Volume 1

A textbook of pharmacology, therapeutics and materia medica.

  • Brunton, T. Lauder (Thomas Lauder), 1844-1916.
Date:
1893
Catalogue details

Licence: Public Domain Mark

Credit: A textbook of pharmacology, therapeutics and materia medica. Source: Wellcome Collection.

Provider: This material has been provided by Royal College of Physicians, London. The original may be consulted at Royal College of Physicians, London.

    175/816 (page 119)
    soda), in very dilute solutions, diminish extensibility; dilute acids (lactic acid) increase it. By the alternate application of Fig. 36.—Shows the action ot caustic potash, 1 in 1,500, ou muscle tor 1« minutes, succeeded by the action of lactic acid for 24 minutes. 1 is the contraction of normal muscle; 2, 3, 4, contractions of alkali-muscle; 5, 6, 7, contractions of acid-muscle on stimulation. (Brunton and Cash.) alkalis and acids the muscle may be made to yield curves which, when recorded on a very slowly-revolving cylinder, are similar in form to the normal contraction curve recorded on a rapidly- revolving cylinder.1 Fig. 34. Irritability of Muscle.—In order to ascertain the irrita- bility of muscle itself or the readiness with which it responds to various stimuli independently of the nerves within it, the muscle is first poisoned by curare, and then exposed to various conditions, or to the action of drugs. The muscle thus poisoned by curare, woorara, woorali, or urari (for the poison has all these names), is much less sensitive to the action of fara- daic currents. The readiest way of testing its excitability is by the making and breaking of a constant current, the strength of which can be estimated very exactly by using du Bois Rey- mond’s rheochord. The excitability of muscles is increased by heat and diminished by cold. It is increased by physostigmine and diminished by most poisons which paralyse muscle.2 Contraction.—When the ends of the muscle are not l$ept apart by force too great for it to overcome, and it is stimulated by heat, mechanical injury, chemical irritants, or electricity, it contracts and then relaxes. The form of this contraction varies according to the species of animal, and the particular muscle tested. In cold-blooded animals, as a rule, the contraction is slower than in warm-blooded animals. It is not alike in all the muscles of the body of mammals. Thus in the rabbit there are two kinds of muscles—red and white; the white muscles contract more quickly and relax more quickly than the red ones. The muscle usually employed in experiments is the gastrocnemius of the frog, freshly prepared, with the nerve and end of the femur attached to it. 1 Brunton and Cash, Phil. Trans., 1884, p. 197. 2 Harnack and Witkowski, Arch. f. exp. Path. u. Pharm. v. 1876, p. 402.