1910. ]- - Action of South African Boxwood, 297 
further injections are without effect ; at this stage muscarine and pilocarpine, 
which normally evoke violent peristaltic movements usually regarded as 
vagal stimulation, fail to have an action, though the muscle still contracts to 
mechanical stimulation or to lead. 
It has been pointed out that there is no evidence that boxwood excites 
directly any form of muscle; indeed, its action appears to be depressant, 
since if it is painted directly upon striped or plain muscle it tends to 
diminish contraction. It must then produce this increased peristalsis 
through the nervous system, and since augmentation of intestinal movements 
can be obtained on the isolated and perfused intestines it follows that it is 
due to some action on the peripheral nervous mechanism. Perhaps the facts 
are best explained by supposing that in small doses it paralyses the 
inhibitory fibres or cells a little before the motor. Some such explanation 
was offered in a previous paper* to account for the purgative action 
of apocodeine. It may be mentioned in support of this hypothesis that 
these effects are only marked when the drug is injected in fairly large 
quantities. When it is taken by the mouth the effects on the alimentary 
canal (purgation) are not apparent, in which respect also it resembles the 
opium alkaloids. Other forms of plain muscle are also excited, and fig. 7 
shows the effect on the uterus. ; 
Liffect on Intact Animals.—The effect of boxwood in small doses is much 
the same in all animals. Frogs exhibit first an exaggeration of reflexes 
followed by paralysis and cessation of respiration. If the animal at this 
stage be pithed the motor nerves are still active, and the heart is vigorous. 
An injection of 1 ¢.c. intravenously into a rabbit of 2 kilogrammes causes in 
about five minutes a well marked exaggeration of all reflexes. This is 
quickly followed by decided muscular weakness and rapid respiration. The 
weakness is shown by the squat attitude adopted by the animal, its hind 
limbs being thrust forward, and also by the difficulty it has in flexing the 
hind limbs and by the tremors. Later it loses the power of drawing up its 
hind limbs, and they le extended and limp. The pupils are not altered. 
A quarter of an hour after injection recovery has commenced and in an hour 
the animal appears normal. The cat shows similar symptoms—exaggerated 
reflexes, great muscular weakness and respiratory trouble. The alkaloid is 
quite non-irritant to the eye or skin, and the nasal catarrh reported to occur 
in poisoning of the workers in the wood may be due either to some nervous 
systemic effect of the alkaloid, since animals after dosing occasionally 
exhibit watering from the eyes, or may be the result of some other 
constituent of the wood or due to the physical nature of the dust. 
* Dixon, ‘ Journ. Physiol.,’ 1903, vol. 30, p. 97. 
