PARATHYROID GLANDS 9 



in these circumstances rises considerably, as has been 

 proved by Oswald in man, and by Hunt and Seidel 

 in dogs. 



What, then, is the relation between iodine 

 metabolism and goitre ? 



In the first place, we may conclude that the 

 thyroid enlarges in goitre because it is necessary 

 for it to do increased work. A certain quantity of 

 iodothyrin is needful for the general well-being of the 

 individual ; if the gland is scantily supplied with 

 iodine, it must enlarge in order to take the fullest 

 possible advantage of all that may be brought to 

 it by the blood-stream. In the same way a kidney 

 hypertrophies when its fellow is degenerated, in order 

 to obtain more urea for excretion, and the red blood- 

 corpuscles double in number when a man takes up 

 his abode in the rarefied atmosphere of great alti- 

 tudes, to make the best use of the diminished supply of 

 oxygen. It has been shown by Oswald in a number 

 of observations that in goitre the thyroid colloid is 

 exceedingly deficient in iodine, both in calves and 

 man. Thus we get a clue to the successful treatment 

 of the affection either by iodiferous compounds 

 or by thyroid extract. It is well known that either 

 of these remedies will cure early cases of goitre, 

 before the enlargement becomes chronic. The 

 success of the iodiferous rock-salt on the American 

 farms may be accounted for in the same way. An 

 explanation is also offered of the fact, noticed 

 previously, that the whelps of bitches from whom 

 a good part of the thyroid has been removed are 

 all goitrous, the plasma supplied to the fcetal glands 



