347 



rior chamber. The pressure is thus communicated by the iris to the 

 lens through the medium of the ciliary processes, zonule of Zinn, 

 and contents of the canal of Petit, the lens being supported and 

 kept forward by cotemporaneous contraction of the ciliary muscle. 

 Bonders is inclined to believe that a very thin layer of fluid is inter- 

 posed between the iris and the structures behind it ; but practically 

 Cramer's opinion appears to be correct. 



Hueck, in attempting to explain ocular adjustment by the move- 

 ment of the lens by the iris, had stated that when viewed in proflle, 

 the iris is seen to project into the anterior chamber during vision of 

 a near object. Volkmann denied this ; but the fact is undoubted ; 

 and Helmholtz has ascertained that the protrusion is about ^ milli- 

 metre. 



Ruete has objected to Cramer's conclusion as to the agency of the 

 iris in altering the form of the lens, on the ground that in cases of 

 congenital deficiency of the iris the power of adjustment is not de- 

 ficient. In such instances some compensating arrangement must 

 exist. 



Senile Presbyopia mainly depends, according to Cramer, on the 

 diminished muscular contractility of the iris and ciUary muscle. 

 Myopia, again, on diminution of the elasticity of the capsule of the 

 lens, which disables the lens from regaining its normal form after 

 each act of adjustment. He denies that the curvature of the cornea 

 is increased in myopia, and states that the apparent increase is due 

 to the continued increased protrusion of the iris into the anterior 

 chamber. 



The following Gentleman was duly elected an Ordinary 



Fellow : — 



David Bryce, Esq., Architect. 



Monday, 21st January 1856. 

 CoiiONEL MADDEN, Councillor, in the Chair. 

 The following Communications were read : — 



1. Memoir of Rear-Admiral Sir John Franklin. By Sir 

 John Richardson, C.B. Communicated by Professor Bal- 

 four. 



