1910. | Action of South African Boxwood. | 293 
for a short period before the depression of the motor nerves is pronounced, 
thus it may be observed after the injection of 30 or 40 milligrammes of the 
alkaloid into cats; sometimes, indeed, the reflexes may be so increased as 
to induce a series of convulsive jerks. The tendency to such movements 
is naturally more pronounced after the administration of the drug to 
decerebrate rather than to anesthetised animals. True tonic and clonic 
convulsions are never observed, This action on the spinal cord is no doubt 
partly masked by the depressant action of the drug on the cerebrum and 
the motor nerve endings ; but these effects can be to some extent eliminated, 
at least for a time, by injecting the drug directly into one of the veins 
of the spinal cord, and in such cases typical strychnine-like convulsions 
occur. Depression of the higher cerebral centres appears to occur simul- 
taneously with the stage of exaggerated spinal reflexes. Normal animals 
injected with this alkaloid may show all the effects of cerebral depression 
at a time when the spinal reflexes are much increased. 
As in the case of curare, apocodeine and coniine, therefore, three effects 
can be analysed which to some extent mask one another: (1) depression of 
the cerebrum, (2) “stimulation” of the spinal cord, (3) paralysis of the 
motor nerve-endings. By appropriate means each of these effects can be 
observed with all three drugs, but whereas with boxwood all three are 
produced nearly simultaneously with a certain dose of drug, with curare 
the motor nerve-endings are paralysed first, or about the same time as the 
central nervous system, and completely mask the convulsions, whilst with 
coniine and apocodeine the paralysis of the central nervous system is the 
marked feature, and the motor nerve-endings are only paralysed after the 
administration of very much larger doses of alkaloid. 
Vagus.—The injection of boxwood causes paralysis of the vagus in all 
mammals. In the rabbit, complete paralysis is not attained until the 
respiration has ceased; but in the cat, vagal paralysis precedes respiratory. 
Thus in a cat of 2 kilos., electrical stimulation of the vagus nerve ceased 
to inhibit the heart after the administration of 30 milligrammes of the 
alkaloid. Immediately paralysis is complete, muscarine, and in a less 
marked degree pilocarpine, still cause inhibition, although if a somewhat 
larger amount of the boxwood is given the paralysis is made as complete 
as by atropine, and muscarine is now quite without action on the cardiac 
rhythm. The usually accepted explanation of phenomena of ‘this description — 
is that the nerve-cells are paralysed a little before the nerve-endings, and 
the boxwood paralyses the nerve-cells whilst the post-ganglionic fibres are 
for a time still intact, as shown by their response to muscarine. 
Sympathetic Nerves—(a) Hye.—Quite small doses of the Loxwood alkaloid, 
Ze 
