THE PARALYTIC SECRETION. 521 



The peripheral nerve-cells 1 in connection with the gland may be 

 spoken of as a local nerve-centre. This local centre is capable of 

 exciting the gland-cells to activity long after the chorda tympani, which 

 normally conveys impulses to it from the central nerve-centre, has 

 degenerated. 



Heidenhain suggested that the paralytic secretion might be due to a 

 stimulation of the gland-cells by the decomposition products of the 

 stagnating saliva. He observed that if the duct were clamped for about 

 a day, a slow secretion of watery saliva ensued. The cases, however, are 

 hardly comparable, inasmuch as, whilst the duct is closed, secretion is 

 formed which partly distends the alveoli and partly is forced out of the 

 ducts and lumina, and bathes all the tissues of the gland. 



A final explanation can hardly yet be given, but some observations 

 made on the cat lead me to think that the secretion is the result of 

 nervous stimuli. In the cat the paralytic secretion is much diminished 

 and even stopped by excess of chloroform and by apnoea ; and is 

 increased markedly by dyspnoea ; the dyspnoeic flow takes place more 

 readily than on the opposite side, and, so far as can be judged, more 

 readily than in a normal gland. These results indicate that the 

 paralytic secretion is due chiefly, at any rate, to a slight continuous 

 excitation of the local nerve mechanism. 



Heidenhain found that the paralytic secretion also occurred in the dog, 

 when the superior cervical ganglion was excised at the time of section of 

 the chorda. In this case the secretion is due wholly to local changes. 

 In the early stage of secretion in the cat, three days after section of the 

 chorda alone, I noticed that section of the cervical sympathetic very 

 much diminished or even stopped both the paralytic secretion and the 

 dyspnoeic secretion, although, in the later stages, section of the cervical 

 sympathetic had little or no effect. Probably, then, if the sympathetic 

 is intact, the secretion which occurs in the first few days after section of 

 the chorda is largely due to impulses travelling down the sympathetic 

 from the central nervous system. 



The loss of weight which occurs in the submaxillary and the sub- 

 lingual glands, after section of the chorda tympani, amounts in a few 

 weeks to one-third to one-half of the original weight of the glands. 

 Bradford has shown that section of Jacobson's nerve causes a similar 

 loss of weight in the parotid gland 2 of the cat. Whether complete 

 atrophy takes place, and if so what time it requires, there is no evidence 

 to show. 



In the submaxillary gland, and no doubt in the others also, the loss 

 of weight is due to a loss of cell substance by the individual cells. And 

 this loss is simply an instance of the gradual atrophy which occurs in 

 tissues in the absence of functional activity. The persistent slight 

 activity, of which the paralytic secretion is the sign, is quite insufficient 

 to replace the normal exercise' of function. 



In the dog, according to Heidenhain, the paralytic gland contains a 

 number of alveoli, presenting the appearance of the alveoli of an active 

 gland. In my experiments, both on the dog and cat, the gland-cells were 

 undoubtedly in the resting state. In the cat the saliva obtained by 



1 Six weeks after section of the chorda in the cat, when the submaxillary gland had lost 

 one-third to one-half of its weight, the nerve-cells in the alcohol-hardened gland presented 

 no certain difference from the nerve-cells of the gland of the opposite side. 



- Bradford did not observe a paralytic secretion from the parotid. 



