810 THE ENDOCRINE ORGANS, OR DUCTLESS GLANDS 



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 tethelin-fed animals 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 51 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 (and Pars Intermedia). As already 

 mentioned, 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 

 of this lobe is the production of an autacoid. The extracts have more or less 

 an epinephrine-like action. Such extracts, rendered protein-free and steril- 

 ized, are obtainable on the market under the various names of pituitrin, 

 hypophysin, etc. From them a crystallizable material has been obtained, 

 but this is probably a mixture of various substances. In discussing the 

 functions of these various extracts, it must be remembered that the inter- 

 mediary part (pars intermedia) is included with the posterior lobe in 

 their preparation. 



Although the effect of pituitary extract on plain muscle fiber (and on 

 glandular tissue) appears, on first sight, to be very like that produced 

 by epinephrine, it has been found on closer examination that the two 

 substances really act in different ways. The rise in blood pressure pro- 

 duced by pituitary autacoid is likely to be more prolonged than that 

 produced by epinephrine. It stimulates increased cardiac activity, but 

 after the vagi have been cut or sufficient atropine administered to para- 



