RESPIRATION AND OXYGEN. 89 



pressure to 6 mm. caused the latter process to cease, and the animal 

 began to move again. 



Hauptfleisch (1892 : 219) pointed out that protoplasmic stream- 

 ing naturally ceased in the absence of oxygen, since this reduces the 

 activity of aerobic plants, and movement is likewise renewed with 

 the access of oxygen. He stated that streaming in the root-hairs of 

 Trianea was gradually brought to a stop when hydrogen was led 

 into the moist chamber. 



Demoor (1894 : 163) studied the effects of different gases, of vacua, 

 and cold upon living cells under the microscope. The plant mate- 

 rial consisted of stamen-hairs of Tradescantia, plasmodia of Chon- 

 drioderma difforme, and chloroplasts of leaves of Funaria. Carbon 

 dioxid brought streaming in the stamen-hairs to a stop in 3 to 6 

 minutes, but the mitotic process continued. However, no cell-wall 

 was formed, unless conditions permitted the renewal of motion. 

 Carbon dioxid stopped the activity of the chloroplasts of Funaria 

 and killed the leucocytes of the blood in 2 to 3 hours. In hydrogen 

 the protoplasm assumed a granular condition, and after 15 to 40 

 minutes movement was no longer visible. Oxygen increased the 

 activity of the protoplasm and its movement. The author's view 

 is that both carbon dioxid and hydrogen hinder respiration by with- 

 drawing oxygen and stopping the protoplasmic movement. The 

 former is the more injurious, because of its poisonous effect. He 

 assumed that the activity of the nucleus is independent of that of 

 the protoplasm, inasmuch as it can continue after the conditions 

 are no longer favorable to the life of the protoplasm. 



Lopriore (1895 : 547) found that CO 2 stopped the movement of 

 protoplasm for a time, but did not have a permanently injurious 

 effect, and concluded that its influence is specific and not due alone 

 to the absence of oxygen. When C0 2 was mixed with 10 or 20 per 

 cent of oxygen, the streaming was not long suppressed. It accom- 

 modated itself gradually to a high content of CO 2 and finally was 

 not inhibited in nearly pure gas. Pure oxygen sometimes exerted a 

 stimulating effect upon slow streaming, but not upon movement of 

 normal rapidity. Pure hydrogen at first hastened movement, but 

 later slowed it down markedly without entirely stopping it. 



Celakowski (1892) found that movement of the protoplasm con- 

 tinued in cells of Tradescantia engulfed by the plasmodium of a slime- 

 mold, indicating that the cells were supplied with oxygen. He also 

 showed that movement could take place in the absence of oxygen 

 in a number of one-celled and several-celled organisms. In con- 

 trast to his earlier results, Kiihne (1898) observed that protoplasmic 

 movement sometimes persisted for 1 to 3 weeks in the absence of 

 oxygen. Ritter (1899) confirmed the observations of Kiihne and 

 Celakowsky upon anaerobic movement in the Characece, and recog- 

 nized that sugar promoted movement and growth in bacteria facul- 



