BY DR. LAUDER BRUNTOX. 471 



the duct with a- pair of fine forceps while the operator lays 

 hold of the other just over the splinter of wood on which 'it 

 rests; open the duct between them with sharp-pointed scif 

 Insert the canula into the duct and tie it in. 15. Put a liga- 

 ture round the jugular vein half an inch or an inch below its 

 bifurcation, so as to be able readily to introduce into it a 

 canula when necessary. 



In the preceding directions, all the steps of the operative 

 procedure required for the complete investigation of the func- 

 tions of the submaxillary gland during life are detailed. The 

 method may. however, be modified, according as it is intended 

 to limit the observation to the influence of direct or reflex ex- 

 citation of chorda tympani on the secretion of the gland, or to 

 extend it to this investigation of the vascular changes and to 

 the functions of the vascular nerves. 



93. Direct and Reflex Excitation of the Chorda 

 Tympani. Proceed as above directed, omitting 13 and 15. 

 2, 3, and 4 may also be omitted, provided that all such veins 

 as are necessarily involved in the succeeding steps are doubly 

 ligatured and divided between the ligatures. Reflex Excitation. 

 Divide the lingual nerve close to its entrance into the mouth, 

 and excite its central end with the secondary coil at a con- 

 siderable distance from the primary. The secretion of saliva 

 is increased. The animal must previously be allowed to recover 

 from the chloroform, or no increase will be observed. The 

 reflex action of the lingual is abolished during narcosis by 

 opium, as well as by chloroform. ** Direct Excitation. Divide 

 the chorda close to the point at which it leaves the lingual, and 

 place the peripheral cut end on theexcitor (fig. 225), removing 

 the secondary coil to a considerable distance from the primary. 

 On opening the ke} r , saliva is discharged from the canula (to 

 which an end of India-rubber leading into a test-tube has been 

 fitted). It begins to flow a few seconds after the excitation, 

 but not immediately. By repeating the excitation at regular 

 short intervals, the discharge can be maintained, and a con- 

 siderable quantity collected. 



** 94. Demonstration that the Pressure produced 

 by Secretion in the Duct of the Submaxillary Gland 

 when it is Obstructed is greater than the Arterial 

 Pressure. A canula having been placed in the carotid of the 

 opposite side of the body and connected with a mercurial ma- 

 nometer, a second manometer is connected with the canula in 

 the duct of the gland. The pressure indicated by the latter 

 gradually increases until it attains a height greater than that 

 indicated by the former. In this experiment it is desirable 

 that the tube of the manometer connected with the duct should 

 be narrow. Its proximal arm should be connected by a side 

 opening with a pressure bottle at a height of about four feet 



