'2U 



Mr. J. N. Langley. 



[Mar. 19, 



the effect of apnoea ; during apnoea both the paralytic and the anti- 

 lytic secretions stop. 



The antilytic secretion is, as far as I have observed, solely of 

 central origin, since it ceases on severing the nerves connecting the 

 gland with the central nervous system ; according to Heidenhain, 

 however, it continues after the nerves have been severed. 



The paralytic secretion is only in its early stage of central origin, 

 very soon local changes come into play, rapidly increase in intensity, 

 and continue long after the central changes have ceased to be effective 

 to produce a secretion. Thus, then, the paralytic secretion in its later 

 stages continues undiminished after section of all the sympathetic 

 fibres running to the gland. When the chorda tympani and sympa- 

 thetic fibres are simultaneously cut, the paralytic secretion which 

 follows is of course of local origin only. There are two ways in which 

 the secretion of local origin might be brought about, either by a change 

 in the gland-cells of such a nature that in their abnormal nutritive con- 

 ditions they secrete continuously, or by a change in a local secretory 

 centre analogous to that which takes place in the central secretory 

 centre. Heidenhain is inclined to adopt the former view, and, on 

 general grounds, it does not seem to me unlikely that gland-cells, nor- 

 mally secreting in response to nervous impulses only, should in certain 

 circumstances secrete continuously without such impulses ; but in 

 this particular case there are I think fair grounds for believing that 

 the secretion is caused by nervous impulses sent out by a local se- 

 cretory centre. 



These grounds I will briefly state. On the course of the nerves 

 between the lobes and lobules of the gland there are many nerve- 

 cells. It is highly probable that some at any rate of these nerve-cells 

 are connected with the secretory nerves, since the chorda tympani 

 nerve-fibres, unlike the nerve-fibres of the skeletal muscles and those 

 sweat glands, degenerate very slowly after severance from the central 

 nervous system. In the cat the chorda tympani fibres on the duct, 

 near its entrance into the sub-maxillary gland, produce a secretion 

 when stimulated, two to three weeks after the nerve trunk has been 

 cut.* 



Further, the secretion of local origin is increased by dyspnoea, is 

 stopped by apnoea, and by anaesthetics when given in considerable 

 excess. That is, the paralytic secretion, when it is produced by 



* Pilocarpin causes a secretion for more than six weeks after section of the chorda 

 tympani, but no conclusion with regard to the condition of the nerves can at present 

 be drawn from this, since it is possible that pilocarpin acts directly on the gland- 

 cells. 



During the paralytic secretion produced by section of the chorda tympani, 

 stimulation of sympathetic nerve causes a flow of saliva very much as if the gland 

 were normal. 



