Organic Ferments. 21 & 



may go on. Dumas proved, "that saccharine liquids are not influenced by ferment 

 through even the shortest columns of liquid, or the thinnest membranes;" and that 

 sonorous vibrations have no influence on fermentation. Many experiments have been 

 made to imitate organic fermentation by chemical action without success. Electricity 

 from a machine or an inductive coil of the galvanic battery is without effect on the 

 movement. It is slower in the dark and slower in a vacuum, but will go on in either. 

 It does not, therefore, require free oxygen, or oxygen as contained in air. 



The chemical composition of the yeast plant differs under different circumstances. 

 One analysis of surface yeast, which may be given as a specimen, is as follows: Carbon 

 49.9, Hydrogen 6.6, Nitrogen 12.1, Oxygen 31.4, Ashes 2.5. Analysis of the ash shows 

 Phosphoric Acid 53.9, Potassium 39.8, Magnesia 6.0, Lime 1.0. Yeast is similar in com- 

 position to the cells of larger plants and of fungi, except that it is richer in nitrogen. 



If fresh yeast be diffused in arterial red blood, or hasmaglobin satu- 

 rated with oxygen, the tint will change rapidly from red to dark blue or 

 black. ' ' A simple agitation of the blood with air is sufficient to restore 

 its ruddy color ; then the phenomena of deoxidation recommence. The 

 same experiment may be repeated a great number of times, especially 

 with fresh and washed yeast." 



In this case the yeast takes the oxygen from the blood (instead of 

 from sugar), and the air restores it. 



This experiment exactly imitates the process by which the blood as it 

 circulates in the animal body is oxidized and deoxidized. The cells of 

 the different tissues, muscular, areolar, epithelial, nervous, glandular, 

 &c. , act just like the yeast in absorbing the oxygen from the plasm of 

 the blood to which it is diffused from the red globules. On the return of 

 the blood to the lungs, the oxygen of the air passes through the walls of 

 the air chambers and again enters and oxidizes the blood. 



To make the experiment with the yeast a complete imitation of this 

 process, red blood was made to pass through tubes composed of gold- 

 beater's skin partly immersed in a solution containing yeast. The yeast 

 cells absorbed the oxygen from the blood through the skin, thus turning 

 the blood black. This process constitutes respiration, and it is shown 

 that the respiration of yeast has a vigor superior to that of a cold-blooded 

 animal like a fish. 



When yeast is kept in a damp state without nourishment, experiments 

 show that it lives at the expense of growing poor. That is, it consumes 

 its own tissues like a starving animal living on its own fat. 



When a considerable amount of yeast is set to ferment a small amount of sugar, after 

 all the sugar is consumed the yeast continues " to react on its tissues and its hydrocar 

 bons with extraordinary energy and rapidity, proceeding more and more slowly as the 

 process goes on." This will happen also if merely water be mixed with the yeast, the 

 vital activity continuing, and carbonic dioxide and alcohol being made at the expense 

 of the substance of the organism itself. If 100 parts of yeast be dried it will be reduced 

 to 30 parts, of which 22 parts constitute the cells of the organism and cannot be dissolved, 

 while 8 parts are soluble and can be washed out. But if the same yeast be kept in a 

 warm place in the form of a damp paste, for a couple of days, the soluble matter will be 

 found to have doubled, its quantity having increased obviously at the expense of the 

 organized cells of the yeast. This soluble matter contains a variety of substances, 

 among which, it is extremely important to observers Zymase, a ferment, a, soluble fer- 

 ment, which accompanies the yeast and to which some of the most important phenomena 



