292 Mr. W. E. Dixon. The Pharmacological [Nov. 1, 
alkaloid may still be given without causing any appreciable depression of 
the heart. The effects described are the same in the frog, rabbit, cat, and 
dog, so that it can hardly be argued that direct cardiac failure is a serious 
feature in poisoning by boxwood. 
Respiration.—If records be taken of the respiratory movements, it will be 
found that the effect of boxwood is to cause at first a gradual increase in 
the depth of respiration without much alteration in the rate. This effect 
can be seen quite well by giving a small injection, 8 or 10 milligrammes, to 
a normal cat and observing without the use of any recording apparatus. 
Figs. 1 and 6 show the effect of the poison recorded graphically ; in each case 
the initial action of boxwood on respiration 1s some increase in depth, the 
volume of air inhaled at each breath is greater, whilst the rate remains 
about the same. As more drug is administered this primary stimulant 
action is quickly followed by depression, as shown by the diminution in 
respiratory movements, and if the dose be sufficiently large, respiration is 
completely paralysed. An effect of this nature is seen in fig. 1, after the 
administration of 65 milligrammes of boxwood alkaloid into the circulation 
of a cat, and in fig. 6 after an injection of 30 milligrammes. In all cases 
the respiration having once ceased never returned, so far as: the length 
of the experiment, sometimes extending for three hours, allowed of 
observations being taken. 
With an active circulation such a failure of respiration may be due either 
to central paralysis of the medulla or to peripheral motor paralysis. If the 
motor nerves of respiration, the phrenics and intercostals, be excited with a 
tetanising current immediately natural respiration has ceased, they are 
found to cause contraction of their respective muscles, though the strength 
of contraction is considerably diminished from the normal; still, no doubt, 
ample activity remains for some kind of respiratory movements to occur 
were a powerful stimulus to proceed from the centre. At this stage, for 
example, strychnine still induces violent muscular twitchings. Electrical 
stimulation of the medulla, however, causes no respiratory movement, and 
the administration of hydrocyanic acid, a drug which powerfully excites the 
respiratory centre, is without effect. At this stage it is also interesting to 
note that in the rabbit the cardiac vagus is still active, whilst in the cat it 
is generally completely paralysed. 
Action on Nerve-cells—Central Nervous System.—The administration of 
moderate non-poisonous doses of the boxwood alkaloid to all normal animals 
causes increased activity of the reflexes. The effect is one apparently upon 
the spinal cord, since in the frog it is still persistent after complete destruction 
of the brain. In anesthetised animals, the effect may also frequently be seen 
