44 PIGMENTARY GROWTH AFTER ABLATION OF 



in growth. 27 It is obvious that a determination of the presence 

 or absence of a growth-'accelerating' principle in an extract 

 or fraction of this gland can hardly be made with the normal 

 animal when the administration of the fresh gland does not call 

 forth such a response. 



The growth rate of the albino; the effect of the adininistration of 

 various hypophysial substances upon this growth rate 



In order to discuss the deviations from normality of the growth 

 rate of the hypophysectomized tadpole and the effect of the 

 administration of fresh bovine anterior lobe and its extractives 

 and residues upon these deviations, it will first be necessa^ to 

 examine the growth rate of the normal unoperated tadpole. 

 The growth curve of a normal tadpole with a liver-lettuce diet 

 consists of three phases, the first two indistinctly separable, 

 the third more pronounced. An early transient and not clearly 

 marked period of slow growth, which perhaps should receive 

 even less emphasis than has been accorded it (Smith, '18), shades 

 insensibly into a protracted second phase of rapid growth during 

 which the tadpole attains nearly its maximum size, and which 

 is in turn terminated rather abruptly by the advent of meta- 

 morphosis (fig. 1). The administration of bovine anterior lobe 

 neither alters the nature of this curve nor produces quantitative 

 results of unquestionable significance, although there appears 

 1 i > result in most cases from this diet a small increment in size 

 and a somewhat earlier completion of metamorphosis. 



The growth curve of albinous frog larvae with a liver-lettuce 

 diel differs in character and in magnitude from that of the nor- 

 mals (fig. 1). I have described these changes previously (Smith, 

 '18), and later work has amply confirmed them. A retardation 

 in growth following the appearance of albinism is unquestioned 

 and becomes progressively greater until approximately a 30- to 



1 iaselli ('00), whole-gland glycerin extracts; Cerletti ('01), a centrifugalized 

 aqueous-glycerin emulsion; Aldrich ('12), fresh desiccated non-defatted anterior- 

 lobe substance; Aldrich ('12 . fresh defatted anterior-lobe substance; Robertson 

 ('16), fresh anterior lobe and bis alcoholic extract, Tethelin, of the desiccated an- 

 terior lobe. 



