ACTION OF CHLOROFORM UPON THE HEART AND ARTERIES. 319 
arterioles 
an observation which Martin and HmeLey themselves confirm—it is 
extremely improbable that, while this centre is in action, the dilating effect, if really 
existent, upon the periphery would be at all apparent. On the other hand, with 
stronger dosage of chloroform, the direct effect upon the arterioles is always one of 
constriction. It follows, therefore, that at the beginning ofa chloroform inhalation there 
will be a tendency to counteract the fall of blood-pressure due to heart weakening, by 
a ili 
iN iNT nl Tn a ia wi 
ET 
S\N ST ep ap oe 
‘ Cl eee! \eeeen eee eae 
/AAARANNINIARAANAVANNRAACANA ayn ian? AASIOBAR DY aeRO ROD AAMEARSIRD AMES A ABAMTAMARRABASIIDABAAMRID AMA KAR IE An KR N 
Fic. 5.—End of a fatal chloroform inhalation, Dog, 6570 g. Inhalation through trachea tube of air strongly charged with 
chloroform vapour. 
A, blood-pressure curve ; B, line 1 centimetre below zero of blood-pressure ; C, costal respiration (the small waves upon 
this are heart movements) ; D, diaphragmatic respiration. Time in 10 secs. The signal marks the removal of chloroform. 
Respirations ceased 20 secs. before the heart. The subterminal rise in blood-pressure which sometimes occurs is shown 
in this tracing. The increase in size of the manometer excursions is due to a gradual slowing of the heart rhythm, and 
does not represent an increase of force of the contractions. 
excitation of the vasomotor centre, and later on, while this may still be active,* a similar 
tendency to counteract the fall by direct excitation of the peripheral arterioles. As a 
general rule, the action of the drug upon the heart is so marked as to more than 
counter-balance the arterial constriction, however produced. But in certain cases a 
* Reflex constriction of bloodvessels can be obtained, on stimulating an afferent nerve, even if chloroform anesthesia 
is very pronounced, showing that even in deep anesthesia the vasomotor centre is still active, although its activity is 
no doubt lessened. Cf. BowprtcH and Minor, op. cit. Further, chloroform does not diminish the sue hie of the 
peripheral vasomotor nerves (SCHEINENSSON, Centralbl. f. d. med. Wiss., 1869, p. 105). 
TRANS. ROY. SOC. EDIN., VOL. XLI. PART II. (NO. 12). 4 
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