Growth / by the late James Lorrain Smith ; edited by J.S. Haldane.

  • Smith, J. Lorrain (James Lorrain), 1862-1931.
Date:
1932
Catalogue details

Licence: Public Domain Mark

Credit: Growth / by the late James Lorrain Smith ; edited by J.S. Haldane. Source: Wellcome Collection.

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    tural modification, and round the nucleus is a zone of cytoplasm which still resembles that of all undifferenti¬ ated cells. The red corpuscle of the blood is also a living cell set aside for a highly specialised function, and the cytoplasm and nucleus in this case are both modified. The cytoplasm is loaded with haemoglobin, and it is not possible to give a satisfactory description of the change in the cytoplasm which has taken place with the coming of the haemoglobin. Before the red cell passes from the marrow to the circulation it has lost all trace of nuclear structure. Yet the cell continues to serve the special function of respiration. While it has no power of growth, it is at the same time numbered in the regulation of the blood as strictly as any other group of cells forming the so-called solid structures. And where by haemorrhage blood-cells are lost, it is as if a wound had been made and the wound heals by the growth of cells, and the red cells are restored to their normal number. The red cells of the blood are cells deprived of their nucleus and reduced to a minimal quantity of granular cytoplasm so small that it cannot be demonstrated except perhaps in the recent reticulo¬ cyte. They are loaded with haemoglobin, and in this condition they survive in the circulation for a short period. From this point of view the study of blood- cells would indicate that differentiation means not only the loss of the capacity to grow, but ultimately means the death of the cell. It would indicate that the nucleus is killed off first and may perhaps be going because the granular cytoplasm has been so far reduced. Finally, we observe the vitality of a cell reduced to cytoplasm only, or, if there be nuclear matter left, at least there is no visible structure left. It has been proved experi-
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