146 ANNUAL REPORTS OF DEPARTMENT OF AGRICULTURE. 



proparrate this disease on our experimental farm, without success. 

 Several samples of material from alfected hogs in six dillerent herds 

 were obtained and healthy pigs were injected with it. In no case 

 was it possible to commvmicate the disease to healthy i)igs by these 

 blood injections. The cause of the trouble is not yet estal)lished. It 

 is interesting, and perhaps suggestive, to note that so far no disease, 

 with the exception of hog cholera, which is prevalent among hogs in 

 this country, has yet been found which can be regularly transmitted 

 by the subcutaneous injection of blood from infected animals. 



An extensive series of experiments with bacterins, particularly bac- 

 terins prepared from Bacillus suipestifer and B. suisepticus^ was ue- 

 gun. A number of different strains of each of these organisms have 

 been procured and the testing of these bacterins in different ways is 

 now in progress. 



• A large number of samples of hog-cholera virus and antihog- 

 cholera serum have been examined during the year for the Division 

 of Virus-Serun^ Control. These examinations have shown that a 

 very large proportion of the commercial serums contain considerable 

 numbers of bacteria, while many samples of hog-cholera virus are 

 likewise contaminated, though, as a rule, to a much less extent than 

 the serum. No pathogenic bacteria have been demonstrated in either 

 product. 



DIPS AND DISINFEtTANTS. 



The laboratory work on dips and disinfectants has followed the 

 same general lines as in ])revious years. A total of 180 samples of 

 dips and disinfectants and miscellaneous materials was received and 

 .analyzed. During the calendar year 1919 there were sent to inspec- 

 tors in the field 1,231 test outfits for arsenical dips, and supplies 

 sufficient to make 638,000 field tests for arsenic : 31 test outfits for lime- 

 and-sulphur dips, and sufficient material to make 14,800 tests of such 

 dips ; 24 outfits for testing nicotin dips, and supplies sufficient to make 

 6,200 field tests for nicotin; a total of 1,286 new test outfits and sup- 

 plies for 659,000 tests. 



In last year's report it was stated that the research work of the 

 dip and disinfectant laboratory had developed the fact that soy-bean 

 oil or the fatty acids derived therefrom could be used with advantage 

 as a substitute for linseed oil in the manufacture of saponified cresol 

 solutions. As a result the regulations governing official dipping and 

 disinfecting operations were modified to permit the use of soy-bean 

 oil or fattj'- acids derived therefrom. In continuation of this work 

 it was found that three-fourths of the vegetable oil may be replaced 

 by rosin, Avhich is very much cheaper. This use of rosin does not 

 change any essential property of this disinfectant but improves it in 

 some respects. The results of this work were published as Depart- 

 ment Bulletin 85.5. 



A new^ method for determining phenol and certain of its homologs 

 was developed, and the results of this Avork were published in the 

 Journal of Industrial and Engineering Chemistry (vol. 12, p. 568). 

 A second paper dealing with other phases of this work has been 

 prepared. 



An investigation of the germicidal value of some of the chlorin 

 disinfectants was completed and the results embodied in an article 

 for the Journal of Agricultural Research. This work led to the 



