Fig. 63 (1), of the seventh pair. The branches of the facial have been noticed in the description of the Parotid and Masseteric regions. Those of the fifth pair are the terminal branches. of the inferior dental, the buccal, the infra-orbital, and the nasal. The inferior dental comes through the mental foramen, which is situated just below the second bicuspid tooth; the buccal enters the buccal region behind the anterior border of the masseter; the infra-orbital emerges from the infraorbital foramen in the upper part of the canine fossa; the nasal comes from the inner canthus of the eye, and from the junction of the lower end of the nasal bone with the cartilage.

To dissect these parts, the skin must be reflected forwards to the median line, and upwards as far as the root of the nose and the attached border of the lower eyelid.

The PLATYSMA MYOIDES is lost in the lower part of the face. The posterior fasciculi which cover the facial artery and the lower portions of the parotid gland and masseter muscle, terminate in the subcutaneous areolar tissue and a fasciculus which turns forwards towards the angle of the mouth, called by Santorini the risorius novus. The middle fasciculi blend with the depressor anguli oris and depressor labii inferioris muscles. The anterior fibres mix with those of the opposite side.

The superficial fascia may now be removed in detached portions while exposing the muscles, arteries, and nerves.

The facial artery, Fig. 1(10), is subcutaneous throughout its whole course, except where it passes beneath the zygomatici major and minor muscles, and can be easily traced. Its branches, consisting of the masseteric, mental, inferior and superior coronary and nasal, are irregular in their origin, and must be looked for as the main trunk is dissected from below upwards. The position of the facial artery where it rests upon the inferior maxilla should be noticed, as pressure applied to it at this point will arrest hemorrhage from it or any of its branches.

The ORBICULARIS ORIS, Fig. 61 (13), is situated in the lips, the principal part of which it forms. It consists of two fasciculi, one for each lip. These blend at the angles of the mouth with the buccinators, and other muscles inserted at these points. To dissect this muscle, the lips must be made tense. Its external surface is mixed, more or less, with fat,

and adheres closely to the skin. The labial glands are placed between its inner surface and the mucous membrane. Its action is to close the mouth, and antagonize the muscles inserted into the lips.

The DEPRESSOR ANGULI ORIS, or TRIANGULARIS, Fig. 61, arises from a ridge on the outer surface of the inferior maxilla, between the insertion of the masseter and the mental foramen. The fibres converge, pass upwards, and are inserted into the angle of the mouth. It partly overlaps the depressor labii inferioris and buccinator muscles, from which it is readily distinguished by the different direction of their fibres. It depresses the angle of the mouth, as its name indicates.

The DEPRESSOR LABII INFERIORIS, or QUADRATUS MENTI, Fig. 64 (10), arises from the base of the inferior maxilla, commencing near the symphysis of the chin, and extending outwards a short distance beneath the preceding muscle. Its fibres pass upwards and inwards, and are inserted into the orbicularis and skin of the lower lip. It is difficult to make a clean dissection of this muscle, on account of the adipose substance mixed with its fibres. The terminal branches of the inferior dental artery and nerve emerge from the mental foramen under this muscle. By detaching a small portion of the muscle from its origin below the second bicuspid, and raising it up, the foramen will be found and the nerve escaping from it. From this point its branches can be easily traced upwards to the skin and mucous membrane of the lip, and upwards and outwards where they interlace with the facial nerve, to form the mental plexus. This nerve is sensor, and supplies, besides the lips, the lower and inner part of the face generally.

The LEVATOR LABII INFERIORIS, or LEVATOR MENTI, Fig. 64 (11), is situated between the mucous membrane and the last muscle. It arises from the alveolar process opposite the incisor teeth; its fibres radiate as they pass downwards and forwards, and are inserted into the integument of the chin.. The lower part of it is blended with fat. To expose it, the lip should be everted, and the mucous membrane dissected away. It elevates the lower lip by drawing up the chin.

The BUCCINATOR, Fig. 64 (8), is a broad, thin muscle, located in the cheek. It has three origins; the lower one arises from

the external surface of the alveolar process of the inferior maxilla in front of the coronoid process; the upper one from the alveolar process of the superior maxilla, in front of the pterygoid process; and the middle one from the pterygo-maxillary ligament, which stretches from the pterygoid to the base of the coronoid process, and to which the superior constrictor muscle of the pharynx is also attached. From these different origins its fibres converge and pass forwards to the angle of the mouth to be inserted, the inferior ones into the upper, and the superior ones into the lower lip. This muscle is separated behind from the ramus of the inferior maxilla and masseter, by a mass of fat, also by two of the buccal glands called molar. It is perforated by the duct of Steno. It is crossed transversely by the buccal branches of the facial and fifth pair of nerves. The facial artery and vein pass over it vertically. The buccal glands separate its internal surface from the mucous membrane. It draws the angle of the mouth backwards, and makes the lips tense; assists in expelling the contents of the mouth, and antagonizes the tongue in keeping the food in the process of mastication between the teeth.

