Volume 1

The works of John Hunter / edited by James F. Palmer.

Date:
1835-37
Catalogue details

Licence: Public Domain Mark

Credit: The works of John Hunter / edited by James F. Palmer. 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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    in other bodies, as concentrated acids, alkalies, &c., in which respect they are pretty similar to one another. Both are capable of being acted on by fire; but in this process we find each yielding some substances peculiar to itself;—animal matter when distilled yields water, volatile alkali, empyreumatic oil, and calcareous earth;—besides these there is a small proportion of iron, which does not appear, however, to be a constituent part of the whole animal body, being chiefly procurable from the blood; a small proportion of other substances may also be found in the blood*. In their decay, both animals and vegetables go through a series of regular spontaneous changes, the succeeding one arising entirely out of the first, and the next out of this, until the whole return to common matter from whence they arose, for to the earth they must return from whence they came. In this natural process we find animals and vege- tables yield many substances not to be found in them before these changes, also not to be found in common matter. This process I call fermentation, and it is peculiar, I believe, to vegetable and animal matter. The processes carried on by chemistry and fermentation, which can only take place when the parts are dead, have been introduced by phy- siologists into the living animal ceconomy ; and, not satisfied with this, they have brought in mechanics to account for many of the operations of vegetables and animals. But, for the purpose of distinguishing more accurately between mechanical, chemical, and vital operations, and the circumstances under which the two first are applied to the living body, let us consider them a little further. The actions and productions of actions, both in vegetable and animal bodies, have been hitherto considered so much under the prepossessions of chemical and mechanical philosophy, that physiologists have entirely lost sight of life; and perhaps they have been led to this mode of rea- soning because these properties are much more familiar, more adapted to our understandings, and more demonstrable than the living proper- ties of organized beings. But unless wre consider life as the immediate cause of all actions occurring either in animals or vegetables, we can * [Vegetable substances are nearly all composed of oxygen, hydrogen, and carbon,— carbon, for the most part, being the preponderating ingredient. In some few examples nitrogen is likewise present. The proximate principles of vegetables, or those sub- stances which exist ready formed in plants, are exceedingly numerous, as gum, starch, sugar, &c., amounting in the whole to not less than forty-five or fifty substances, cha- racterized by different properties. Animal substances, on the contrary, at least all the principal animal substances, contain nitrogen as well as oxygen, hydrogen, and carbon, and the proximate elements are not so numerous as those of vegetables. The animal fats, which are considered by many as a natural store of nutriment, contain no nitrogen, and therefore approximate to vegetable products.]