ORGANIC STIMULANTS AND POISONS. 245 



another property of this substance, as already mentioned on 

 pp. 179, 1 80, vol. ii. 



Though corrosive sublimate hns been shown by WERNKE (I.) 

 and WEHMER (VII.) to have but a separatively slight toxic effect 

 on yeast, its otherwise strongly poisonous properties render it 

 unsuitable for use in practical fermentation. Other substances 

 also devoid of practical importance are : bismuth nitrate, zinc 

 sulphate, zinc chloride, ferrous sulphate, ferrous chloride, man- 

 ganous chloride, potassium permanganate, aluminium sulphate, 

 aluminium chloride, and potassium alum, the influence of which 

 on yeast was studied by H. WILL (I.). 



As shown by J. DUMAS (V.) and subsequently more closely 

 investigated by U. GAYON and E. DUBOURG (IV.), a considerable 

 amount of cell juice, rich in nitrogen, can be extracted from yeast 

 cells by exposure to the influence of a saturated solution of a 

 suitable salt, such as sodium acetate, phosphate or sulphate, 

 potassium acetate, oxalate, tartrate or iodide, magnesium sul- 

 phate, calcium chloride, &c. A. BECHAMP (VIII. and XI.) 

 obtained a still higher yield by kneading pressed yeast with the 

 powdered, dry salts, an almost immediate liquefaction of the 

 pasty mixture occurring in most cases. Saccharose is also suitable, 

 when used in the proportion of two parts to three of yeast, and 

 the same applies to gum arabic, &c. The auto-fermentation 

 frequently occurring under these conditions was investigated by 

 C. J. LINTNER (III.), in a series of experiments to which further 

 reference will be made in chapter Ixv. 



270. Organic Stimulants and Poisons. 



The mutual relations between yeasts and the organic acids of 

 the aliphatic series are varied. Some of them, succinic acid, for 

 instance, occur as decomposition products of the cell substance 

 (see chapters Ixiv. and Ixvi.). In other cases similar acids play 

 the part of a source of carbon, and therefore supply material for the 

 process of metabolism, as already mentioned on p. 205, vol. ii. ; whilst 

 in still other instances, with which we shall now deal, they excite 

 interest on account of their stimulant or poisonous action. Yeasts 

 are very susceptible to butyric acid, and must therefore be pro- 

 tected from the clanger with which they are menaced by this acid 

 in distillery work (see vol. i. p, 245). The general rule that 

 yeasts of different species are variously influenced by any given 

 stimulant has found practical utilisation in connection with tar- 

 taric acid. On the occasion of his critical examination of Pasteur's 

 method of purifying the pitching yeast used in the brewery, 

 E. C. HANSEN (XXXIV.) found that the beer yeasts, Sacch. cere- 

 visice /., Hansen, Carlsburg bottom yeast No. 2, &c., are more 

 susceptible to tartaric acid than the wild yeasts (Sacch. Pastorianus 

 I. and ///., Sacch. ellipsoideus II.) ; so that in a mixture of the two 



