28 INFLUENCE OF FOOD PRESERVATIVES ON HEALTH. 



but not quite all. Small amounts of nitrogen are separated from the 

 body in the hair, the nails, and the desquamations from the surface of 

 tha body. Thus in a perfectly normal state of the body the sum of 

 the nitrogen excreted in the urine and the feces would not represent 

 the total amount ingested in the food. On the other hand, in abnor- 

 mal states of the body, where the breaking down of the tissues is 

 going on more rapidly than their building up, just the reverse condi- 

 tion would prove true. The same statements may be made with refer- 

 ence to the sulphur and phosphorus. 



It is evident, however, that if a relation can be established between 

 the total amount of these substances entering the food and that leav- 

 ing the body in the urine and feces, any disturbance of that relation 

 by the addition of an abnormal constituent to the food, such as a pre- 

 servative, can be easily detected. Therefore, for the purposes of these 

 investigations, the fact that complete collection of these elements from 

 the body is not secured is not a valid objection to the deductions 

 which are made from the data. Nevertheless, it should be pointed out 

 with clearness and frankness that in the conditions in which these 

 experiments were made there are possibilities of error which must not 

 be overlooked. Carelessness on the part of the observer himself in 

 the collection of the excreta, a violation of the pledge in regard to the 

 conduct of life," or an error in analysis would each tend to render the 

 results of less value. That such errors have been wholly excluded 

 from the data submitted is not likely. On the other hand, errors of 

 this kind which may have been introduced could not have been pur- 

 posely made in order to modify the final results of the investigation. 

 Hence it is fair to assume that such errors are to a certain extent com- 

 pensatory and that they do not affect seriously the conclusions based 

 upon the data as a whole. Those who have worked in investigations 

 of this kind, however, will understand the great difficulties which 

 attend them, as well as the care which has to be exercised in their con- 

 duct, and will be the more ready to excuse any unavoidable error which 

 may have crept in, either in the conduct of the work or in the morale 

 of those who were subjected to the experiment. 

 >. 



EFFECT OF REGULAR HABITS. 



Another important factor must be considered in the interpretation 

 of the data which have been obtained in these experiments, namely, 

 the effect upon the physical well-being of the subject produced by reg- 

 ular habits of living, uniform quantity of diet, and general control of 

 the appetites. 



It is usually considered by physiologists and physicians that regular 

 habits of life conduce to health and strength. This theory has been 

 corroborated by the results of the experimental work here detailed. 

 While it is true that in many instances during the progress of the 



