APPENDIX 295 



their outer clothing or effectively cover the same by the 

 use of gowns or other satisfactory garments. 



REGULATION 20. BACTEBINS, VACCINES, TOXINS, ETC. 



SECTION 1. Paragraph 1. Viruses entering into the 

 preparation of bacterins, vaccines, or toxins shall be de- 

 rived from animals which are affected with no disease 

 other than that for which the bacterins, vaccines, or 

 toxins are intended to be used. 



Paragraph 2. All bacterins, vaccines, and toxins, shall 

 be derived from the specific cause of the diseases for 

 which they are intended to be used, or from the secon- 

 dary invaders of the respective diseases. 



SECTION 2. Paragraph 1. The return date on the 

 trade labels of blackleg vaccine prepared from attenu- 

 ated B. gangrcence emphysematosce or blackleg muscle 

 virus, shall be a date not more than 6 months later than 

 the date on which the preparation of the product is 

 completed, without regard to the filling of final con- 

 tainers. 



Paragraph 2. The return date on the trade labels of 

 anthrax vaccine prepared by the Pasteur method shall be 

 a date not more than 3 months later than that on which 

 the preparation of the product is completed without 

 regard to the filling of final containers. 



SECTION 3. The immunity unit for measuring the 

 strength of tetanus antitoxin shall be 10 times the least 

 quantity of antitetanic serum necessary to save the life 

 of a 350-gram guinea pig for 96 hours against the official- 

 test dose of the standard toxin furnished by the Hy- 

 gienic Laboratory of the United States Public Health 

 Service. The number of the immunity units recom- 

 mended for the prevention of tetanus in a horse shall 

 be at least 500 units. 



