372 J. M. D. OLMSTED 



with strychnine and especially with quinine, Synaptula re- 

 sponds vigorously to very weak stimuli of any sort. An ap- 

 plication of 0.5 cc. of 1/10,000 M quinine will for hours after- 

 wards render useless all further experimentation on an individual, 

 and after one or two drops of 1/1000 M, the slightest touch on 

 the tentacles is sufficient to cause a sudden and violent with- 

 drawal of all the tentacles into the mouth region, even twenty- 

 four hours after the application of the quinine. Henri ('03) 

 found that after an application of a w r eak solution of strychnine 

 sulphate to the holothurian Stichopus regalis there was a very 

 marked augmentation of sensitivity. Jennings ('07, p. 69) 

 found that the starfish Asterias forreri, after stimulation by 

 certain chemical substances, gave a much readier response to 

 mechanical stimulation. Crozier ('14 a, p. 285) obtained sim- 

 ilar results on Holothuria. Even in man this is true, since in 

 cases of strychnine poisoning ''the slightest stimulus, such as 

 a faint noise, a draught of air, etc., is sufficient to throw the 

 patient into general convulsions" (Lickley, '12, p. 17; cf. Her- 

 rick, '15, p. 65). 



Not only does this marked increase in the sensitivity of 

 Synaptula to weak stimuli follow after application of alkaloids, 

 but also after excessive or severe stimulation, such as keeping 

 them in water at 42C. for several minutes. 



If the kations of the chlorides used in the experiments on 

 stimulation with salts are arranged in a progressive series be- 

 ginning with Mg, which is the least stimulating, and therefore 

 has the greatest limiting concentration, we find the order, Mg, 

 Na, NH 4 , Ca, K, this being the usual so-called liatropic series 

 (Hober, '11, p. 497; Crozier, '14, p. 289, '16 a, p. 345). But 

 since 1/2.5 M MgCl 2 in sea-water has a total concentration of 

 1 M, the response to this salt is probably one to increased os- 

 motic pressure only. 



An anion series where Na was the kation of each salt runs as 

 follows: chloride, sulphate, acetate (Hober, '11, p. 487). Al- 

 though the limiting concentrations of KC1 and KBr appear 

 the same in the table, KBr is slightly the more stimulating of 

 the two, since the number of reactions to 1/40 M KBr was at 

 least 50 per cent greater than to 1/40 M KC1. This is also 



