HOKMONE FACTOKS IN GROWTH AND DEVELOPMENT 189 



sively that it is only the anterior lobe of the pituitary body which exercises 

 a growth-controlling influence ; and, according to Marinus, not the entire 

 anterior lobe, but only the anterior lobe proper with exclusion of the pars 

 tuberalis contains the growth-accelerating principle. 



It was thought, at first, that the excessive growth in acromegaly is 

 due to a destruction of the gland (Marie), and consequently the theory 

 was developed that the hypophysis hormone inhibits excessive growth in 

 the normal individual. Our present knowledge, however, contains ample 

 evidence as to the contrary; the anterior lobe of the hypophysis manu- 

 factures a substance which stimulates growth and at least certain processes 

 of development. Perhaps the most conclusive results, in this respect, 

 have been obtained in the amphibians. 



Relations in Lower Forms. Even in the lowest organisms of the 

 animal kingdom anterior lobe substance causes an acceleration of growth. 

 Wulzen (b) has shown this to be the case in planarians, certain low worms. 

 Several investigators (Nowikoff, Shumway, Chambers) studied the influ- 

 ence of pituitary extracts on the division rate of protozoa, but did not 

 obtain conclusive results. Flather observed an increase in the rate of 

 pulsation of the contractile vacuoles of infusorians kept in pituitary 

 extract. It would be of great interest to know if plants are affected in 

 their growth activities by pituitary gland, since this would throw light 

 upon the question how far the effects of the active principle of the anterior 

 lobe are due to the chemical structure of this substance and how far they 

 are due to the specific structure of the organisms. Unfortunately only pre- 

 liminary attempts have been made to determine the effect of the hy- 

 pophysis substance in plants (Budington) and these have been negative. 



Relations in Amphibia. In 1914 Adler (a) removed the hypophysis 

 from young larvae of frogs and found that this resulted in a complete in- 

 hibition of development; the transformation of the hypophysectomized 

 Iarva3 was suppressed. This result was confirmed by the more elaborate 

 experiments of Smith and of Allen (a) (&), who found that in hypophy- 

 sectomized frog larvae first an inhibition of the development of the hind 

 limbs is effected, while later on growth and development of the entire body 

 is checked. The feeding of anterior lobe to tadpoles, in the experiments of 

 Gudernatsch and Abderhalden, has not yielded conclusive results; but 

 the more recent experiments carried out by Smith (c) (e) and by Hoskins 

 (c) and Hoskins show that feeding of anterior lobe to the larvaa of frogs 

 causes an acceleration of growth during the late larval period and a slightly 

 precocious metamorphosis. Uhlenhuth has fed anterior lobe to salaman- 

 ders ; he was unable to demonstrate any influence during the larval period, 

 but observed soon after metamorphosis an enormous acceleration of growth. 

 The feeding was continued after metamorphosis and into the period of 

 sexual maturity ; this latter part of the experiment was of special interest, 

 because the salamanders did not cease growing after they had reached 



