the pars buccalis of the hypophysis 55 



Further, it was believed that if this number of animals should 

 show an unequivocal response to hypophysial administration, 

 it would furnish convincing evidence of either the presence or 

 the absence of the growth-maintaining principle in these special 

 substances — a belief which we feel has been amply sustained. 



The growth curves of the albinous frog tadpoles supplied 

 with either alcoholic or aqueous residues show the same main- 

 tenance of growth as is exhibited by their fellows fed with the 

 fresh anterior lobe (figs. 3, 4). No 'critical point' appears; 

 the three curves are coincident. 



This is not the case with frog albinos receiving aqueous ex- 

 tract, Tethelin, or colloid (figs. 3, 4, 5). Their curves are quite 

 similar to that of the liver-fed albinous larvae. The same early 

 retardation is noted, the 'critical point' is well marked, but 

 appears at a somewhat earlier period (twelve days) and at a 

 somewhat smaller average stage (6 mm.) than their liver-fed 

 companions. Following the critical point, some divergence ap- 

 pears in the three curves. The specimens supplied with aqueous 

 extract exhibit a slight secondary acceleration in growth, but 

 they do not attain quite the average length of their liver-fed 

 mates. The 'Tethelin' group does not. exhibit any secondary 

 acceleration subsequent to the 'critical point,' while the colloid 

 group exhibits an even greater retardation than its fellows sup- 

 plied with Tethelin. 



In order to further test the growth effects of hypophysectomy 

 and its response to an anterior-lobe diet, a series of experiments 

 similar in every way to those just reported upon were carried 

 out with toad larvae. These larvae respond in general in the 

 same way as the similarly treated frog tadpoles. The early 

 retardation, the usual midlarval slowing ('critical point'), fol- 

 lowed by slow growth, appears as in the frog tadpole (fig. 6). 

 In this, my observations are somewhat at variance with those 

 of Allen, who reports no retardation in the velocity of growth 

 in hypophysectomized toads. Fuller reports may explain this 

 essential difference in our results. I wish to emphasize, how- 

 ever, that the early retardation, the 'critical point,' and the 

 later period of slow growth are not so distinctly shown in the 



