THE DUCTLESS GLANDS 319 
one kilogram, the seal of 432 kilos had .03 gm. of thyroid, 
lion had .18 gm., leopard had .46 gm., a serval .36 gm., 
a skunk 2.35 gm., (was this normal?) while a single 
herbivore Avith the weight given was a porcupine having 
.25 gm. per kilo. The average of Murray's carnivores 
is therefore .67 gm. per kilo of body weight, whereas our 
figure is .55 gm. That the incidence of thyroid abnor- 
malities stands in direct relation to carnivorous character 
has been recognized before, and is abundantly borne out 
by our statistics, as will appear at a later place. 
Anatomy. 
The minute anatomy of the normal thyroid is fully 
given in text-books, and is doubtless pictured in the minds 
of all but students of the subject as a fixed and definite 
affair. Such is not the case. There is certainly a variation 
in gross size under conditions of seasonal and sexual 
activity, and it would seem acceptably demonstrated that 
changes in diet, especially where meat is concerned, are 
associated with swellings or shrinkage of the glands. 
These gross changes must be due to alterations in his- 
tology. In youth also the bulk is larger, a condition due 
to cellular activity, while as middle age advances the 
thyroid becomes smaller and more balanced in its colloid 
and cellular proportions. I need not detail the ultimate 
constituents of the gland, but it is well to emphasize a few 
points which must be taken into consideration in micro- 
scopical diagnosis. In the first place, the lobules or acini 
are not all of the same size in normal organs. This is 
especially true in the noniial adult gland but may be so in 
youth. The cells which form the inner lining of the acinus 
are low cuboidal in shape but the elements which lie under 
them are oval and do not change with hyperplasia of the 
former. The colloid which fills the glandular spaces is 
very susceptible to mechanical and chemical agencies. In 
material preserved in alcohol it may be shrunken away 
from the cells or heavily vacuolated, while in tissue 
