Phatyu.r 137 



focation by blocking the laryngeal opening, or by setting up a spasmodic 

 contraction of the muscles which close it. 



The finger, thrust directly backwards along the dorsum of the 

 tongue, comes in contact with the body of the axis, and, when slanted 

 slightly upwards, with the anterior ring of the atlas. On thrusting it 

 somewhat downwards the body of the third vertebra is touched. 



In the case of fracture or displacement of any one of these three 

 vertebrae valuable information may be obtained by digital exploration 

 through the mouth. 



Relations of the pharynx. Behind are the vertebral column 

 with the longus colli and rectus anticus major, and the layer of 

 prasvertebral fascia. Suppuration in this region constitutes post- 

 pharyngeal abscess (p. 210). 



Laterally are the sterno-mastoid, the lobe of the thyroid, the com- 

 mon, internal, and external carotids ; the lingual artery ; the internal 

 jugular vein; and the vagus, glosso-pharyngeal and hypoglossal nerves. 



Infro7it are the nares, mouth, tongue, hyoid bone, and larynx. 



. The imiscular coat consists of three constrictors, which are gener- 

 ally described from below upwards, because the lowest is the most ex- 

 ternal. They are of striated tissue. 



The inferior constrictor, the thickest of the three, arises from the 

 side of the cricoid cartilage, and from the thyroid cartilage behind 

 the oblique line. Its lowest fibres are continuous with those of the 

 oesophagus, and beneath them ascends the recurrent laryngeal nerve 

 (p. 70) ; the other fibres pass upwards and inwards to the median 

 raphe over the lower part of the middle constrictor. 



The middle constrictor arises from the greater and lesser cornua 

 of the hyoid bone, and is inserted into the median raphe. Its lowest 

 fibres pass beneath the inferior constrictor, and its highest over those 

 of the superior constrictor, from which it is separated by the stylo- 

 pharyngeus. As the inferior constrictor arises from the thyroid carti- 

 lage, and the middle arises from the hyoid bone, the superior laryngeal 

 nerve, which traverses the thyro-hyoid membrane, necessarily passes 

 between their adjacent borders. 



The superior constrictor arises from the internal pterygoid plate, 

 and from the pterygo-maxillary ligament, which takes it to the mylo-hyoid 

 ridge, from which also it arises, as well as from the side of the tongue. 

 The fibres curve backwards to be inserted into the median raphe. 



Just beneath the base of the skull, where muscular fibres could be 

 of no use, the superior constrictor is deficient ; thus, above the upper 

 border of the muscle there is a gap, the sinus of Morgagni, through 

 which the levator palati, the Eustachian tube, and branches of the 

 ascending pharyngeal artery enter the pharynx. 



The plan of the pharynx is like that of the canvas * wind-sail ' 

 which is used on board ship to carry fresh air into the hold it is closed 

 at the top and sides, whilst its anterior part is held wide open by being 



