2 BULLETIN" 1023, U. S. DEPARTMENT OF AGRICULTURE. 



killed a rat with 1 milligram of strychnine injected per rectum. 

 Hunt 3 found the lethal subcutaneous dose to be 3 milligrams per 

 kilo, and reported (12) that the toxicity of strychnine remained con- 

 stant under thyroid feeding, a condition which appreciably influ- 

 enced the susceptibility to some other substances. No references 

 giving the oral lethal dose of strychnine were found, although many 

 articles deal with its use as a rat poison. Rucker (21) states that 

 poisoned grain is of little use because of its bitter taste. Boelter 

 (3) says that "with a poison such as strychnine as the active in- 

 gredient, mice, as a rule, die on the spot, while rats die in their 

 holes." 



In a previous communication (23) it was shown that the efficient 

 concentration of barium carbonate in a rat bait is equal to three 

 times the lethal dose contained in a meal of average size. This 

 method of calculation, however, does not seem to be applicable to 

 strychnine at present, because of the fact that, according to previous 

 investigators, rats refuse to eat bait containing it. It has been shown 

 also (23) that soft, mealy food is consumed by rats more quickly than 

 grain or dog biscuit. Whether or not the rapid eating of a bait has 

 any practical significance other than to favor the chances for the 

 ultimate consumption of a fatal dose of a particular strychnine bait 

 apparently has yet to be determined. 



PHARMACOLOGICAL ACTION OF STRYCHNINE. 



The story of the action of strychnine is one of the most interesting 

 in the field of comparative pharmacology. Although strychnine 

 possesses the properties of a general protoplasmic poison, it is im- 

 portant chiefly for its marked selective action upon the central 

 nervous system. Its abilit}^ to pervert the function of the segmental 

 reflex mechanism is general in the case of all vertebrates thus far 

 studied. The earthworm (13), the simplest form in which neurone 

 synapses have been described, has also been shown to give the typical 

 strychnine spasm. This perversion, frequently termed the- abolition 

 of reciprocal innervation (27), consists in the destruction of that 

 function which permits the release of opposing muscles when certain 

 other muscles perform a motion. Under the influence of enough 

 strychnine, all musculature tends to contract simultaneously, produc- 

 ing a muscle-bound condition. The position assumed by the poisoned 

 animals is that which results from the action of the stronger or 

 sometimes the more advantageously situated sets of muscles. 



While this perversion- of function has been preserved in verte- 

 brates throughout evolution, from time to time certain changes have 



3 Personal communication from Dr. Reid Hunt, Boston, Mass. 



