6 ^lASS. EXPERIMENT STATION BULLETIN 374 



catalase and peroxidase, both of which Hberate oxygen from peroxide in 

 milk. Lipase, a fat digesting enzyme, also occurs in milk. It is not im- 

 portant that the reader comprehend the exact chemical activity involved 

 in the action of these enzymes, but rather that the effect of iodine on the 

 enzymes ma}' indicate its effect on other enzymes whose activities are 

 better known. 



The enzymes from the digestive system studied were two stomach 

 enzymes — ^rennin which curdles milk, and pepsin which digests protein; 

 and two enzymes poured from the pancreas into the intestine— steapsin 

 which digests fat, and trypsin which digests protein. Both organic and 

 inorganic forms of iodine were employed. The results of the experiments 

 are given in detail in section V. The effects of the iodine varied with 

 the different enzymes. In general, where there was a stimulating effect on 

 enzyme action, organic iodine was mainly responsible and any inhibition 

 observed was usually in the presence of inorganic iodine. 



In section VI are reported some experiments concerning the effect of 

 iodine on the fecal bacteria of white rats. This research was based upon 

 the premise that bacteria which digest nitrogenous substances in the in- 

 testine may produce chemical compounds that are injurious to health 

 when they are absorbed into the intestine. The colon bacilli are the most 

 numerous bacteria of this kind in the intestines of meat-eating animals. 

 On the other hand, large numbers of acidophilus bacilli are supposed to 

 be beneficial in the intestine, largely because the conditions that encourage 

 their growth reduce the numbers of colon bacilli. 



White rats were employed in this study because their food requirements 

 are much like those of man. One group of rats was fed a preliminary 

 meat diet to increase the numbers of colon bacilli in the feces, and another 

 group was fed a preliminary diet of cereal and lactose to increase the 

 numbers of acidophilus bacilli. Then both groups of rats were subdivided 

 into smaller groups which were given separately tincture of iodine, potas- 

 sium iodide, or organic iodine. Both raw and pasteurized milk were 

 employed. 



Results indicated that the iodine in any form had no effect on the num- 

 bers of either kind of bacteria studied. In later experiments kelp was 

 added to the diet instead of iodine, and no effect was observed. 



The study reported in section VII dealt with the effect of different 

 forms of iodine on the bacterial content of milk, in an investigation of 

 the possibility that iodine might be added to milk as a substitute for 

 pasteurization, and might also have value as a food supplement. Tincture 

 of iodine, potassium iodide and iodine solution, and organic iodine were 

 employed separately. Studies were made with pure cultures of bacteria 

 as well as milk. The results are briefly summarized in the first part of 

 the section. The effectiveness of pasteurization was compared with iodine 

 treatment for the control of milk bacteria. None of the studies indicated 

 that iodine in quantities that the body should receive would control bac- 

 teria sufificiently to justify its use for that purpose. 



Detailed reports of the studies of the several departments follow in 

 the order in which they have been treated in this review. Much of the 

 experimental work undertaken is so large in scope that the results are 

 necessarily preliminary. A great deal more could and will be done in this 

 Experiment Station to add to the gradually accumulating knowledge of 

 nutrition -deficiency diseases. 



