1893.] Arrow-Poison of the Wa Nyiha and other Tribes. 157 



the muscles, and, in a very brief period thereafter, the muscles 

 become inexcitable, acid in reaction, and rigid. 



On analysing the action of the active principle we have found 

 that, in the frog, the slowing, irregularity, and cessation of respira- 

 tion, and the gaping movements of the mouth are not necessarily 

 primary actions, but may be secondary to the arrest of the circula- 

 tion, because control frogs, whose circulation has been mechanically 

 arrested, exhibit these phenomena within a similar period of time. 

 In rabbits, artificial respiration does not prevent death from cardiac 

 failure ; but the impairment of respiration probably contributes in 

 them to the fatal result in the case of doses bordering upon the 

 minimum lethal. 



The fibrillary muscular twitchings which occur iu rabbits as well 

 as in frogs are due to a primary action upon the endings of motor 

 nerves. 



The disappearance of reflex and voluntary movements after the 

 administration of small lethal doses is due to paralysis of the nerve 

 centres, and not to a peripheral action, for when one part of the body 

 is protected, reflex and voluntary movements cease in the protected 

 and unprotected parts at the same time. This central paralysis, 

 however, is almost entirely due to the failure of the circulation, and 

 resembles the paralysis in unpoisoned control frogs whose circula- 

 tion is arrested. When large doses of the poison are administered 

 subcutaneously to frogs, the depression of reflexes is partly due to peri- 

 pheral causes, because, when one part is protected, that part exhibits 

 more rapid and vigorous reflexes than the unprotected parts. This 

 difference is largely due to a paralysing action on the muscles. It may, 

 however, be partly caused by depression of sensibility, for when the 

 action is limited to one part, stimulation of the skin in the poisoned 

 area fails, after a time, to cause reflexes in the unpoisoned parts, 

 although stimulation of a poisoned nerve trunk still excites reflex 

 movements. The action of large doses upon the sensory nerves is 

 well shown by applying l/100th of a grain in solution to the cornea 

 of the rabbit, when anaesthesia, lasting for several hours, along with 

 some contraction of the pupil, is produced. 



The motor nerves retain their influence upon the muscles until the 

 latter show distinct signs of poisoning ; but the muscles still react to 

 strong, although not to moderate, electrical stimulation after stimu- 

 lation of their motor nerves is no longer able to excite contractions. 



The action on the heart is very pronounced. When a large dose is 

 injected subcutaneously in the frog, or applied directly to the heart, 

 the pulsations become slow owing to a great increase in the duration 

 of the systole. Unequal contraction and relaxation of parts of the 

 ventricular wall occur, the diastolic expansion becomes less and less, 

 and, within twenty minutes after poisoning, the ventricle is arrested 



