A manual of physiology : including physiological anatomy / by William B. Carpenter.

  • William Benjamin Carpenter
Date:
1856
Catalogue details

Licence: Public Domain Mark

Credit: A manual of physiology : including physiological anatomy / by William B. Carpenter. Source: Wellcome Collection.

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    which it sprang. The reproductive molecules or cell-germs are formed, like the tissue and the contents of the parent-cell, from the nutrient materials which it has the power of bringing together and combining ; in their turn they pass through a corresponding series of changes ; and at length they produce a new generation of similar molecules, by which the race is destined to be continued. Notwith- standing the mystery which has been supposed to attach itself to this process, it is obvious that there is nothing in reality more difficult to understand in the fact, that the parent-cell organizes and vitalizes the protoplasma which it has elaborated, so that it should form the germ of a new individual possessing similar properties with itself, than in its incorporating the same material with its oivn structure, and causing it to take a share in its own .actions. 34. Finally, the parent-cell having arrived at its full develop- ment, having passed through the whole series of changes which is characteristic of the species, and having prepared the germs by which the race is to be propagated, dies and decays ;—that is, all those operations, which distinguish living organized structures from inert matter, cease to be performed ; and it is given up to the influence of chemical forces only, which speedily occasion a separa- tion of its elements, and cause them to return to their original forms, namely, water, carbonic acid, and ammonia. It is not, however, in the dead organism alone, that this decomposition occurs ; for it is certain that interstitial death and decay are incessantly taking-place during the whole life of the being ; and that the maintenance of its healthy or normal condition depends upon the constant removal of the products of that decay, and upon their continual replacement. If, on the one hand, those products be retained, they act in the manner of poisons ; being quite as in- jurious to the welfare of the body as the most deleterious sub- stances introduced from without. On the other hand, if they be duly carried-oif, but be not replaced, the conditions essential to vital action are not fulfilled, and the death of the organism must be the result, 35. Now it is to be observed that, as Plants obtain the chief materials of their growth from water and carbonic acid, taking the carbon from the latter and setting-free the oxygen, so do they require, as the condition for their decay, the presence of oxygen, which may reunite with the carbon that is to be given back to the atmosphere. If secluded from this, the vegetable tissues may be preserved for a long time without decomposition. Generally speaking, indeed, they are not prone to rapid decay, except at a high temperature ; and hence it is that we have so little evidence, in Plants, of that constant interstitial change of which mention has just been made. Its existence, however (at least in all the softer portions of the structure), is made evident by the fact, that