Immunity After One Attack. — Mortality. 37 



milder form. Sex gives no immunity; bulls suffer aa 

 much as cows, and oxen and calves, if equally exposed, 

 furnish no fewer victims than bulls and cows. 



Immunity Confeeeed by a First Attack. 



Like the different forms of variola (small-pox, sheep- 

 pox, cow-pox, etc.), rinderpest, measles and scarlatina, 

 the lung plague is usually taken but once by the same 

 individual. Some claim that the immunity lasts but 

 about two years, after which the disease may be con- 

 tracted anew; but the mass of evidence goes to show 

 that second attacks are exceptional, and they are proba- 

 bly no more common than second attacks of small-pox, 

 measles or scarlatina. The acquired immunity in infected 

 districts gives a special value to animals that have passed 

 through the disease, and upon this are based the prac- 

 tices of protective inoculation, and of the exposure of 

 young and valueless calves to the infection, that the 

 losses irom the plague may be materially reduced. 



Mortality. 



In recording the mortality caused by the plague the 

 most varied figures are set down by authors. Much of the 

 discrepancy arises from the point of view taken. Thus 

 if we estimate the losses as a percentage of all the cattle 

 in a district, they will appear very small inasmuch as it 

 is rare to find all the herds affected. Thus Loieet states 

 the losses for the entire bovine race of the department du 

 Nord, France, at 4 per cent, per annum. For distillery 

 stables, sugar factory stables, etc., it was 12 per cent., 

 and for farms but 2 per cent. This is accounted for by 

 the frequent changes in the former and the inevitable in- 

 troduction of contagion. The same applies to city dairies 

 where he found a mortality of 25 or 26 per cent. In the 

 Nord in 19 years it had killed 212,800 beasts of a total 

 value of 52,000 000 francs (over $10,000,000). 

 4 



