OUTLINES OF ANATOMY. 



line drawn downward from it. The portion in front has a distinct floor, composed, in 

 great part, by the mylo-hyoid muscle, and behind this by a portion of the hyo- 

 glossus muscle. 



The parts exposed during the dissection of the digastric space may be classified 

 according to the subdivision in which they lie : 



ANTERIOR PART. 



1. Submaxillary gland. 



2. Facial artery and vein. 



3. Branches from -v a. Ascending palatine. 



facial artery f b. Tonsillitic. 

 in this part \ c . Submaxillary. 

 of its course. ; d. Submental. 



4. Hypoglossal nerve. 



5. Mylo-hyoid nerve. 



6. Mylo-hyoid artery. 



7. Lymphatic glands. 



POSTERIOR PART. 



1. Portion of the parotid gland. 



2. External carotid artery. 



3. Posterior auricular artery. 



The most conspicuous object in the fore part of the digastric triangle is the sub- 

 maxillary gland. The facial artery passes upward and forward in the midst of this 

 gland, whilst the facial vein lies superficial toil. But whilst the facial artery runs 

 through the gland, the dissector should note that it can be separated from it with- 

 out any laceration of the gland lobules. The gland is, as it were, wrapped round it, 

 so that, although at first sight the artery seems to pierce it, it is in reality merely 

 contained in a deep furrow in its substance. Before entering the gland, the facial 

 artery gives off its tonsillitic and ascending palatine branches, whilst its submental 

 and Submaxillary branches arise within the gland. The submental artery runs for- 

 ward toward the chin. The mylo hyoid nerve and artery will be seen passing for- 

 ward and downward upon the mylo-hyoid muscle under cover of the Submaxillary 

 gland. The twigs of the nerve to the muscle of the same name and to the anterior 

 belly of the digastric should be followed out. Only a very small part of the hypo- 

 glossal nerve is seen in this space. It lies upon the hyoglossus muscle immediately 

 above the hyoid bone, and disappears under cover of the posterior border of the 

 mylo-hyoid muscle. Numerous small lymphatic glands lie under shelter of the base 

 of the lower jaw. 



The external carotid artery enters the posterior part of the digastric triangle. 

 Here it lies under cover of the lower part of the parotid gland, and gives off its 

 posterior auricular branch, which passes upward and backward along the upper 

 border of the posterior belly of the digastric muscle. 



Middle Line of the Neck. Before the parts are further disturbed the dissector 

 should examine the structures which occupy the middle line of the neck a region, 

 more especially in its lower part, of the highest importance and interest to 

 the surgeon. The middle line of the neck may be divided by means of the hyoid 

 bone into an upper supra-hyoid and a lower infra-hyoid portion. 



In the supra-hyoid part are found structures which are concerned in the construc- 

 tion of the floor of the mouth. The student has already noticed that the fatty 

 superficial fascia is more fully developed here than elsewhere in the neck, and that 

 the anterior margins of the two platysma muscles meet in the mesial plane about half- 

 an-inch or so below the chin. Above this point their fibres decussate. In the pres- 

 ent condition of parts the two anterior bellies of the digastric muscles are observed 

 attached to the mandible on either side of the symphysis. From this they descend 

 toward the hyoid bone, and diverge slightly from each other so as to leave a narrow 

 triangular space between them. The floor of this space is formed by anterior portions 

 of the two mylo-hyoid muscles, whilst bisecting the triangle in the mesial plane in 

 the fibrous raphe, into which these muscles are inserted. Not unfrequently the inner 

 margins of the digastric muscles send decussating fibres across the interval between 

 them. 



The infra-hyoid part of the middle line of the neck extends from the hyoid bone 



