172 NASAL GROUP. 



with the broad tarsal ligament and with the tarsal cartilages. This 

 fascia the author terms, the tunica vaginalis oculi* it is pierced ante- 

 riorly for the passage of the six orbital muscles, by six openings 

 through which the tendons of the muscles play as through pulleys. 

 The use assigned to it by Mr. Ferrall is to protect the eyeball from 

 the pressure of its muscles during their action. By means of this 

 structure the recti muscles are enabled to impress a rotatory movement 

 upon the eyeball ; and in animals provided with a retractor muscle, 

 they also act as antagonists to its action. 



Actions. The levator palpebrae raises the upper eyelid. The four 

 recti, acting singly, pull the eyeball in the four directions ; upwards, 

 downwards, inwards, and outwards. Acting by pairs, they carry the 

 eyeball in the diagonal of these directions, viz. upwards and inwards, 

 upwards and outwards, downwards and inwards, or downwards and 

 outwards. Acting all together, they directly retract the globe within 

 the orbit The superior oblique muscle, acting alone, rolls the globe 

 inwards and forwards, and carries the pupil outwards and downwards 

 to the lower and outer angle of the orbit. The inferior oblique, act- 

 ing alone, rolls the globe outwards and backwards, and carries the 

 pupil outwards and upwards to the upper and outer angle of the eye. 

 Both muscles acting together, draw the eyeball forwards, and give the 

 pupil that slight degree of eversion which enables it to admit the 

 largest field of vision. 



4. Nasal Group. Pyramidalis nasi, 

 Compressor nasi, 

 Dilatator naris. 



The PYRAMIDALIS NASI is a small pyramidal slip of muscular 

 fibres sent downwards upon the bridge of the nose by the occipito- 

 frontalis. It is inserted into the tendinous expansion of the compres- 

 sores nasi. 



Relations. By its upper surface with the integument ; by its under 

 surface with the periosteum of the frontal and nasal bone. Its outer 

 border corresponds with the edge of the orbicularis palpebrarum, and 

 its inner border with its fellow, from which it is separated by a slight 

 interval. 



The COMPRESSOR NASI is a thin and triangular muscle ; it arises 

 by its apex from the canine fossa of the superior maxillary bone, and 

 spreads out upon the side of the nose into a thin tendinous ex- 

 pansion, which is continuous across its ridge with the muscle of the 

 opposite side. 



_ Relations. By its superficial surface with the levator labii supe- 

 rioris proprius, the levator labii superioris alseque nasi, and the inte- 

 gument ; by its deep surface with the superior maxillary and nasal 

 bone, and with the alar and lateral cartilages of the nose. 



* This fascia was first described by Mr. Dalrymple in his work on the " Ana- 

 tomy of the Human Eye." 1834. 



