172 



A MANUAL OF PHYSIOLOGY 



vagus crosses diagonally between them (Fig. 63). Above the vagus 

 trunk, running parallel to it, and separated from it by a thin muscle 

 and a blood-vessel (the carotid artery), lies its laryngeal branch. The 

 vagus should be traced up to the ganglion situated on it near its exit 

 from the skull. 



(2) Then cut away the lower jaw, dividing and reflecting the 

 membrane covering the roof of the mouth. At the junction of the 



n 



FIG. 62. ARRANGEMENT KOK. RECORDING AURICULAR AND VENTRICULAR 

 CONTRACTIONS (AND STUDYING THE INFLUENCE OF TEMPERATURE ON 

 THE HEART). 



C, clamp holding the heart at the auriculo-ventricnlar groove. P, pulley round 

 which a thread attached to the apex of the ventricle passes to the lever L'; L, lever 

 connected with auricle. (The rest of the arrangement is for studying the influence of 

 temperature on the heart and its nerves, G being a vessel filled with normal saline 

 solution in which the heart is immersed ; R. an inflow tube from a reservoir containing 

 salt solution at the temperature required ; O', an outflow tube by which G may be 

 emptied into the beaker B' ; O, a tube passing to the beaker B to prevent overflow from 

 G ; T, a thermometer. ) 



skull and the backbone will be seen on each side the levator anguli 

 scapulae muscle (Fig. 64). Remove this muscle carefully with fine 

 forceps. Clear away a little connective tissue lying just over the upper 

 cervical vertebrae, and the sympathetic chain, with its ganglia, will 

 be seen. Pass a fine silk thread beneath the sympathetic about the 

 level of the large brachial nerve, by means of a sewing-needle which 

 has been slightly bent in a flame and fastened in a handle. Tie the 



