IODINE IN THE ANIMAL ORGANISM. 



THE disease called Myxcedema is due to morbid con- 

 ditions of the thyroid gland in which it no longer 

 exercises its normal role in the metabolic cycle. It is now a 

 matter of common knowledge that injection of extracts from 

 the thyroids of other animals cures the disease, by replacing 

 the lost internal secretion of the diseased or absent gland. 

 This very remarkable practical outcome of physiological 

 research has prompted several investigators to attempt the 

 discovery of the active chemical substance secreted by the 

 thyroid by which that organ normally influences the 

 nutrition of the nervous system, and to which thyroid 

 extracts owe their efficacy. Though this search can hardly 

 yet be said to have completely attained its object many 

 interesting facts have come to light during its progress, and 

 by no means the least of these is the discovery that there 

 are certain substances in the thyroid which contain iodine 

 in organic combination ; as an integral part of living 

 animal structures this element was previously not known 

 to exist. 



The work was carried out in Baumann's laboratory at 

 Freiburg, and began with an investigation by Ernst Roos 1 

 on the influence of the thyroid gland on metabolism. In 

 Roos' paper the history of the subject, so far as it relates to 

 the use of thyroid extracts in the relief of myxedematous 

 conditions is fully given. The experimental part of the 

 paper describes observations on human beings during 

 treatment, who showed a marked increase in the amount of 

 phosphoric acid which they excreted. The majority of the 

 experiments were, however, performed on dogs ; the thyroid 

 had been previously removed, and the gland was adminis- 

 tered as food to them. The excreta were analysed and com- 

 pared with those in healthy dogs. In the latter there is an 

 increase in the excretion of nitrogen (more than can be 

 explained by the nitrogen in the gland given) of sodium 



1 Zeitsch. f. physiol. Chem., xxi., p. 19, 1895. 



