CAUSES OF GLANDERS. 205 



fevers, and in dysentery : these, once generated, become contagi- 

 ous; notwithstanding no such cause could possibly give them 

 origin. Itch, the Professor believes, is often produced in the 

 absence of contagion : it is bred in personal uncleanliness. Why, 

 then, may not hooping-cough, small-pox, &c. arise spontaneously, 

 i. e. from the same causes which originally produced them ? Those 

 who are most conversant in the habits and diseases of horses now 

 know, that glanders, although demonstrably contagious, much more 

 frequently arises from other causes : it is a disease that rarely or 

 never spreads among horses at pasture, though a glandered subject 

 may have been grazing among them ; for we learn from experi- 

 ment, that, although the disease is communicable by contact, the 

 poisonous matter must be applied to a part bare of hair, and that, 

 even then, the chances are in favour of the animal escaping infec- 

 tion unless the part have previously been, or happen to be in the 

 act, abraded." 



" There are two casual experimental results by which practi- 

 tioners, in investigating this subject, have suffered their judgment to 

 be misled, and thence have come to erroneous conclusions. The one 

 is, that, because a horse has been subjected without effect to inocu- 

 lation, ergo, the animal from whom the matter of infection was taken 

 cannot be glandered ; the other, that, because the former became 

 glandered, ergo, the latter must of necessity have the disease. 

 Two circumstances are absolutely and indispensably necessary for 

 the production of a disease by contagion ; — the application of the 

 poison, and the susceptibility of the animal or part to which it is 

 applied. You may inoculate without success from insusceptibility 

 of the inoculated subject, on the same ^principle that you may ad- 

 minister the same doses of aloes to two horses, and effect violent 

 purgation in one, but make no impression upon the other. It is by 

 no means uncommon to see persons inoculated for cow-pox and 

 small-pox without effect : the explanation of which is, that they 

 are not susceptible of that degree of poisonous excitation at that 

 particular period. Again, it has been argued that a disease could 

 not be glanders from which a horse recovered, even though it 

 shewed every characteristic outward sign of glanders. But the 

 very groundwork of this position is untenable : the Professor has 



