Till: M'N<! PLAGUE OF CATTLi:. 43 



sutlicient lor the mult iplication of the germs so us bo render the solution 

 quite turbid. 



It should be added that hot climates and seasons appear to abridge 

 the period of latency ; thus, the disease will develop more rapidly in. 

 summer than in winter, and in the South than the North. Any febrile 

 condition of the system will also favor its rapid development ; therefore, 

 symptoms are often hastened by parturition, by heat (n-xtrum}* and by 

 other exciting causes. 



PKOLMMJF.l) I.\< IHATION A SOURCE OF (ilMlAT DA.NiiKU. 



The Short-horn cow which infected Australia must luive been 112 days 

 from the time of sailing from Kngland to the iirst symptoms of disease 

 in Australia. The case, however, is not quite clear, for there is a report 

 that she had sutVered from the same disease over a. year before in Eng- 

 land; and, if so, this may have been a relapse, after the infection had 

 been carried for at least an entire year encysted in the chest. Such 

 second attacks are met with, though only very exceptionally, in the case 

 of all diseases small pox, cow-pox, scarlet fever, measles, &c. in which, 

 as a rule, the first attack fortifies against another. 



No such objection can be made to the case of Norway, where the cattle 

 were found to be diseased !K> days after leaving the Scottish coast, nor 

 in the case of South Africa, where the disease was observed 102 days 

 after the bull had sailed from Holland. 



During all this period of three months and a half the most skillful ex- 

 pert would fail to detect the slightest sign of lung disease, or even of ill 

 health; in such a case, therefore, the examination of the individual ani- 

 mal can give no guarantee whatever of soundness. Even the examina- 

 tion of an entire herd may similarly fail to detect any trace of this disease, 

 though the seeds of it are present, and it is only by a series of exami- 

 nations of the entire herd, extended over the period of the longest- 

 known incubation (90 to 112 days), that any assurance of safety can be 

 obtained. 



This is a sufficient answer to the constantly repeated demand (hat im- 

 ported animals should be examined, and, if no sickness can be detected, 

 should be allowed to pass into the interior; also, that animals for export 

 should be examined, and in the absence of any sign of disease should 

 be furnished with a certificate of health. A similar demand is constantly 

 made that cattle in transit from place to place of the same country 

 should be examined and certified sound, irrespective of any examination 

 of the herd from which they come or the risks of infection during transit. 

 Certificates based on no more than such examinations are, at best, but 

 so much waste paper. In case of the infection of any of the animals 

 examined they become great and positive evils. They certify, on insuf- 

 ficient data, to what is not a fact; they mislead the unwary buyer into 

 the conviction that his purchase is assuredly sound, and not only induce, 

 him to take the diseased stock upon his farm, but to pasture or stable it 

 with his healthy herd. It may even be made an accessory to the profit- 

 able sale of cattle known to be infected, by an unprincipled vender. The 

 owner of the herd infected with this plague is submitted to the constant 

 temptation to turn off, at a fair sound price, animals that he knows will 

 almost certainly fall victims to the pestilence; and by the long period of 

 incubation, during which no sign of the presence of the disease can be 

 detected, he is furnished with the amplest opportunity to make such sale 

 without suspicion. Honorable men would scorn to take advantage of 

 such an opportunity, yet it cannot be denied that every community con- 



