FUNCTION. 205 



aspect. Standing alone, the above exposition conveys an 

 idea that is both inadequate and erroneous. The divisions 

 and subdivisions of function, becoming definite as they be- 

 come multiplied, do not lead to a more and more complete 

 independence of functions; as they would do were the pro- 

 cess nothing beyond that just described; but by a simul- 

 taneous process they are rendered more mutually dependent. 

 While in one respect they are separating from each other, 

 they are in another respect combining with each other. At 

 the same time that they are being differentiated they are also 

 being integrated. Some illustrations will make this plain. 



In animals which display little beyond the primary dif- 

 ferentiation of functions, the activity of that part which 

 absorbs nutriment or accumulates energy, is not immediately 

 bound up with the activity of that part which, in producing 

 motion, expends energy. In the higher animals, however, the 

 performance of the alimentary functions depends on the per- 

 formance of various muscular and nervous functions. Masti- 

 cation and swallowing are nervo-muscular acts; the rhyth- 

 mical contractions of the stomach and the allied vermicular 

 motions of the intestines, result from the reflex stimulation 

 of certain muscular coats caused by food; the secretion of 

 the several digestive fluids by their respective glands, is due 

 to nervous excitation of them ; and digestion, besides requir- 

 ing these special aids, is not properly performed in the 

 absence of a continuous discharge of energy from the great 

 nervous centres. Again, the function of transferring 



nutriment or latent energy, from part to part, though at first 

 not closely connected with the other functions, eventually 

 becomes so. The short contractile tube which propels back- 

 wards and forwards the blood contained in the peri-visceral 

 cavity of an ascidian, is neither structurally nor functionally 

 much entangled with the creature's other organs. But on 

 passing upwards through higher types, in which this simple 

 tube is replaced by a system of branched tubes, that deliver 

 their contents through their open ends into the tissues at 



