THE DISEASES OF CATTLE. 71 



stable cow has to linger and die by inches. It must be evident 

 therefore, that if the results following an extreme vitiation of 

 a local atmosphere be so destructive, then those arising from 

 every minor degree, are no less certain, ultimately, to impair 

 an animal's health. 



The most important matter to be borne in mind, whatever 

 mode of ventilation we adopt, is, 'air once respired should not 

 again come within the sphere of respiration^ but should be made 

 to pass off, or be replenished with a fresh supply introduced 

 into the stable by a steady current. In a ventilated stable, we 

 find that the air which has just been expired, is lighter than 

 the surrounding medium, consequently ascends, and before a 

 second inspiration commences, the impure air is out of reach 

 of the nostrils. 



In order to secure a current of pure air, it is only necessary 

 to make openings in the ceiling, introduce square or circular 

 chimneys with caps, and make provision for the admission of 

 pure air in the vicinity of the floor, which can be done by cut- 

 ting square holes in the wall, and inserting into them a wooden 

 frame, covered on the outside with a wire grating. A harness 

 room or stable office may be ventilated by making a circular 

 hole into a disused chimney, the upper edge of the hole being 

 on a level with the ceiling ; the foul air naturally ascends, 

 and having the benefit of the draught of the chimney, is 

 readily carried upwards ; fresh air is admitted through the 

 doorway in summer, and beneath it in winter, so that it is an 

 easy matter to get rid of the unpleasant atmosphere, which al- 

 most invariably pervades such places, and with which arrange- 

 ment so many persons who labor in, and visit the same, have 

 occasion to find fault. 



Prof. Wyman, in his work on ventilation, informs us that 

 this simple plan of ventilation, is carried out in two of the 

 largest printing establishments in the city of London, in which, 

 for several years previous, the workmen employed had been 

 exposed to the full influence of vitiated air, which was so sick- 

 ening and oppressive (just like that of some harness rooms), 

 that they were continually the subject of disease, hut so soon 



