xi PRACTICAL DIRECTIONS 551 



Sketch the heart and origins of the main vessels. 



III. Now dissect out certain of the nerves and other structures in the 

 neck, as follows : 



1. The vagiis (Fig. 135), running to the outer side of each common 

 carotid : with the seeker carefully separate it from the carotid, and trace 

 it forwards to the angle between the head and neck at which point it 

 enlarges to form a ganglion, and backwards to the thorax. Branches are 

 given off to the larynx (anterior and posterior or recurrent laryngeal 

 nerves] and to the heart (depressor] nerves, but the dissection of these 

 may be omitted by the beginner. 



2. The sympathetic (Fig. 135), running on the dorsal side of the 

 carotid artery. This is most easily distinguished by seizing the carotid 

 with the small forceps just at the junction of the head and neck and 

 putting it slightly on the stretch : the vagus ganglion will then be seen 

 on the outer side of the artery, and the more elongated anterior cervical 

 ganglion of the sympathetic on its inner side : trace the sympathetic 

 nerve from this ganglion backwards to the thorax, at the anterior end 

 of which (close to the subclavian artery) it enlarges to form \\\z posterior 

 cervical ganglion, and then becomes continuous with the thoracic portion 

 of the cord. 



3. The hypoglossal nerve will be seen at about the level of the vagus 

 ganglion, passing forwards to the tongue. 



4. Note a, the thyroid gland ; b, the thyroid and cricoid cartilages of 

 the larynx ; c, the brachial and vertebral branches of the subclavian 

 artery ; and d, the brachial plexus (p. 532). 



IV. Remove the heart and lungs from the body, together with the 

 posterior end of the trachea and recognisable portions of the aorta, 

 precaval, and postcaval. Fasten out the organs under water with their 

 ventral surface uppermost, and after making out the course of the pul- 

 monary arteries and veins, cut through them close to the lungs and 

 separate the latter from the heart. Note : 



1. The two main lobes of each lung and the two accessory lobes on the 

 right side. 



2. The cartilages of the trachea and bronchi ; trace the bronchi for a 

 short distance into the lungs. Sketch. 



V. Cut away the outer walls of both auricles so as to expose their 

 cavities, taking care not to injure the veins which enter them. Wash 

 out the contained clots of blood, and note 



i. a, The appendix of each auricle, and the network of muscular 



