766 THE ENDOCRINE ORGANS, OR DUCTLESS GLANDS 



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

 but recently Brailsford Robertson 81 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 

 acceleration of the latter portion of this cycle. When fully grown, 

 tethelin-fed mice also differ from normal animals in being smaller in 

 size but of greater weight, with a distinct difference in the condition of 

 the coat. Normal animals at fourteen months of age have "shaggy, 

 staring and discolored coats," whereas in tethelin-fed animals they have 

 the glossy and silky appearance of young animals. During growth, nor- 

 mal animals display a greater variability in weight than tethelin-fed 

 animals. 



Extraordinary effects have been observed by Clark 85 to be produced 

 by feeding laying hens with pituitary gland. Thus, by giving to one- 

 year-old hens, in addition to their usual food, 20 milligrams of fresh 

 pituitary substance for four days, it was found that the average daily 

 number of eggs laid by a batch of 655 hens was raised from 273 during 

 the four days preceding the pituitary feeding to 352 during the four 

 days of the administration, these results being obtained at a time of 

 year when the natural egg-production of the hens was diminishing. It 

 was further observed that not only is the output of eggs greatly increased 

 as a result of the pituitary feeding, but likewise their fertility, for in 

 another experiment in which 35 hens were kept along with two cockerels 

 of the same breed, not only was the output of eggs increased (from 18 up 

 to 33), but the fertility of the eggs was greatly enhanced. 



Functions of the Posterior Lobe or Pars Nervosa. As already men- 

 tioned, excision of this part of the pituitary can be tolerably well with- 

 stood by the animal, so much so indeed that from its behavior after the 

 operation we can conclude little as to the function of the lobe. On the 

 other hand, extracts of the posterior lobe injected into normal animals 

 produce effects that are very striking, indicating that the main function 



*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. 



