68 
L. Kaufman; 
poles having thyroid glands which already exert their function, it 
accelerates their influence. 
Comparing histological changes in axolotls fed on thyroidine 
with those which accompany normal metamorphosis of amphibians, 
I was confronted with some difficulties. Previous authors generally 
take into consideration the atrophy of the tail of Anura ; they did 
not investigate other organs nor the metamophosis of Urodela. 
1 therefore restricted myself to a comparison with such phenomena 
as have been described. 
A diminution of cells, characteristic of the tissues of axol¬ 
otls fed on thyroidine and of animals subjected to starvation, was 
observed by Barfurth and by Loos in the epithelium of the 
skin of the tail in tadpoles undergoing resorption. 
An increase of the quantity of pigment in the skin 
of the tail of tadpoles during metamorphosis was ascertained by 
Barfurth, Loos and Bataillon. Bataillon found that the 
pigment formed is the product of nuclear chromatin. According to 
Ruzicka, the formation of pigment from albuminous substances 
accuses accelerated metabolism caused by starvation; and I have 
observed a similar increase of the quantity of pigment in the skin 
of axolotls fed on thyroidine; I consider thus the behaviour of the 
skin of the degenerating tail of tadpoles (with respect to the form¬ 
ation of pigment) as a further proof that, in the organism of am¬ 
phibians in transformation, processes of disassimilation occur an¬ 
alogous to those observed in animals fed on thyroidine. 
Bataillon says that histolytical processes take place not only 
in tissues undergoing resorption; that they can also be observed in 
general in the organism during the period of transformation. He 
writes: „Lhistolyse est générale“. From this we conclude that the 
atrophy of the larval apparatus is not caused by local changes; 
that in the organism at large processes occur which first affect less 
resistant organs. In the histological part of the present paper I de¬ 
scribed changes not only in the gills and fins of axolotls fed on thyr¬ 
oidine, but also in their skin, intestine, pancreas etc. 
From a comparison of the data known with respect to meta¬ 
morphosis of amphibians under normal conditions with the behav¬ 
iour of axolotls fed on thyroidine it follows that what I observed 
cannot be considered as pathological, but rather as physiological 
