INTERNAL SECRETIONS 151 



when a small part of the gland is retained or when the 

 thyroid gland is transplanted to the peritoneal cavity or when 

 fresh or dried thyroid glands are given by mouth. The 

 abnormal enlargement of the thyroid (goitre) can also be 

 relieved by feeding on thyroid glands. 



One of the most striking effects of the therapeutical use of 

 thyroid preparation is the rapid fall in body weight and the 

 disappearance of body fat. This loss of weight is due, as 

 has been shown by experiments in metabolism, partly to 

 the withdrawal of water from the tissues, the water in the 

 urine being increased, and partly by the not inconsiderable 

 increase in combustion. By feeding a rabbit sufficiently with 

 thyroid glands, the combustion processes can be doubled. 

 The combustion of proteid, is, however, little affected as 

 long as non-nitrogenous material, especially fat, is present. 



The thyroid gland is therefore indispensable for life. 

 Most likely its importance lies in the fact that it produces 

 one or more substances which are absolutely essential for the 

 normal course of life's processes. An excess of these sub- 

 stances produces severe disturbances in the nervous system 

 and metabolism, and can also produce death. From the 

 thyroid gland there has been isolated a substance containing 

 iodine, thyroiodin, which is believed to be the active principle 

 of the gland, for iodine has a certain therapeutical action 

 upon hypertrophic thyroid glands. But, as all thyroid glands 

 do not contain this substance, and as thyroiodin does not 

 show all the actions of the thyroid gland, we can hardly 

 regard it as the active substance. 



The thymus is supposed to have the same function as the 

 thyroid gland, for feeding on thymus is said to have the same 

 result as feeding on thyroid glands. 



II. Suprarenal capsules. The suprarenal capsules con- 

 sist of cellular parenchyma surrounded by connective tissue 

 capsules. The parenchyma forms a clear cortical and a dark 

 red medullary portion. In both the cortical and the medul- 

 lary portion numerous nerve elements (non-medullated nerve 

 fibres, sympathetic ganglionic cells) are present. Because 



