THE THYEOID GLAND AND ITS DISEASES 233 



metamorphosis in tadpoles to result from the administration of iodin even 

 after both thyroid and pituitary had been extirpated. 3 



Morse finds that iodized blood^albumin will produce these changes in 

 metamorphosis. The reaction therefore is not a specific thyroid reaction. 

 This writer suggests that perhaps the heightening of the opsonic index, 

 which is known to result in other organisms after thyroid feeding, is re- 

 sponsible for the effects on the larvae. 4 



The balance of evidence is in favor of the view that the effects first 

 observed by Gudernatsch are not due to thyroid as thyroid but are the 

 result of some non-specific action on the organisms of certain organic 

 iodin compounds. 5 



It is\ stated that injection of an active thyroid extract into the circula- 

 tion causes a markedly increased sensitiveness to adrenin as tested by 

 the rise of blood-pressure caused by the administration of a certain dose 

 of this drug. The observation is being used clinically as a test for hyper- 

 thyroidism. (Levy, Goetsch (&), Anon. Endocrin 1918.) 



A further illustration of the action of the thyroid secretion on growth 

 is found in the observation of Carrel that brain and other tissues grow 

 in vitro increase several times as rapidly in the presence of thyroid sub- 

 stance as in its absence. 



Several series of feeding experiments upon white rats have been 

 carried out during the past seven or eight years. 



Schafer in 1912 administered small amounts of thyroid to groups of 

 white rats and found that the effect, especially in females, was to stimulate 

 growth. There was a greater nitrogen excretion and greater nitrogen 

 retention than in animals treated with substance from other glands. 



Fordyce fed young white rats with thyroid and reports emaciation in 

 all cases. The glands examined after death were full of colloid, while in 

 the controls this was absent or small in amount. He considers that in 

 animals treated with thyroid substance the colloid is retained, while in 

 the others the glands are in active secretion and the colloid is rapidly 

 absorbed. 



E. R. Hoskins studied the effect of thyroid feeding on the growth 

 of white rats, using animals from the same litter for comparison. He 

 found that neither male nor female animals are affected in body weight by 

 the treatment, and attributed the depressing effects upon growth and 

 body weight obtained by previous investigators to a toxic effect produced 

 by too large a dose. 



Large doses caused hypertrophy of heart, liver, spleen, suprarenal 



8 For a further discussion of this subject see Uhlenhuth. 



4 See also Rogoff and Marine. 



5 Kendall states that the action on metamorphosis (which occurs with small doses 

 of his "thyroxin") is not due to the organic nucleus, but is due to the iodin in the 

 molecule, which breaks off as hypoiodous acid (HIO). 



