668 INFECTIOUS DISEASES. 



disease is still unknown. Some investigators have described intra- 

 cellular parasites, others extra-cellular parasites, others, again, blood 

 parasites, etc., but the exact cause has always eluded research. 



It is, however, known that filtration of vaccine, pure or diluted, 

 through porcelain removes the active material, which remains in the 

 residue arrested by the filter. 



Prolonged exposure to a temperature above 104° Fahr. (40° C.) 

 greatly diminishes the activity of the vaccine. Simple desiccation has 

 no action. Warming to 140° Fahr. (60° C.) for fifteen minutes also 

 destroys its action completely. 



These facts explain why it has always been so difficult to preserve 

 and cultivate vaccine in tropical regions. 



Mixed with equal parts of neutral glycerine, the virulent material 

 preserves its activity unimpaired for from six to eight months. 



The disease develops equally in man, the horse, the ox, the buffalo, 

 the goat, and the camel. Its development is less typical in the pig, 

 sheep, dog, and rabbit. Young animals are best adapted for its 

 cultivation. 



The blood and serum of animals suffering from cow-pox possess 

 immunising properties, but only when administered in very large 

 doses, say from 6 to 12 lbs. of blood, or ^ to 1 lb. of serum. 



The curative action of this serum against small-pox is compara- 

 tively trifling. 



The diagnosis of cow-pox is not very difficult. 



At first the disease might be mistaken for false cow-pox, the erup- 

 tions of foot-and-mouth disease, or gangrenous coryza. 



In false cow-pox, the nature of which is also little understood, 

 although it is known to be contagious and is regarded by some as 

 true vaccinia, the pustules are smaller and thinner, while the vesicle 

 is more developed, and the disease runs a more rapid course. 



In foot-and-mouth disease the eruptions are of the nature of 

 vesicles or bullae, not pustules. The eruption occurs in twenty-four 

 hours or less, and can only be mistaken for vaccinia during the 

 period of desiccation and the formation of crusts. 



Finally, as regards gangrenous coryza, the hardened pustules do 

 not produce vesicles. 



The prognosis is generally favourable. The disease runs its course 

 within relatively fixed periods, according to the development of the 

 pustules, and recovery occurs without complications. 



Treatment. No curative treatment can be laid down, the develop- 

 ment of the disease being perfectly regular and tending to recovery. 

 Simple hygienic precautions and cleanliness are sufficient to avoid 

 complications due to suppuration. 



