402 STATE BOARD OF AGRICULTURE. 



as Expt. 387 was treated do not furnish a serum agglutinating at a 

 dilution higher than 1-500. We think we are justified in concluding that 

 the agglutinative power of the blood of Expt. 387 increased from 1-500 

 to 1-8000 during the injections of filtered virus which contained no 

 organisms capable of producing cloudiness in the diluted filtrate. 



Another evidence of the absence of B. cholerae suis in the filtrate 

 lies in the fact that no abscesses were produced as a result of injecting 

 extra large volumes of diluted virus. It is a common experience to find 

 that the injections of unfiltered virus blood produce the so-called B. 

 cholerae suis abscesses or caverns filled with a thick, dirty fluid usually 

 walled off by connective tissue. We must admit our ignorance of the 

 cause of the increase in agglutinative power of the serum from Expt. 

 387. 



The potency of the serum from Expt. 387 was tested on small pigs 

 against both the filtered and unfiltered hog cholera virus. The two 

 bleedings were mixed and termed "Mixed Serum Expt. 387." Table 

 VI shows the tests made with mixed serum Expt. 387 against virus 

 Expt. 53G. Table VII shows the tests made against virus Expt. 536 

 diluted with equal parts of .85% NaCl solution and filtered through 

 a Chamberland filter. 



It is seen from a study of these two tables that the serum, drawn from 

 a pig hyperimmunized with filtered virus only, protects against either 

 the filtered or unfiltered virus. However, the protective power against 

 the filtered virus is much greater than against the unfiltered virus. Only 

 the pig receiving 5 c.c. of serum dies of cholera when treated with the 

 unfiltered virus, whereas the pig receiving 20 c.c. of serum together with 

 the unfiltered virus dies of cholera. These experiments tend to show 

 that in filtering hog cholera virus through a Chamberland filter, some 

 thing is removed that has considerable to do with producing hog 

 cholera. Perhaps the filter has an effect of only weakening the virus 

 by permitting the serum to pass but retaining a proportionately large 

 number of the ultra-microscopic organisms, rather than by keeping 

 back a virulent pathogens of an entirely different species such as B. 

 cholerae suis. While it is hardly worth while to speculate, it may be of 

 interest to note that the suggestion has been made that the filterable 

 virus, incapable itself of growing in vitro, is only a peculiar fomi of 

 a microscopic organism which is capable of growing in vitro. In this 

 case, of coui'se, filtration would weaken the virus by removing a portion 

 of its active principle. 



The experiments recorded in Tables VIII and IX furnish additional 

 evidence for the belief that it is easier to protect against the filtered 

 virus than against the unfiltered hog cholera blood. Table VIII shows 

 that 10 c.c. and 15 c.c. of Mixed Serum 35 furaish complete and endur- 

 ing protection to small pigs against hog cholera when injected simul- 

 taneously with 2 c.c. of the filtrate of virus 13G diluted with equal parts 

 of .85 per cent NaCl solution and passed through a Chamberland filter. 

 The filtrate furnished no growth when incubated. Table IX shows that 

 neither 10 c.c. nor 15 c.c. of Mixed Serum 35 protects against 2 c.c. of 

 virus 130 diluted with equal parts of .85 per cent NaCi solution and 

 not filtered. Virulent cultures of B. cholerae suis were found in pure 

 culture in the blood and organs of virus pig 136. 



