§1] MODIFICATION OF VITAL ACTIONS 3 



pressure of 6 to 8 cm. of Hg, or 0.08 to 0.1 of an atmosphere 

 (p. 71). In one hour, on the average, the protoplasmic move- 

 ments were affected, and in most cells ceased in 2 to 3 hours, 

 slight oscillations only of granules occurring. Thus, not death, 

 but arrest of activity, occurred during this period as a result 

 of reduction of atmospheric pressure — upon which the amount 

 of oxygen held in the water depends. That death did not 

 occur is shown by the fact that when air was readmitted at 

 the normal pressure the protoplasm promptly regained its nor- 

 mal activity. Cells immobilized during 24 hours regain their 

 movements in less than 5 minutes, and these become normal in 

 from 10 to 20 minutes. 



Pure oxygen acts in an opposite fashion from diminished oxy- 

 gen tension, exaggerating the activity of protoplasm. Under 

 its action the protoplasmic movements are much accelerated, 

 but preserve, meantime, their normal character. (Tradescantia 

 hairs, leucocytes; Demook, '94, pp. 192, 218.) In Ciliata the 

 rate of the contractile vesicle does not, however, seem to be 

 altered. (Rossbach, '72, p. 40.) 



Ozone and hydrogen peroxide produce atomistic " active " oxy- 

 gen by becoming split up in the plasma. Ozone (Og) is said 

 to kill quickly bacteria in water, if the latter does not contain 

 too much organic substance ; in the dry state, however, bacte- 

 ria are injured only slowly by it. (Ohlmullbr, '92, p. 861.) 



Other substances which, with a greater or less degree of 

 probability, may be said to act through oxidation of the pro- 

 toplasm, may be treated of here. 



Hydrogen peroxide (HgOj). — Paneth ('89) added one part 

 of neutralized H2O2 to 10,000 (0.01%) of hay infusion, and 

 found that all Ciliata were dead within 15 to 30 minutes. 

 Stronger solutions act more rapidly ; and even in a 0.005% 

 solution, only part of the animals survived. Algse survived 

 only 10 to 12 hours in a completely neutral 0.1% solution. 

 A 10% solution is fatal in a few minutes. (Cf. Bokoeny, 

 '86, p. 355.) 



Salts of chromic, manganic, permanganic, and hypochlorous 



the periphery of the diaphragm, and an inner cylinder at the inner margin of 

 the diaphragm. An inlet and an outlet tube communicate with each of the 

 spaces, — the central space and that between the two cylinders. 



