CHANGES DURING SECRETION. 



487 



Three experiments were made ; the chorda tympani was stimulated on 

 the left side. 



Iii these experiments the left gland was the one that was caused to 

 secrete, and there is some reason to think that the left gland is normally 

 heavier than the right, for Bidder found this to be the case in eleven 

 cases, and Heidenhain in two. 1 Pawlow, 2 however, noticed no appre- 

 ciable difference in the amount of nitrogen contained by ten right 

 and by ten left subniaxillary glands of the dog. But so long as it is not 

 shown that the right gland may be normally heavier than the left, we 

 may fairly conclude that there is a loss of weight by the gland during 

 secretion and a gain of weight during rest. 



The question may be approached from another side. Microscopical 

 examination shows decisively that during secretion the gland cells 

 become smaller ; they must then, taken together, decrease in weight 

 unless the percentage of solids in them increases. But, according to 

 Heidenhain, the percentage does not increase during secretion ; on the 

 contrary, it decreases. Thus, in one experiment upon a dog, in which 

 about 220 c.c. of saliva were obtained by stimulating the chorda tympani, 

 the percentage of solids in the resting gland was 2 8 '3 per cent., and in 

 the stimulated gland it was only 21 '3 per cent., so that there were 7 per 

 cent, less solids on the stimulated side. 



This, it must be remembered, applies to the gland as a whole. In con- 

 cluding that there is a decrease in the percentage of solids in the actual gland 

 cells, we assume that the percentage composition of the glands on the two sides 

 is approximately the same, that there is no appreciable difference in the amount 

 of blood and lymph upon the two sides, and that the connective tissues in the 

 gland are too small in amount or too constant in composition to affect the result ; 

 these assumptions, however, appear to be justifiable. 



The other experiments made by Heidenhain 3 were as follows : 



1. The left chorda tympani was stimulated and 75 c.c. of saliva obtained. 

 The right subniaxillary gland contained 23 per cent, of solids, the left gland 

 18 '6 per cent. a decrease of 4 '4 per cent. 



2. The left chorda tympani was stimulated and 55 c.c. of saliva obtained. 

 The right subniaxillary gland contained 24 per cent, of solids, the left gland 

 21 '5 per cent. a decrease of 3 '5 per cent. 



Heidenhain found a slight decrease also in the percentage of solids on 

 stimulating the cervical sympathetic. 4 The time of stimulation is given, but 

 not the amount of saliva obtained. 



1 Op. tit., p. 57. 



2 Centralbl. f. PhysioL, Leipzig u. Wien, 1888, S. 137. 



3 Stud. d. physiol. Inst. zu Brcslau, Leipzig, 1868, Heft 4, S. 55. 



4 Op. tit., p. '66. 



