THE MODERN HORSE DOCTOR. 325 



them with powdered charcoal and bloodrcot, equal parts. "Warts 

 about the sheath or penis should be removed by excision : to do 

 this, we often have to cast the animal, the consequent hemor- 

 rhage to be arrested with tincture of muriate of iron or styptic. 

 See Styptic. 



CONSIDERATIONS AND EXPERIMENTS RELATING TO 

 CONTAGIOUS DISEASES. 



" Prevention is cheaper than cure." 



In these remarks M. Magendie's object has been to examine 

 into the channels through which deleterious substances find admis- 

 sion into the animal economy. 



u Respiration is the principal one. Through it we are continu- 

 ally exposed to the action of gases, vapors, emanations, virulent 

 and caustic poisons, germs and seeds, the ulterior development 

 of which may entail mortal results. The majority of substances 

 thus introduced are of a nature to alter the composition of the 

 blood, and disturb its vital operations. 



" The vapors have divers chemical compositions. Some there 

 are which have the power of quickly extinguishing the nervous 

 energy ; and although not many of them possess this fatal prop- 

 erty, it no less becomes our duty to inquire into their mode 

 of action. At the head of these we must place prussic acid, a 

 substance so volatile that it condenses while evaporating. Ma- 

 gendie illustrated this by experiment. He mixed, in a conical 

 vessel, a portion of medicinal prussic acid in combination with 

 three fourths of alcohol, and one fourth of the acid. He then 

 took a rabbit, and held its nose to the mouth of the glass vessel, 

 so that it was fully exposed to the vapor rising from the mixture. 

 The animal became convulsed, and in a few seconds died. In 

 this case, the blood of the rabbit became impregnated with the 

 gas of the acid, without the pulmonary vessels being involved. 

 The lungs are constituted of a myriad of tubes, whose mem- 

 branous walls, being extremely thin and porous, have the property 

 of being permeable to vapor. The vapors arising from the 

 blood in the same manner pass out, constituting the pulmonary 

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