FERMENTATION 219 



is that of formic acid (Omelianski, 1903).] The numberless bodies which arise 

 in consequence of these decompositions need not be referred to at present ; nor 

 need we treat of the various fermentation products of the higher alcohols, 

 e. g. glycerine, mannite, dulcite, &c. We need only note that none of the 

 products of such fermentations accumulate in nature, but that other organisms 

 are always at hand which have the power of breaking down these primary pro- 

 ducts, till finally the organic substances are transformed into simple inorganic 

 compounds which are once more available for the nourishment of higher 

 plants. Thus we begin to appreciate the fact that over the earth's surface 

 there exists a perpetual transformation, a continuous circulation of materials 

 which we will take a later opportunity of once more referring to (Lecture XIX). 



But it is not only the simple organic bodies, such as carbohydrates, acids, 

 and alcohols, which are broken down by the fermentative power of micro- 

 organisms, when these bodies are removed from the living organism, but com- 

 plicated bodies, and indeed the most complicated of all, the proteids, undergo 

 the same fate. In the first place, these proteids are broken down more or less com- 

 pletely by various excreted enzymes, and the products so formed suffer appro- 

 priate fermentations. Although Bacteria are known which are able to produce 

 fermentation in proteids, and although much research has been carried out on the 

 resulting products, we are in no case so fully acquainted with the chemical and 

 biological conditions of such fermentations that we can present a complete 

 picture of the course of the fermentative process. Our remarks on the subject 

 must therefore be brief. When proteid is acted on by anaerobic Bacteria, we 

 term it putrefaction, and this is characterized by the appearance of evil-smelling 

 compounds (indol, skatol, &c.), but in the presence of air these substances dis- 

 appear. In nature these processes go on hand-in-hand as, for example, in the 

 putrefying bodies of animals or plants ; soon the aerobic forms have consumed 

 all the oxygen in the interior of the body, and the anaerobic forms then proceed 

 to carry out a further decomposition which we term putrefaction. Owing to 

 the activities of a series of living organisms following each other or living side 

 by side, the proteid molecules, after passing through numerous intermediate 

 stages, are finally broken down into a few simple bodies, viz. carbon-dioxide, 

 methane, hydrogen, ammonia, nitrogen, sulphuretted hydrogen and phosphoric 

 acid. 



In the following lectures we will return to the consideration of certain of 

 these final products of proteid fermentation. 



Bibliography to Lecture XVII. 



Albert. 1901. Centrbl. Bakt. II, 7, 473. 



Banning. 1902. Centrbl. Bakt. II, 8, 395. 



Behrens. 1902. Centrbl. Bakt. II, 8, 114. 



Beijerinck. 1894. Archives neerlandaises, 29, i. 



Beijerinck. 1899. Ibid. II, 2; Centrbl. Bakt. 1900, II, 6, p. 341. 



BucHNER, E. 1897. Alkoholische Garung ohne Hefezellen (Bar. d. chem. Gesell. 

 1897, p. 1 17 ; also numerous papers in the same Journal, from 1897 onwards. 

 Compare also the summaries in Bot. Ztg. 1898 onwards). 



BucHNER, E. and H. and Rapp. 1903. Die Zymasegarung. Munich and Berlin. 



[BucHNER and Meisenheimer, 1905. Ber. chem. Gesell. 38, 620.] 



Chudiakow. 1896. Zur Lehre von d. Anaerobiose. Review by Rothert, Centrbl. 

 Bakt. 1898, II, 4, 389. 



DiAKONOw. 1886. Ber. d. bot. Gesell. 4, 2. 



DucLAUX. 1900. Traite de microbiologie, 3, 308. Paris. 



EwART. 1897. Journal Linn. Soc. Bot. 33, 123. 



Fischer, E. 1898. Zeit. f. physiol. Ch. 26, 60-87. 



GiLTAY and Aberson. 1894. Jahrb. f. wiss. Bot. 26, 543. 



GoDLEWSKi and Polzeniusz. 1901. Bullet. Acad, de Cracovie. 



Hansen. 1888. Rech. s. la phys. et la morphologic des ferments alcoohques, VII. 

 Action des ferments alcool. sur les diverses especes de sucre (Meddel. f. Carls- 

 berg Laborat, 2, Heft 5). 



