it must be recognized that no corpus- 

 cles, neither red nor white, arise from nuclei. 



The origin of red corpuscles from nuclei has been maintained several 

 times. This notion is based upon defective observations. It is very 

 easy in the chick, for example, to convince oneself that the first blood 

 corpuscles are cells; in the area vasculosa, at the time of the blood 

 formation, the red blood cells are readily seen, in part lying singly, in 

 part in groups (blood islands), adherent to the vascular walls; the free 

 cells are constituted chiefly by the nucleus, which is surrounded by a 

 very thin layer of j^rotoplasm, which is very easily overlooked, especially if 

 the preparation is not suitably stained ; this explains, I think, the state- 

 ment made by Balfour (Works, vol. i) and others, that the blood corpus- 

 cles consist only of nuclei. By following the development along further 

 we find that the protoplasm enlarges for several days, and that during 

 the same time there is a progressive diminution in size of the nucleus, 

 which however is completed before the layer of protoplasm reaches 

 its ultimate size. The nucleus is at first granular, and its nucleolus, 

 or nucleoli, stands out clearly ; as the nucleolus shrinks it becomes 



* From the American Naturalist, November, 1890, vol. xxiv, pp. 1020-1023. 



429 



