MANUFACTURE OF HOG-CHOLERA SERUM 343 



or any evidence of blood-poisoning. Slight pneumonia is permis- 

 sible, but I question if blood should be used where there is marked 

 consolidation of one entire lung or of both lungs. The object 

 should be to obtain a virus that is absolutely pure, and of just as 

 high a strength as it is possible to produce. 



Especially should this be insisted upon where virus is being 

 drawn to send into the field for use in giving the double method of 

 treatment. Virus blood intended for use for this purpose must be 

 of unquestionable quahty. Any mixed infection with the germs 

 of other diseases might prove sufficient to cause very disappointing 

 results. Hog-cholera serum which is used to counteract the effects 

 of the virus in these injections is only a protective agent against the 

 germs of hog-cholera, and will not afford protection against the 

 germs of pneumonia, pyemia, and various other infectious diseases. 



Cultures as a Source of Virus. — Eecent investigators in Ger- 

 many have made attempts to culture the virus of hog-cholera on 

 artificial media. Some success has been reported recently in this 

 regard. Some workers have reported that they have been able to 

 carry the cholera virus through several generations on culture- 

 media, and then, by injection into pigs, have again produced the 

 disease. This is a statement that carries large possibilities. If 

 this be possible, we may have placed in our hands a method of 

 securing cholera virus at a very small expense and in a very pure 

 form. Such a source of virus would have a most beneficial result 

 in lowering its cost, and, incidentally, would very much decrease the 

 cost of production of serum itself, as the cost of the virus is one of 

 the principal elements in the high cost of serum production. 

 Further investigations along this line are being carried on both in 

 this country and in Europe, and with the vast number of capable 

 men now engaged in the work there can be but little question that 

 the outcome is certain to be favorable in the near future. It seems 

 ahnost impossible for the actual cause of the disease to remain a 

 mystery very much longer, and with the discovery of the cause of 

 the disease it seems highly probable that methods for its successful 

 culture will rapidly follow. This will at once simplify the matter 

 of virus production and serum manufacture. 



Method of Hjrperimmunization. — After the virus blood has been 

 withdrawn and the clot removed it is set aside in a cool place until 



