Carbohydrate metabolism and insulin / by John James Rickard Macleod.

  • John James Rickard Macleod
Date:
1926
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Licence: In copyright

Credit: Carbohydrate metabolism and insulin / by John James Rickard Macleod. Source: Wellcome Collection.

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    to descend at a rate with which the tension in the tissues does not keep pace (see p. 277). (3) Sometimes convulsions or symptoms simulating them appear before the blood sugar has reached the usual convulsive level (Macleod and Orr, Grevenstuk and Laqueur). (4) The method at best only indicates whether the blood sugar has reached the possible convulsive level, and it gives no infor- mation with regard to the duration of the hypoglycsemic effect. (5) For use in the treatment of diabetes mellitus, it is not the tendency of the preparation to produce convulsions that is of importance, but its influence on the blood sugar. Other Methods of Assay.—Methods of assay based on other principles than the lowering of blood sugar or the incidence of hypoglycaemic symptoms have been tried from time to time. Several of these have been referred to incidentally in other chapters and will require little further notice in this one : — (1) Since the curve expressing the relationship between the units of insulin injected and the degree of lowering of blood sugar shows that the greatest differences in the latter are ob- tained when small doses are used, it was considered possible that an extension of this part of the curve might be obtained by increasing the amount of blood sugar on which the insulin could act. This was done either (exogenously) by the injection of glucose solutions (see p. 207), or (endogenously) by the use of epinephrin (Eadie and Macleod). In actually applying the former method 2 gms. of glucose per kilo body weight were injected subcutaneously into each of several rabbits which had received varying doses of insulin seventy-five minutes previously. It was hoped that the extent to which the blood sugar rose would then bear a simple relationship to the dose of insulin, but the results were no more satisfactory than those obtained on normal animals. In the latter method, which had previously been suggested by Zuelzer for the pancreatic extracts prepared by him (p. 57), equal quantities of a carefully standardised pre- paration of epinephrin, and varying amounts of insulin, were injected into well-fed rabbits, and although an interesting relationship was found to exist (see p. 230), the method did not prove to be of practical service (Eadie and Macleod). (2) There can be little doubt that the variability of different animals towards insulin, after every precaution has been taken