THE DIGASTRIC MUSCLE. f,01 



ai -terr is now seen. Placed on the outer side of the artery, the 



vein ends below by uniting with the subclaviaii to form the 



innominate trunk. Its proximity to the carotid is not equally 



close throughout, for at the lower part of the neck there is a space is close to 



between the two, in which the vagus nerve is seen crossing (on the J^^f 



right side only) the subclaviaii artery. Sometimes the vein overlaps excep t 



the artery to a considerable extent. \#lo\f : 



The lower part of the vein is marked by a dilatation or sinus. 

 Near its ending it becomes contracted, and is provided with a 

 single or double valve. 



In this part of its course the vein receives the superior and branches, 

 middle thyroid branches. 



Peculiarities of the carotid. The origin of the artery on the right pmerences 

 side may be above or below the point stated. Mention has been 

 made of the difference in the place of bifurcation, and of the fact 

 that the common carotid may not be divided into two. As a very in division, 

 rare occurrence, instead of one there may be two trunks issuing 

 from beneath the hyoid muscles. 



Dissection. The dissector may next trace out completely the Dissection, 

 trunk of the external carotid (fig. 217, p. 603), and follow its 

 branches until they disappear beneath different parts. Afterwards 

 he may separate from one another the digastric and stylo-hyoid 

 muscles, which cross the carotid, and define their origin and 

 insertion. 



The DIGASTRIC MUSCLE (fig. 213, 9 , p. 589) Consists of two fleshy Digastric 



bellies, united by an intervening tendon. The posterior, the t^o bellies 

 larger of the two, arises from the digastric fossa on the inner side 

 of the mastoid process ; while the anterior belly is fixed to the 

 depression by the side of the symphysis of the lower jaw. From 

 these attachments the fibres are directed to the intervening tendon, 

 which is .surrounded by fibres of the stylo-hyoid, and is united by an which are 

 aponeurotic expansion to its fellow and to the body and part of tendon ? & 

 the great coriiu of the hyoid bone. 



The arch formed by the digastric is superficial, except at the position to 

 posterior end, where it is beneath the sterno-mastoid and splenius other l m t s - 

 muscles. The posterior belly covers the carotid vessels and the 

 accompanying veins and nerves ; and is placed across the anterior 

 triangular space of the neck in the position of a line from the 

 mastoid process to the fore part of the hyoid bone. Along its 

 lower border lie the occipital artery and the hypoglossal nerve, the 

 former passing backwards, the latter forwards. The anterior belly 

 rests on the mylo-hyoid muscle. 



The muscle forms the lower boundary of a space between it, the The muscle 

 jaw, and the base of the skull, which is subdivided into two by the ^^f 8 * 

 stylo-maxillary ligament. In the posterior portion are contained containing 

 the parotid gland ( 10 ), and the vessels and nerves in connection ' 

 with it ; in the anterior, are the submaxillary gland ( n ;, with the 

 facial and submental vessels, and deeper still, the muscles between 

 the chin and the hyoid bone. 



Action. The lower jaw being moveable, the muscle depresses Use. 



