METABOLISM, NUTRITION AND DIETETICS 485 



above the original amount, while it has no effect on the 

 metabolism of the uncastrated animal. Oophorin also brings 

 about a notable increase in metabolism in the castrated male 

 dog, while, curiously enough, extract of testicle causes only 

 a small increase. But the orchitic extract is not without 

 influence in other ways. It certainly increases the capacity 

 for muscular work, as tested by the ergograph (p. 621), and 

 this distinct physiological action is sufficient to encourage 

 the hope that it may possess some therapeutic value, 

 although far from what has been claimed for it by its more 

 enthusiastic advocates. 



But the capacity of manufacturing internal secretions of 

 high importance can neither be attributed to all glands with 

 ducts nor denied to all other organs. For the salivary, 

 mammary and gastric glands may be completely removed 

 without causing any serious effects, while death follows 

 excision of the, so far as mere bulk is concerned, apparently 

 insignificant masses of tissue in the ductless thyroid, supra- 

 renal and pituitary bodies. 



Thyroid. When the thyroid is completely removed, symp- 

 toms and pathological changes ensue which differ in different 

 species of animals. In man, after excision of the whole thyroid 

 for goitre, an operation not infrequently performed before 

 the consequences of thyroidectomy were known, the condi- 

 tion called cachexia strumipriva supervenes. The symptoms 

 resemble those of the disease known as myxoedema, in which 

 the characteristic anatomical change is an increase (a hyper- 

 plasia) of the connective tissue in and under the true skin. 

 Newly formed connective tissue always contains an excess of 

 mucin, and for this reason in the early stages of myxoedema 

 there is somewhat more than the usual amount of that sub- 

 stance in the subcutaneous tissue. The skin is dry, and the 

 hair falls off. The features are swollen and heavy; the 

 movements clumsy, trembling, and often spasmodic. As the 

 disease progresses, the mental powers deteriorate too ; the 

 patient becomes stupid and slow, and perhaps, at last, 

 imbecile. When the gland is extensively affected in early 

 life a peculiar condition of idiocy (cretinism) results. 

 Monkeys, after removal of the thyroids, develop symptoms 

 resembling those of myxoedema. Carnivorous animals do 



