17 



be important also* Of the many possible intermediate 

 products ethyl alcohol is perhaps the most common, 

 but it is probable that organic acids are very common 

 also, especially in the normal respiration which is com- 

 pleted at once by the action of atmospheric oxygen. 



Tl See page It , note 



2. On production of organic acids in plants 

 see Mayer,- Die Sauerstoffabscheidung fleischiger Pflan- 

 zen, 1876; Krause,- Die Stoffwechsel bei den Grassulaceen, 



Abh. Hat. Ges. Halle, 16, 1886, Flora : 54 (1897 J; 



Warburg,- Unters. bot. Inst. [Tubingen 2: 53 (1886). 

 Other literatute is cited by rfeffer,- Physiology of 

 Plants, vol. 1, pp. 327-329, 485-491 (1900) and Haas and 

 Hill,- Chem. of Plant Products, pp. ( ). 

 On the production of lactic acid in muscle see Bayliss,- 

 Principles of General i-'hysiology, pp. 441-451 (1915). 

 Propionic acid is produced by certain anaerobic worms, 

 Weinland,- Zeits. Biol. 42: 55-90 (1901). On the recent 

 work of MacDougal, Richards, Spoehr and associates on 

 the relations between respiration, acid formation and 

 growth in cacti see: liacBougal,- Physiol. Res. 1_: 289- 

 292, 292-298 (1915), Gar. Inst, of Wash. Yearbook 14: 

 57-59, 71-72 (1915), 15: 61-62 (1916), Bull. H. Y. Bot. 



Gard. : (1916); Richards,- Oar. Inst. Of 



Wash., Yearbook 10: 66 (1911), 11: 65-66 (1912), 12: 

 84-86 (1913), 13: 89-91 (1914), Car. Inst, of Wash., 



