THE HEAD AND NECK, POSTERIOR, 141 



separate parts usually described are only so separated 

 by anatomists for convenience of description, and that such 

 divisions do not exist as separate from the other parts or 

 layers, but that all are united into a complicated whole. 



The influence that the cervical fascia has upon determin- 

 ing the course of certain surgical affections, as abscesses 

 and tumors, is a good deal more theoretical than real. 

 It is found in practice that abscesses from cervical caries 

 may descend into the thorax, but usually will point along 

 the lateral region of the neck if above the sixth cervical 

 vertebra. The postpharyngeal abscess will usually point 

 in the pharynx. Abscesses in the lower part of the neck, 

 unless behind the third layer of fascia, will usually point 

 above the clavicle or sternum. 



The Pharynx (concluded), Larynx, and Nasal Fossae. 



DISSECTION. 



The dissection of the back of the neck having been completed, the remain- 

 ing muscles which hold the head to the spine should be severed, and the skull 

 separated from the atlas by the division of the connecting ligaments, or the skull 

 should be sawn transversely across in front of the foramen magnum. The 

 trachea should be separated from the larynx by dividing it just below the cri- 

 coid cartilage and the oesophagus cut across at the same level. Now remove 

 the head and attached portions of the pharynx, larynx, and the arteries, veins, 

 and nerves, which emerge from the base of the skull. 



Identify all those structures which have been found already in the dissec- 

 tion of the deep neck. 



Divide the pharynx along the median raphe and open its cavity. 



The Structures seen on Opening- the Pharynx. 



Posterior nares, separated by the vomer, and within 

 which can be seen the posterior extremities of the middle 

 and inferior turbinated bones. 



The opening 1 for the Eustachian tube is behind the 

 lower portion of the posterior nares ; it leads into the middle 

 ear. 



