320 MATHEWS. 



quinine, or atropin, or compression of the gland's artery, liquid 

 is prevented from entering the gland. A few stimulations of 

 the sympathetic suffice to expell all, or most, of the available 

 saliva in the gland, and the nerve thereafter appears paralyzed. 

 If, now, the ducts and alveoli be passively redistended by the 

 injection of liquid into the duct the nerve again causes a 

 compression of the duct, and the fluid is again expelled and gives 

 a secretion. This renewed secretion cannot, however, be re- 

 ferred to the action of the gland cell, because the latter has been 

 in one case paralyzed by the action of quinine, and in the other 

 case by suffocation. Nor could it be referred to the action of 

 the cell, even were the latter not paralyzed, for the mere hypo- 

 thetical taking-up of fluid into the cell from the duct, and its 

 discharge again into the latter, would in no way alter the bulk 

 of fluid in the ducts plus the bulk of the cell. There would, 

 hence, be no pressure to drive the secretion from the gland. 



e. The Character of Sympathetic Saliva. 



Evidence that the sympathetic nerve innervates the gland cell 

 has been derived from the character of the sympathetic saliva. 

 This, as is well known, is richer in organic matters than the 

 saliva secreted under the influence of the gland's dilator nerve. 

 This greater richness Heidenhain attributes to the predominance 

 in this nerve of so-called '' trophic " fibres, the function of w^hich 

 is to render the stored-up metabolic products of the cell (hylo- 

 gens) more soluble, and the juice consequently more concen- 

 trated. This assumption involves such consequences that by 

 common consent it has been considered the most unsatisfactory 

 part of the Heidenhain theory. It is, however, practically the 

 only probable explanation, wath one exception, which has been 

 offered. The exception is the view suggested by Schiff, dis- 

 cussed below. 



If the sympathetic simply drives out the saliva already present 

 in the gland the sympathetic saliva must be of the character of 

 that present in the ducts and alveoli at the moment of stimulation. 

 There is evidence that this is the case. That the saliva in the 

 ducts of the dog's parotid is very viscid has been shown by 



