BUREAU OF ANIMAL INDUSTRY. 245 



content of the diet of hens upon the yield, fertility, hatchability, and 

 vitamin content of the e^gs. A second project involves a study of 

 the effect of the vitamin content of the diet upon the development of 

 pigs and upon the vitamin content of their tissues. 



THE RANCIDITY OF FATS. 



Further progress was made in the study of the rancidity of fats. 

 Some of the results were published in the Journal of Engineering 

 Chemistry, January, 1923, and another paper giving additional 

 results has been prepared. 



EMACIATION IN CATTLE. 



A continuation of the chemical study of emaciation in cattle has 

 confirmed the previous conclusion that there are clear-cut differences 

 in the comj)Osition of the flesh of cattle condemned for emaciation 

 and that of normal cattle passed for food. Work has been ham- 

 pered by the difficulty in getting suitable carcasses for investigation^ 

 but progress is being made toward finding an accurate chemical 

 means of judging in connection with post-mortem findings in meat 

 inspection whether a certain carcass should be condemned for ema- 

 ciation or passed for food. 



DIPS AND DISINFECTANTS. 



During the calendar year 1922 there were sent out to inspectors in 

 the field for testing the strength of dipping baths 1,912 new test 

 outfits for arsenical dips and supplies sufficient to make 962,000 field 

 tests ; 32 new test outfits for lime-sulphur dips and sufficient supplies 

 to make 21,000 tests; and 3 new outfits for testing nicotin dips and 

 supplies sufficient to make 2,925 tests. The total number of tests for 

 which supplies have been furnished was practically double that for 

 the preceding year. 



Studies with a view to improving the saponified cresol solution 

 which is used principally for official disinfection were continued. 

 It has been found that the soap used in compounding such disin- 

 fectants is of great influence upon the bactericidal properties of the 

 disinfectant. When certain kinds of soap are used without change 

 in the cresol the germicidal efficiency of the finished disinfectant may 

 be enhanced several hundred per cent against certain bacteria. The 

 cause of these differences in bactericidal power has been traced 

 to the particular fatty acids present in the soap, and it has even been 

 found that the soap used alone entirely without cresol is in itself a 

 decidedly powerful disinfectant against certain microorganisms. 

 As these powerful soaps may be readily and cheaply obtained, it is 

 believed that the results of the investigations will have much practi- 

 cal value. 



Some advance has been made in the investigation of the mode of 

 action of those classes of disinfectants which do not appear to enter 

 into definite chemical combinations with the substance of the bac- 

 teria, such as, for example, phenols and soaps. The hypothesis ad- 

 vanced last year that differences in effectiveness are parallel to cer- 

 tain physical differences has been confirmed. 



The study of colloidal phenomena which was referred to in the 

 preceding year's report has been continued. The subject is complex. 



