The Action of Thyroid upon the Organs of the White Rat 249 



of hypertrophy sliown in my series of rats, more especially of the supra- 

 renals, heart, kidneys, and pancreas. The heart and kidneys may be more 

 than trebk'd, and the suprarenals and pancreas more than doubled in 

 weight by thyroid-feeding. 



The enlargement of the liver, spleen, testes, and ovaries may be 

 ascribable, as Hoskins suggests, to the general increase of metabolism in 

 the body. But the greater enlargement of the suprarenals, heart, kidneys, 

 and pancreas points to .something further than this. There is an increased 

 production of adrenalin by the suprarenals of thyroid-fed animals, and the 

 maintenance of health appears to be bound up with the attainment of a high 

 adrenalin content in such animals. It is suggested that the adrenalin output 

 is compensatory to the thyroid, more especially in its action upon the circula- 

 tion. The combination of these factors along with the increased metabolism 

 may be the cause of the great hypertrophy of the heart and kidneys. 



The hypertrophy of the pancreas may be concerned in regulating 

 carbohydrate metabolism, which would otherwise be upset by the increased 

 production of adrenalin. 



The uterus of the young rat appears to be checked in its growth by 

 thyroid-feeding. The small uterus is associated with a similar check in 

 the growth of the pituitary body, and the idea suggests itself that there 

 is a close correlation between these two organs. 



I have to thank Mrs Donald Mills for her help in looking after the 

 animals during the last part of the work. To Mr Niven of Strathkinness 

 I am indebted for a plentiful supply of fresh ox thyroid. 



The expenses of the research have been met by a grant from the 

 research fund of the Carnegie Trust for the Universities of Scotland. 



VI. Literature Cited. 



(1) BiEDL, Innere Sekretion, Wien, 1913. 



(2) BiRCHKR, Med. Klinik, 1910, 391. 



(3) Cramer and Krause, Proc. R. Soc, B, 1913, Ixxxvi. 550. 



(4) Donaldson, The rat, Wistar Institute Memoirs, 1915. 



(5) Eppingbr, Falta, and Rudinger, Zeitschr. f. klin. Med., 1908, Ixvi. 1. 



(6) GuDERNATSCH, Amer. Journ. Anat., 1913-14, xv. 431. 



(7) Hatai, Anat. Rec, 1915, ix. 647. 



(8) Hatai, Amer. Journ. Anat., 1913, xv. 87. 



(9) Herring, Quart. Journ. Exper. Physiol., 1916, ix. 391. 



(10) Herring, Quart. Journ. Exper. Physiol., 1917, xi. 47. 



(11) Hoskins, E. R., Journ. Exper. Zool., 1916, xxi. 295. 



(12) Hoskins, R. G., Journ. Amer. Med. Assoc, 1910, Iv. 1724. 



(13) Iscovesco, Compt. rend. d. 1. soc. d. Biol., 1913, Ixxv. 361. 



(14) Jackson, Amer. Journ. Anat., 1913, xv. 1. 



(15) King, Anat. Rec, 1915, ix. 751. 

 (16).KoJiMA, Proc R. Soc Edin., 1916, xxxvi. 240. 



