118 ANNUAL KEPORTS OF DEPAETMENT OF AGEICULTURE. 



The disease in Maryland lasted throughout the montn of August, 

 and a study was made of it and the attendant conditions. The feed 

 of the animals in all cases but one consisted of native hay, bran, 

 corn stover, and immature corn affected with weevils. The corn 

 stover and a great part of the corn were, badly contaminated by 

 molds. Most of the animals were allowed to graze a little, and in the 

 exception noted above the animals (Chincoteague ponies) obtained 

 all their subsistence by grazing. 



Blood drawn aseptically from a case in the early stages of the 

 disease and from another case in a very late stage proved by culture 

 media inoculations to be sterile. Fresh defibrinated blood from 

 these two horses injected intravenously into other horses in doses of 

 30 c. c. at the Bethesda experiment station did not engender any 

 symptoms of disease. Corn chaff and bran from local millers and 

 corn and corn stover from the various farms where the disease 

 occurred were fed to horses at the experiment station, but did not 

 cause any symptoms of the disease. 



EXPERIMENTS ON ANTHRAX VACCINATION. 



The Pasteur treatment, which has been almost exclusively em- 

 ployed in this country for vaccination against anthrax, while effec- 

 tive in cases where the vaccine is of a desired potency, has its 

 disadvantages in that this product deteriorates at times very rap- 

 idly under normal conditions, as, for instance, when it is exposed to 

 light and high temperature. Samples have been examined from time 

 to time by this bureau, with the result that vaccine purchased in 

 the South was at times found to have become inert in from two to 

 three months from the time of manufacture. The use of such vac- 

 cine would, of course, impart a false security to the owners, and 

 subsequent outbreaks would tend to bring this method of prevention 

 into disrepute. 



Experiments have been conducted on the preparation of immune 

 serum to be used in connection with the spore vaccine for the immuni- 

 zation of animals against anthrax. Horses were employed for the 

 preparation of the serum, and after several months of treatment 

 with increasing doses of anthrax culture the serum attained a very 

 high potency for immunizing purposes. The serum is injected 

 simultaneously with the spore vaccine, and this gives the method 

 an additional advantage over that of Pasteur, since only one han- 

 dling of the animal is necessary instead of two as with the latter 

 method. 



The experiments on both small and large animals proved the 

 effectiveness of this method of vaccination beyond a doubt. An 

 opportunity was also afforded to test it out in actual outbreaks of 

 anthrax. One of these outbreaks occurred in INIississippi, where a 

 considerable number of animals have been lost from anthrax. Fol- 

 lowing the immunization not a single death resulted. Similar re- 

 sults were obtained in an outbreak of anthrax among hogs in Mary- 

 land, where the disease was effectively checked by the administration 

 of immune serum. An outbreak on the Eastern Shore of Maryland 

 gave still another opportunity of testing the potency of simultaneous 

 vaccination, with equally good results. 



