22 INTERNAL SECRETION 



of an organ (or both organs in the case of bilateral structures) 

 is removed at once. Better still and more fruitful of results 

 are operations in which the organs are crushed, damaged, or 

 infected artificially with the germs of disease, or inoculated 

 with toxins, or partially destroyed by chemical poisons, or in 

 which the blood-supply is interfered with to a more or less 

 complete degree. 



Further, extirpation experiments, as usually performed, 

 are only likely to give us useful information in cases where the 

 organ or tissue extirpated normally provides an internal 

 secretion which is needful for the body as a whole. If we 

 remove the submaxillary glands, for example, we find that the 

 animal is apparently unaffected, and the same applies to the 

 mammary and gastric glands. But we are not justified in 

 concluding from these experiments that the glands in question 

 have no internal secretion, but merely that if there be such a 

 secretion, it cannot be regarded as essential to the body as a 

 whole. As a matter of fact, it is now believed that the gastric 

 mucous membrane secretes a specific hormone (vide infra, p. 

 65), and the same has been alleged to be the case with the 

 salivary glands. 



Proceedings of a reverse character, such as grafting, feeding, 

 and subcutaneous and intravenous injections, have also been 

 extensively employed in the search for the functions of the 

 ductless and other glands supposed to possess an internal 

 secretion. Experiments in grafting have been chiefly carried 

 out in connection with the thyroid and parathyroid glands, 

 and the reproductive organs. Some work in the same direction 

 has also been done with the adrenals. The object of these 

 experiments has been to replace the extirpated tissue by freshly 

 implanted tissue of the same kind, either in the original 

 situation or in some other part of the body. The earlier 

 attempts were not very successful, and the effects were of a 

 temporary character. The graft became absorbed, and so the 

 final result was no more than that of the administration of a 

 certain dose of the substance of the gland. Some recent 

 experiments, however, have been more successful, and have 

 yielded interesting and important results. An account of 

 these grafting experiments will be given in their appropriate 

 place under the heads of Thyr^d, Adrenal, and Reproductive 

 Organs. 



