E. B. Hart and H. Steenbock 319 
sources as in the previous experiments and as far as analytical 
methods could show, contained no more iodine than those used 
in our first ration. 
The difference between the two types of rations was not in 
the iodine content, but the percentage of protein and the per- 
centage of roughage. The first ration contained 14 to 15 per 
cent of protein and the second about 10 per cent. The first 
ration contained but 15 per cent of alfalfa and the second 25 
per cent. 
It has been believed for some time that the thyroid gland 
serves as a detoxicating agent-and that the hyperplasia results 
from stimulation to the gland to produce more and more colloid 
for purposes of detoxication. Such an hypothesis must assume 
that the iodine compound produced by the thyroid is, under 
conditions of high toxicity, either eliminated from the blood 
stream at a more rapid rate than normally, or is insoluble in the 
blood stream and cannot transfuse the placental wall. It as- 
sumes that there is just as much iodine coming into the blood 
stream through the intestinal walls as under normal conditions. 
If this is the case, however, it is difficult to comprehend why there 
should be a deficiency of iodine for the fetal thyroid unless we 
assume, as stated above, that there is a more rapid elimination 
of iodine compounds or the formation of iodine compounds in- 
soluble in the blood. 
The fact that our first ration was high in protein and low in 
roughage would suggest an alternate hypothesis. Such a ration 
would lead to more or less intestinal putrefaction with the ac- 
companying conditions of faulty assimilation. A faulty assimi- 
lation of the iodine compounds in the food would lower the 
iodine supply in the blood. This would lead to the hyperplasia 
of the thyroid gland of the mother as well as that of the fetus. 
Or it is possible that the selective absorption of iodine, instead 
of being wholly referred to the intestine, may be referred directly 
to the thyroid gland. Toxic substances produced through 
putrefaction in the intestine or coming directly from the food 
may, after absorption into the blood, cause a derangement of the 
iodine-absorbing mechanism of the thyroid gland; only then as 
the mass of iodine in the blood is further increased by the admin- 
istration of iodine, can normal abserption by the thyroid gland 
