262 
THOMAS WALLEY. 
words, it is in the lungs that the change from venous to arterial 
blood takes place. Watery vapor too is exhaled by the lungs, 
and probably, to some extent, volatile matters also. Interference 
with the excretion of carbonic acid by the lungs tends to produce 
plasticity of the blood and favors congestive processes. 
The.skin , though last to be considered, is not the least in im¬ 
portance, particularly to the sheep. 
From this structure, under ordinary circumstances, watery 
vapor is constantly being exhaled, constituting insensible per¬ 
spiration ; and in the event of any derangement of the kidneys 
it takes on, if allowed to do so, compensatory action and assists 
in getting rid of the excess of water from the blood. Not only 
does it give off water, but it also, under certain conditions, absorbs 
water; that it possesses this function is shown by the fact that if 
an animal is placed in a bath and retained there for a time, it 
gains in weight. 
Warmth favors the evaporation of moisture, cold retards or 
arrests it; and this is a matter of great importance to the sheep 
because when its fleece, as so often happens, is saturated with 
water and the weather is cold the skin cannot perspire; on the 
contrary, water is absorbed and this is often aggravated by the 
watery nature of the food, and by inactivity, from disease, of the 
kidneys, and dropsy results. 
The facts just noted account for a further fact, viz., that while 
the sheep can withstand the effects of almost any degree of cold 
it is almost injuriously affected by cold and wet combined; and 
this is especially true of lambs. 
The perspiratory function of the skin is not the only function 
of importance that it performs. It is a breathing or respiratory 
organ also, though its powers in this direction are limited; never¬ 
theless, if the skin is covered with some impermeable material, 
such as varnish, or, as is frequently done in the case of affiliation 
of lambs, with a lamb skin, the animal dies. It was at one time 
thought that death in these cases was due to suffocation ; now, 
however, it is believed to be due to poisoning. As the temperature 
lowers materially, such a proceeding would certainly arrest the 
excretory function of the skin most effectually. 
