40 THE DATA OP BIOLOGY. 



nitrogen, cells that grow by assimilating the nitrogenous 

 matter contained in wort. Similarly, the " vinegar-plant," 

 which greatly facilitates the formation of acetic acid from 

 alcohol, is a fungoid growth that is doubtless, like others of 

 its class, rich in nitrogenous compounds. Diastase, by which 

 the transformation of starch into sugar is effected during 

 the process of malting, is also a nitrogenous body. So too is 

 a substance called synaptase an albumenous principle con- 

 tained in almonds, which has the power of working several 

 metamorphoses in the matters associated with it. These 

 nitrogenized compounds, like the rest of their family, are 

 remarkable for the rapidity with which they decompose ; and 

 the extensive changes produced by them in the accompanying 

 carbo-hydrates, are found to vary in their kinds accord- 

 ing as the decompositions of the ferments vary in their 

 stages. We have next to note, as having here a 



meaning for us, the chemical contrasts between those organ- 

 isms which' carry on their functions by the help of external 

 forces, and those which carry on their functions by forces 

 evolved from within. If we compare animals and plants, we 

 see that whereas plants, characterized as a class by containing 

 but little nitrogen, are dependent on the solar rays for their 

 vital activities; animals, the vital activities of which are not 

 thus dependent, mainly consist of nitrogenous substances. 

 There is one marked exception to this broad distinction, how- 

 ever; and this exception is specially instructive. Among 

 plants there is a considerable group the Fungi many mem- 

 bers of which, if not all, can live and grow in the dark; and 

 it is their peculiarity that they are .very much more nitro- 

 genous than other plants. Yet a third class of facts 

 of like significance is disclosed when we compare different 

 portions of the same organism. The seed of a plant contains 

 nitrogenous substance in a far higher ratio than the rest of 

 the plant ; and the seed differs from the rest of the plant in 

 its ability to initiate, in the absence of light, extensive vital 

 changes the changes constituting germination. Similarly 



