40 THE LUNG PLAGUE OF CATTLE. 



mingled in the fields with infected cattle for thirty-seven years without any observed 

 transmission of the malady to the sheep. The same is true of Australia and the Cape 

 of Good Hope, where the plague has driven many colonists to replace their cattle by 

 sheep. Goats live in a large proportion of the stables of New York and Brooklyn, yet 

 we have never seen a goat infected. As respects deer, the lung plague prevailed for 

 a series of years in the deer park at Biel, Scotland, but the deer never suffered. These, 

 it is true, are but negative proofs ; they show only that in certain climates and con- 

 ditions exposure fails to produce infection ; what might occur in a different environ- 

 ment, which materially modified the disease, remains to be shown. At present there 

 is no reliable testimony that other animals than cattle will contract the affection. 



Among cattle no race, breed, nor age materially modifies the susceptibility. In 

 countries where the malady has prevailed for centuries the attacks are somewhat less 

 severe ; but this holds true of all plagues of man or beast. In time the more suscepti- 

 ble races die off, and by a natural selection the survivors have the disease in a milder 

 form. Sex gives no immunity; bulls suffer as much as cows, and oxen and calves, if 

 equally exposed, furnish no fewer victims than bulls and cows. 



IMMUNITY CONFERRED BY A FIRST ATTACK. 



Like the different forms of variola (small-pox, sheep pox, cow-pox, &c.), rinderpest, 

 msasles and scarlatina, the lung plague is usually taken but once by the same indi- 

 vidual. Some claim that the immunity lasts but about two years, after which the 

 disease may be contracted anew ; but the mass of evidence goes to show that second 

 attacks are exceptional, and they are probably 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 practices of protective inoculation, and of the exposure of young and 

 valueless calves to the infection, that the losses from the plague may be materially re- 

 duced. 



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 Loiset 

 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, &c., 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 introduction 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). 



Yvart, estimating for infected herds only, stated the losses in Aveyron, 

 Cantal, and Lozere at 30, 40, 50. 68 and even 77 per cent., the average 

 being at least 35 per cent. 



Gamgee secured records of 88 dairies in the city of Edinburgh for the 

 year 1861-62, and found that with an average holding of 1,830 the plague 

 cut off 1,075, or over 58 per cent. The yearly loss was 14,5] 2 ($70,000). 

 The actual losses in Dublin and other large cities were found to corre- 

 spond, those of London alone being estimated at 80,000. The losses 

 for the British Isles, computed from agricultural statistics, the records of 

 insurance companies, &c., were close upon 2,000,000 ($10,000,000) per 

 annum. 



Finlay Dunn shows from the English Cattle Insurance Company's 

 statistics that from 1863 to 1866 the losses from this plague were 50 to 

 63 per cent, per annum. 



In Holland Sauberg records a yearly loss of 49.661 head, while in 

 Wurtemberg it amounted to 39 per cent. 



The French commission of 1849 found that out of 20 cattle exposed, 

 16 took the disease, 10 severely. (The Lung Plague Law.) 



MORTALITY ENHANCED IN WARM CLIMATES AND SEASONS. 



The ratio of deaths has been found to rise with the heat of the weather. 

 Thus, while in France 20 per cent, resisted the contagion and 50 per cent. 



