CONTAGIOUS DISEASES OF DOMESTICATED ANIMALS. 331 



woujkI. All this is easily accounted for if the hacilU and their germs 

 constitute the infectious principle, and if the mode and manner in which 

 they obstruct and clog the capillary vessels is taken into con.sideration; 

 but it is utterly irreconcilable with the non-appearance of any local reac- 

 tion after an inoculation by means of a wound too slight to cause conges- 

 tion if the infectious i^rinciple possesses the nature of a virus or of a 

 chemical agency. 



2. Swine plague, until the last days of December, or until the ground 

 becomes covered with snow and the Aveather exceeding cold, v/as spread- 

 ing from farm to farm and from place to place, but as soon as the tem- 

 perature commenced to rgraain below the freezing point, at noon as well 

 as at night, it at once ceased to spread from one fiirm or locality to 

 another. At the same time, however, it vras also observed that the 

 very cold weather of the last daj's of December and of the first days of 

 January — at seven o'clock in the moruing of the 2d day of January the 

 thermometer indicated at Gap Grove, Lee County, Illinois, a tempera iTire 

 of 28° below zero, and at the same hour on the day following a tempera- 

 ture of 24P — did not materially interfere with the spreading of swine 

 plague from one animal to another in all pens and hog-lots in which the 

 disease had previously made its appearance, and in which the way of feed- 

 ing and watering the animals was such as to allovr a contamination of the 

 food and of the water for drinking with the excrements or other excre- 

 tions of the diseased hogs, or in which the hogs and pigs, still healthy, 

 had open wounds, sores, or scratches, and had to sleep together with 

 the diseased hogs in the same sleei)ing place and on the same litter — 

 old straw^ and manure, for instance. Afterwards, when milder weather 

 had set in, the spreading from one place to another very slowly com- 

 menced again. 



Kow, if the bacilli and their germs do not constitute the infectious 

 princi])Ie and the cause of the disease; if, on the contrary, the latter 

 consist in some mysterious poison, or an in\isible chemical fluidum, the 

 facts and observations just related cannot be explained, because it must 

 be supposed that the low temperature prevailing at the end of the old 

 and the beginning of the new year, woidd have affected the infectious 

 agency either not at all, or just the same within as without the hog-lot, 

 and, at any rate, would not have prevented the spreading of the plague 

 except by destroying the infectious jninciple. The latter, however, is 

 not easily destroyed by frost, but only caused to become dormant till 

 the temperature rises again, otherwise the exceedingly cold weather and 

 continuous fi-ost of last winter would have been sufficient to extinguish 

 the disease; and the new outbreaks, or the renev/ed spreadiug, which 

 t^ok place when the weather became warmer, net only in one locahty 

 but in a great many, would not have been possible. All the facts and 

 observations, howevei-, will become perfectly harmonious, and be fully 

 explained, if the means by which the disease is produced and coinmu- 

 niciitcd consists of something corporeal, endovv'cd with vitality and 

 means of propagation; in other words, if the hacilU and their germs 

 constitute the infectious principle and the cause of morbid process, as 

 will become more evident by the following results of my investigation : 



Last summer and fall it was found that the hacilU and their germs, 

 present in immense numbers in the excrements, urine, and all other 

 excretions of the animals diseased with swine plague, were earned up- 

 ward into the air by the evaporation of the fluid parts or watery con- 

 stituents of those excretions, and came down again with the dew, the 

 rain, and other precipitates of atmospheric moistme, an<l were deposited 

 on the surface of everything wetted by the dew or the rain, on the grass 



