34 NATURE AND OBJECTS OF PHYSIOLOGICAL SCIENCE. 



the organizable from the unorganizable material, to the simple operation 

 of the same agencies as those which determine the production of the 

 different isomeric compounds ; for the properties of Fibrin are much 

 more vitally distinct from those of Albumen, than they are either che- 

 mically or physically ; that is, we find in the one an incipient manifes- 

 tation of Life, of which the other shows no indications. The spontane- 

 ous coagulation of fibrin, which takes place very soon after it has been 

 withdrawn from the vessels of the living body, is a phenomenon to which 

 nothing analogous can be found elsewhere ; for it has been clearly shown 

 not to be occasioned by any mere physical or chemical change in its 

 constitution ; and it takes place in a manner which indicates that a new 

 arrangement of particles has been effected in it, preparatory to its being 

 converted into a living solid. For this coagulation is not the mere ho- 

 mogeneous setting r , which takes place in a solution of gelatine in cooling ; 

 nor is it the aggregation of particles in a mere granular state (closely 

 resembling that of a chemical precipitate), which takes place in the 

 coagulation of albumen : it is the actual production of a simple fibrous 

 tissue, by the union of the particles of fibrin in a determinate manner, 

 bearing a close resemblance to the similar process in the living body 

 ( 188). We say, then, that the coagulation of Fibrin, and the produc- 

 tion of a fibrous tissue, are the manifestation of its vital properties, 

 rather than the direct result of chemical or physical agencies ; because 

 no substance is known to perform any such actions, without having been 

 subjected to the influence of a living body ; and because the actions 

 themselves are altogether different from any which we witness else- 

 where. 



32. The act of Formation seems to consist of a continuation of the 

 same kind of change, that is, a new arrangement of the particles, pro- 

 ducing substances which differ both as to structure and properties from 

 the materials employed, but which may be so closely allied to them in 

 chemical composition, that the difference cannot be detected. Thus, 

 from the " protoplasma"* of Plants are generated, in the process of cell- 

 development, the membranes which constitute the walls of the cells : 

 chemically speaking, there seems to be no essential distinction between 

 these substances ; and yet between the living, growing, reproducing cell, 

 and the gelatinous, semifluid matter in which they are imbedded, how 

 wide the difference ! So in the Animal body, we find that the composi- 

 tion of the proper muscular tissue scarcely differs, in regard to the pro- 

 portion of its elements, from the fibrin, or even from the albumen, of 

 the blood ; and yet what an entire rearrangement must take place in 

 the particles of either, before a tissue so complex in structure, and so 

 peculiar in properties, as muscular fibre, can be generated ! 



33. Both in the Plant and the Animal, we find that tissues presenting 

 great diversities both in structure and properties, may take their origin 

 in the same organizable material ; but in every case (at least in the 

 ordinary processes of growth and reparation) the new tissue of each 

 kind is formed in continuity with that previously existing. Thus in 



* This term is now commonly employed to designate that combination of starchy and 

 albuminous matters, in which all newly-forming cells appear to originate. See \ 28. 



