334 Journal of Agricultural Research voi. vi, no. 9 



well established that the virus is killed by 5 minutes' exposure to a 

 temperature of 60°. 



Experimental work has shown that defibrinated hog-cholera-immune 

 blood may be heated to 50° C. for 1 2 hours without destroying the anti- 

 bodies and without materially altering the physical character of the 

 defibrinated blood. Heating to higher temperatures — 60°, for example — 

 results in more or less complete coagulation of the defibrinated blood, 

 and therefore in the destruction of the serum in so far as its commercial 

 worth is concerned. While heating at 50° for 12 hours might appear 

 to be satisfactory, in practice it would be difficult and expensive to carry 

 out such a process. 



Experiments with clear serum, separated from the red cells, have 

 shown that, unlike the defibrinated blood, which coagulates at 60°, the 

 serum, separated from the red blood cells, withstands heating at 60° 

 for 30 minutes without alteration of its physical characters and without 

 noticeable impairment of its antitoxic power. 



With the above facts in mind, renewed efforts have been made to 

 devise a cheap and simple process for preparing hog-cholera antitoxin 

 in the form of a clear serum free from the red blood corpuscles and from 

 corpuscular debris. 



PREPARATION OF THE SERU]\I 



If ordinary defibrinated hog's blood be subjected to centrifugalization, 

 there may be secured ordinarily about 50 per cent of serum. The time 

 required will naturally depend to a large extent upon the precipitating 

 force developed by the centrifuge. We have found that a force equiva- 

 lent to approximately 1,700 times gravity serves to attain this result in 

 from 20 to 30 minutes. The serum which separates is usually cloudy, 

 and, owing to the fact that the red blood corpuscles are not firmly packed, 

 it is impossible to remove all of the serum without at the same time 

 carrying over some of the red cells. Therefore, simple centrifugalization 

 has not seemed practicable for the following reasons: (i) Antibodies are 

 lost because of inability to separate all of the serum from the corpuscles, 

 (2) the serum secured is generally not clear, and (3) the removal of the 

 serum from the cells is a difficult and tedious procedure. 



In endeavoring to overcome the difficulties enumerated above, we have 

 used extracts of the seed of different varieties of the common garden 

 bean (Phascolus multifiorus and P. vulgaris). Extracts of these beans 

 are known to possess the property of agglutinating the red corpuscles of 

 hog's blood, and they are said to be nontoxic.^ Our own experience has 

 shown that, although the extracts ^ exert no general systemic effect 

 upon rabbits, guinea pigs, or hogs, certain varieties of these beans do 

 yield extracts which act as intense local irritants, resulting, in guinea pigs 



1 Mendel, L. B. Observations on vegetable hxmagglutinins. /« Arch. Fisiol., v. 7, p. 168-177. 1909. 



2 Extracts made with water or normal salt solution. 



