164 ON ANAESTHETICS 
tant principle, that there are two essentially different ways in which chloroform 
may kill, viz. by a directly sedative action on the heart when the chloroform is 
in large proportion to the air, and by a suspension of the respiratory function, 
while the heart is still acting, when the chloroform is largely diluted. They 
also show how different individuals of the same species, and even the same 
individual at different times, may differ in susceptibility to chloroform. And 
in the third place they indicate, I fear, but too plainly, that we cannot by any 
means trust implicitly to the existence of Paul Bert’s three distinct zones. For 
we have seen that a proportion of chloroform which produced anaesthesia so 
extremely slowly that, if 1t was within the anaesthesic zone at all, it must have 
been at its very lowest limit, nevertheless exerted a gradually increasing dele- 
terious influence, tending at last to a fatal result. And when the proportion 
was increased so as to make any approach to the ‘ very rapid’ anaesthetizing 
effect which, as M. Bert tells us, characterizes the middle of the zone maniable, 
a similar but more rapid deleterious action was observed, causing death con- 
siderably within the two hours referred to by M. Bert. We see, therefore, that, 
for those animals at least, there existed no efficiently anaesthetic mixture of 
chloroform and air, which could safely be left in continuous action for such 
a length of time as is not unfrequently occupied by a surgical operation. 
Hence, whether we regard the various degrees of susceptibility to chloro- 
form shown by different individuals, or the sure though gradual lethal effects 
of even the smallest proportion which suffices to be anaesthetic, I fear the pro- 
posal which I understand M. Bert to make, that the zone manzable having been 
ascertained for man, a corresponding atmosphere should be provided in a large 
reservoir, from which the patient should be allowed to inspire continuously 
throughout the duration of an operation, must be rejected as highly dangerous. 
But, although I have thus failed to verify M. Paul Bert’s precise conclusions, 
yet I believe we owe him a deep debt of gratitude for his researches. The 
experiments which I have conducted on the lines which he has laid down have 
made manifest an important truth entirely new to me. I had always supposed 
that a chloroform atmosphere sufficiently strong to produce anaesthesia would, 
if continued, soon lead to a fatal result. Such certainly is apt to be the case 
with chloroform administered by means of a folded towel. It once fell to my 
lot to see a patient who had been left for only a few minutes with the cloth 
lying over the face after full anaesthesia had been produced, in consequence 
of the attention of the administrator having been distracted by other matters, 
and I shall never forget the result. Respiratory movements had entirely ceased, 
and the face had a deadly pallor, and for a while it appeared as if the patient 
was dead, though happily revival took place after protracted artificial respiration. 
