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ration of the chloroform was somewhat more rapid in the earlier stages than in the later, when
most of the chloroform had volatilised and the surface of fluid exposed to the air was diminish--
ed; but, even allowing for this, it is certain that at no time was the amount of chloroform
vapour in the air over 3 per cent., and even when more chloroform was added before the first
minim had evaporated, the strength was always kept under 4 per cent.
Different samples of chloroform (obtained from Messrs. Morson and Son, Martindale, and
others) were used. Each of the samples was carefully tested, and the following results were
obtained:—
(1) Appearance and smell characteristic of pure chloroform; (2) specific gravity 1497;
(3) absolutely neutral to litmus paper; (4) when dropped into distilled water transparent
globules were formed, with no milky halo of opalescence; (5) not coloured on agitation with
sulphuric acid; (6) when shaken with distilled water nitrate of silver gives no precipitate; (7)
no green colour with chromic acid; (8) iodine gives a violet colour.
-When ether (specific gravity 0.725) was used instead of chloroform the amounts injected
info the bottle were much larger—15 to 25 minims at a dose,
(For the sake of brevity I shall refer to the bottle in which the anæsthetics were admin-
istered as the " anaæsthetic bottle.")
PART II.
Mode of Conducting the Experiment.—During the whole progress of the experiments the
animal was kept in an unconscious state. In addition to the necessity of obviating any chance
of suffering, it was essential for the accurate working of the registering apparatus and the
success of the experiment that the animal should be motionless; the slightest movement or
displacement might seriously interfere with the precision and regularity of the graphic records.
And of course the use of other drugs, such as morphine or chloral, was contra-indicated, as they
would complicate, and might vitiate, the results. The animal was accordingly kept under
chloroform during the whole of the time, excepting the periods when ether was given instead
of chloroform. Thus the experiments consisted in the administration of a further amount of
the anæsthetic to an already unconscious animal, so as to induce a deeper anæsthesia. When
the increase of chloroform was about to be given, the condition of the animal was frequently
such that it was unconscious and motionless, the heart action and blood-pressure steady and
regular, the majority of the reflexes abolished; but unconscious winking of the eyelid on touch--
ing the conjunctiva was commonly present. A further amount of chloroform (usually I minim
at a time) was then injected into the anæsthetic bottle, and there it evaporated and mingled
with the air pumped through the bottle by the bellows, Only a small portion of the air passing
through the bottle entered time animal's lungs; the greater part escaped through the side tubes.
Thus only a small portion of the chloroform introduced into the bottle reached the pulmonary air-
cells. Meanwhile the state of the conjunctival reflex was closely watched, and it afforded very
valuable indications as to the action of the drug. In many cases chloroform was given in sufficient
amount to cause a complete abolition of the conjunctival reflex; but frequently there were
changes of a marked character both in the state of the heart and the blood-pressure before the
influence of the chloroform was sufficient to cause a disappearance of the conjunctival reflex.