540 Scientific Proceedings (132) 



sented by a practically straight' line. The slope of this portion 

 of the curve is constant for the same sheep upon administration 

 of varying amounts of insulin. 



The portion of the curve representing recovery from hypo- 

 glycemia shows characteristic differences : When 5 units of in- 

 sulin were administered, the recovery to normal sugar values 

 began immediately after the low values had been reached. With 

 10 to 15 units the minimum sugar values obtained were only 

 slightly lower than for the smaller doses, although analyses were 

 taken at sufficiently close intervals (10 to 20 minutes) to enable 

 a fair approximation to the minimum. The larger doses, how- 

 ever, showed an extensive flat portion in the curves before re- 

 covery began. The results with five units were reproducible with 

 the same sheep and similar in different sheep. 



Five units were therefore selected as the standard dose of 

 insulin to be tested against varying amounts of thyroxin 

 under different conditions. Administered alone, the effects pro- 

 duced are represented by curves A and D. Curve B shows the 

 effect of a preliminary administration of thyroxin (1 mg. intra- 

 venously). Curve C shows the effect of a similar injection of 

 thyroxin after the recovery from insulin had begun. The si- 

 multaneous administration of thyroxin (1.5 mg.) and insulin 

 produced a typical divergence of the ascending arm of curve E 

 from that of curve D (insulin alone). With a smaller dose of 

 thyroxin (0.75 mg.) in another sheep a similar effect was ob- 

 tained, though not quite as pronounced as in Sheep H. 



These results may be explained tentatively on the following 

 assumptions : Insulin causes an accumulation of glycogen in the 

 liver, simulating the condition in a well fed animal; subse- 

 quent administration of thyroxin produces the marked hypergly- 

 cemia due to increased glycogenolysis, shown in Curve C. A 

 preliminary administration of thyroxin increases sugar meta- 

 bolism, depletes the glycogen store, thus simulating the condi- 

 tion in a poorly nourished animal, when recovery from a sub- 

 sequent administration of insulin occurs, the normal blood-sugar 

 levels are not reached therefore within the usual time. 



This work was carried out under a grant from the Heckscher 

 Research Foundation to Professor Sutherland Simpson. Fur- 

 ther work is in progress on the relations of thyroxin and insulin, 

 and their possible application to the assay of insulin. 



