BUREAU OF ANIMAL INDUSTEY. 119 



serum thus prepared was subjected to heat at 58° to 60° C. and 

 tested for potency, after being treated with phenol. The test 

 showed the serum to be potent, and it was then held for somewhat 

 more than nine months, when it was again tested and found to have 

 retained its potency without noticeable diminution. This serum 

 will be hold for still longer periods and again tested to determine the 

 limits of its keeping qualities. 



A number of studies have been made of the agglutinins of various 

 beans, and the reactions of various bean extracts have been tested 

 with blood from ten different species of animals. The results show 

 that there is a sharp difference in the agglutination reaction of 

 different animal bloods with the same bean extract. The navy-bean 

 extracts which have been employed in the production of hog-cholera 

 serum are also very powerful agglutinins for horse's blood. 



Additional work has been done with the process for refining old 

 defibrinated blood antitoxin by diluting it with strong solutions of 

 sodium chlorid and heating. While this process necessarily results 

 in some loss of antitoxin, we have been able by its use to convert 

 old defibrinated blood antitoxin into a clear serum free of blood 

 cells and bacteria. 



Patents have been obtained covering both the preparation of 

 clear serum by the use of bean extract and salt and the process 

 for refining old defibrinated blood antitoxin. These patents are 

 dedicated to the public, so that the Government or any of its officers 

 or employees or any other person in the United States may use 

 these processes without the payment of royalty. 



In order to ascertain the effect of heating on infections that might 

 be present in serum as it is drawn from hogs, and in order also to 

 ascertain the effect of weak mixtures of phenol on such infections, a 

 series of studies has been begun by adding various pathogenic bacteria 

 to sterile serum prepared by the bean-extract-salt method. The 

 serums were than heated and phenolized. Tests for the presence 

 of the pathogenic bacteria were made at different sta':;;es. Part of 

 the investigations have been completed, and it has been found tliat 

 the tuberculosis l)acillus in clear serum is destroyed when the serum 

 is heated for 30 minutes at 58° to 60° C. Studies of the effect of 

 phenol (0.5) on the tuberculosis bacillus in clear serum have shown 

 that the bacillus appears to be attenuated in two weeks and in the 

 experiments thus far carried out it was destroyed in four weeks. 

 These results are not to be taken as indications of what would take 

 place in the case of defibrinated blood antitoxin; the presence of 

 large quantities of red blood cells in the latter case would tend to 

 afford a certain amount of protection to the bacilli. 



MODES OP SPREAD OF HOO CHOLERA. 



Experiments described in last year's report have in many cases 

 been repeated and increased in number. Thirty-four additional 

 experiments to determine the length of time that pens remain infec- 

 tious after the removal therefrom of pigs sick of cholera have been 

 completed. The infection seems to die out quickly in warm weather 

 (as a rule within 24 hours), whereas in cold weather it remains active 



