12 Papers from the Marine Biological Laboratory at Tortugas. 



case. Heringi was the first to publish the fact that vertebrate skeletal 

 muscle may develop rhythmical contractions in a solution of sodium 

 chloride, and Mines ^ has conducted a thorough study of this reaction, 

 obtaining graphic records of the movements of amphibian skeletal mus- 

 cles ; he finds that under certain conditions a 6 or 7 per cent solution of 

 NaCl will give rise to pulsations of the muscle which are comparable in 

 regularity of rhythm to those of lymph-hearts or even of the heart itself. 

 These movements may, however, be stopped by calcium chloride, and 

 are, indeed, probably due to the abstraction of calcium from the muscle 

 by the sodium solution. Hence calcium tends to inhibit the movements. 

 Mines finds also that potassium chloride at first increases the rhythmical 

 movements, but afterwards stops them entirely. It is evident that the 

 action of sodium, potassium, and calcium is similar upon skeletal muscle 

 and on Scyphomedusae, Annelids, Lepas arms, and the heart of Limulns. 

 (See Carlson.) 



Indeed in all essential respects the Annelids behave as does the 

 Scyphomedusa Cassiopea to ionic sodium, potassium, magnesium, 

 calcium, ammonium (NH^Cl), weak concentrations of acids (H), and 

 ionic CO3. For example in Cassiopea the pulsation stimulus is trans- 

 mitted by the nerves and is independent of muscular contraction, and 

 also in the Annelid Eunice fucata the mid-region of the worm may be 

 rendered inert through immersion in molecular MgSO^, and yet if the 

 anterior end of the worm be stimulated in any manner the posterior 

 end may respond at once while the middle region remains inert. Thus 

 the nerve-chain of the middle region may still transmit the stimulus 

 without causing the magnesiumized segments to respond to it by mus- 

 cular movement. This middle region will, however, still be capable of 

 transmitting slowly from segment to segment a wave of myogenic peri- 

 stalsis in the manner demonstrated by Friedlaender ^ for the earthworm. 



It is well known that neurogenic stimuli pass more vigorously from 

 head to tail than from tail to head, and in killing worms if one wishes 

 to avoid contraction one should cause the killing fluid to pass from tail 

 to head. 



Contractions are caused by 0.625 molecular NaCl in severed parts 

 of Annelids and in Lepas from which the central nervous system has been 

 removed, but I am not sure that such pieces can be said to contract in 

 a wholly myogenic manner. Distilled water gives the same effect in 

 Annelids, and indeed any marked change in osmotic pressure of the 

 fluid surrounding them causes a vigorous series of contractions. 



If any part of the length of a worm be immersed in an excess of 

 calcium, clonic tetanus with a pectiliar convulsive twitching of the 

 longitudinal muscles appears in the part affected, but this twitching 

 does not spread to other parts of the worm, which remain quiescent if 

 in normal sea-water. In Cassiopea also the local tetanus caused by 

 calcium does not spread to parts of the medusa not affected by the 

 calcium. If we touch the calcium-affected part of the worm with a 



' Hering, 1879, Sitzungs. Wien. Akad., Bd. 89, Abth. 3, p. i. 



^ Mines, 1908, Journal Physiol. Cambridge, vol. 37, pp. 40S-444. 



^Friedlaender, 1894, Pfliiger's Archiv ges. Physiol., Bd. 58, pp. 168-206. 



