METHODS OF INVESTIGATION 23 



/ Feeding with fresh tissues, or with tissue extracts prepared 

 in various ways, has been very extensively employed. The 

 therapeutic method called " opotherapy " is based upon the 

 principle that the active substance, the " hormone," or the 

 " internal secretion," is absorbed unaltered into the circulation. 

 This is apparently a matter for discussion in some cases, as, 

 for example, in the case of the adrenals (vide infra, p. 211). On 

 the other hand, feeding with thyroid glands or thyroid extracts 

 (or even with the so-called active principle, iodothyrin or 

 thyroiodin or thyroxin [Kendall]) has proved a most valuable 

 mode of treatment in cases of cretinism and of myxcedema, 

 and has, besides, been used by physiologists for experimental 

 purposes. But our knowledge of the functions and internal 

 secretions of most of the glands, and especially of their true and 

 intimate relationships to morbid processes and pathological 

 conditions, is still so limited and inexact that it can hardly be 

 expected to furnish guidance in treatment. More especially 

 is this true in regard to the pituitary body, the thymus, and 

 even the pancreas. Among the tissues which have been con- 

 sidered from the standpoint of opotherapy or organotherapy 

 are, in addition to the thyroid apparatus and the adrenals, 

 the glands of the alimentary tract, the ovary, the testis, the 

 pituitary body, the thymus, the spleen, the bone-marrow, the 

 lymphatic glands, muscle, nerve, and the placenta. 



In feeding experiments the effects produced upon metabolism 

 have been carefully studied in many cases. Thus the addition 

 of thyroid substance to the normal dietary of growing rats 

 causes a great increase of food consumption, with alteration of 

 growth and retention of nitrogen in the body. At the same 

 time the nitrogenous metabolism is greatly increased. 



Gudernatsch has carried out a very interesting series of 

 experiments showing that certain mammalian ductless glands, 

 when given as food, can exert a decided influence on the growth 

 ^ and differentiation of amphibian embryos, the thyroid stimu- 

 lates differentiation, but it lacks the power to cause growth. 

 The thymus and spleen stimulate growth, but are wanting in 

 power to excite differentiation. 



A word of caution is necessary in respect to the mode of 

 preparation of commercial gland substances. In order to 

 obtain a clean, easily manipulated product, it is usual to re- 

 move all fatty matters before desiccation. It is possible, 



