DEPARTMENT OF GENETICS. 119 



greatest increase is coincident with the act of ovulation. The mean size 

 increase found in the four groups was approximately 40 per cent. The 

 diseases commonly met with in our birds usually produce very marked 

 suprarenal hypertrophy; and all birds with disease recognizable to us have 

 been separately classified and tabulated as diseased birds. Without this 

 separation of healthy and diseased birds a definite relation of suprarenal 

 hypertrophy to ovulation could scarcely be obtained from any reasonable 

 number of birds by our method of study, since the glands of diseased birds 

 are extraordinarily variable in size. 



"Previous studies on suprarenal hypertrophy during pregnancy and lacta- 

 tion have apparently overlooked hypertrophy in connection with ovulation; 

 if the latter occurs also in mammals, this is a possible source of error in many 

 results reported. The changes in the suprarenals of mammals at ovulation 

 should be investigated. The suprarenals of male pigeons are probably 

 slightly larger than those of females, even after fully correcting for differ- 

 ences in body-weight. 



"When doves are provided with heated quarters and are made to repro- 

 duce throughout the year, as were the birds used in this study, it does not 

 appear from the considerable data at hand that season is in itself associated 

 with any change in suprarenal size. If such seasonal changes do occur they 

 do not affect the results reported. Adequate histological studies have not yet 

 been made, but it is probable that both medulla and cortex share in hyper- 

 trophy at ovulation. 



"These results constitute a contribution to our definite knowledge of the 

 conditions associated with previously observed changes in size of ova, of sex- 

 ratios, and of sexual development in the offspring of pigeons made to repro- 

 duce rapidly and continuously throughout the year. They demonstrate that 

 some elements of a new and intimate environment are provided for ova thus 

 made to develop under prolonged and nearly continuous suprarenal hyper- 

 trophy." 



The studies on the changes in blood-sugar concentration which accompany 

 the suprarenal hypertrophy described above have been made in collaboration 

 with Dr. H. E. Honeywell. These studies have led to the following con- 

 clusions : 



"Each ovulation period in the pigeon is accompanied by an increase of 

 approximately 20 per cent in the amount of sugar in the blood. The sugar- 

 content of the blood begins to increase at about 108 hours preceding the 

 ovulation of the first egg; it is then maintained at the highest level until the 

 second ovulation 44 hours later; following this period it probably gradually 

 decUnes to the normal non-ovulation level in an additional 108 hours — 

 unless new ova meanwhile begin their final period of rapid growth and a 

 new ovulation cycle is begun. The curve which thus describes blood-sugar 

 values as related to ovulation is essentially similar to the curve for suprarenal 

 hypertrophy at ovulation earlier described by Riddle. The above results 

 apply to various species of doves, pigeons, and their hybrids. Female 

 pigeons forced to rapid and continuous ovulation throughout the year are 

 thus forced to an almost continuous maintenance of their bodily functions — 

 and to the production of their eggs — under altered and unusual conditions as 

 regards their carbohydrate metabolism." 



Relation of Storage Metabolism to Insulin. 

 Dr. Riddle has made further experiments on this matter with the thyroid 

 secretion referred to in my last report and gets only confirmation of the 

 results reported previously. Insulin, the incretion of the pancreas which 



