336 MATHEWS. 



during a weak stimulus is derived from a portion of the gland 

 only in the following manner : Let us stimulate the chorda nerve 

 carefully with a very weak current, until a large amount of se- 

 cretion has been obtained. If this secretion has been derived 

 from the whole gland a stronger stimulus should yield a se- 

 cretion much less concentrated than a stimulus of equal strength 

 before the weak stimulus. The glands should show, in other 

 words, a considerable exhaustion of the gland products. If, on 

 the contrary, the whole of this secretion has been derived from 

 a portion only of the gland the rest of the alveoli must remain 

 practically unaltered, and a stronger stimulus arousing these 

 should yield a juice, little, if any, poorer in organic matters than 

 was yielded by a stronger stimulus before the weak. 



Werther^'^ has unintentionally tried this experiment and found 

 the latter possibility to be what actually occurs. A very weak 

 stimulus, with the secondary coil at 300-240 mm., was em- 

 ployed for over three hours, and more than 20 cc. of saliva 

 were secreted. The percentage of organic solids secreted in the 

 slowly flowing saliva steadily fell, but the percentage of such 

 bodies in the saliva secreted on a succeeding stronger stimulus 

 was little if any less, after this long secretion, than it was with 

 an equally strong stimulus before. If, however, a somewhat 

 stronger stimulus was employed, the secretion from a still 

 stronger stimulus was much poorer in organic solids, than the 

 similar stimulus before the weak. 



The fact that rapidly secreted saliva is not a pure solution, 

 and the considerations just presented concerning the independ- 

 ence of the alveoli of the gland render this observatoin of Hei- 

 denhain of doubtful value as evidence of the existence of se- 

 cretory nerves. 



Moreover, there is good reason for doubting the truth of 

 Heidenhain's statement, in the quotation on page 333, that the 

 liquid derived from the blood is incapable of dissolvmg the con- 

 stituents of the cells in the absence of nerve influence. As has 

 already been pointed out, in treating of sympathetic saliva, 

 (page 322), if the thin chorda saliva be simply left in the gland 

 for twenty minutes, or more, it is converted into a dense, vis- 



