18 INFLUENCE OF FOOD PRESERVATIVES ON HEALTH. 



Four such increases are desirable at least, and hence the period of the 

 experimental study of the preservatives, as a rule, should not be less 

 than twenty days. 



Unless a great disturbance of the normal functions has been pro- 

 duced by the preservatives administered, an "after period" of ten days 

 will be found sufficient in most cases to restore the functions of the 

 body to their normal state and to bring the weight of the body, if it 

 has been changed, back to the normal. In many cases, however, there 

 may be an accumulation of the preservative in the body, requiring a 

 considerable part of the after period for its complete removal. In such 

 cases any effects which may have been produced are likely to be mani- 

 fested for many days. 



In the discussion of the data which follow, the duration of the 

 periods of observation will be indicated in each case. 



COLLECTION OF EXCRETA. 



Where the individual is under constant observation and is devoting 

 his whole time to the experiment, the matter of the collection of the 

 excreta is simplified; but the problem of making collections from so 

 many persons engaged in the usual vocations of life was a matter of 

 some difficulty. 



The importance of regularity in the hours of voiding the excreta 

 was impressed upon all. Bottles were provided which each individual 

 could take with him during the day or during his absence from the lab- 

 oratory, and in so far as the urine was concerned little difficulty was 

 experienced in collecting it without undue annoyance. The matter 

 of the collection of the feces was much more difficult. The problem 

 was studied from many points of view, and the final decision was to 

 adopt a special form of can, which was found both cheap and efficient. 

 This can is described under the head of analysis of feces. (See fig. 1, 

 p. 26.) 



MEDICAL SUPERVISION. 



It was deemed important to have competent medical supervision of 

 the members of the experimental class in order that the results of the 

 investigations might be studied also from the point of view of the 

 physician. It was also thought best that this supervision should come 

 for this purpose from an official source. To this end the Secretary of 

 Agriculture addressed the following communication to the Secretary 

 of the Treasur}^: 



I have the honor to ask that you request the Surgeon-General of Public Health 

 and Marine-Hospital Service to detail a physician from his staff to make physical 

 and medical examinations of the young men employed in this Department in testing 

 the effect of preservatives upon the health of the consumer. 



There will not be any great drain upon the time of this expert, since the examina- 

 tions are to be made only about once in ten days, on six young men, and will not 



