192 E. TJHLENHUTH 



periments yielding negative results are nearly as numerous as those that 

 were positive, it appears that in most cases in which no acceleration of 

 growth could be observed, either the period of growth was not long enough 

 (Aldrich) or the accelerating influence was overlooked on account of the 

 small difference it caused, or the doses employed were too small (Hoskins 

 (a) ). Robertson fed anterior lobe to white mice and observed a slight but 

 constant acceleration in growth ; he also reports that abnormally large mice 

 may be obtained by stopping administration of the glandular substance at 

 a certain period of life (see below). In rats several recent observers 

 (Goetsch (a-), Marinus, Klinger) found that feeding anterior lobe results 

 in an increased rate of growth, and Goetsch (a) (whose experiments, how- 

 ever, appear to be very poorly checked and small in number) and Marinus 

 observed precocious development of the sex glands accompanied by early 

 development of the secondary sexual characters, libido, and potency, re- 

 sulting in early and more frequent breeding. These experiments are sup- 

 ported by the results of the extirpation experiments. The partial 

 extirpation of the anterior lobe (total extirpation is fatal) leads to a 

 retardation of growth and an inhibition of the development of the sex 

 glands accompanied by suppression of the secondary sex characters and 

 failure of the libido and potency to develop, if extirpation is carried out 

 in a prepubertal stage, while atrophy of primary and secondary sex char- 

 acters accompanied by adiposity ensues after hypophysectomy in adult 

 stages (Paulesco, Gushing (&) and his collaborators). Fully in accord 

 with these observations are Exner's (&) experiments, according to which 

 homoplastic transplantation of a sufficient number of anterior lobes to one 

 individual results in 9 out of 11 rats in an increased rate of growth (see 

 also Gushing). 



Very little is known about the exact mechanism that underlies the 

 growth-controlling and development-stimulating action of the anterior lobe 

 of the hypophysis, although from the feeding experiments as well as 

 from the study of the anatomical and histological structure of the gland 

 it is to be regarded as certain that a hormone is elaborated in the anterior 

 lobe, which passes into the circulation (Herring (a), Gushing and 

 Goetsch). Robertson has even claimed to have isolated the growth-con- 

 trolling principle (tethelin) from the anterior lobe, but it seems that the 

 claim is based on rather inadequate grounds. Regarding the mechanism 

 of the anterior lobe action the following facts are important. 



Mechanism of Operation of Hypophyseal Factors. Although in the 

 main the anterior lobe substance stimulates growth and development in 

 most organisms, there are considerable differences as to the details of 

 the effects produced. These differences indicate clearly that a large part of 

 the final effect is due to the specific reaction of a specific organic struc- 

 ture upon the active principle of anterior lobe hormone, a fact which is 

 frequently neglected in the discussion of experiments on different species. 



