326 ORGANS OP EXPRESSION. 



muscle, arising from the canine fossa of the upper maxilla, 

 and then spreading over the ala nasi, is inserted along 

 with its fellow upon the dorsum of the nose, by a thin 

 aponeurosis. 



function. It can either compress or dilate the nostril, 

 as one or the other of its attachments becomes the fixed 

 point of action. In panting, as in violent respiration after 

 running, as seen in the horse, this muscle becomes a pow- 

 erful dilator, and has received the name of the dilator na-si. 



Orbicularis palpebrarum, (Fig. 55.) Dissection. The 

 same incision for exposing the corrugator supercilii, being 

 carried round the lower margin of the orbit to the inner 

 canthus of the eye, also exposes this muscle as well as the 

 compressor nasi. 



It arises fleshy from the internal angular process of the 

 os frontis, and upper edge of the tendo oculi its fibres then 

 proceed upward and outward, broad and thin, along the 

 upper edge of the orbit and tarsal cartilage, describing 

 curves in their course to the external commissure of the 

 eyelids ; from this it is continued round in similar curves 

 upon the lower edge of the orbit and lower eyelid to the 

 internal canthus of the eye, where it is inserted into the 

 nasal process of the superior maxilla, the inner third of 

 the edge of the orbit, and the lower edge of the tendo oculi. 

 The tendo oculi or tendo palpebrarum is a short, horizontal 

 tendon, about a quarter of an inch in length, attached to 

 the superior end of the nasal process of the upper maxilla, 

 and extending thence transversely to the inner canthus of 

 the eye, where it is distinctly felt. At this point it forks ; 

 the divided portions enclose the caruncula lachrymalis and 

 are connected with the tarsal cartilages and lachrymal 

 duct. This tendon also passes across the lachrymal sac, 

 and sends off a strong aponeurosis which covers its anterior 

 surface.* 



Function. To close the eyelids, which is done by the 

 fibres of this muscle being drawn in a straight line. 



*The palpebral portion of this muscle, running along the margin of the eye- 

 lids, is called the Ciliaris Muscle. 



