654 



DISSECTION OF THE PHARYNX. 



SECTION XL 



Direction. 



Detach 

 pharynx 

 from spine, 



detach 

 head, 



Separate 

 pharynx 

 from verte- 

 bral column 



chisel 

 through 

 basi-occipi- 

 tal, 



direction of 

 a saw-cut, 



complete 

 division 

 with chisel. 



Preserve 

 piece of 

 spine. 



Fasten 

 pharynx, 



then clean 



muscles, 



viz. 



THE PHARYNX AND THE CAVITY OF THE MOUTH. 



Direction. In this section the students of the two sides must work 

 together. 



The pharynx can be examined only when it has been separated 

 from the back of the head and the spinal column ; and it will 

 therefore be necessary to cut through the base of the skull in the 

 manner indicated below, so as to have the anterior half, with the 

 pharynx connected to it, detached from the posterior half. 



Dissection. The head is to be separated from the trunk by 

 sawing through the vertebral column at the third dorsal vertebra 

 unless the dissector of the thorax has already done this in his 

 examination of the ligaments. The block then being removed from 

 beneath the neck, the head is to be placed downwards, so that it may 

 stand on the cut edge of the skull. Next the trachea and oesophagus, 

 together with the vagus and sympathetic nerves, are to be cut near 

 the first rib, and all are to be separated from the spine by drawing 

 them forwards as high as the basilar process of the occipital bone, 

 defining the base of the skull between the pharynx and the pre- 

 vertebral muscles, but being careful not to injure either. Then incise 

 the periosteum on the under surface of the exposed basilar part of 

 the occipital and cut through this part of the bone with a sharp 

 chisel, directing the chisel somewhat backwards as it is driven into 

 the skull cavity a block being placed inside the skull against the 

 base to give the necessary support. Next turn the head on its side 

 and make a saw-cut on each side passing close behind the mastoid 

 process and extending, internally, to the posterior limit of the jugular 

 foramen. The division of the skull will then be completed by 

 chiselling, from within the cranial cavity, backwards through the base 

 between the outer end of the chisel-cut through the basi-occipital 

 and the inner end of the saw-cut behind the jugular foramen, taking 

 care that the chisel passes in this operation on the inner side of the 

 jugular foramen and the inferior petrosal sinus. The base of the 

 skull is now divided into two parts (one having the pharynx attached 

 to it, the other articulating with the spine), which can be readily 

 separated with a scalpel. 



The spinal column with the piece of the occipital bone connected 

 with it should be set aside, and kept for after examination by the 

 workers on the two sides together. 



Dissection of the pharynx (fig. 232, p. 656). Let the student take 

 the anterior part of the divided skull, and, after moderately filling 

 the pharynx with tow, fasten it with hooks on a block, so that the 

 oesophagus may be pendent and towards him. 



He will then proceed to remove the fascia from the constrictor 

 muscles, in the direction of their fibres, and complete the separation 



