SECRETION OF THE DUCTLESS GLANDS. 879 



regulated remains to be discovered. Cannon and Cattell* have 

 given some evidence to show that the thyroids possess secretory 

 nerves supplied through the sympathetic autonomies, and, on the 

 other hand, that adrenalin injected into the blood stimulates the 

 thyroid to greater activity. In line with this latter result several 

 observers f report an interrelation in the activity of the thyroid 

 and adrenal bodies. Thyroid extracts or stimulation of the nerves 

 supplying the thyroid gland greatly augments the effect of a sub- 

 sequent injection of adrenalin. According to these results thyroid 

 secretion increases the efficacy of adrenalin, and, on the other hand, 

 adrenalin augments the secretion of the thyroid hormone. The 

 nature of the thyroid hormone has been studied with success. As 

 was stated above, Baumann isolated from the thyroid a peculiar 

 substance, iodothyrin, which is characterized chemically by a large 

 percentage of iodin, and physiologically by the fact that when used 

 upon patients suffering from a deficiency in functional activity of 

 the thyroid (myxedema, goiter) it gives beneficial results. Recently 

 Kendall | has isolated from the gland a simpler crystalline com- 

 pound containing iodin which possesses the physiological proper- 

 ties of thyroid extracts. He gives to this compound the formula 

 of CiiHioOsNIa, and designates it as thyro-oxy-indol, or thyroxin. 

 It is stated by Kendall that this substance is as efficacious as 

 desiccated thyroid in the treatment of myxedema and cretinism. 

 There has been much discussion regarding the iodin constituent 

 of the thyroid tissue. Extensive observations have shown that 

 in some entirely healthy animals iodin is absent or is present only 

 in traces, and in animals in which it is present the amount may 

 vary greatly with the character of the food. Hunt gives the fol- 

 lowing table : 



Per cent, of iodin. 



Children's thyroid none. 



Maltese kid thyroid none. 



Guinea-pig thyroid 0.05 



Dog thyroid 0.061 



Cat thyroid 0.08 



Sheep thyroid 0.176 



Beef thyroid 0.25 



Hog thyroid 0.33 



Human (Wells) 0.236 



Human (goitre) 0.04 



Opinions in regard to the significance of the iodin have varied 

 from the view, on the one hand, that it is an essential constituent 

 of the physiologically active substance secreted by the gland, to 



* Cannon and Cattell, "American Journal of Physiology," 41, pp. 39, 58, 

 74, 1916. 



t Asher, "Deutsch. Med. Wochenschrift," 34, 1, 1916, and Levy, "Ameri- 

 can Journal of Physiology," 41, 492, 1916. 



J Kendall, "Jour. Amer. Med. Assoc.," 66, 811, 1916; also "American 

 Journal of Physiology," Proc. Physiolog. Soc., vol. 45, No. 4, 1918. 



