ELEMENTARY DEMONSTRATIONS 155 



gland appear in the upper part. The gland itself lies a little more 

 to the back. 



On exciting the cervical sympathetic, or the sympathetic nerve 

 filaments which accompany the artery of the gland, the gland will 

 pale owing to vaso-constriction. A little thick secretion will at the 

 same time appear in the cannula. On exciting the chorda tympani, an 

 abundant secretion of thin watery saliva appears. At the same time 

 the gland becomes red and turgid. The same effect may be produced 

 reflexly by excitation of the central end of the lingual nerve. 



The submaxillary gland is enclosed in a firm capsule. It is fed by a 

 branch of the external maxillary artery which enters the hilus of the 

 gland. The gland also receives small branches from the great or 

 posterior auricular artery. The veins are usually two, but are variable. 

 One enters the internal and the other the external maxillary vein close 

 to where these veins join to form the external jugular vein. The blood 

 coming from the salivary gland can be collected by tying a cannula 

 in the external jugular vein and ligating all branches excepting those 

 coming from the gland. The exchange of blood-gases in the gland can 

 thus be determined. 



Nicotine, 30-40 mgrms. in dog, 10 mgrms in cat, injected intra- 

 venously, paralyses the preganglionic fibres of the chorda tympani for 

 about 15 minutes. The ganglion cells of the submaxillary gland are in 

 or near the hilus of the gland. 



Atropine sulphate, 10-14 mgrms. in dog, 5-15 mgrms. in cat, injected 

 into the blood paralyses the secretory fibres of the chorda tympani, 

 while it leaves the vaso-dilator fibres untouched. Pilocarpine nitrate, 

 1-2 mgrms, produces prolonged and plenteous secretion. The anta- 

 gonism may be shown by injecting atropine into the blood and then 

 injecting a little 2 per cent, solution of pilocarpine into the gland by 

 way of the duct cannula. 



If the duct cannula is connected with a mercury manometer and the 

 chorda tympani stimulated, the secretory pressure will be observed to 

 rise higher than the pressure in the carotid artery. 



The submaxillary gland can be placed in a plethysmograph and its 

 volume recorded (Bunch). Stimulation of the cervical sympathetic 

 causes very considerable diminution in volume and a scanty secretion. 

 Excitation of the chorda tympani is followed by diminution in volume 

 in spite of vaso-dilatation. This is due to the copious secretion. 

 After injection of atropine the volume is increased by chorda excitation. 

 If a cannula be placed in the cervical lymphatic just above where it 

 enters the thoracic duct the effect of stimulating the salivary gland on 

 the outflow of lymph can be observed (Bainbridge). 



