374 ANNUAL REPORTS OF DEPARTMENT OF AGRICULTURE. 



coal-tar creosote baths, siifTer projjressive diminution in the contained 

 j)eroentag:o of active infrrcdients through continued dipi)ing. In the 

 case of baths prepared from crosol dip the few results so far obtained 

 are not decisive. Such a well-marked diminution in strength neces- 

 sarily involves a certain degree, though not necessarily an equal 

 degree, of impairment to the efliciency of these baths. It would 

 appear, therefore, that eventually one of two courses must be adopted, 

 either the bath must be renewed with a stronger solution than was 

 originally employed or methods of assay must be developed suffi- 

 ciently rapid and simple to permit frequent tests to be made by the 

 men in charge of the vats. 



Experiments previously projected to determine the degree of ab- 

 sorption and retention of arsenic by the various tissues of cattle 

 dipped in arsenical solutions have been prosecuted to some extent. 

 Decisive results involve more time and the killing of more cattle than 

 has yet seemed advisable, but certain facts have been clearly estab- 

 lished : {a) Arsenic is considerably absorbed and long retained by 

 the skin of dipped animals, particularly in the deeper layer; (&) 

 from the skin arsenic is partly absorbed into other tissues of the 

 body and partly eliminated through the urine and the milk; (c) as 

 respects the possibility that arsenic may be present in edible products 

 derived from dipped animals, it is certain that continued dipping will 

 introduce only traces in either muscular tissues or in milk. In the 

 case of milk these traces only appear in the first few milkings after 

 dipping. Somewhat larger amounts may accumulate in the liver 

 and the kidneys. These organs, however, are eaten only occasionally, 

 not daily, as is muscular tissue ; hence there does not seem to be war- 

 rant for apprehension that arsenical poisoning or impairment of 

 health may result from the use of food products derived from dipped 

 animals. 



At a suggestion from one of the field agents of the bureau in the 

 first part of the year, efforts were made to develop a simple method 

 for testing arsenical solutions adapted for use in the field. A 

 method that seemed promising having been devised, two experimental 

 outfits were prepared and sent out in the field for trial. A large 

 number of samples of baths in actual use were examined by various 

 employees in the field and the results forwarded to the laboratory, 

 together with a sample of the dips themselves, so that the accuracy 

 of the field tests could be determined by laboratory analysis. The 

 results showed that the method, while of course not jnelding figures 

 as highly accurate as would be obtained in a fully equipped chemical 

 laboratory, was very satisfactory from a practical point of view. 

 They also showed very plainly the pressing need for some test of the 

 sort, since a large proportion of the samples contained a percentage 

 of arsenic much different from that supposed to be present, usually 

 less. These outfits are being supplied to tne field men. 



Occasioned by the necessity for analyzing mercuric chlorid tablets 

 used in large quantities by the inspection service of the bureau, a 

 study has been made of some methods for the analysis of such tablets 

 and a paper prepared, as yet unpublished. 



HOG-CHOLERA INVESTIGATIONS. 



In my last report it was stated that an investigation of the effect 

 of pheiiol, thymol, and formaldehyde upon the virus of hog cholera 



