Abstract
The pancreatic extract used by us is prepared under the name iletin (insulin, Lilly); it was supplied by the makers and bore the date of preparation. It is prepared by the method of Banting 1 and Macleod 2 , one unit of the extract being the amount necessary to reduce the blood sugar of a kilogram rabbit to 0.045 per cent. At this percentage the rabbit often goes into convulsions and death sometimes follows. This unit of iletin or insulin may therefore be considered the lethal dose for a kilogram rabbit.
We are using the pancreatic hormone as a part of a more general study on the relation of the various incretions to reproduction and to sex. Our specific purpose here was to learn whether as a consequence of the hypoglycemia induced by this extract all ovulations would be suppressed in the pigeon by a dosage which should leave the other conditions necessary for reproduction essentially undisturbed. I have earlier reported 3 a marked hypertrophy of the suprarenals at the ovulation period, and in collaboration with Honeywell 4 have shown that parallel with this hypertrophy there regularly occurs in pigeons a marked increase of blood sugar coincident with ovulation. Other unpublished work by Honeywell and myself has made it clear that in each of two very common causes of suppressed ovulation the blood sugar is abnormally low. Such earlier observations have led to the view that a low blood sugar tends to suppress ovulation in birds. This conception is again supported by the results of the present study. It that found that most ovulations are successfully suppressed by subcutaneous injections of quantities of insulin which certainly leave the birds feeding and mating normally, and which do not affect the body weight more adversely (average initial weight = l76g…) than do some other tested tissue extracts which do not suppress ovulation.
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