Vigour and heredity / by J. Lewis Bonhote.

  • Bonhote, J. Lewis (John Lewis), 1875-1922.
Date:
1915
Catalogue details

Licence: Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)

Credit: Vigour and heredity / by J. Lewis Bonhote. Source: Wellcome Collection.

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    CHAPTER II. OUTLINE OF VIGOUR. What is meant by Vigour ? By vigour is meant activity of nutrition and function, i.e. a state of high metabolism, and where the rate of metabohsm in one individual is greater than in another the vigour is said to be higher. A not inapt simile of vi^hat is meant by vigour may be taken from two clocks, in one of which the ticking is twice as fast as the other—viewed externally the hands of each do the same work in the same time, but internally the mechanism of the one works at double the rate of the other ; and so it is with animals during their lifetime, they each perform similar functions, eat, sleep, and reproduce their kind, but the metabolism of the one may be twice as active as that of the other. How, then, can we tell the amount of vigour present in any individual? At present we have no index, and no method of definitely ascertaining or measuring the rate of metabolism ; but by actions, colour and condition we can get a very fair idea of the vigour of any individual. Before, however, dealing with that point, which is more cognate to experimental breeding, let us consider the causes which determine vigour. First and foremost, we have the vigour of the parents, and the combination of their respective vigours gives an animal what we may call its initial vigour. This is the vigour with which the zygote starts life before environ¬ ment in any shape or form has begun to act. This initial vigour depends upon the rate of meta¬ bolism of the parents at the time of copulation, and this rate of metabolism or vigour will depend on their (the parents') initial vigour modified by the environment in which they have lived.* The initial vigour of any animal will bear a fixed relation to the mean vigour of its parents, and colour is, as * See Chapter XI.
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