Fig. 43. Orbital and Nasal Cavities in a Child. Frontal Section. 



Portion of a frozen section through the head of a girl, 1^/2 years old. 



A comparison with Fig. i shews, how different the accessory cavities of 

 the Nose and Upper Jaw are in the child when compared with those in the adult. 

 The Frontal Sinuses are formed at the end of the first year by ethmoidal cells 

 growing into the diploe of the Frontal Bone. They attain the size of a pea at 

 the 6th or 7th year; they are fully developed when the nose and frontal bone 

 cease growing — about the 20th year — . The Antrum of Highmore is virtuall)' 

 present before the middle of Intra-uterine life; in the newborn it appears as a 

 bulging of the middle nasal meatus the upper jaw being almost completely filled 

 with developing teeth. With the beginning of the 2nd dentition, it increases rapidl\' 

 in size. The Infraorbital Nerve is still external to the Antrum in our figure. The 

 Outer Rectus Muscles of the Eye were so contracted on both sides, in our body, 

 that the posterior segment of the eyeball was markedly directed inwards: this ex- 

 plains why the Optic Nerve has been divided by this section. 



Fig. 44. Orbital Cavity and surrounding Structures in the Child. 

 Vertical Section through Axis of Optic Nerve. 



From a frozen section through the head of a child, i^j, years old. Tenon's 

 Capsule, Periosteum, and Orbital Septum, blue. 



This figure shews that the upper eyelid covers a greater portion of the 

 cornea than the lower. The rima palpebrarum therefore lies, when the eyes are 

 closed, below the middle of the cornea. 



The Orbital Septum (cf. figure) is a plate of connective-tissue which runs 

 from the margin of the orbit, downwards ; behind the Orbicularis Palpebrarum, in 

 the upper eyeUd, it blends with the anterior slip of the Levator Palpebrae Superioris 

 Muscle and is separated from the tarsal plate by loose connective tissue. In the 

 lower lid, it enters the subtarsal connective tissue. It is a structure of no parti- 

 cular value ; it is merely the Aponeurosis of the Orbicularis palpebrarum Muscle. 



This figure also shews the termination of Tenon's Capsule at the Con- 

 junctiva. It splits into 2 layers, and blends with the Tunica Propria of the Con- 

 junctiva lining the eyeball and of the palpebral conjunctiva. 



Very complicated is the arrangement of Tenon's Capsule, where it is 

 crossed by the Inferior Oblique. From the under surface of the capsular portion 

 of tlie fascia of the Inferior Rectus a lamina — "the Accessory Fascia" — runs 

 forwards under the Inferior Oblique, blends with its sheath, and terminates in the 

 subtarsal connective tissue of the lower eyelid, where the capsule proper also ends. 



Above the Pharyngeal Tonsil lies the basilar fibrocartilage, above this 

 again lies the Spheno-Occipital Synchondrosis which may be injured in the too- 

 energetic scraping of adenoids. 



