Dr Alison on the Principle of Vital A^nity. 273 



globules or corpuscules of that fluid. Most of the textures 

 seem to be formed by the gradual transformation, elongation, 

 or flattening of cells, which have sprung from nuclei attached 

 to previously existing cells ; and it seems to be only by the 

 successive formation, distension, rupture, and disappearance 

 of cells, that secretions make their way into the excreting 

 ducts of glands, or on the surface of membranes. 



The dependence of all living structures, and of all secre- 

 tions, not simply on vascular action, by which nourishing 

 fluids are circulated through them, but on cellular action^ by 

 which this nourishing fluid is changed, appropriated, and re- 

 tained, or restored to the circulation, is the great step which 

 has been recently gained in physiology by the use of the 

 microscope ; and seems to me to be one of the clearest proofs 

 of the dependence of all vital phenomena on peculiar attrac- 

 tions and repulsions, actuating both solids and fluids, and 

 causing motions in the latter, — not on any vital powers re- 

 siding exclusively in solids. When it is stated, e.g, by Mr 

 Paget, that " the purpose to which the capillaries are habitu- 

 ally subservient, is only the passive one of conveying blood 

 close to those parts of the body which either grow or secrete, 

 and that it is proved that if a part be only able to imbibe the 

 fluid portion of the blood from an adjacent vessel, it nourishes 

 itself as completely, and after the same method, as one whose 

 substance is traversed by numerous capillaries,'^* — it be- 

 comes obvious that the movements of the fluid portion of the 

 blood, whereby they are applied to growth and secretion, must 

 be determined by causes quite distinct from the contractions 

 of vessels. 



2. Living and growing cells, therefore, whether acting on 

 the nourishing fluid just taken into the system (as in the case 

 of the intestinal villi, or the tufts of the placenta), or on the 

 blood brought to them by the capillaries (as in the nutrition 

 of the different textures), appear always to have two functions 

 to perform, — to extract from the nourishing fluid the matter 

 of which they are themselves composed, and to extract from 



* R«port in Forbes's Medical Review, July 1843. 



