362 MATHEWS. 



such secretions are the salivary secretions following stimulation 

 of the sympathetic, certain secretions of sweat, the secretion of 

 the cephalopod salivary glands and of the skin glands of am- 

 phibia. 



Whether those secretions which are normally accompanied by 

 vaso-dilation, such, for instance, as the salivary secretions follow- 

 ing stimulation of the cerebral nerves and the secretions of the 

 alimentary tract and its appendages, are governed by nerves act- 

 ing directly on the gland cells, or indirectly through the vascu- 

 lar system, cannot with certainty be said. But I believe it has 

 been shown in the present paper that the evidence which has 

 hitherto been offered that such secretions are controlled by 

 nerve action on the gland cell is open to serious criticism. The 

 remarkable parallelism between the hypothetical secretory and 

 vaso-dilator fibres, the close dependence of such secretions on 

 the vascular system, the general features of such secretions and 

 the structure of glands, all indicate, I believe, that osmosis is 

 the essential cause of these secretions, and that they are con- 

 trolled by the action of nerves on the vascular system. No 

 one would deny that the course of these secretions is modified 

 by the condition of the gland or capillary wall, and that that 

 condition is easily affected by drugs, but that nerve action di- 

 rectly affects that condition, I do not believe the evidence 

 entitles us to say. 



Probably the study of these secretions from the standpoint of 

 osmosis will bring to light facts difficult to reconcile with our 

 present knowledge of osmosis. But while our knowledge of the 

 latter process through membranes undergoing chemical change, 

 such as gland membranes, remains in its present fragmentary 

 state, I do not believe that we are justified in assuming a special 

 sort of secretory activity on the part of the gland, or capillary 

 cell, unless the facts are certainly irreconcilable with any other 

 hypothesis. 



In short, while fully admitting the possibility that nerves may 

 act on gland cells, in some way affecting osmosis through them, 

 it appears to me that, in the present state of our knowledge of 

 secretion, the assumption of a particular secretory function of 



