THE SO-CALLED "RETTING" OF FLAX AND HEMP 151 



on this point were made by H. TAPPEINER (I.) in 1884, who showed the fate 

 of all cellulose taken into the body and not evacuated in the faeces to be, not 

 digestion and absorption into the arterial circulation, but fermentation into 

 marsh-gas. The operation, however, does not proceed exactly according to the 

 above equation, but yields, in addition to methane, volatile fatty acids (chiefly 

 acetic acid, then butyric acid, &c.). Bearing this in mind, this decomposition 

 process cannot be regarded as totally without value for the animal body, although, 

 naturally, the coefficient of digestibility, hitherto usually assumed, necessarily 

 suffered considerable depreciation. Moreover, this process is indirectly favour- 

 able, in so far that, by the solution of the cell-walls, the cell contents of the 

 vegetable nutriment are laid bare, and thus rendered more readily accessible 

 to the digestible fluids. Although by this discovery the chief source of the 

 intestinal gases so copiously evacuated by herbivorous animals is made manifest, 

 still it should not be assumed that the methane therein is exclusively derived 

 from the fermentation of cellulose, since Huge and Planer proved that, even in 

 cases of a purely flesh diet, methane is to be found in the intestinal gases (of 

 man and the dog). 



Cellulose fermentation also plays a part in the preparation of brown hay, 

 sweet ensilage, and sour fodder, considered in chapter xxvii., where it forms 

 one of the causes of the great loss of matter inherent in these processes, in 

 connection wherewith reports have been made by Weiske, 0. Kellner, 

 M. Maercker, and others. This process also goes on as shown in 1884 by 

 P. DEHERAIX (I.) and U. GAYON (I.) in manures. If, favoured by special 

 circumstances, it proceeds more rapidly than the decomposition of all the other 

 (and especially the nitrogenous) constituents, then an irregularly fermented 

 product deficient in the fibres necessary to impart porosity to the mass and 

 known as fatty manure, is the result. 



The evolution of marsh-gas and hydrogen by the agency of bacteria also 

 occurs, not infrequently, in other situations ; for instance, in the diffusers in 

 sugar-works, and very often so strongly that the amount of gas suffices to 

 produce powerful explosions when the diffusers are incautiously approached 

 with a naked light. The teaching of experience, that frozen beet is particularly 

 liable to such a form of decomposition, is probably explicable by the circum- 

 stance that such beet cannot be entirely freed from adherent particles of soil, 

 and the ferments present therein. It is also conceivable that, by the agency of 

 frost, the pectins in the beet are transformed into a more readily decomposable 

 condition. On this point a few observations have been made by Millot and 

 Maquenne, and, more recently, by P. DEHERAIN (II.) ; more accurate investiga- 

 tions thereon are, however, still lacking. 



119. The So-called " Retting" " of Flax and Hemp. 



The present forms the most fitting occasion for making a few explanatory 

 remarks on this matter. As is well known, it is the bast fibre of these plants 

 that is referred to when hemp or flax is spoken of in the textile industry. In 

 order to lay these fibres bare and obtain them in a pure state, it is necessary to 

 dissolve the intermediate intercellular substance (the so-called central lamella) 

 which consists, not of Pectose, as stated by J. Kolb, but (according to the 

 researches of Mangin) of calcium pectate. This can be effected by chemical 

 means, by a (patented) process which Baur successfully introduced into Silesia 

 on a large scale in 1882, and which consists mainly in treating the plants with 

 very dilute sulphuric acid, and then neutralising the adherent acid by a weak 

 alkali bath. The solution of the cementing calcium pectate can, however, be 

 brought about by a fermentation, known as "retting," that has been practised 



