28 VETERINARY SURGICAL THERAPEUTICS. 
2d, Diseases of the respiratory organs (emphysema, chronic pneu- 
monia, and pleurisy). These affections predispose to rapid and to 
slowsyncope. Ether seems to be the chosen anesthetic for animals 
suffering from emphysema or from dilatation of the right side of the 
heart; chloroform does better for affections of the left side of the 
heart ; chloral is the most advantageous when there are intermittent 
effects. (Arloing.) 
For bloody operations upon the face (sinuses and nasal cavities) 
if anesthesia is used, the head must be secured so as to assist the 
flow of the blood outwards; one must prevent its running into the 
respiratory tract, where it will give rise to suffocation. 
Narcosis being the result of the special action produced directly 
upon the nervous centers by that which gives rise to it, there is one 
indispensable condition to its realization, viz., the reception on these 
centers of a sufficient quantity of the anesthetic used. 
While some fixed anesthetics may be administered through various 
agencies (veins, mucous or serous membranes or subcutaneous 
cellular tissue), volatile anesthetics, to. produce all their effects, 
must enter by the respiratory mucous membrane. Injected into the 
organs or into the veins, the former run through the pulmonary 
capillaries without sensible loss and act in mass upon the centers ; 
the others escape, in great proportion, through the walls of these 
plood-vessels, and what remains in the arterialized blood is not 
sufficient to’ produce anesthesia. On the contrary, if these volatile 
agents are introduced in the shape of vapor into the respiratory 
tract, they penetrate, in great part, into the blood which goes down 
to the left side of the heart, and this quantity, thrown intact into the 
arterial tree, rapidly produces anesthesia, which soon becomes 
complete. 
Thus directly carried in the respiratory tract, anzesthesia gives rise 
to a series of phenomena, following one another in regular order. 
The progress of anesthesia may be divided into three periods : 
ist, That of excitement; 2d, that of anesthesia, anesthetic tolerance, 
or the surgical period ; 3d, that of collapse or intoxication, 
The first, or period of excitement, due to the action of the anesthetic 
vapors upon the ends of the nerves of the mucous membrane of the 
superior respiratory organs (nasalycavities, larynx), and again, to- 
the action of those vapors upon the nervous centers themselves, is 
characterized by disturbance of the sensibilities, by restlessness, 
and by the hypereethesia of the organs of sense. Violent reactions 
take place, the respiration and circulation are accelerated, the mucous 
membranes congested, the pupil dilated ; butsoon the heart becomes 
slower in its movements ; the respiration more regular, easier and 
slower ; the pupils contract, the restlessness subsides, sleep begins. 
During this first period, anesthetic vapors may give rise, in those so 
