152 APPENDIX 



class-room the vago-sympathetic is necessarily exposed when the carotid is ligated ; one can 

 then usually note whether the nerve-trunk is obviously three-stranded and if it is so allocate 

 the preparation for this exercise. If the student fail to distinguish the depressor nerve as a 

 separate branch, the closely similar depressor effect from stimulation of the vagus trunk 

 below its superior laryngeal branch attains practically the same object for him, especially 

 after paralysing the cardio-inhibitory efferent endings with atropine. 



EXERCISE XV 



Obs. 73. The raising of the pelvis somewhat above the table-top by placing a support 

 (hot-water bottle) under it greatly lessons the risk of venous bleeding during the lateral 

 widening of the laminectomy wound. Such bleeding can seriously impede the dissection by 

 obscuring the nerve-roots ; with the above precaution very little bleeding occurs. 



Obs. 74. The employment of Galvani's experiment with metals for diagnosing rapidly 

 between efferent and afferent roots in the cauda equina region after the dural theca has been 

 opened is often helpful to those tracing the roots for the first time. 



EXERCISE XVI 



Obs. 76. This takes advantage of the fact that the ganglion and junction of the dorsal 

 and ventral roots of 2nd cervical nerve lie outside the vertebral canal. They can therefore 

 be exposed with minimal exposure of the spinal cord itself. Risk of cooling and of other- 

 wise damaging the cord is thus lessened, with avoidance of the consequent depression of the 

 reflex reactions, a likely source of failure in the reflex part of the previous exercise. 



The tracheal cannula is introduced far back, close to the sternum, to escape the neck-block 

 on which the neck-stump rests, which will otherwise interfere with the air-supply to the 

 chest. 



In decerebrating for this exercise the pinnae and occipital skin should, when the animal 

 is fixed in the decerebrator, be drawn backward as far as practicable. Retraction of the pinnae 

 is favoured by a transverse skin incision through the scalp across the posterior end of the 

 median longitudinal scalp incision made for decerebration. 



EXERCISE XVII 



Obs. 78. In making the decerebrate preparation the pinnae should be preserved as for 

 exerc. XVI. A small animal, not black-haired, is preferable. 



Obs. 80. For Bayliss's gum-saline gum-acacia may be used, if desired, instead of gum- 

 arabic. A suitable gum-acacia is that sold as ^Turkey-elect', but any clean variety will 

 serve. Tap-water can be used for dissolving. 



EXERCISE XVIII 



Obs. 84. An occasional source of trouble is a '■ spontaneous ' twitching of the tibialis 

 muscle which may arise in the reflex stage of the exercise. 



It might be thought that the tendons of extensor longus digitorum and peroneus longus 

 should be severed in order to avoid complication of the tibialis record. Experience shows 



