186 CARNEGIE INSTITUTION OF WASHINGTON. 



mechanical injury was sustained by the medusa rings, which, however, could 

 at once be restored to normal pulsation by an induction shock if their pulsa- 

 tion had ceased. It was also observed that the lacerated area regenerated at 

 a normal rate. 



Professor J. F. McClendon suggested that fishes with swim-bladders might 

 prove to be more sensitive to explosive shocks than those without swim- 

 bladders, and experiments showed that a half stick of dynamite may be 

 exploded within 3 feet of a small shark, which has no swim-bladder, without 

 producing any apparent injury. This also applies to such teleosts as lack 

 swim-bladders. Dr. S. C. Ball kindly dissected some of the fishes with swim- 

 bladders, which had been killed by the explosions, and found that the swim- 

 bladder had burst and the tissues were crushed in around it, often breaking the 

 vertebral column of the fish. Moreover, Professor W. H. Longley, who has 

 had much experience in the use of dynamite, tells me that echinoderms and 

 Crustacea, if not mechanically torn apart, show no apparent ill effects, but 

 nevertheless, move away from the site of the explosion. 



It appears, then, that the nervous system of these lower forms is extraor- 

 dinarily insensitive to shock due to explosion of dynamite and that the 

 injurious effects of the explosion if present are due to mechanical laceration 

 of tissues and especially the crushing inward of air-filled cavities. It seems 

 possible, therefore, that the cavities of the middle ear and eustachian tubes 

 may be a means of danger to men standing near exploding shells. 



It has been suggested that the sudden reduction in atmospheric pressure 

 in the close proximity of an exploding shell might set free dissolved gases in 

 the blood and elsewhere, thus vacuolating the tissues and producing pressure 

 and other effects upon the nerves ; but our experiments with pulsating rings of 

 Cassiopea seem opposed to this hypothesis, for no injurious effects other than 

 those of simple asphyxiation were produced by sudden exhaustion of the air 

 surrounding the animals, and recovery, when replaced in normal sea-water, 

 was almost immediate. 



These results are in accord with the conclusions of Grasset (1915), Eder 

 (1917), Babinski et Froment (1917), and others, that "war-shock" is allied 

 to hysteria and is a psychological rather than a physiological phenomenon. 



Efficacy of Holothurians in Dissolving Limestone, by Alfred G. Mayer. 



No one appears to have attempted to evaluate the effect of holothurians in 

 dissolving limestone until, in the summer of 1917, an experiment was made 

 upon Stichopus mobii at Tortugas, Florida. A specimen, 210 mm. long 

 and 70 mm. wide, was kept for 2 months in a rectangular glass tank 68 cm. 

 long by 30.5 cm. wide and containing sea-water flowing constantly through it 

 so as to maintain a uniform depth of about 5 inches. The bottom of this tank, 

 which was 2,074 sq. cm. in area, was covered with 3,447 grams of limestone 

 sand taken from the reef-flat upon which this species of holothurian is abund- 

 ant. The sand consisted chiefly of fragments of Halimeda together with 

 broken coral and pieces of molluscan shells. 



Between June 3 and 25 the holothurian swallowed very little of the sand and 

 appeared to be extremely sensitive, contracting whenever the tank was shaken 

 or anyone came near it. Moreover, the tank was kept in the diffuse light 

 of the laboratory, and this dull light seemed to inhibit the activities of the 

 animal. Accordingly, on June 25, the sand was removed and reweighed and 

 found to have lost none of its weight. It was then replaced in the tank and 

 the tank placed in the sunlight in a region where shocks and jars were infre- 

 quent. The holothurian at once began to swallow large quantities of sand as 

 in nature, about 25 grams passing through it every 24 hours. 



