64 SURGICAL APPLIED ANATOMY. [Ci>a P i\. 



upon the optic nerve produces those flashes of light 

 and other spectra which occur in the disease. The 

 weakest part of the sclerotic is at the disc at the 

 lamina cribrosa. This part i m apidly yields under the 

 pressure, and so produces the " glaucomatous cup." 

 Pressure in the opposite direction pushes the lens 

 forward, and thus narrows the anterior chamber ; 

 while the general interference with the ocular circula- 

 tion is shown in the distended vessels that appear 

 upon the globe. 



The eyelids. The skrn over the eyelids is ex- 

 tremely thin and delicate, and shows readily through 

 its substance any extravasation of blood that may 

 form beneath it. Its laxity, moreover, renders it very 

 well adapted for certain plastic operations that are 

 performed upon the part. Its loose attachments 

 cause it to be 1'eadily influenced by traction, and the 

 shrinking of cicatrices below the lower lid is very apt 

 to draw that fold away from the globe, and so produce 

 the condition of eversion of the lid known as ectropion. 

 The contraction of the conjunctiva after inflammatory 

 conditions, or after it has been subjected to destructive 

 agencies, is prone, on the other hand, to curl either lid 

 inwards towards the globe, and to thus produce entro- 

 pion. The lids present many transverse folds ; one of 

 these on the upper lid, deeper and more marked than 

 the rest, divides the lid into two parts, the part belo\v 

 being that that covers the globe, the part above being 

 that in relation with the soft structures of the orbit. 

 In emaciation the lid becomes much sunken in the 

 line of this fold. Incisions should follow the direc- 

 tion of these folds. The lids are very freely supplied 

 with blood, and are often the seat of nsevi and other 

 vascular growths. Rodent ulcer so frequently attacks 

 this part that it was originally known as " Jacob's 

 ulcer of the eyelid." 



The following layers are found in either lid in 



