CORRELATION OF VITAL AND PHYSICAL FORCES. 163 



what is far more wonderful and significant is, that, associated with 

 each of these ferments, except diastase, and therefore with each of 

 these descensive changes, except the change from starch to sugar, or 

 saccharification, there is a peculiar form of life. Associated with alco- 

 holic fermentation, there is the yeast-plant ; with acetification, the 

 vinegar-plant; and, with the decomposition of vinegar, a peculiar 

 kind of mould. We w^ill take the one which is best understood, viz., 

 yeast-plant (saccharomyce), and its relation to alcoholic fermentation. 



It is well known that, in connection with alcoholic fermentation, 

 there is a peculiar unicelled plant which grows and multiplies. Fer- 

 mentation never takes place without the presence of this plant ; this 

 plant never grows without producing fermentation, and the rapidity 

 of the fermentation is in exact proportion to the rapidity of the growth 

 of the plant. But, as far as I know, the fact has not been distinctly 

 brought out that the decomposition of the sugar into alcohol and car- 

 bonic acid furnishes the force by which the plant grows and multi- 

 plies. If the growing cells of the yeast-plant be observed under the 

 microscope, it will be seen that the carbonic-acid bubbles form, and 

 therefore probably the decomposition of sugar takes place only in con- 

 tact with the surface of the yeast-cells. The yeast-plant not only 

 assimilates matter, but also force. It decomposes the sugar, in order 

 that it may assimilate the chemical force set free. 



We have already said that the change from starch to sugar, deter- 

 mined by diastase (saccharification), is the only one in connection with 

 which there is no life. Now, it is a most significant fact, in this con- 

 nection, that this is also the only change which is not, in a proper 

 sense, descensive, or, at least, where there is no decomposition. 



We now pass from the phenomena of vegetable to the phenomena 

 of animal life. 



7. Development op the Egg in Incubation. — The development 

 of the egg in incubation is very similar to the germination of a seed. 

 An egg consists of albuminous and fatty matters, so inclosed that, 

 while oxygen of the air is admitted, nutrient matters are excluded. 

 During incubation the egg changes into an embryo ; it passes from an 

 almost unorganized to a highly-organized condition, from a lower to a 

 higher condition. There is work done : there must be expenditure of 

 force ; but, as we have already seen, vital force is always derived from 

 decomposition. But, as the matters to be decomposed are not taken 

 ab extra, the egg must consume itself ; that it does so, is proved by 

 the fact that in incubation the egg absorbs oxygen, eliminates C0 2 and 

 probably H 3 0, and loses weight. As in the seed, a portion of the mat- 

 ters contained in the egg is consumed in order to create force to or- 

 ganize the remainder. Matter runs down from plane No. 4 to plane 

 No. 2, and generates force to do the work of organization on plane 

 No. 4. The amount of CO, and H 2 formed, and therefore the loss 

 of weight, is a measure of the amount of plastic work done. 



