398 THE RESPIRATION 



and dilatation of the artery occurs, although on blood vessels alone 

 epinephrine in similar dosage produces constriction. Of course in show- 

 ing that local chemical products of activity serve as the excitant of local 

 dilatation, we do not mean to imply that the vasodilator fibers going to 

 the blood vessels are of no use. Indeed we know that such fibers do be- 

 come active in the case of a salivary gland whose cells have been para- 

 lyzed by atropine, but it is a significant fact that this dilatation is of rela- 

 tively short duration, whereas that produced by glandular activity lasts 

 for some time. The suggestion seems therefore not out of place that un- 

 der normal conditions the initial dilatation of an acting gland may be 

 brought about through nervous stimuli, but the later dilatation is main- 

 tained by metabolic products. 



