METABOLISM 25 



clinically ; for were fat alone affected we would possess 

 in the thyroid an ideal remedy for obesity, but the 

 simultaneous destruction of fixed nitrogenous tissues 

 renders it a dangerous drug to employ for that purpose. 

 Considering the extremely minute quantity of iodothyrin 

 which is required to produce a profound metabolic effect, 

 one must regard it as one of the most potent of all the 

 agents at our command for influencing chemical changes 

 in the body, and the close resemblance of its action in 

 this respect to that of the poisons of many infective 

 processes renders it of the greatest interest to the 

 physician. 



Further, the influence which the thyroid secretion 

 exerts upon metabolism explains fully the results 

 observed in disease of the gland. Myxoedema, for 

 example, is pre-eminently a condition in which meta- 

 bolic change has undergone a partial arrest, resulting 

 in the accumulation of an immature connective tissue 

 beneath the skin, the cells of which have not undergone 

 the normal process of division and maturation. In the 

 scalp, again, the development of young hairs is at a 

 standstill, and when the effete hairs fall out there are 

 no fresh ones to take their place, and the patient 

 becomes bald. Fat also accumulates in the body, and 

 from the lessened production of heat the patient has 

 a subnormal temperature and a constant feeling of 

 chilliness. In this way one could run through all the 

 well-known symptoms and signs of myxoedema, and 

 show that they are all the result of a partial arrest of 

 metabolism brought about by the failure of the stimulus 

 which the thyroid secretion should normally supply. 



