Volume 1

Health lectures for the people.

Date:
1883-1892
Catalogue details

Licence: Public Domain Mark

Credit: Health lectures for the people. Source: Wellcome Collection.

    489/896 (page 25)
    charged into it, so that it has to be purified in the lungs and kidneys before it is again fit for use. Thus a contracting muscle which in virtue of its life required some blood before, requires not only more blood to give it new material and to carry off its waste products, but it requires also leisure and rest to build up new fuel for future contractions. Mr Gaskell of Cambridge has seen under the microscope that the arteries going to a muscle and the veins coming from it are much distended with blood during its contraction, and thus we see how the demand is fully met by the supply; and, as to the requisite for leisure, we all of us know that the greatest trial is an even steady strain, since nothing is more tiring than a continuous cramped position, much more so than a more violent but intermittent effort. All these appar- ently dry details on the changes going on in muscle during con- traction and the resulting alteration in the blood, the increased quantity of blood passing through exercised muscle, and the requisite for alternation in muscular contraction, have an important bearing on physical science as we shall afterwards see, so I must ask you to note them carefully now. At the same time, too, I may point out that similar conditions hold good for all the other tissues of the body in their condition of vital activity, whether it be the brain in thought or mental excitement, or the Various glands such as the liver and kidneys, all requiring and usino- more blood during the period of their activity, and calling for times of leisure to build up new^ material against a repetition of the same. Before leaving the subject of muscles and their contraction, let me remind you briefly of what we have seen, viz., that muscles are the agents for all the movements of our body, and this in the larger movements by acting on the bones; that the growth of bones goes on with that of muscles; that muscles are very numerous, have nerves communicating with the brain running into them, and can be made to associate with each other in what is called co-ordination; that besides nerve stimulus they require a large blood supply, the character of which is altered as it passes through the contracting muscle. These latter will much help us