MEMOTRS OF A VETERINARY SURGEON. 15 
best suited for him under the circumstances ; bearing always 
in mind this fact, that whilst the various membranes and 
organs are in this highly sensitive and susceptible state, 
they are most impressionable, and, consequently, more easily 
acted upon by restorative influences. It is to me great 
gratification to know that the internal organization is acces¬ 
sible through this avenue, for it needs but little reflection 
to convince us that there are some parts of the organism, 
the delicacy of which the human mind is inadequate to form 
the slightest conception, and which are nevertheless of the 
highest importance in the maintenance of life. 
FOUL CONFINED AIR, AND VENTILATION. 
We always find that whenever air is allowed to stagnate 
in places having a resemblance to a well, it has a strong 
tendency to become heated and vitiated, when of course it 
cannot be long respired without injury to health. It is, 
therefore, our duty to provide against this as much as pos¬ 
sible. As the air becomes warmer it expands and ascends; 
the pure as well as the impure. And here let me remark, 
we may have a smoky atmosphere, and yet it shall not be 
necessarily unhealthy; whilst, on the other hand, we may 
have a clear, transparent atmosphere, which is all the time 
most deleterious and highly prejudicial to health. If the 
cold fresh air is allowed to enter from above, it obeys the 
natural laws of gravitation ; the cold and heavier air forces 
itself in by pressing downward, and passes underneath the 
air that is warmer, and thus operates in impelling the warm 
air on in its upward tendency, like unto small pebbles 
thrown into a vessel of water, which force the water up over 
the top. But the parallel holds good only to a certain ex¬ 
tent ; for the cold air receives heat as it descends, and also 
gives out its cold to the surrounding air; therefore, before it 
reaches the lower stratum of the atmosphere, an equilibrium 
has become established, and, consequently, this lower stra¬ 
tum is very little, if at all, affected. The best contrivance 
for effecting this kind of ventilation is the cc Four Points 5 
Ventilator,” or diaphragm, patented by Mr. Muir of Man¬ 
chester. My own experiments have not as yet convinced 
me of the correctness of this theory, and I am very strongly in 
favour of the cold fresh air being allowed to have ingress from 
apertures on the ground surface. By this means it disposes 
of itself in altogether a different manner, it being drawn into 
the compartment in accordance with and agreeable to a law 
regulating demand and supply, there being a constant ten- 
