381 
ON THE EXTERNAL CAUSES OF DISEASE. 
completely mephitic or noxious in a few hours. And in chinches 
and theatres, when a number of persons are assembled together, 
especially if the air circulates in them slowly, it would soon 
become vitiated. 
It is to the principles of chemistry that we are indebted for the 
better ventilating of apartments; and had she stopped here, and 
merely explained the method in which the air is vitiated by re¬ 
spiration, and the manner in which those noxious vapours are to 
be dispelled, she would have bestowed on mankind an incom¬ 
parable blessing. Modern science may be regarded as one vast 
miracle, whether we view it in relation to the Almighty Being 
by whom its objects and its laws are performed, or to the feeble 
intellect of man, by which its depths have been sounded and 
its mysteries explored. 
The present Professor of the Veterinary College directed his 
attention to the ventilating of stables at a very early period of 
his professional career; and has, accordingly, ventilated the 
stables of the several cavalry regiments in Great Britain. The 
following system is the one that he has adopted and taught in 
his lectures'at the College. We give it in his own words*. 
“ By ventilation,” says the Professor, “ is meant not any degree 
of temperature, either hot or cold, but a constant change of 
atmosphere, a constant supply of pure air. The common mode 
of ventilating stables was by means of windows, which were 
opened or closed at the pleasure and will of the groom. But the 
plan which I have adopted is to have openings made both at the 
top and the bottom of stables. Thus, in the formation of stables, 
the rack should be in the centre : two apertures about 2 inches 
by 3 inches, or 3 inches by 4 inches, should be made on each 
side, as close to the horse's nostrils as possible, and two holes of 
a similar size at the bottom. The holes at the bottom should be 
close to the pavement, because it is the purest air: the heavier 
the air, the purer it is, and the better jit for respiration—the 
heavy air containing more oxygen than any other . By this plan 
we have all the heavy air,"which contains the most oxygen, 
coming into the room by the apertures near the pavement, and 
all the impure or rarefied air going out at the upper holes. 
The upper holes being so near to the nostrils of the horse , you 
might, d priori, suppose that the air would pass in, as well as 
pass out, through these apertures; but this is not the case.” 
The reader will perceive the mistake under which the worthy 
Professor has laboured for so long a time, as it regards the 
* Lectures taken in short-hand notes, in the years 1823 and 1824, by 
the author. 
VOL. VII. 3 D 
