SECRETION PHYSIOLOGY. 337 



cous fluid having all the characteristics of sympathetic sahva. 

 This conversion takes place with equal readiness whether the 

 gland nerves be intact or divided. 



Heidenhain's own explanation, also, will be found on an- 

 alysis, I believ^e, to involve such assumptions as to arouse seri- 

 ous doubt of its truth. To explain this phenomenon on the 

 basis of secretoiy cell activity, he assumed separate "trophic" 

 nerve fibers acting on the cells. He thus necessitated the im- 

 probable conclusion, that at least many of the cells of the sub- 

 maxillary gland received at least four different nerve ends, i. c, 

 trophic and secretory of the sympathetic, and trophic and secre- 

 tory of the chorda ; and at least two entirely different nerve 

 impulses, /. c\, trophic and secretory. That such a conse- 

 quence should not have aroused suspicion in his own mind of 

 the truth of his explanation is difficult to understand. 



b. Post-mortem Chorda Salivary Secretion. 



Another strong argument that the chorda does not produce 

 its secretion by its dilator action on the blood vessels, but by di- 

 rect action on the gland cell, has been derived from the so-called 

 post-mortem chorda secretion. Ludwig and Heidenhain found 

 that if the gland's artery be completely closed, or if the head be 

 rapidly cut off, and the chorda at once stimulated, a fairly copious 

 secretion ensued. This secretion was most abundant in the first 

 minute after section, and thereafter rapidly diminished, but a lit- 

 tle could still be obtained four, and in some cases five, minutes 

 after decapitation, or compression of the artery. Thereafter the 

 nerve was ineffectiv^e. Heidenhain believed this secretion to be 

 due to the action of the nerve on the gland cell, and its rapid fail- 

 ure to lack of oxygen and water. Both Ludwig and Heidenhain 

 beheved that by the conditions of the experiment they entirely 

 eliminated the factor of the nerve's vaso-motor action, and hence 

 thought it demonstrative evidence that the secretory and dilator 

 functions of the nerve were independent. 



I think it may be questioned, however, whether the condi- 

 tions of the experiment do entirely obviate the vaso-motor action 

 of the nerv^e, and whether it is not still possible that this dila- 



