S8 HORSE.BACK RIDING. 



concur equally in producing the phenomenon of nutri- 

 tion, but in different manner. The plasma consists 

 principally of water, which serves as a vehicle for the 

 albumen and fibrin, and combines with the anatom- 

 ical elements of the tissues, incarnates itself, so to 

 speak, and is metamorphosed with the elements which 

 it has just regenerated. It is thus that musculine, ner- 

 vine, osseine, chondrine, etc., are formed, all derived 

 from the albumen and fibrin, transformed by fixing of 

 a certain quantity of the equivalents of oxygen and 

 hydrogen in the proportions of water. In the same 

 way the saccharine matter in solution, fatty matters in 

 emulsion and mineral substances in the form of salts 

 in solution, pass through the walls of the capillaries, 

 and are carried wherever they are required. The 

 organized materials of the tissues, on their part, are 

 subjected to oxidation from the oxygen exhaled 

 from the vessels with the plasma, an oxidation more 

 or less complete, which transforms them, renders them 

 unfit to do their duty, and they return to the circu- 

 latory mass, and are carried by the veins to the different 

 emunctories to be eliminated in the form of creatine, 

 urea, uric acid, choleic acid, etc. Such is the process 

 of assimilation and elimination Avhich takes place in 

 the tissues, and it is active just in proportion to the 

 circulation it augments or diminishes. It is particu- 

 larly in the muscles that this incontestable fact may 

 be seen. 



It is in the rich vascular net-work of the circulatory 



