Further proof of the antagonism existing between the thymus and parathyroid. 1

Abstract

Larvæ of the salamander Amblystoma opacum when fed on thymus soon after hatching develop tetanic convulsions at an age of from 35 to 40 days. Since at this time the larvæ develop, in their own thymus glands, the structures characteristic for the secretory stage of the glands, it was concluded that the amphibian thymus like that of the mammalian thymus excretes a toxic substance producing tetanic convulsions, and that tetany results if the animal's own secretion is added to that introduced by the thymus diet.

This is confirmed by further experiments (Table I., first four horizontal rows), which show that the interval between the beginning of the thymus feeding and the outbreak of tetanic convulsions becomes shorter, the later the thymus feeding is started, while the age at which tetany develops, remains constant.

If thymus feeding is started after the development of the functional stage of the animal's own thymus glands has taken place, tetany develops as soon as a certain amount of the tetany toxin has been accumulated in the organism (Table 1, Series XXV, 1918). The time required for accumulation of that amount is far shorter than the intervals in the first two series. It is, however, longer than in the fourth series, because the animals of series XXV. had been fed twice as long on normal diet and besides had almost twice as much time to grow before the thymus diet was started, and larger animals need more of the tetany toxin than small ones to develop tetany.

Hence, it is evident that the amphibian thymus gland manufactures a secretion similar to that of the mammalian thymus, and that the amphibian organism even in the absence of parathyroid glands can antagonize a certain amount of the toxin, be it excreted from its own thymus glands or introduced by thymus feeding before the animal's own thymus glands have developed; but excretion of their own thymus glands and thymus feeding at the same time lead finally to the accumulation of an excess amount of the tetany toxin, of which the parathyroidless organism of the salamander larva cannot dispose, and consequently tetany results.