VITIATION OF THE SYSTEM. 27 



Through the Air-passages it is that disease finds the 

 most facile road to sap the constitution. Considering how 

 accessible, and at the same time how susceptible these parts 

 are, it becomes no matter of surprise to us that they should 

 prove so frail a medium. The air an animal breathes is a 

 common vehicle of the seeds of disease : miasm, influenza, 

 animal and malignant effluvia, all by turns pervade the 

 atmosphere, and exert their several influences on the delicate 

 and sensitive membrane lining the air-passages. The na- 

 tural stimulus of this membrane is pure air ; whereas, the 

 atmosphere of the stable is rarely free from animal exhala- 

 tions, and but too often imbued with animal poison. The 

 subject of atmospheric influences is one on which we greatly 

 lack information ; and he will be serving veterinary science 

 who may embark in its investigation. 



Through the Skin, densely clothed as almost every part is 

 with hair, disease finds a difficult entry. "We know, how- 

 ever, that many medicaments rubbed where the skin is thin 

 — the insides of the thighs, muzzle, &c., — will take efi'ect on 

 the constitution ; we therefore cannot doubt the possibility 

 of disease being introduced in a similar manner, though we 

 believe instances of it to be rare. So long as the cuticle re- 

 mains entire, there is an evident indisposition to imbibe any 

 morbific matters : destroy, however, the cuticular covering, 

 and the disinclination ceases to exist. Even upon the bare 

 membrane of the nose I have frequently applied glanderous 

 matter without any ill consequence ; although its efi'ect has 

 proved certain on any part of the body by inoculation. 

 Such is generally the case, likewise, with the virus of rabies: 

 so long as the integrity of the skin remains unbroken, there 

 is little reason for apprehension. 



