198 ANNUAL OF SCIENTIFIC DISCOVERY. 



during four weeks. Second experiment. Addition of tartrate of am- 

 monia to such solutions as the above produced no perceptible effect. 

 Third experiment, Straw cleaned as mentioned, together with cream 

 of tartar, induced no fermentation in either cane or grape sugar. 

 Fourth experiment. Pulverized quartz added to solutions of cane and 

 grape sugar caused no fermentation. In the course of some weeks 

 mucor or mould was formed, which fructified and yielded spores. Fifth 

 experiment. A solution of cane-sugar was mixed with uncleaned nat- 

 ural straw in order to see if it excited fermentation, and if so, to as- 

 certain if it might not be owing to the development of fungi. After 

 twelve days, fermentation commenced, and at the same time micro- 

 scopical examination of the liquor showed the presence of vegetable 

 cells identical with upper yeast. Sixth experiment. The same ex- 

 periment performed with grape-sugar yielded the same results, but 

 fermentation commenced some days earlier. Experiments seventh to 

 eleventh. These experiments were made upon yeast. Rousseau made 

 known the supposed fact, that fermentation may be induced by yeast 

 even in the presence of vegetable or mineral poisons, if rendered acid 

 when mixed with the sugar solution. The trials of Mr. Erni did not 

 confirm these statements. He found : 



1. That upper yeast in cane-sugar solution, acidified with tartaric 

 acid, and poisoned with arsenious acid, produced no fermentation. 

 The same mixture, without the addition of oxide of arsenic, fermented 

 after two days. The liquor was strongly acid to the taste, became 

 sweet again, and fermentation commenced. 2. The same trial was 

 made in a liquor acidulated with acetic acid, and no fermentation took 

 place. The same mixture, without the oxide of arsenic, produced 

 fermentation. 3. The above two experiments were repeated, using oil 

 of turpentine as a poison instead of arsenious acid, and the same nega- 

 tive results obtained. 4. Yeast, added to cane or grape sugar solution, 

 acidified with tartaric or acetic acid, and poisoned with a few drops 

 of creosote, excited no fermentation whatever. 5. Mixtures of cane 

 and grape sugar with yeast, acidified with cream of tartar, and poi- 

 soned with considerable quantities of arsenious acid, produced fermen- 

 tation. G. The same experiment repeated, with the difference that, in 

 the place of arsenious acid, creosote and oil of turpentine were em- 

 ployed, showed no fermentation. When the poisoned liquors were 

 examined under the microscope, it could easily be seen when the poi- 

 son had taken effect ; the nitrogenous layer on the cell-membrane 

 seemed to have undergone a change similar to that produced by 

 boiling. 



A !r. Erni's investigations have thus far led him to the conclusion, 

 that alcoholic fermentation is caused by the development of fungi. He 

 could never trace fermentation, without observing at the very first ev- 

 olution of carbonic acid the formation of yeast-cells, although it is 

 verv difficult to decide certainly which precedes the other. He was 

 rather in favor of the yeast-cells being the original movers, the re- 

 sults of Mitscherlich's experiments. Helmholz has also observed that 

 the fermentation of grape-juice is not communicated to another portion 

 of grape-juice which is contained in a vessel closed by a bladder and 



