( 200 J [April, 



IY. ON " TEOPHIC NEKYES." 



By Geoege Bolleston, M.D., F.B.S., Linacre Professor of 

 Anatomy and Physiology, Oxford. 



All physiologists, and indeed all observers, whether physiologists 

 or not, are agreed that the nervous system intervenes most power- 

 fully, and that not rarely, in controlling and modifying the pro- 

 cesses of what we call " organic life." Growth and development, it 

 is true, may be carried on, food may be assimilated, and secretions 

 may be elaborated, independently of nerves and nerve-centres in 

 many lower animals ; but, on the other hand, it is equally true that 

 in more highly organized creatures there are but few processes of 

 vegetable fife which may not be, at times and to a greater or less 

 degree, brought under the influence of their cerebro-spinal systems. 

 As to the facts, there is no question; as to the way in which the 

 facts are brought about, however, there is a very wide difference of 

 opinion. This difference is expressed in the contradictory answers 

 given by representatives of various biological schools to such ques- 

 tions as : — Can the nerves act directly upon cells other than mus- 

 cular fibre cells ? Can nerve-force interfere with the cell territory 

 otherwise than by regulating the stream of nutriment brought 

 within the borders of that territory by the blood-vessels ? Are there, 

 finally, " trophic " and secretory as well as vasomotor nerves ? The 

 indirect action of nerves upon tissues in the way of vasomotor regu- 

 lation of the blood-vessels supplying them is more readily compre- 

 hensible by us, but that nerves can act directly upon cells pigmentary, 

 secretory, and other cells, as well as upon contractile cells and fibres, 

 appears to the present writer all but equally demonstrable. Change 

 of colour in ourselves is usually dependent upon vasomotor change ; 

 but change of colour in the frog has been most conclusively shown 

 by Professor Lister to be dependent upon molecular movements car- 

 ried on in the interior of cells under the influence of the nervous, 

 and under circumstances which exclude the intervention of the blood- 

 vascular system. A force which can be seen to produce molecular 

 movement within a pigment cell, may well be supposed to be com- 

 petent to produce nutritional or chemical changes in the interior of 

 cells of other characters. But if our knowledge of the convertibility 

 of force makes us ready to allow that nerve-force may show itself 

 by modifying nutrition or by producing secretion as well as by pro- 

 ducing motion, our knowledge of the convertibility of function 

 which nerves possess accordingly as they are distributed in one or 

 in another class of tissues makes us slow to accept as a necessity the 

 establishment of a division of " trophic " nerves. Messrs. .G. H. 

 Lewes, Philippeaux, and Yulpian have shown that nerves are sensory 



