Volume 1

A text-book of human physiology : including histology and microscopical anatomy with special reference to the requirements of practical medicine / by L. Landois ; translated from the seventh German edition with additions by William Stirling.

Landois, L. (Leonard), 1837-1902. Lehrbuch der Physiologie des Menschen. English

Date:: 1891

Credit: A text-book of human physiology : including histology and microscopical anatomy with special reference to the requirements of practical medicine / by L. Landois ; translated from the seventh German edition with additions by William Stirling. Source: Wellcome Collection.

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$(C) Later Formation.—Most observers agree that the red bloocl-corpiiscles are formed from special nucleated cells, which gradually assume the form and colour of the perfect red corpuscle. According to ^s^eumann, however, these corpuscles are pigmented from the first. In the tailed amphibians and fishes, the spleen, in all other vertebrates the red marrow of bone, are the seats of formation of these corpuscles, which subsequently increase by division {Neumann, Rindfleisch, Bizzozero). In the red marrow of bone we can study all the stages of the transformation; especially pale contractile cells similar to colourless corpuscles, and also red nucleated corpuscles, which are similar to the nucleated corpuscles of the embryo, and the progenitors of the red corpuscles. These transition cells are said by Erb to be more numerous after severe haemorrhage, the number of them occurring in the blood corresponding with the energy of the formative process. After copious haemorrhage these transition forms appear in numbers in the blood- stream. The small veins, and perhaps the capillaries of the red marrow of bone and the spleen have no proper walls, so that the red corpuscles when formed can pass into the circulation. Red or blood-forming marrow occurs in the bones of the skull, and in most of the bones of the trunk, while the bones of the extremities either contain yellow marrow (which is essentially fatty in its nature), or, at most, it is only the heads of the long bones that contain red marrow. Where the blood-regeneration process is very active, however, the yellow marrow may be changed into red, even throughout all the bones of the extremities {Nemnanii). [The most recent observers {Löwit, Bizzozero, and Denys), regard the red and white blood-corpuscles as being developed independently of each other. Löwit calls the early stages of the former erythroblasts and of the latter leucoblasts. In the red marrow of the bones of birds, the red corpuscles are developed within the blood-vessels of the marrow, and the colourless ones in the tissue which lies in the vascular meshes. The erythroblasts are originally colourless, and between them and the complete red corpuscle there is a complete series of gradations. The erythroblasts have a large, spherical, central nucleus with a pronounced nuclein network and homogeneous or sHghtly granular protoplasm. The leucoblasts, on the contrary, contain a small nucleus of variable form, with numerous nucleoH, and often placed peripherally. The protoplasm contains many eosinophile granules. Both exhibit amoeboid movement, but this is more active in the leucoblasts. Both divide by mitosis. Some of the erythroblasts pass out directly in the blood-stream, while the leucocytes in virtue of their amoeboid movements pass by diapedesis into the vessels. Eepeated haemorrhages lead to rapid mitotic division of both forms.] [In extra-uterine life, in mammals, the red marrow of bone is undoubtedly the chief seat of the formation of red blood-corpuscles. In it are to be found a large number of nucleated red blood-corpuscles, i.e., embryonic forms, which ultimately lose their nuclei, pass into the circulation as perfect red corpuscles. After copious haemorrhage, when the animal forms a larger number of corpuscles than usual, as it were striving to make up the deficiency, the number of nucleated red corpuscles in the red blood-forming marrow is greatly increased, and even parts of what was previously yellow marrow appear somewhat reddish. The blood-forming function of the red marrow is greatly increased after haemorrhage {Neumann and Bizzozero). _ Often, however, there is an additional factor, as shown by Bizzozero and Salvioli in the case of guinea-pigs and dogs. In these animals after severe anaemia, due to repeated haemorrhages, the spleen also participates in the formation of red corpuscles, for in it are found nucleated red corpuscles similar to those of the red marrow.] [In birds also red blood-corpuscles are formed in the red marrow, but so far as the spleen has been investigated, Bizzozero has not found any reason to believe that this organ is concerned in the formation of red blood-corpuscles in these animals.]$