BUREAU OF CHEMISTRY. 153 



cultivation of microorganisms, to assist in preparing materials for the 

 chemical investigations. 



The use of microorganisms in connection with analytical opera- 

 tions, and for the manufacture of various substances in the laboratory 

 and in the factor}", is a field promising rich rewards to diligent inves- 

 tigators and one that has hitherto been but comparatively little 

 worked. A beginning was made in the Division of Chemistry eight 

 years ago, when investigations relative to the organisms of nitrifica- 

 tion and denitrification were begun. The funds available have never 

 permitted a vigorous prosecution of these important investigations. 

 It is believed, however, that the appropriation of the present year 

 will permit the preparation of the material at hand for publication 

 and a renewal of the laboratory investigations. An item is inserted 

 in the estimates for the collaborative work with other Departments, 

 in ascertaining the quality of goods to be purchased, and also for the 

 investigation of the microorganisms in soils and fertilizers of interest 

 to agriculture. 



NEW WORK. 



Through the liberality of Congress provision has been made for the 

 inauguration of two very important additional lines of investigation 

 in the Bureau of Chemistry during the current year. The first of 

 these is the experimental study of the effect of i^reservatives, coloring 

 matters, and other substances added to foods, upon the health of the 

 consumer. To this end direct experiments will be made to determine 

 the influence which these bodies have upon the metabolic changes 

 which food undergoes when ingested into the human organism and 

 which the organism itself suffers. In this connection, series of experi- 

 ments will be conducted in which ordinary foods, containing none of 

 the substances under stud}^, will be fed under careful chemical super- 

 vision, the digestibility of the food determined, and the gain or loss in 

 the body ascertained. The same foods will then be fed in connection 

 with preservatives and coloring matters and other added bodies, and 

 a similar series of observations secured. 



The importance of this work is at once evident. There are certain 

 bodies which are uniformly employed as preservatives, which are com- 

 monly supposed to be wholesome, perhaps on account of the univer- 

 sality of their employment. Among these may be mentioned vinegar 

 and salt and wood smoke. Other preservatives have a real food 

 value, such as sugar, and the use of this body as a preservative can 

 not be open to any objection whatever. Still other preservatives have 

 a partial food value and are stimulating. Of this class alcohol is a 

 type. The propriety of using alcohol as a preservative is open to grave 

 question. 



The coloring matters are usually divided into mineral, vegetable, 

 and coal-tar colors. There is a universal feeling that mineral color- 

 ing matters are objectionable, while vegetable coloring matters are not. 

 Of the coal-tar dyes, some are certainly objectionable and others are 

 considered unobjectionable. The time has come, however, when some 

 authoritative data on all these subjects are imperatively demanded. 



It is to be regretted that many of the investigations which have 

 been made on these bodies have been, to a certain extent, ex parte. 

 As an instance of this, it may be said that manufacturers of certain 

 products added to foods employ experts to study the effect of these 

 bodies upon metabolism. It is not intended to throw any doubt upon 



