112 ANNUAL EEPORTS OP DEPARTMENT OF AGEICULTUKE. 



BIOCHEMIC DIVISION. 



M. Dorset, Chief. 



HOG-CHOLERA INVESTIGATIONS. 



The work on hog cholera has consisted ahnost entirely of research 

 work on various problems connected with the control of that disease. 

 This work was carried out under three major projects, which are 

 reported upon separately, as follows : 



METHODS OF PKODUCING IMMUNITY AGAINST HOG CHOLERA. 



In the report for the preceding fiscal year it was stated that a 

 method of separating the blood corpuscles from the serum of de- 

 fibrinated hog's blood had been devised. This offered what appeared 

 to be a practicable method of producing a serum which could be 

 subjected to heat and thus effectively sterilized against foot-and- 

 mouth disease. Experiments with this method have been continued. 

 It has been found that clear anti-hog-cholera serum produced by the 

 bean-salt method, heated at a temperature sufficient to destroy foot- 

 and-mouth disease virus, retains its potency at least as long as eight 

 months. This is in accord with observations made by others on 

 diphtheria antitoxin and confirms the view that the heating does not 

 shorten the time during which the serum will remain potent when 

 kept under proper conditions. Several large commercial producers 

 of anti-hog-cholera serum have adopted this method and have oper- 

 ated it successfully for more than a year. At first difficulty was 

 encountered in preparing from beans an agglutinin which would 

 keep in good condition for considerable periods of time. This is a 

 matter of practical importance to serum producers. Experiments 

 during the year have resulted in the development of a method for 

 producing an agglutinin which, either in the form of a powder or in 

 solution, will keep in good condition for longer periods. A descrip- 

 tion of the method was published in the Journal of the American 

 Veterinary Medical Association for February, 1917. (Vol. L, N. S. 6, 

 pp. 699 to 702.) 



In the investigation of various plant seeds with reference to their 

 suitability for producing agglutinins, extracts from 54 different varie- 

 ties of seed were tested on hog blood, horse blood, and ox blood. The 

 seed represented all of the procurable varieties of beans and many 

 varieties of peas and lentils, as well as peanuts and acorns. None of 

 the extracts agglutinated ox blood. Most of the extracts from beans 

 agglutinated hog blood and horse blood, while extracts from the jack 

 bean, asparagus, lentils, and black-eyed pea agglutinated only horse 

 blood. 



Chemical tests indicate that the agglutinins derived from beans are 

 probably of the nature of albumins. They are destroyed by heat at 

 80° C. (176° F.). A full report of these experiments is being pre- 

 pared for publication. 



As long as hog-cholera serum is prepared in the form of defibri- 

 nated blood there may at times arise, owing to outbreaks of foot- 

 and-mouth disease, or for other reasons, the necessity to heat or to 

 concentrate the antitoxin. Previously such refinement has been car- 

 ried out by precipitating the globulins by means of ammonium sul- 



