BUKEAU OP ANIMAL INDUSTRY. 123 



that defibrinated blood serum can not be heated with safety at a 

 temperature greatly in excess of 50° C. Above 55° C. there is a 

 tendency to coagulate, and at 60° C. the defibrinated blood becomes 

 a semisolid mass. When the defibrinated blood was coagulated by 

 the heat the fluid portion was separated from the clot by pressure 

 and sufficient serum thus obtained to inject pigs. It was found that 

 all of the heated serums retained their potency. It thus appears 

 from these experiments (1) that hog-cholera serum in the form of 

 defibrinated blood can not, with safety, be heated at 60° C., although 

 the antitoxin is not destroyed even by 1£ hours' heating at that 

 temperature; and (2) that the antibodies of the serum will withstand 

 heating at 50° C. for 24 hours. 



One experiment was carried out to test the effect of drying on hog- 

 cholera serum by subjecting the serum to freezing and drying in 

 vacuo according to the method originally developed by Harris for the 

 preparation of antirabic vaccine and later applied by Rogers to the 

 drying of cultures of Bacillus bulgaricus. Test of the serum thus 

 prepared showed that the antitoxic properties of the serum were not 

 impaired by drying, and that pigs treated with the dried material 

 which was taken up in water before injection were completely pro- 

 tected against hog cholera. 



Certain cases of foot-and-mouth disease occurring in the course of 

 the outbreak of 1914-1916 were found to have been due to the use of 

 hog-cholera serum that was contaminated with the virus of the 

 former disease. This led to experiments with a view to developing 

 a process that would safeguard hog-cholera serum against the infec- 

 tion of foot-and-mouth disease in case that infection should by acci- 

 dent occur in the blood of the serum-producing hogs. Tests on ani- 

 mals on a scale that would be commercially practicable can not be 

 relied upon to eliminate the possibility of such infection ; none of the 

 ordinary antiseptics suitable for the preservation of serum can be 

 relied upon to destroy the virus of foot-and-mouth disease; and no 

 practicable process of filtration would be sufficient to remove the 

 virus, since it can pass through laboratory filters. It therefore ap- 

 pears that only by the application of heat, to which the virus of foot- 

 and-mouth disease is comparatively sensitive, and which, within 

 limits sufficient to destroy the virus, does not destroy the potency of 

 the serum, is it possible to accomplish the desired object. As the 

 serum in the form of defibrinated blood can not be heated safely 

 much above 50° C, owing to the fact that the blood undergoes coagu- 

 lation, it was also desirable to eliminate the red blood cells so that the 

 proper degree of heat for rapid sterilization might be applied. 

 Efforts were therefore made to devise a means of separating the red 

 blood cells from the serum in a simple and yet effective manner. 

 After experimentation it was found that this could be accomplished 

 by adding to the defibrinated blood a minute quantity of extract of 

 the common garden bean. A successful and practicable process has 

 thus been worked out, by which the red cells are agglutinated by the 

 bean extract and the resulting clear serum is sterilized against foot- 

 and-mouth disease by heating for 30 minutes at 59° or 60° C. The 

 experiments and the process are described in detail in a paper in the 

 Journal of Agricultural Research. 1 Preliminary work for the com- 



1 "A method for producing clear and sterilized antihog-cholera serum." By M. Dorset 

 and R. R. Henley. Journal of Agricultural Research, vol. 6, p. 333. 



72412°— age 1916 9 



