Sect. V, 1922 [31] Trans. R.S.C. 



IV. The Effect of Insulin on Normal Rabbits and on Rabbits rendered 

 Hyperglycaemic in Various Ways 



By F. G. Banting, M.C, M.B., C. H. Best, M.A., J. B. Collip, Ph.D., 

 J. J. R. MACLEOD, M B., Ch.B., F. R.S.C, and E. C. Noble, M.A. 



(Read May Meeting, 1922) 



The successful demonstration of the beneficial influence of 

 insulin in the diabetes of depancreated animals raised in our minds 

 the question whether it would also afifect the blood sugar of normal 

 animals and of those made diabetic in other ways than by pancreatec- 

 tomy. If such were the case a ready means would be at hand by 

 which to test the activity of the extracts at various stages in their 

 production. In the present communication we record briefly results 

 bearing on these two questions. 



1. The Effect of Insulin on Normal Rabbits. 



In over 150 normal rabbits, fed with oats and sometimes also 

 with sugar, the percentage of sugar in blood from the marginal ear 

 vein was determined, before and at various intervals following sub- 

 cutaneous injections of insulin. The average percentage of sugar in 

 90 of these rabbits prior to the injections was 0.133 with a maximum 

 of 0.186 and a minimum of 0.095 (Schaffer-Hartman method). A 

 marked fall from the initial values was observed to occur within an hour 

 or so of the injection and for purposes of physiological assay we have 

 come to designate as one rabbit d^se the amount of insulin (given 

 subcutaneously) which lowers the blood-sugar by 50 per cent, in 1-3 

 hours. This method of evaluation of the potency of insulin seems to 

 be fairly satisfactory, for we have found that relatively greater 

 effects in reducing the blood sugar, are obtained when the same 

 extract is used on diabetic dogs. Thus, 10 c.c. of a certain extract 

 injected into a rabbit reduced the blood sugar from 135 to 071 

 in IJ^hours, after which it began to rise again, whereas 20 c.c. of 

 the same extract given to a diabetic dog weighing about five times 

 more than the rabbit caused the blood sugar to fail from 0.375 to 

 0.030 in 7 hours. The lowest percentage of blood sugar observed in 

 rabbits treated with insulin was 0.01 in 2 hours 45 minutes after the 

 injection. The purer the preparation of insulin used the more rapid 

 is the fall in blood sugar. The fall seems to be equally rapid in well- 

 fed and starving animals. 



