24 GLANDS IN HEALTH AND DISEASE 



the extract must be administered at regular inter- 

 vals and kept up indefinitely, otherwise there is a 

 relapse. The discordant results that have been 

 reported with thyroid feeding in myxedema are 

 almost invariably due to the type of thyroid extract 

 used. The various samples of these on the market 

 vary greatly in efficacy, due no doubt to the method 

 and source of extraction. Two commercial houses 

 justly famous for the preparation of such extracts 

 are Burroughs Wellcome, of London, and Parke, 

 Davis, of Detroit, Mich. Now that Kendall has 

 succeeded in isolating the active principle of the 

 thyroid, there need be little occasion for future 

 variation. 



Evidently the administration of the thyroid sub- 

 stance does not give rise to any accumulation of 

 the material in the system. A certain amount is, 

 as it were, used up in each operation. Under nor- 

 mal conditions, when the gland in the body func- 

 tions properly, the amount of hormone necessary 

 for regulating metabolic processes and nerve re- 

 sponses is manufactured whenever required. This, 

 of course, is no longer possible when the gland is in 

 an atrophied condition. 



Many cases are on record which show the de- 

 velopment of myxedema when the thyroid is re- 

 moved removed because, let us say, of a tumor 

 growth. Both the removal of the thyroid and the 

 atrophy of this organ give rise to the same disease. 



