348 EXPERIMENTAL GIGANTISM 



lobe substance can increase the size of the indiAddual over the normal 

 "maximum" size of the species. It is well known that growth of 

 every individual stops as soon as the specific size of the species is 

 reached. Many problems pertaining to this phenomenon would 

 appear in a new light if it were possible to cause gigantism by a par- 

 ticular substance. 



Clinical observations point to the conclusion that at least one form 

 of gigantism is caused by an excessive production of anterior lobe 

 substance; nevertheless, attempts to produce experimental gigantism 

 have so far been unsuccessful. The only way to attack this problem 

 seems to be the feeding of the anterior lobe substance by mouth. 

 Such experiments have been attempted in large numbers but the re- 

 sults have for the most part been contradictory and difficult to inter- 

 pret. The majority of investigators have merely desired to determine 

 whether or not feeding of anterior lobe modifies in a specific way the 

 rate of growth. It will be pointed out later that the greatest care 

 is necessary in the interpretation of results obtained from feeding 

 experiments. From the more recent feeding experiments, and espe- 

 cially those performed by Hoskins and Hoskins^ and by Smith^ on 

 tadpoles, by Robertson'^ and his coworkers on white mice, and by 

 Wulzen^' ^ on chickens, most students of endocrinology have concluded 

 that the anterior lobe substance retards growth in early periods of life, 

 while later on it may cause an acceleration of growth. 



But in these experiments none of the animals fed with anterior lobe 

 developed into giants, except in two cases in which the slightly greater 

 size of the experimental animals may have been due to the effect of 

 the anterior lobe substance. Robertson and Ray^*^ claim that they 

 obtained unusually large mice, when the feeding of anterior lobe 

 substance was started at an age of 4 weeks and discontinued at an age 



^ Hoskins, E. R., and Hoskins, M. M., Endocrinology, 1920, iv, 1. 



« Smith, P. E., Univ. California Pub., Physiol., 1918, v, 11. 



7 Robertson, T. B., /. Biol. Chem., 1916, xxiv, 385, 397, 409. Robertson, T. B., 

 and Delprat, M., 1917, xxxi, 567. Robertson, T. B., and Ray, L. A., 1919, xxxvii, 

 393, 427, 455. 



8 Wulzen, R., Am. J. Physiol, 1914, xxxiv, 127. 

 « Wulzen, R., /. Biol. Chem., 1916, xxv, 625. 



" Robertson, T. B., and Ray, L. A., J. Biol. Chem., 1919, xxxvii, 455. 



