THE PHARMACOLOGICAL ACTION OF HARMINE. 93 
that, though the dose injected in this case was so large as one-third of the minimum 
lethal, no effect was produced on respiration. 
The second injection produced a rapid decline of blood pressure, accompanied by 
slowing, and later by great feebleness, of the heart’s contractions. Respiration was not 
much affected until the blood pressure reached a very low level. This, together with 
the facts that respirations continue as long as the heart beats and that respirations are 
unaffected except by doses which produce a grave fall of blood pressure, goes to show 
that death from intravenous injection of harmine is mainly, if not solely, due to cardiac 
failure. 
Taste VII.—ExprrimMent 24. 
Totes ‘ ee ee Es Rate of pee 
: 3; verage BP. ate espirations espiration 
Bae . i caceaie in mm. per 10 oe 10 eee NGI 
puieevenouely- seconds.| seconds. 
11.37 58 100 48 10 2 mm. 
11.38 0-01 grm. per kilo. He nae Sn a Fig. 9. 
11.38.30" oe 82 42 10 2mm. 
11.40 ya 92 46 10 Die ies 
11.48 a8 98 40 10 ioe. 
11.50 0:03 grm. per kilo. - a a sist Fig. 10, 
11.50.30” eas 60 37 7 2 mm. 
11.51 a 50 14 5 |S ae 
11.52 Si 35 16 3 Orr 3; Pulse waves very 
| small, 
11.54 ue 28 10 3 a “5 
11.56 ae 0 0 0 ee 
The effects of harmine on blood pressure, as deduced from this and other experiments, 
may be briefly summarised. Apart from very small doses, which sometimes produce 
an insignificant rise of blood pressure, the chief action of harmine is to produce a fall of 
blood pressure, due to slowing of the heart, and, in the case of lethal doses, also to 
enfeeblement of the heart’s contractions. The slowing of the heart is not prevented by 
previous administration of a dose of atropine sufficient to paralyse the vagal endings, 
so that it is due to an action on the cardiac muscle, as was found also in the case of the 
frog’s heart. 
The only point of importance which remains to be discussed is whether the fall of 
pressure is due solely to cardiac causes or is due partly to vascular dilatation. To 
determine this, several experiments were made in which a record was taken of the 
blood pressure and also of the volume of the kidney or of a loop of intestine. 
Expervment 25 (fig. 11).—Cat, 2700 grammes. Blood pressure was recorded as 
in the previous experiment, and the kidney volume was recorded by an oncometer and 
air-piston recorder. An injection of 0:004 gramme per kilo was given, about one- 
eighth of the minimum lethal dose. This reduced the blood pressure in one minute 
from 120 mm. to 88 mm., and the pulse rate from 18 to 13 per ten seconds. There 
