NOVEMBEE IS, 1904.] 



SCIENCE. 



687 



on the muscle even at a greater dilution than 

 1-100, their action on the nerve-cord is much 

 more rapid and intense, and they, furthermore, 

 act on the ganglion at a dilution which fails 

 to affect the muscle. Part of the difference in 

 the reaction of the muscle and the ganglion to 

 these drugs is probably to be sought in dif- 

 ference in permeability of the muscle cell and 

 the nerve cell. 



The failure of these aU^aloids (with the ex- 

 ception of veratrin) to produce initial inhibit- 

 ory or depressor effects on the ganglion or 

 the muscle is not due to the absence of an 

 inhibitory nervous mechanism in the Limulus 

 heart. Two pairs of inhibitory nerves pass 

 from the posterior and dorsal surface of the 

 peri-cesophageal ganglion to the median nerve 

 cord on the dorsal side of the heart. 



Before the action of these drugs on the 

 ganglion and the heart muscle of Limulus 

 was taken up an extensive study of the ac- 

 tion of curare, atropin and nicotin on the 

 molluscan and the crustacean heart had been 

 carried out with the view of finding a drug 

 that would paralyze the cardio-inhibitory 

 nervous mechanism in these animals. None 

 of the crustaceans or the molluscs allow a 

 determination of the point of action of the 

 drugs in the heart similar to the heart prepara- 

 tion of Limulus, but the reaction of the 

 crustacean and the molluscan heart to these 

 three alkaloids is identical with the reaction 

 of the ganglion-free segments of the heaj-t of 

 Limulus on application of these drugs to the 

 ganglion, which fact suggests that the rela- 

 tion of the ganglion cells to the heart-beat in 

 these animals in no wise differs from that in 

 the heart of Limulus. 



We know of no drug which will paralyze 

 the motor nerves or nerve-endings in the heart 

 without destroying the excitability and con- 

 tractility of the muscle. The heart-muscle 

 responds to the stimulation of the nerves that 

 pass from the nerve-cord to the muscle fifteen 

 to twenty hours after the activity of the gan- 

 glion has ceased from exhaustion. After bath- 

 ing the heart in one per cent, curare, one per 

 cent, atropin, or one tenth per cent, nicotin 

 for two or three hours the stimulation of these 

 nerves is still effective. Nor does curare 



paralyze the motor nerve-endings in the body 

 muscles of crustaceans and molluscs as main- 

 tained by some observers. In these animals 

 curare acts like strychnia in the vertebrates, 

 that is, causing primary excitation of the cen- 

 tral nervous system, leading to tetanus and 

 spasm and subsequent paralysis if the dose is 

 suificiently strong, but after such paralysis 

 the body muscles still respond to stimulation 

 of the motor nerves. 



Alcohol in concentrations of 1-100 or 1-200 

 stimulates the ganglion cells both as regards 

 the rapidity and the intensity of the nervous 

 discharges. 



The Action of Certain Inorganic Salts on -the 

 Ganglion Cells. — Barium chloride, rubidinum 

 chloride, potassium chloride and sodium 

 chloride stimulate the ganglion cells, the 

 chlorides of calcium and csesium depress the 

 activity of the ganglion without primary 

 stimulation. 



When the nerve-cord is removed from the 

 heart and the heart immersed in isotonic 

 (fm.) sodium chloride the heart begins to 

 contract more or less rhythmically after a 

 latent period of from thirty to forty-five 

 minutes. The addition of a small amount 

 of calcium chloride prevents the development 

 of this rhythm or stops it after it is once de- 

 veloped. The action of these salts on the 

 ganglion-free heart-muscle of Limulus is 

 thus identical with their action on the apex 

 of the frog's or the tortoise's ventricle. The 

 fm. ISTaCl solution applied to the nerve-cord 

 stimulates at once or after a latent time of 

 less than a second. The stimulation of the 

 ganglion cells appears in increased rate as 

 well as amplitude of contraction, the ampli- 

 tude of the beats becoming gradually dimin- 

 ished, until after ten to fifteen minutes the 

 activity of the ganglion ceases completely. 

 A small amount of calcium chloride counter- 

 acts the stimulating and subsequent depressor 

 action of the pure sodium chloride. 



Calcium chloride in isotonic concentration 

 down to a dilution represented by one part 

 CaCl,(fm.) to twenty parts of sea water or 

 plasma depresses the activity of the ganglion 

 cells. This effect appears inxmediately on 

 application of the solution to the ganglion. 



