DIGESTION 367 



Indeed, the distinction between chorda and sympathetic 

 saliva, which, by taking account of the parotid as well as the sub- 

 maxillary and sublingual glands, has been generalized into a dis- 

 tinction between cerebral and sympathetic saliva, and which, 

 when the vasomoior conditions are left out of account, appears 

 to hold good in the dog and the rabbit, breaks down before a 

 wider induction. For in the cat the sympathetic saliva of the 

 submaxillary gland, although much more scanty, is more watery 

 than the chorda saliva (Langley), which, however is by no means 

 viscid ; and the two secretions differ far less than in the dog. 

 The discovery of Carlson that the cat's cervical sympathetic 

 contains so many vaso-dilator fibres for the submaxillary gland 

 that the usual effect of its stimulation with a weak interrupted 

 current is a marked augmentation in the blood-flow affords an 

 explanation. In accordance with this functional similarity, 

 there is a much smaller difference in the action of atropine on 

 the two sets of fibres in the cat than in the dog, although even 

 in the cat the sympathetic is less readily paralyzed than the 

 chorda. 



In their secretory action there is not even an apparent anta- 

 gonism in the cat, with minimal stimulation of both nerves, which 

 causes as much secretion as would be produced if both were 

 separately excited. Further, even in the dog, after prolonged 

 stimulation of the sympathetic, the submaxillary saliva is no 

 longer viscid, but watery, the proportion of solids, and especially 

 of organic solids, being much lessened, as it is also in chorda 

 saliva after long excitation. When the cerebral nerve of 

 the resting gland is strongly excited, it is found that up to a 

 certain limit the percentage of organic matter in a small sample 

 of saliva subsequently collected during a brief weak excitation 

 increases with the strength of the previous stimulation ; this is 

 also true of the inorganic solids. But there is a striking difference 

 when the experiment is made on a gland after a long period of 

 activity ; here increase of stimulation causes no increase in the 

 percentage of organic material, while the inorganic solids are still 

 increased. In both cases the absolute quantity of water, and 

 therefore the rate of flow of the secretion, is augmented. 



All this points to the same conclusion as the microscopic 

 appearances in* the gland-cells, that the cells during rest manufac- 

 ture the organic constituents of the secretion, or some of them, 

 and store them up, to be discharged during activity. The water 

 and the inorganic salts, on the other hand, seem rather to be 

 secreted on the spur of the moment, so to speak, and not to require 

 such elaborate preparation. And it has been stated that when 

 the chorda tympani is stimulated with currents of varying 

 strength, the quantity of organic substances in small samples ot 



