ON CIRCULATION GENERALLY 39 



junction with the play of vital force along well-defined 

 lines, or those of least resistance, throughout all the 

 structures. These lines or channels are composed, in 

 many cases, of highly organised hollow structures, in the 

 form of canals such as the alimentary, of vessels such as 

 the arteries, veins, and capillaries, of organised tubes such 

 as the lymphatics proper, of interstitial lymph spaces, 

 where lymph, or fluid material, first collects through cell 

 and fibral osmosis, and of the apparently homogeneous 

 walls of cells, nuclei and nucleoli, which are nevertheless 

 permeable to or by fluids under the influence of vital 

 impulse, and in obedience to the chemico-physiological 

 laws regulating the processes of growth and decay. 



Circulation, as we have said, takes place along what 

 may be called the lines of least resistance, and must be 

 looked for along those lines only ; thus, along the 

 alimentary canal, secured by its valves and sphincters, 

 circulation, under peristaltic compression and compulsion, 

 is easily accomplished by the highly organised and com- 

 plex machinery provided in its walls, where a series of 

 escape tubes is laid down, by which the fluid or less 

 consistent parts of the contents are run or drawn ofl", 

 leaving only a residuum of unutilisable material to be 

 excreted. Following these escape tubes, we notice that 

 they converge to form a single large tube, the thoracic 

 duct, which empties itself into the current of the blood, 

 where its contents are whirled on through multitudinous 

 "turnings and twistings" until they reach the structures 

 for whose growth and repair these elaborate processes are 

 but- preparatory, and where they are disposed of according 

 to the necessities and by the laws of the process of 

 nutrition. Once disposed of thus, a reverse, or inverse, 

 process, viz., that of disintegration, or waste, sets in, 

 necessitating the provision of a set of collecting spaces 

 and vessels, whereby the waste products, suspended in 

 the haemal lymph, may be collected and conveyed to the 

 appropriate cardiac and pulmonary areas for re-oxygenation, 

 and to the excretory organs and surfaces for elimination, 

 in order to prevent the re-introduction into the healthy 

 textures of materials which have now become effete, and 

 therefore toxic. The lymphatic system of vessels here 



