I2 4 



BIOLOGICAL PHYSICS 



whereby these lymph cisterns can be replenished, and the 

 integrity of the apparatus of audition maintained, and this 

 means, we think, is to be found in the endothelial linings 

 of the inner ears generally, with their surroundings and 

 supporting blood supply. A dual mechanism, therefore, 

 we think, exists in this cryptic region for securing the 

 continuity of auditory sense-impressions and supplying 

 the higher cerebral centres with a highly specialised 



FIG. 47. VERTICAL SECTION OF THE LEFT ORBIT AND ITS CONTENTS. 

 (Allen Thomson.) 



The section has been carried first obliquely through the middle of the optic foramen 

 and optic nerve as far as the back of the eyeball, and thence forward through the 

 eyeball, eyelids, etc. a, frontal bone; b, superior maxillary; c, eyebrow ; d, the 

 upper, and if, the lower eyelid, partially open, showing the section of the tarsi, 

 the eyelashes, etc. ; e, e, the reflection of the conjunctiva from the upper and 

 lower eyelids to the surface of the eyeball ; _f, the levator palpebrae superioris 

 muscle ; g, the upper, g, the lower rectus muscle ; h, the inferior oblique muscle 

 divided; i, i, the optic nerve divided in its sheath; 2, the cornea; 2', the 

 sclerotic ; 3, aqueous chamber ; 4, crystalline lens ; 5, vitreous chamber. 



tributary to the continually needed stream of information 

 from the outer world. 



Another region " watered " by the cerebro-spinal fluid, 

 and which affords a means of exit to that fluid when 

 required, is the ophthalmic (Figs. 46, 47), which, divided 

 into two and situated at the anterior aspect of the head 

 where the head and face join, constitutes the most 

 prominent and tell-tale feature of the physical and 

 intellectual microcosm within the organisms of both man 

 and animal. 



