172 MICROBIOLOGY 



these cases there are usually marked local cell infiltrations, 

 with inflammation of one or more of the serous membranes 

 and possibly metastatic abscesses. 



Hog cholera. Experimental animals are not susceptible 

 to the filterable virus of hog cholera. It is often necessary to 

 inoculate a pig with the blood of the hog suspected of being 

 affected with hog cholera. A pig inoculated with from 1 to 

 2 cc. of blood develops the disease in about ten days. The 

 disease of hogs due to Bacillus suipestifer can be diagnosed 

 by inoculating rabbits subcutaneously with a small quantity 

 of crushed spleen or liver or with 0.1 to 0.2 cc. of a pure 

 bouillon culture of the organism. The rabbit will die in from 

 5 to 10 days with a much enlarged spleen and frequently with 

 areas of coagulation necrosis in the liver. With attenuated 

 organisms the lesions are modified and the time extended. 



Anthrax. Mice or guinea pigs should be used. They are 

 inoculated subcutaneously. They die of septicemia usually in 

 from 24 to 72 hours. It is not always necessary to resort to 

 animal inoculation with this disease. Occasionally, however, 

 it is a very necessary procedure in making a positive diag- 

 nosis. 



Diphtheria. Guinea pigs are nearly always used. In 

 certain rare cases of mixed cultures taken directly from the 

 suspected throat it is desirable to inoculate one or more guinea 

 pigs to determine w r hether the suspected organism present is 

 a virulent Klebs-Loeffler bacterium. In these cases a suspen- 

 sion of the growth on the serum may be injected. The guinea 

 pig dies usually in from 36 to 80 hours. The lesions produced 

 have been described by Park as follows : 



"At the seat of inoculation there is a grayish focus sur- 

 rounded by an area of congestion ; the subcutaneous tissues 

 for some distance around are oedematous ; the adjacent lymph 

 nodes are swollen ; and the serous cavities, especially the 

 pleural and the pericardial, frequently contain an excess of 

 fluid, usually clear, but at times turbid; the lungs are gen- 

 erally congested. In the organs are found numerous smaller 

 and larger masses of necrotic cells, which are permeated by 



