THE PITUITARY BODY 809 



develop. The animal, though small, becomes very fat and may therefore in- 

 crease in weight. There is distinct evidence of mental dullness. From these 

 results it is concluded that the anterior lobe of the pituitary produces 

 autacoids having to do with the development of the skeletal and other 

 structures of the growing animal. That this autacoid is not derived from 

 the posterior lobe is indicated by the fact that partial injury of this 

 lobe, or indeed its entire removal, is not followed by similar symptoms. 



Closer examination of the metabolic function in hypophysectomized 

 animals has shown that there is a marked depression in the respiratory 

 exchange of oxygen and carbon dioxide, and that the ability to metabo- 

 lize carbohydrate becomes heightened ; that is to say, the animal can tolerate 

 a larger quantity of sugar than the normal animal without develop- 

 ing glycosuria. This effect on carbohydrate metabolism may how- 

 ever be associated not so much with the function of the anterior lobe as 

 with that of the posterior, for, as we shall see later, Gushing and his 

 pupils have found that extract of the posterior lobe has a marked influence 

 on the assimilation limit of carbohydrate. 



Attempts have been made to graft the pituitary, especially the anterior 

 lobe, into various parts of the body. It has been found, however, that 

 within a few days the grafts atrophy and disappear unless there has 

 been complete removal of the pituitary itself, in which case the graft 

 may remain for a month or so and the otherwise fatal outcome of hypophy- 

 sectomy be warded off. Sometimes, where the graft has remained for a 

 longer time, it is said that a temporary increase in the growth of the 

 animal has been noticed. 



Other observers have investigated the effects in normal animals of 

 continuous oral administration of pituitary substance or of subcutaneous 

 injection of extract. The earlier results were indefinite and confusing, 

 but recently Brailsford Robertson 50 has succeeded in isolating from the 

 anterior lobe a substance called tethelin, which accelerates growth in 

 young animals and is thought to have a possible value in hastening the 

 healing process in wounds. 



Tethelin is precipitated by dry ether from an alcoholic extract of the 

 carefully isolated anterior lobes. It contains 1.4 per cent of phosphorus, 

 and nitrogen in the proportion of four atoms for every atom of phos- 

 phorus, two of the nitrogen atoms being present as amino groups and 

 one in an imino group. The effects on growth of mice are in every par- 

 ticular like those of the administration of anterior lobes, and consist in 

 retardation of the first portion of the third growth cycle,* followed by 



*Robertson has contributed valuable and very extensive data on the normal curve of growth of 

 white mice kept under carefully controlled conditions. Three growth cycles are present: the first 

 attains its maximum velocity between seven and fourteen days after birth; the second, between 

 twenty-one and twenty-eight days; and the third about six weeks, after which the velocity decreases 

 progressively, until further growth ceases between the fiftieth and sixtieth weeks succeeding birth. 



