THE DUCTLESS GLANDS. 183 



The colloid material subsequently finds its way into the general 

 circulation, either by passing between the intact cells of the alveolus 

 (Fig. 157), or after a passage has been prepared for it through altera- 

 tions in certain of those cells (Fig. 158). The colloid is then taken 

 up by the lymphatics, through which it reaches the general circula- 

 tion. This is an example of internal secretion which presents much 

 of interest. It is probable that a similar, but much less obvious, 

 process takes place in some of the ordinary secreting glands of the 

 body, certain elaborated materials being returned to the circulation 

 by the cells of the gland, while others are utilized for their nourish- 

 ment and for the elaboration of the more obvious secretion. 



That the secretion of the thyroid gland is of importance to the 

 general organism is shown by the effects of disease or removal of 

 the gland upon the general nutrition. Total extirpation of the 

 thyroid, together with the parathyroids, occasions the death of an 

 animal within a few days, after symptoms of grave disturbances in 

 the central nervous system, among which are tetanic convulsions. 

 A partial removal of the gland, or its removal without that of the 

 parathyroids, causes profound disturbances of nutrition, grouped 

 under the title " cachexia strumipriva." The animal becomes weak, 

 drowsy, and emaciated ; the skin dry and scaly, with a loosening 

 of the hairs. In young animals the growth is retarded, especially 

 the development of the bones, through degenerative changes in the 

 epiphysial cartilages. In these, the intercellular substance becomes 

 swollen and disintegrated ; the cells atrophied or destroyed. Marked 

 changes, designated as myxredema, also appear in the subcutaneous 

 tissue, which is converted into a species of mucoid tissue, probably 

 as the result of an altered metabolism within the pre-existent cells 

 of the tissue. The functional activity of the kidney is modified ; 

 after a while, albuminuria results. Exactly similar disturbances have 

 been observed in people suffering from disease of the thyroid gland. 



The foregoing facts are cited here in order to emphasize by a 

 striking example the statement previously made, that the organs of 

 the body are mutually dependent upon each other. 



Experimentation and clinical study have further shown that the 

 symptoms of myxoedema may be moderated or perhaps entirely 

 arrested by feeding with thyroid extracts, or still more markedly 

 by injecting extracts from thyroid glands beneath the skin, where 

 they would speedily pass into the lymphatics and thence into the 

 general circulation. 



