THE IMPORTANCE OF RESPIRATION 569 



An insufficient supply of energy or unfavourable external conditions 

 usually leads at first to the stoppage of single characteristic functions, 

 such as growth, movement, &c., and only after a longer or shorter period 

 of such inactivity does death ensue. This result is produced by chloroform, 

 high temperatures, an excessive oxygen-pressure, &c., and in aerobes by the 

 absence of oxygen also. In the latter case all the reactions and properties 

 which are indissolubly connected with the power of exhibiting vital activity 

 are retained so long as intramolecular respiration continues. Moreover the 

 physical and plastic properties of the protoplasm remain the same, and 

 hence the phenomena of turgidity, diosmosis, passive secretion, aggregation, 

 &c., are unmodified l . Similarly all processes due to the action of enzymes 

 or other preformed substances continue in the absence of oxygen, and even 

 when vital activity is totally suppressed. 



On the other hand, a number of activities may be temporarily 

 suppressed in the absence of oxygen: thus aerobes cease to grow, the 

 power of movement is lost, the streaming of cytoplasm slows and stops. 

 Facultative temporary or permanent anaerobes may continue the above 

 functions in the absence of oxygen for a very short or a longer time, or 

 even permanently if appropriately nourished, and these organisms exhibit 

 all stages of transition to typical aerobes, among which certain plants are 

 able to perform special processes of growth and movement for a short 

 time in the complete absence of free oxygen. Thus certain obligately 

 aerobic bacteria may continue to" move for from five to sixty minutes. 

 Correns found that the tentacles of Drosera responded to mechanical and 

 chemical stimuli for a short time after all free oxygen had been with- 

 drawn, and, according to Demoor, the division of the nucleus, when once 

 commenced, proceeds to a certain point in the absence of this gas 2 . 

 Similarly a frog's muscle retains the power of contractility for a long time 

 in an oxygenless atmosphere, and an hour's deprivation of oxygen does 

 not take from many chloroplastids the power of immediately resuming the 

 assimilation of carbon dioxide when exposed to light, although after several 

 hours' exposure a latent period of half an hour or longer may intervene, 

 during which the power of photosynthetic assimilation is in abeyance 3 . 



It requires a little time to remove all free oxygen from the plant, 

 and hence even when a function rapidly ceases it may possibly have 

 continued for a time in the complete absence of the gas. This is certainly 



1 Pfeffer, Unters. a. d. Bot. Inst. z. Tubingen, 1886, Bd. II, p. 284; Osmot. Unters., 1877, p. 133. 

 Cf. Chap. iv. The protoplasmic aggregation induced by induction-shocks was first observed by Kiihne, 

 Unters. iiber d. Protoplasma, 1864, p. 106. Cf. Klemm, Jahrb. f. wiss. Bot., 1895, Bd. xxvin, p. 627. 



3 Correns, Flora, 1892, p. 144; Demoor, Contrib. a 1'etude d. 1. physiol. d. 1. cellule, 1894, p. 76 

 (Sep.-abdr. a. d. Archiv d. Biol., Bd. xm). Cf. Sect. 9. 



3 [A simple method suited for class-demonstration is mentioned by Darwin, Proc. Camb. Phil. 

 Soc., Vol. ix, p. 338.] 



