876 PHYSIOLOGY OF DIGESTION AND SECRETION. 



little as 60 to 130 mgm. every three or four days. Later Baumann * 

 succeeding in isolating from the glands a substance designated as 

 iodothyrin or thyroiodin, which shows in large measure the beneficial 

 influence exerted by thyroid extracts in cases of myxedema and 

 parenchymatous goiter. This substance is characterized by con- 

 taining a large -amount of iodin (9.3 per cent, of the dry weight). 

 It is contained in the gland in combination with protein bodies, 

 from which it may be separated by digestion with gastric juice or 

 by boiling with acids. 



The Function of the Parathyroids. Most of the results des- 

 cribed above were obtained before the existence of the parathy- 

 roids was recognized. Early in the history of the subject it was 

 discovered that complete removal of the thyroids proper in herbiv- 

 orous animals (rats, rabbits) is not attended by a fatal result. 

 Gley and others, however, proved that if the parathyroids also are 

 removed these animals die with the symptoms described in the 

 case of dogs, cats, and other carnivorous animals. This result 

 attracted attention to the parathyroids. Numerous experiments 

 by Moussu, Gley, Vassale and Generale, and others have seemed 

 to show a marked difference between the results of thyroi- 

 dectomy and parathyroidectomy. When the parathyroids alone are 

 removed the animal dies quickly with acute symptoms, muscular 

 convulsions (tetany), etc.; when the thyroids alone are removed 

 the animal may survive for a long period, but develops a condition 

 of chronic malnutrition, a slowly increasing cachexia which may 

 exhibit itself in a condition resembling myxedema in man. This 

 distinction has been generally accepted, and it throws much light 

 upon the discrepancy in the results obtained by some of the earlier 

 observers. Complete thyroidectomy with the acutely fatal results 

 usually described includes those cases in which both thyroids and 

 parathyroids were removed, while probably many of the apparently 

 negative results obtained after excision of the thyroids are expli- 

 cable on the supposition that one or more of the parathyroids were 

 left in the animal. It should be stated, however, that two recent 

 observers, Vincent and Jolly, as the result of numerous experi- 

 ments made upon different varieties of animals, throw some doubt 

 upon these conclusions. They contend that in herbivorous animals 

 fully half of those operated upon survive complete removal of all 

 thyroid tissue, showing no evil symptoms except perhaps a di- 

 minished resistance to infection. Carnivorous animals, on the con- 

 trary, usually die after such an operation.! In spite of such con- 

 tradictory results in the hands of some observers the general opinion 



1910. 



' "Zeitschrift f. physiolog. Chemie," 21, 319, and 481, 1896. 



t See also Halpenny in "Surgery, Gynecology, and Obstetrics," May, 



