The graft theory of disease : being an application of Mr. Darwin's hypothesis of pangenesis to the explanation of the phenomena of the zymotic diseases / by James Ross.

Date:
1872
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Licence: Public Domain Mark

Credit: The graft theory of disease : being an application of Mr. Darwin's hypothesis of pangenesis to the explanation of the phenomena of the zymotic diseases / by James Ross. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

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    THE GRAFT THEORY OF DISEASE. tion °f one of the protozoa maintains its existence for a short time and grow, it is certain that it will become differentiated into an envelope and central portion, whether our means of observa- tion enable us to detect the difference or not. In this case, then, one gemmule was sufficient to give oiigin to a protozoa which, in what may be called its adult condition, becomes differentiated into an outer and central portion. If we now ascend to those organisms which consist, not of a single cel], but of an aggregation of cells, it is certain that the difference between the forces which will fall upon the outer and central portions will be greater than in the unicellular organisms, and therefore that the differentiation between the outer and central jior- tions will also be greater. But another factor may now come into operation, which will produce a still further modification. One of the other assumptions of Mr. Darwin is that the gemmules, which circu- late freely throughout the body, become developed into cells by union with other gemmules or partially developed cells, which precede them in the regular order of growth. If, then, the outer portion of an organism which consists of an aggregation of cells casts off gemmules, these will come into contact with the central portion, or with gemmules from the central portion, and a third cell may result, differing from both the outer and central parts to a slight extent. This being the case, then, an or- ganism may become developed by the continued