294 MATHEWS. 



I. INTRODUCTION. 



A Criticism of the Secretory-nerve Theory. 



Nearly fifty years ago it was suggested by Ludwig^^ that se- 

 cretion was a function of the gland cells controlled by the ac- 

 tivity of special nerve fibres. Upon the gland cell, thus em- 

 phasized as the prime factor in secretion, and upon its relation 

 to nerve action, most of the subsequent study of the physiology 

 of secretion has been focussed. This study has unearthed such 

 evidences of the truth of Ludwig's hypothesis that to-day few 

 theories of physiology rest upon a foundation apparently firmer, 

 or are more widely accepted, than the hypothesis of secretory 

 nerves. Indeed, the recent discovery,^ by means of the Golgi 

 and Ehrlich methylen-blue methods, of the remarkably rich 

 distribution of nerves to glands, and of the endings of these 

 nerves about the gland cells, has seemed the final convincing 

 demonstration of the truth of the theory which so many years 

 ago foretold their existence. 



The theory of secretory nerves did not long remain in the 

 simple form suggested by Ludwig, for it soon received, at the 

 hands of Heidenhain, a more complete and definite shape. 

 First seriously worked out by him in 1868^^ the theory was 

 further developed in 1878^^ and took its final form in his great 

 treatise on secretion embodied in Hermann's Handbuch der 

 Physiologic in 1880."^ The Ludwig-Heidenhain theory, thus 

 crystallized by Heidenhain, has been the lens through which 

 the facts of secretion accumulated from 1868 to the present 

 time, have been viewed. This theory may be briefly stated as 

 follows : 



Secretion is a specific function of the gland cells controlled by 

 special secretory nerve fibres, acting directly upon these cells. 

 There are two kinds of these nerve fibres : trophic fibres, which 

 render the cell contents soluble ; and secretory fibres, which 

 diminish the resistance to filtration offered by the lumen end of 

 the cell. In consequence of this decreased resistance, the con- 

 tents of the cell, which are under high endosmotic pressure, 

 escape into the lumen. At the same time the cell imbibes liquid 

 from the lymph space. 



