608 LECTURE XXVI. 



We are still very far from being able to trace the functions of the thyroid 

 gland to definite chemical processes. We merely understand the effect 

 of its extirpation, and know, furthermore, that it stands in some relation 

 to the sexual organs. It has been observed that at the time of menstru- 

 ation, during pregnancy and lactation, there is frequently a swelling of the 

 gland. To be sure, processes may be involved here which have nothing 

 whatever to do with the cell-functions of this organ, but may be caused by 

 vascular influences. Again, the observation that in cretins the sexual 

 organs frequently remain undeveloped, does not necessarily prove that 

 there is a direct relation between the thyroid gland and the sexual organs. 

 It is certainly not remarkable that in the general metabolic disturbance 

 even the sexual organs, which as a rule require a constant supply of mate- 

 rial as they in a certain sense are constantly growing, will likewise suffer 

 to a marked extent. At present it is impossible for us to distinguish here 

 between primary and secondary phenomena. 



That the thyroid gland yields a secretion, cannot be doubted. This is 

 evident alone from its histological structure. Apparently the follicular 

 cells produce the specific secretion. It then passes through openings in 

 the follicular walls into the lymph, and is then given up to the blood. 1 

 We will merely mention the fact that Oswald isolated from the secretion 

 of the follicles (the so-called colloid) two proteins, the so-called thyreo- 

 globulin and a nucleoproteid. The former alone contains iodine. 2 



Our limited knowledge concerning the chemical processes taking place 

 in the thyroid gland makes it impossible for us to in any way give a precise 

 description of the nature of the function of this very important organ. 

 Everything is hypothetical. According to the autotoxication theory, it is 

 the purpose of the thyroid gland to remove, or render innocuous, one or 

 more toxic substances which would otherwise accumulate in the blood. 

 There is no ground for this assumption, but it is perfectly conceivable that 

 the organ can secrete substances which are capable of combining with other 

 products. It is possible that the iodine content of the thyroid gland 

 serves such a purpose and perhaps indicates the presence of easily replace- 

 able substances. It is, however, also very probable that the thyroid 

 gland secretes substances that take part in the general metabolism and 

 regulate chiefly the transformations which albumin undergoes. It is not 

 at all difficult to formulate assumptions in this direction, particularly after 

 repeatedly meeting with facts which show that in order to accomplish 

 fermentation, a number of different body-cells act together. One cell 

 yields an activator of the ferment, and another the ferment itself. It is 

 perfectly conceivable that the thyroid gland is active in this sense, and 



1 Hiirthle: Pfliiger's Arch. 56, 1 (1894). 



2 Z. physiol. Chem. 27, 14 (1899). Hofmeister's Beitrage, 2, 545 (1902). Z. physiol. 

 Chem. 32, 123 (1901). 



