1 62 BIOLOGICAL PHYSICS 



With these introductory observations, we now proceed 

 to summarise, and to place the results of our observations, 

 and reflections, with all their original and acquired im- 

 perfections, before our contemporaries, apologising for the 

 omission of mention of our sources of knowledge, a work 

 which we have found impossible, inasmuch as, they, the 

 subjects of our remarks, consist of material first gathered 

 from the lips of revered teachers, and of colleagues in the 

 work of life, from information derived from text-books, 

 and accessible works of authority, from articles scat- 

 tered up and down the serial literature, and publications, 

 of the time, and from independent, and personal sources, 

 presenting themselves during the course of professional 

 life and work. 



Returning from this introductory digression, we shall 

 resume the discussion of the subject of " circulation." 

 We had, to some extent, pursued the subject with a view 

 to obtaining a firmer grasp of it in that department which 

 relates to the movement, or circulation, of plastic, or more 

 or less fluid, materials, within more or less well-defined 

 vessels and inter-spaces, such as are met with both in 

 animal and vegetable structures. We shall now, there- 

 fore, again take up in its deeper, and so to speak, 

 underlying aspects, more especially as related to such 

 subjects as nutrition, assimilation, disintegration, and 

 excretion, processes which largely make up the problems 

 of life and " organic activity," the cessation of which 

 constitutes death. 



Circulation, in its more usual biological aspects, is charac- 

 terised by forward movement of material, or matter, in 

 contrast to backward movement, and is due to the opera- 

 tion of forces acting both from before and from behind, 

 as well as, it may be, to latent, or intrinsic, forces acting 

 from within. That being so, we perceive that nutrition is 

 made possible only through that forward, or onward, 

 movement, of the nutritive plasma propelled and regu- 

 lated, by these modes of force, in virtue of the continued, 

 and, in normal vital conditions, the regular replacement 

 of used up, disintegrated, or effete, matter, by fresh, or 

 nutritive matter; which process necessitates the continuous 

 onward, as distinguished from the backward, movement 



