12 



Scientific Proceedings (109). 



that at least one form of gigantism is due to an overfunction of the 

 hypophysis gland. Attempts, however, to produce gigantism by 

 feeding hypophysis to animals have been unsuccessful. 



The experiments to be discussed presently will show that in 

 salamanders hypophysis feeding produces gigantism and that it 

 is the anterior lobe alone which possesses the ability of maintaining 

 growth after the normal size of the species is reached. 



The effect of the hypophysis diet depends, however, on the 

 developmental stage of the salamanders. Larvae do not respond 

 to the anterior lobe diet ; the growth-promoting effect of the gland 

 commences after metamorphosis has taken place. 



Of the species Amby stoma opacutn, quite a number of speci- 

 mens have been kept and measured for several years in my labor- 

 atory. In a chart the growth during three years is shown for 

 four specimens; after the first year the animals grow very little 

 and, at certain periods, may show even a decrease in size. The 

 largest animal of this species raised in my laboratory was 115 mm. 

 long, the largest normal animal in my possession at present is 

 1 1 1.5 mm. long. I went through the collections of several mu- 

 seums; the largest specimen I found measured 11 7.7 mm.; of 

 two breeding females caught recently, one measured 112 mm., the 

 other one 106 mm. 



Of four animals raised in the laboratory from eggs of the same 

 female and kept on a normal diet two were started on the anterior 

 lobe at an age of 62 weeks, about 12 months after metamorphosis 

 and about 4 months after sex maturity had been reached, and 

 two animals were kept as controls. The result is shown in the 

 growth curves. In spite of the advanced age both hypophysis-fed 

 animals started to grow at a rate that, under normal conditions, 

 would be characteristic of an early period after metamorphosis, 

 while the controls continued to grow at a low rate, although 

 they were fed so excessively large quantities of normal food that 

 both of them succumbed finally. The largest control animal 

 measured 115 mm., when it died; would it have survived and 

 increased steadily at the same rate — which, however, would not 

 be expected from the curves of other normal animals — it would 

 measure 118 mm. today, whereas the largest hypophysis-fed 

 animal, which died a few days ago, measured 138 mm. The 



