306 THE MUSCLES AND FASCIA. 



(3) The fascia covering the eyeball Tenon's capsule Avill be described in 

 the sequel. 



Surgical Anatomy. The position and exact point of insertion of the tendons of the 

 Internal and External recti muscles into the globe should be carefully examined from the front of 

 the eyeball, as the surgeon is often required to divide the one or the other muscle for the cure 

 of strabismus. In convergent strabismus, which is the more common form of the disease, the 

 eye is turned inward, requiring the division of the Internal rectus. In the divergent form, 

 which is more rare, the eye is turned outward, the External rectus being especially implicated. 

 The deformity produced in either case is to be remedied by division of one or the other muscle. 

 The operation is thus performed : The lids are to be well separated ; the eyeball being rotated 

 outward or inward, the conjunctiva should be raised by a pair of forceps and divided immediately 

 beneath the lower border of the tendon of the muscle to be divided, a little behind its insertion 

 into the sclerotic ; the submucous areolar tissue is then divided, and into the small aperture 

 thus made a blunt hook is passed upward between the muscle and the globe, and the tdndon of 

 the muscle and conjunctiva covering it divided by a pair of blunt-pointed scissors. Or the 

 tendon may be divided by a subconjunctival incision, one blade of the scissors being passed 

 upward between the tendon and the conjunctiva, and the other between the tendon and the 

 sclerotic. The student, when dissecting these muscles, should remove on one side of the subject 

 the conjunctiva from the front of the eye, in order to see more, accurately the position of the 

 tendons, while on the opposite side the operation may be performed. 



5. Nasal Region (Fig. 195). 



Pyramidalis nasi. Dilatator naris anterior. 



Levator labii superioris al?eque nasi. Compressor nasi. 



Dilatator naris posterior. Compressor narium minor. 



Depressor alae nasi. 



The Pyramidalis nasi is a small pyramidal slip placed over the nasal bone. Its 

 origin is by tendinous fibres from the fascia covering the lower part of the nasal 

 bone and upper part of the cartilage, where it blends Avith the Compressor nasi, 

 and it is inserted into the skin over the lower part of* the forehead between the 

 two eyebrows, its fibres decussating with those of the Occipito-frontalis. 



Relations. By its upper surface, with the skin ; by its under surface, with the 

 frontal and nasal bones. 



The Levator labii superioris alseque nasi is a thin triangular muscle placed 

 by the side of the nose, and extending between the inner margin of the orbit and 

 upper lip. It arises by a pointed extremity from the upper part of the nasal 

 process of the superior maxillary bone, and, passing obliquely downward and 

 outward, divides into two slips, one of which is inserted into the cartilage of the 

 ala of the nose ; the other is prolonged into the upper lip, becoming blended with 

 the Orbicularis oris and Levator labii superioris proprius. 



Relations. In front, with the integument, and with a small part of the 

 Orbicularis palpebrarum above. 



The Dilatator naris posterior is a small muscle which is placed partly beneath 

 the elevator of the nose and lip. It arises from the margin of the nasal notch of 

 the superior maxilla and from the sesamoid cartilages, and is inserted into the 

 skin near the margin of the nostril. 



The Dilatator naris anterior is a thin delicate fasciculus passing from the 

 cartilage of the ala of the nose to the integument near its margin. This muscle is 

 situated in front of the preceding. 



The Compressor nasi is a small, thin, triangular muscle arising by its apex 

 from the superior maxillary bone, above and a little external to the incisive fossa ; 

 its fibres proceed upward and inward, expanding into a thin aponeurosis which 

 is attached to the fibro-cartilage of the nose and is continuous on the bridge of 

 the nose with that of the muscle of the opposite side and with the aponeurosis of 

 the Pyramidalis nasi. 



The Compressor narium minor is a small muscle attached by one end to the alar 

 cartilage, and by the other to the integument at the end of the nose. 



The Depressor alae nasi is a short radiated muscle arising from the incisive 

 fossa of the superior maxilla ; its fibres ascend to be inserted into the septum and 



