PHYSIOLOGY: A. R. MOORE 
601 
to the median line of the body and show continuous tremors. At this 
stage, the animal, when stimulated, invariably swims forward, and is 
entirely unable to move backward. This is due to the fact that the 
swimmerets are able to make only the stroke which carries the animal 
forward. This fact may indicate that camphor acts selectively on the 
gangHa of the abdominal nerve cord, paralyzing the motor elements 
which control backward swimming, and rendering more sensitive the 
nervous elements controlling forward movement. Eventually complete 
paralysis supervenes. 
Further tests were made to determine the character of the action of 
strychnine, atropin, caffein and camphor on starfish (Asterias), medusa 
(Gonionemus) and the sea anemone (Metridium) . In the case of medusa 
and sea anemone, atropin alone was an effective reagent in increasing 
the animal's sensitivity. A sea anemone put into atropin sulfate solu- 
tion (1 : 2000) upon stimulation withdraws the tentacles, contracts the 
sphincter, and spasmodically contracts the longitudinal muscles. The 
animal does not fully recover the relaxed condition in the atropin solution 
but revives in a few minutes in a stream of fresh sea water. Specimens 
of m.edusa put into atropin sulfate solution (1:2500) contract their 
tentacles and show continuous activity of the bell with an abnormally 
high rate of pulsation. Starfish were affected by atropin in the same 
way as by strychnine, viz: the animals show a strong tendency to bend 
the rays dorsalward, which is increased by stimulation. Caffein and 
camphor are not effective in increasing the irritability of starfish. 
These results indicate an increased chemical complexity of the central 
nervous system developing pari passu with an increase in morphological 
complexity. Thus, in the actinian and coelenterate where the diffuse 
nerve net system obtains, strychnine, caffein and camphor exert no 
excitatory action. With the development of localized nerve tracts and 
the beginning of a central nervous system in the asteroids, strychnine, in 
comparatively high concentrations, produces its characteristic effects. 
In Crustacea and the cephalopod mollusca with their highly developed 
central nervous systems, the strychnine is, as we should expect, effective 
in low concentrations. Caffein and camphor act as excitants only 
where the histological elements of the nervous system are completely 
elaborated, viz.: in Crustacea and the cephalopod mullusca. 
Atropine stands in a separate category, since it is effective as a nerve 
excitant in members of all the classes tested. It would seem, then, 
that atropine forms a compound with a fundamental constituent of all 
the nerve cells, while strychnine, caffein and camphor combine with 
neuronic molecules which are the products of a higher organization. 
