INFLUENCE OF THYMUS FEEDING UPON DEVELOPMENT 149 
Of course the quantity of food to be given each day was always 
standardized from the series which desired the smallest amount 
to eat. At the beginning these were the worm series, and of 
these the cold worm series showed less avidity for food than did 
the warm worm series. As a result the thymus series at first 
received less than they would have liked to eat. The reasons 
for this comparatively small appetite in the worm animals 
have been specified above when discussing the first experimental 
group. From the time that the series of warm thymus animals 
began to undergo metamorphosis, the animals of this series 
showed the least desire to eat; after that it was the worm animals 
in general, and the warm worm series in particular which received 
less than they could have consumed. 
It may be emphasized at this point that when this method of 
distributing quantitatively equal amounts of food is followed, 
tetany exerts a very slight influence on growth. Sometimes the 
rate of growth is reduced at such points where the tetany curve 
reaches its apex, but in other cases, on the contrary it increases 
or reaches even a maximum when the tetany curve does. 
The condition which exerts an influence on growth in compari- 
son with which all other influences are reduced to insignificance, 
is metamorphosis, as will be apparent from the following 
description. 
During the first few weeks the warm thymus animals are seen 
to lead in size; next in order come the cold thymus animals, 
then the warm worm series, and finally the cold worm series. 
Nevertheless no special importance must be attributed to this 
relationship, for as has already been stated, given an equal volume 
of food, the thymus animals probably obtain more nourishment 
from their pieces of thymus than do the worm animals from an 
equal quantity of worm fragments. The relationship of size 
which has just been mentioned lasts until the 10th week, and the 
acute tetany which has meanwhile set in among the warm 
thymus animals and reached its climax has failed to influence 
this relation at all. In the 11th week a pronounced change sets 
in; at this stage the warm thymus animals are all ready for 
metamorphosis, the first individuals being 14 days removed from 
