Volume 1

The principles of psychology / by Herbert Spencer.

  • Herbert Spencer
Date:
1897
Catalogue details

Licence: Public Domain Mark

Credit: The principles of psychology / by Herbert Spencer. Source: Wellcome Collection.

    41/670 page 23
    away materials, must be numerous in proportion as com- position and decomposition are quick; we may infer a great difference between the rates of destructive change in the two tissues. Another contrast supports this con- clusion no less strongly. The unstable granular protoplasm contained in the corpuscles, is shielded from adjacent dis- turbing forces by a membrane which, even where thickest, is so delicate that its existence can be demonstrated only by the help of re-agents; and which in many corpuscles cannot be made visible at all. Hence between the matter contained in these corpuscles, or vesicles, and the streams of blood that run among them so abundantly, are interposed little else than the delicate walls of the capillary blood-vessels; and thus the disturbing substances brought by each capillary, can pass with the least possible hindrance into the unstably-arranged contents of the neighbouring vesicles. Quite otherwise is it with the relations of the blood to the contents of nerve-tubes. The wall of each nerve-tube'is thick enough to make it easily demonstrated; and between it and the central thread of essential matter, comes the coat of nerve-medulla. Through these barriers the disturbing agents, carried among the nerve-tubes by sparingly-distributed capillaries, cannot readily pass; and the essential nerve-thread is prevented from having molecular changes set up in it at places between its two extremes. This protection suffices so long as the disturbing agents remain normal in their amounts; but when they become excessive, as they do if the blood-vessels become congested, local changes in the nerve-threads are caused: whence one kind of neuralgia. It should be added that by shape. Hence it is needful to draw an equal number of parallel longitu- dinal lines ; and to repeat with them this process of averaging. By tak- ing the means between the resulting numbers and the previous numbers, we get a correct representation of the relative frequencies with which the vessels occur in space of one dimension. To ascertain their relative frequencies in space of three dimensions, or in solid tissue, it is of course needful simply to cube the two numbers so arrived at.
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