DISEASES OF SWINE AND OTHER ANIMALS. 41 



and pigs, consequently the wind, usually in the south, carried the efflu- 

 via and the foul atmosphere of the former almost constantly into the 

 yard occui)ied by the old liogs. The latter, notwithstanding, remained 

 exempted. It may yet be stated that the old hogs were fed exclusively 

 with corn, and received nothing but well-water for drinking. On the other 

 hand, I have not been able to learn of any herd remaining exempted 

 after the disease had once made its appearance in the immediate neigh- 

 borhood, unless the animals constituting the herd were free from any ex- 

 ternal lesions, were watered from a well, fed with clean food, and shut up 

 during the night and in the morning till the dew had disappeared from 

 the grass, either in a bare yard not containing any old straw-stacks, or in 

 sties or pens. Animals allowed to run out on a pasture or on grass, clover, 

 or stubble fields at all times of the day, and animals that had external 

 sores or wounds, contracted the disease sooner or later in every instance 

 where the plague made its appearance in the neighborhood. Further, 

 the plague, at least during the summer or while south wind was prevail- 

 ing, seemed to have a special tendency to spread from south to north. If 

 the history of swine-plague is inquired into it will probably be found 

 that that tendency has been prevailing every year. This year, for 

 instance, the disease made its appearance, as I have been informed, for 

 the first time, in Wisconsin. These facts, of course, could not fail to be 

 suggestive. So I conceived the idea that the contagious or infectious 

 principle, abundant in the excretions of the diseased animals, might rise in 

 the air in daytime, be carried oft' a certain distance by winds, and come 

 down again during the night with the dew. That such might be the 

 case appeared to be possible, because the excrements of hogs, if exposed 

 to the influence of sunhght, heat, rain, and wind, are soon ground to 

 powder (partially at least), which is fine enough to be raised into the 

 air and to be carried oft" by winds. Moreover, as the bacillus-germs, 

 which, I have no doubt, must be looked upon as the infectious principle, 

 are so exceedingly small, it appears to be possible and even probable 

 that they are carried up into the air by the aqueous vapors arising from 

 evaporating urine and moisture contained in the excrements, and from 

 other evaporating fluids (small pools of water), which may have become 

 polluted with the excretions of sick hogs. To ascertain the facts, I col- 

 lected dew from the herbage of a hog-lot occupied by diseased animals, 

 and also from the grass of an adjoining pasture, and on examining the 

 same under the microscope I found the identical hacilli and bacillus- 

 germs invariably found in the blood, other fluids, and morbid tissues 

 of swine aflected with the plague. (See drawing VII, fig. 5.) Conse- 

 quently I have come to the conclusion that the bacillus-germs rise into 

 the air during the day, are carried from one place to another by the 

 wind, and are introduced into the organism of the animal either by eat- 

 ing herbage (grass, clover, &c.), or old straw covered with dew, or by 

 entering Avounds and being absorbed by the veins and lymphatics. 

 There is, however, still another way by which the contagious or infec- 

 tious principle is conveyed from one place to another. It is by means 

 of running water. It has been observed that wherever swine-plague 

 prevaded among hogs that had access to running water (as small 

 creeks, streamlets, &c.), that all the hogs and pigs which had access 

 to the creek or streandet below contracted the disease, usually within 

 a short time, while all the animals which had access above remained 

 exempted, unless they became iniected by other means. I could cite a 

 large number of instances, but as this observation has been made every- 

 where, i)rol)ably nobody who is at all acquainted with swine-plague will 

 ask for any further jjroof. 



