MOLECULAR FORCES. 165 



Thus, too, we had occasion to notice, at the close of our descrip- 

 tion of animal matters, that even those more organised atoms 

 which constitute the more simple substrata of the animal tissues 

 are always formed in accordance with the functions which they 

 control or the forces with which they are connected. However 

 strikingly this observation seems to be confirmed, wherever the 

 chemical movements of the animal body fall under our notice, it 

 need not excite our surprise ; for when we only observe the known 

 laws of molecular motions, we perceive that their manifestations 

 in these particles of matter must be different from those in 

 inorganic nature. The manifestation of each force is connected 

 with the nature of the mass which is to be acted upon, whilst the 

 effects depend upon the circumstances under which the force is 

 brought to bear upon the mass. If, therefore, we wholly disregard 

 the question whether other forces than those with which the 

 physicist is familiar may not act upon these masses, such forces 

 appertaining exclusively to life, it follows a priori that the resulting 

 action of these physical forces will be very different when exercised 

 upon inorganic particles, (which, although differently formed, 

 present identical principles of structure,) than when applied to the 

 simpler forms of mineral substances. This proposition requires 

 no further demonstration, but it indicates the direction we must 

 follow if we would attempt to trace the internal connection of vital 

 phenomena in their individual phases, and thus investigate the 

 various processes of animal life. 



We have, in accordance with the plan of our work, passed in 

 review the general mechanism of the animal organism, and con- 

 sidered the chemical nature of the individual parts ; we proceeded 

 next to investigate matter and its endless variety of forms, without 

 however directing more than a cursory glance at the motions of the 

 individual parts, or the various phenomena of physical life. We 

 have now to enter into the phenomenology of the individual mem- 

 bers of this vast series, postponing our investigation of the forces 

 through the agency of which the phenomena are called forth, until 

 we have gained a sufficient knowledge of the qualitative and quan- 

 titative relations of the individual phenomena. This is the simple 

 and only practicable method of conducting every physical inquiry, 

 and hence we ought not to neglect it in physiology. Nor can we 

 enter into a causal investigation of the objects of our inquiry 

 before we have considered the phenomena in the living organism 

 from all points of view, and ascertained its relations of mass and 

 weight. We shall have occasion to perceive, in our attempts to 

 refer individual phenomena to their controlling causes, and to 