The ZYGOMATICUS MAJOR, Fig. 61 (13), arises from the malar bone, just above its lower border, passes downwards and inwards, and is inserted into the angle of the mouth. It is generally surrounded by more or less fat, and its upper part is covered by the orbicularis palpebrarum; it crosses over the facial artery and vein. Its action is to draw the angle of the mouth upwards and backwards, as in smiling.

The ZYGOMATICUS MINOR, Fig. 61 (12), is often a fasciculus. from the orbicularis palpebrarum. When a distinct muscle, it arises from the malar bone, above the last muscle, and is inserted into the upper lip with the levator labii superioris, with which it acts, at the same time drawing the lip outwards.

The LEVATOR LABII SUPERIORIS, Fig. 61 (s), arises from the anterior border of the floor of the orbit, above the canine fossa, where it is overlapped by the orbicularis palpebrarum. Its fibres converge as they pass downwards to be inserted into the skin of the upper lip, and the orbicularis oris. All the lower part of this muscle is subcutaneous. Its action is indicated by its name.

The infra-orbital nerve and artery will be found escaping from the infra-orbital foramen, beneath the upper part of this

muscle. To expose these, cut down through the muscle in the direction of its fibres, upon the foramen, and gently raise the nerve, when its filaments will be seen to radiate upwards to the lower eyelid, inwards to the nose, downwards to the upper lip, and outwards and downwards to the cheek. They intermix and anastomose with the facial to form the infraorbital plexus. It requires a good deal of care and patience to trace these filaments to their termination. The infraorbital artery is one of the terminal branches of the internal maxillary. It inosculates with the facial, transverse facial, and ophthalmic.

The LEVATOR ANGULI ORIS, or CANINUS, Fig. 64 (6), arises from the canine fossa, below the infra-orbital foramen, and beneath the preceding muscle; passes downwards, and is inserted into the angle of the mouth. It raises the angle of the mouth, and antagonizes the depressor anguli oris, with which some of its fibres are continuous.

The LEVATOR LABII SUPERIORIS ALÆQUE NASI, Fig. 61 (8), arises from the upper part of the nasal process of the superior maxilla. It passes downwards on the side of the nose, divides into the nasal and labial portions, and is inserted, the former into the ala of the nose, and the latter into the upper lip. Its name indicates its use.

The COMPRESSOR NASI, or TRIANGULARIS NASI, Fig. 64 (5), is partly concealed by the preceding muscle. It arises from the inner part of the canine fossa, passes forwards to spread out over the ala of the nose, and is inserted into a thin aponeurosis, common to it and its fellow on the opposite side; it is also connected with the pyramidalis. It compresses the nostril when it acts alone, but may expand it when it acts in conjunction with the pyramidalis.

The DEPRESSOR LABII SUPERIORIS ALEQUE NASI, or MYRTIFORMIS, Fig. 64 (7), is exposed by everting the upper lip, and dissecting off the mucous membrane on the side of the frænum. It arises from the alveolar process of the superior maxilla in front of the incisor teeth, passes upwards and forwards, and is inserted into the upper lip and the fibrocartilage of the ala and septum of the nose. Its name indicates its actions.

The PYRAMIDALIS NASI, Fig. 64 (3), appears to be a fasciculus of the occipito-frontalis prolonged downwards on the nose.

It is inserted into the aponeurosis of the compressor nasi. It causes the vertical ridge sometimes seen at the root of the nose. The integument of the nose is supplied with nerves from the infra-orbital and the internal and external nasal. The facial artery, after giving off the branches already enumerated, ascends to the forehead between the eyebrows; its terminal branch is called the angularis.

SECT. II.-APPENDAGES OF THE EYE OUTSIDE OF THE ORBIT.

The dissection of the orbital region will embrace those appendages of the eye which can be exposed and studied without removing any portion of the walls of the orbit. These consist of the orbicularis palpebrarum, corrugator supercilii, and tensor tarsi muscles; the eyebrows, eyelashes, tarsal cartilages, Meibomian glands, conjunctiva, caruncula lachrymalis, lachrymal gland and ducts, puncta lachrymalia, lachrymal canals and sac, and nasal duct.

The integument in this region should be removed by cutting in the direction of the fibres of the orbicularis, but in the first place the eyelids should be made tense by inserting beneath them cotton or tow, and then stitching their edges together.

The EYEBROW, Fig. 4 (1), on each side, is situated just above

Fig. 4.

A FRONT VIEW OF THE LEFT EYE, MODE

RATELY OPENED. The supercilia. 2. The cilia of each eyelid. 3. The inferior palpe

bra. 4. The internal canthus. 5. The external canthus. 6. The caruncula lachrymalis. 7. The plica semilunaris. 8. The eyeball. 9. The pupil.

the attached border of the upper eyelid, and rests on the superciliary ridge of the frontal bone. It is generally arched and covered with hairs, which have a direction from within outwards. The integument is separated from the orbicularis and occipito-frontalis muscles by a thick, dense cellulo-adipose layer. The eyebrows can be moved upwards, downwards, or towards each other.

The EYELASHES, Fig. 4 (2), consist of three or