8 Centralblatt f. d. Med. Wissenschaften, Bd. xix.
9 Fortschritte der Medicin, 1885, No. 1.
(3) Hayem believes that the red corpuscles develop from the small hæmatoblasts, but, so far as I know, his observations have never been confirmed. He states that in normal blood they occur in the proportion of about 1 to 20 red. In all states of blood reparation they increase greatly. He describes a hæmatoblastic crisis as occurring after hemorrhage, fevers, etc., when the number of these elements rapidly augments, and is succeeded by the addition of many small pale-red corpuscles, which he looks upon as intermediate between the hæmatoblasts and the ordinary red forms.
The colorless corpuscles are regarded as the direct offspring of the cells of the follicular cords in the lymph-glands and adenoid tissue, but whether by process of division of existing leucocytes or by sprouting from the endothelial places, or from the protoplasm in the fibres of the reticulum, remains to be settled.
The nucleated red corpuscles are in the healthy adult confined to red marrow, in which they probably develop from colorless cells, and may be regarded, as Neumann originally suggested, as transitional or intermediate forms between white and red cells. In anæmic states they may occur in the spleen and in the lymph-glands.
Of the origin of the hæmatoblasts or blood-plates we know absolutely nothing. They occur most abundantly under two most opposite conditions—in the young growing animal just entering upon life, and in the diseased, cachectic, wornout animal just preparing to abandon it.
Our knowledge of the relation of the cytogenetic organs to blood-formation may be thus briefly stated: The spleen certainly takes part in the development of colorless corpuscles, but its participation in red blood-formation is more doubtful. The nucleated red or embryonal forms do not occur, at least in any numbers, in health, though some observers have noted that after a repeated bleeding the organ was swollen and contained many such cells, as if it was the seat of an active development. Though the opinion prevails widely that the spleen is one of the important organs in the formation of red corpuscles, the evidence for this belief is of an exceedingly scanty nature.
The lymphatic glands and the adenoid tissue in other regions are the seats of constant production of colorless corpuscles, but of their relation to the red corpuscles there is the same lack of information as in the spleen. I do not know of any corroboration of the observation of Johnstone above mentioned, and in any case the number of red cells in the efferent vessels of a lymph-gland is so small—and indeed in the thoracic duct itself—that we cannot believe they are produced as red corpuscles in large numbers within the lymphatic system.
The red bone-marrow, as pointed out by Neumann10 and Bizzozero,11 appears to be the seat of blood-formation, and in the adult body is the only region in which the embryonic or nucleated red cells are found. It is a tissue similar in many respects to the spleen, and, though confined to the short and flat bones, the total amount in the body is very considerable. In the young it also fills the long bones. The evidence of the development of red corpuscles in the marrow rests upon the constant presence of nucleated cells infiltrated with hæmoglobin, and of their fission. Forms undergoing the process of karyokinesis can be seen without difficulty. In excessive hemorrhage, natural or induced, it appears to undergo an active proliferation, and in the long bones a red marrow may replace the fatty tissue.
10 Centralblatt f. d. Med. Wissenschaften, 1868.