Experimental Gigantism. 



13 



surviving anterior lobe-fed animal is passed around together with 

 the largest normal animal kept at present in the laboratory. 

 The hypophysis-fed animal is about 131 mm. long and two years 

 old, the normal animal measures 11 1.5 mm. and is three years old. 

 In the species A. opacum feeding of the anterior lobe resulted 

 in gigantism. 



Similar experiments were made in the species A. tigrinum. 

 The normal growth curve of this species seems to resemble the 

 growth curve of A . opacum. After the first year the rate of growth 

 becomes very low as shown in the slides; the records of this species 

 do not go, however, beyond 80 weeks and it is uncertain, when 

 growth in A. tigrinum stops. The largest animal that I could 

 find in the museum collections measured 208.7 mm. Larger 

 specimens are found in the western states, but these are most 

 likely derived from larvae in which by abnormal processes of the 

 inner secretory system growth was greatly stimulated already 

 during the larva? period, and which on account of this abnormal 

 condition studied as yet very little, cannot be used for comparison 

 with our eastern race. The largest normal animal raised in my 

 laboratory measures 195 mm. 



Every single individual of this species fed on the anterior lobe 

 of the hypophysis not only outgrew all the controls and other 

 normal animals raised in my laboratory, but also the largest 

 animals which I found so far in museum collections. In one series 

 of five specimens the two smaller individuals were selected for 

 the purpose of the experiment and started on anterior lobe at an 

 age of 37 weeks, about 27 weeks after metamorphosis; the three 

 larger specimens were kept as controls. The controls grew only 

 little after this time and were soon outgrown by the experimental 

 animals in which the high rate of growth that prevailed during the 

 early period was not only maintained but even surpassed by the 

 rate of growth produced by the hypophysis diet. The largest 

 hypophysis-fed animal of this series measures now 264 mm. and 

 still is growing most vigorously, while the largest control animal 

 measures only 192 mm. Both animals are passed around. Similar 

 results were obtained in the other series and at present I possess 

 five hypophyseal giants of this species, coming from two different 

 broods. 



