120 GENERAL PHYSIOLOGY 



differences between the two. If the former be compared with a 

 liquid rather than with a crystal, it is found that in its structural 

 relations it differs no more from lifeless liquid mixtures than 

 these differ among themselves, and, indeed, not so much as they 

 differ from a crystal. 



2. Genetic Differences 



A second series of differences which, it is believed, have been 

 found between organisms and inorganic substances has reference 

 to reproduction and derivation. These differences likewise are not 

 fundamental, and it is easy to perceive that between the two 

 groups no real contrast in this respect exists. 



It is regarded as a characteristic sign of difference that 

 organisms reproduce, while inorganic bodies cannot do so. This 

 is not an absolute difference, for many organisms are known that 

 live and yet can never reproduce. Thus, it is well known that the 

 power of reproduction is wanting throughout life in the so-called 

 workers, those individuals in communities of ants and bees 

 which form the great majority of the community and in which the 

 sexual organs are undeveloped ; notwithstanding this latter fact 

 they must be regarded as living organisms. Further, reproduction 

 in organisms consists simplj' in a giving-off of a certain portion 

 of the body-substance, a division of the individual bod}'. This 

 fact shows most distinctly, i.e., is less masked by accompanying 

 accessory phenomena, in unicellular organisms. An Amoeba, for 

 example, constricts itself into halves, and each half continues to 

 live as a new Amcchu. But if reproduction in its essentials con- 

 sists merely in the division of substance, no fundamental difference 

 exists between the process in a living cell and that in an 

 inorganic body. A drop of mercury that falls upon the floor is 

 divided into a number of small globules, all of which are drops of 

 mercury. 



It has been said, further, that organisms are always derived from 

 other organisms, while inorganic bodies can be derived from both 

 organisms and inorganic bodies. Thus, it is impossible to manu- 

 facture even the simplest organism artificially from inorganic 

 substances, while it is not difficult to obtain inorganic bodies — 

 e.g., water — in a variety of ways from both organic and inorganic 

 substances. This appears to be an absolute difference, for it is 

 true that in spite of all endeavours no one has succeeded in 

 demonstrating that organisms can be formed from inorganic 

 matters either in nature or in the laboratorj'. Nevertheless, this 

 difference cannot be regarded as really absolute, for it can be 

 replied that organic substance is constantly being built out of in- 

 organic substance in the plant-body, this being the exclusive 

 method of construction in plants. To this it has been rejoined in 



