those organic substances are formed which are the basis of living: bodies. The belief which from day to day is gaining confirmation from the labors of physiologists is that so boldly expressed by Claude Bernard, viz., that as the chemist, starting with the knowledge of inorganic bodies, subjects them to his will and creates new bodies, so the physiologist, starting from organic matter, "by imposing upon it special conditions, will be able to produce new physiological modifications and new series of phenomena, thus modifying at will living-bodies, and even creating them."
At the same time, by comparing and analyzing the different branches of biology, certain very general laws have been established, particularly in physiology proper, having a bearing upon the development of the individual and the relations of the functions to their organs. We are in possession of a certain number of very broad though purely empiric generalizations on the phenomena upon which the superiority of living things over one another depends. These are, properly speaking, laws of organic Nature.
First, we have the law of the increase of the mass of the organism, in virtue of which each living thing attains its full development only by passing through a series of phases characterized by an augmentation of its mass, and consequently by an augmentation of the quantity of force applicable for its physiological actions, as also by an augmentation of the quantity of functional products.
Then there is the law of the multiplication of parts in proportion as we ascend in the series of living things, this multiplication being determined by an increase of complexity in the organic machine, in virtue of the diversity both of the functions which make their appearance and of the organs which result from this diversity of functions.
Again, we have the law of coördination and subordination of functions and organs, in virtue of which, in proportion as complexity is introduced into the organism and as the functions and organs take on a more special character, certain functions and the organs performing them become dependent on other functions and other organs. Besides, a tie of solidarity is established between all the parts of the living body, so as to guide them toward a common end, the conservation of the individual, while at the same time all of the parts feel the reverberation of the actions to which each is subject.
Next comes the law of adaptation, in virtue of which an organism tends to be so modified as to seem to be specially created to suit the circumstances amid which it exists and the kind of life imposed upon it by them. This law is still, for many thinkers, the basis of ideas of final causes by means of which they strive to explain the structure of living things and the variations observed therein.
Finally, there is the law of heredity, in virtue of which organisms produce new organisms which repeat their type. Heredity is the law of fixity; it expresses the tendency to perpetuate a condition of things
