~ KE. B. Hart and H. Steenbock 321 
with our own observations. One of two sows, reared on the same 
ration and in the same pen, produced hairless pigs and the other 
produced sound and vigorous offspring. These results can be 
ascribed to constitutional differences, inherited factors which al- 
ways display themselves with any group of animals. The ration 
that is near the border line of deficiency in iodine and at the same 
time is slightly out of balance in some other respect may well 
affect some individuals more than others. 
The sows that had been reared on grain and alfalfa (75 to 25 
parts) with successful reproduction, were next taken to higher 
protein levels and lower roughage,—a ration of 15 parts of alfalfa, 
45 parts of corn, 15 parts of oil meal, and 25 parts of middlings. 
Here there has also been successful reproduction. The young 
pigs were well haired, and the thyroids normal and with normal 
iodine content. It appears probable, therefore, that the dis- 
turbances to thyroid metabolism are more likely to be developed 
during the period of most rapid growth of this species than after 
maturity, but final conclusions in this respect cannot as yet be 
made. 
SUMMARY. 
A brief summary of our experience with the hairless pig malady 
supports the view that it is occasioned by a low iodine assimila- 
tion by either intestine or thyroid, resulting in a goitrous condi- 
tion in both mother and young. This condition interferes more 
severely with fetal development than with the normal mainte- 
nance of the mother. . 
It appears to be produced by rations with high protein levels 
and low laxative effects, with the accompanying condition of 
lack of exercise and unclean surroundings. Young sows exposed 
to such conditions are more prone to develop thyroid enlarge- 
ment than are mature sows. We recognize, of course, that there 
is the possibility that some rations from certain regions are 
naturally so low in iodine as to make the scarcity of iodine the 
direct cause. : i 
We have found it possible to grow sows to maturity on natural 
feeding materials grown in southern Wisconsin, but of relatively 
low protein content and good laxative properties, with the pro- 
duction of normal offspring. On the other hand, these same 
