RESPIRATION AND OXYGEN. 57 



mass of results, the primary divisions are based upon the functions 

 and organs studied. These are respiration itself, photosynthesis, 

 transpiration, germination, growth, protoplasmic movement, and 

 irritability. The fungi are discussed separately, in consequence of 

 their more or less peculiar behavior. The effects of the various 

 agents employed in producing anaerobic conditions are summarized 

 in the discussion at the end of each section and the significance of 

 anaerobic respiration in explaining the problems discussed is dealt 

 with in the succeeding chapters. 



RESPIRATION. 



Early researches. As already indicated, Huygens and Papin (1674) 

 were the first to show that plants could not grow in vacua, while 

 shortly afterward Ray (1686) and Homberg (1699) found that under 

 similar conditions seeds failed to germinate or did so only with diffi- 

 culty. Ingenhousz (1779) observed that plants died in air unfavor- 

 able to animal life as well as in pure carbon dioxid. Humboldt 

 (1794) and Rollo (1798) thought that seeds germinated more readily 

 in oxygen than in air, and Lefebure (1801) observed that germination 

 was greatly retarded by low oxygen-content. The classic experi- 

 ments were those of Huber and Senebier (1801) and Saussure (1804) 

 upon germination and growth, which are considered in detail under 

 these sections. Rollo (1798 : 37) was the first to observe the phe- 

 nomenon of anaerobic respiration in noting that barley grains gave 

 off a considerable quantity of carbon dioxid for several days when 

 oxygen was absent. Dumont (1819) and Dobereiner (1822) found 

 that fruits, especially apples and pears, developed a demonstrable 

 amount of alcohol after they had been subjected to an atmosphere of 

 C0 2 for a certain time. Berard (1821) demonstrated that fruit kept 

 in an atmosphere of carbon dioxid exhibited the phenomena of fer- 

 mentation. When oxygen was withheld, green fruits were unable to 

 ripen, but the ripening process was resumed when they were again 

 placed in air, providing the anaerobic conditions were not too pro- 

 longed. Cahours (1864 : 635) likewise found that oranges respired 

 in the absence of air, evolving carbon dioxid in an atmosphere of 

 nitrogen. 



Later researches. The proper understanding of the nature of anae- 

 robic respiration was first made possible by Pasteur's researches in 

 fermentation (1861, 1872, 1876). He stated that the yeast of beer 

 behaved altogether like an ordinary plant and that it was probable 

 that certain lower plants could live without air in the presence of 

 sugar, producing under these conditions a fermentation similar to 

 that of yeast. He later experimented with wine grapes kept in an 

 atmosphere of C0 2 and came finally to the view that the respiration 

 was analogous to that of yeast. He concluded that the formation 

 of alcohol was due to the fact that the cells of the fruit continue to 



