560 ACTION OF CUIL\RE, ATROPINE, AND NICOTINE 



the works of Plateau (1880) and Krukenberg (1880). According to 

 Bert (1867) and Yung (1879, 1881), the action of curare in the crus- 

 taceans and in the cephalopod molluscs is the same as in the verte- 

 brates, only less strong. In the lamellibranch molluscs Yung did not 

 obtain a permanent paralysis by curare. Vulpian (1879) states that 

 curare paralyzes both arthropods and molluscs, but its action is not as 

 strong as in the vertebrates. Krukenberg holds that the action of 

 curare in crustaceans and molluscs is mainly on the central nervous 

 system, but there is also paralysis of motor nerve endings. Bieder- 

 mann (1890) and Fiirst (1890) states that curare will paralyze the 

 motor nerve endings in Lumbricus but this is denied by Straub 

 (1900). 



A drug may cause paralysis by depressing the motor nerve endings 

 or by paralyzing the central nervous system. My own results go to 

 show that the primary action of curare and nicotine in arthropods 

 and molluscs is on the central nervous system and the peripheral 

 ganglia and not on the motor nerve endings in the muscle. The 

 action on the nerve centers is a primary stimulation followed by 

 temporary or permanent paralysis if the dose is of sufficient strength. 



There are great differences in the tolerance or degree of resistance to 

 the action of curare in the different invertebrates. The nudibranchs 

 and the pulmonates (excepting Ariolimax) are very sensitive to the 

 drug. Octopus is far more resistant than the decapods, and of the 

 latter Ommastrephes is more resistant that Loligo. Of the arthropods, 

 Limiiliis shows the greatest resistance to the drug. 



The stimulating action of curare on the nerve centers appears im- 

 mediately on the application of the solution. In the squid the 

 stimulation results in spasms and tetanus. The primary stimulation 

 is less in evidence in the crustaceans. In the gasteropods it appears in 

 prolonged and extreme contraction of the body muscles. In all the 

 animals studied stimulation of the motor nerves causes contraction 

 of the skeletal and visceral muscles after a dose of curare that com- 

 pletely paralyzed the central nervous system. 



Atropine appears to paralyze motor nerve endings to some smooth 

 muscles {e.g. lungs, gastrointestinal tract) in vertebrates. The body 

 muscles of arthropods are of the transversely striated type, but the 

 muscle of molluscs approaches more closely to the smooth variety. 



