202 METAMORPHOSIS OF TISSUE. 



regarded by many as the essence and seat of all vital activity. In 

 endeavouring to trace the intimate relations existing between these 

 mutually allied substances from a chemical as well as a physical 

 point of view, we were necessarily led to the consideration of the 

 continuous metamorphoses which they had undergone during life, 

 and of the causal connection of those. phenomena which seemed to 

 correspond with definite purposes in the living organism. It only 

 remains, therefore, for us to take a collective and general view of 

 the mutual relations in which the different juices stand to one 

 another, the interchange of their constituents, and the dependence 

 of the changes of any one upon another, or upon all the others, 

 and thus to arrive at a general conclusion regarding those pro- 

 cesses known as the metamorphosis of animal matter. 



Finally, in this, the third volume, we have treated of the 

 mechanical and chemical relations of the masses, which are con- 

 solidated into cells, fibres, and membranes, as far as this is possible 

 in the present very imperfect state of our knowledge ; and in these 

 structures we have recognised not merely the hollow skeleton or 

 framework between the parts of which the separate currents of 

 these fluid masses move and circulate in uninterrupted motion in 

 order to satisfy the different requirements of life, but we have also 

 discovered in them the apparatus by which the most intense and 

 peculiar actions of the animal organism are manifested. 



Many might be led at first sight to suppose that we had 

 accumulated a sufficient mass of materials from all directions to 

 enable us to gain a deeper insight into the vital phenomena of 

 animal life, or at all events, to delineate in few but characteristic 

 outlines the chemistry of the animal organism ; but the more 

 deeply we penetrate into the obscurity of the metamorphosis of 

 animal matter, and the more carefully we investigate the materials 

 in our hands, the more plainly do we perceive the deficiencies 

 with which we have to contend. We have already frequently 

 taken occasion to notice how little aid we have derived from 

 previous scientific investigations in establishing general con- 

 clusions regarding any special group of animal molecular motions. 

 It is therefore wholly unnecessary to enlarge upon these de- 

 ficiencies, which we have already noticed in detail in the methodo- 

 logical introduction to the first volume (see vol. i., p. 8). We 

 shall certainly not exceed the bounds of truth, if we maintain that 

 we are still entirely deficient in the very first principles necessary 

 for a scientific treatment of the theory of the metamorphosis of 

 matter in the animal organism. It is merely to clear ourselves 



