95 [JeflTries. 



of this change and found it was quite sufficient to account for all the 

 range of accommodation: i. e., sufficient to enable the eye to focus 

 all the differently diverging rays coming from objects at the distance 

 of six inches to fifteen feet. The question now was how the change 

 was produced. By pressure of the iris on the lens ? By pressure of the 

 ciliary processes on the lens ? By both these combined ? These 

 theories are all shown to be wrong from a case of Professor Grcefe's 

 where, by accident, during an operation on the eye, the entire 

 iris was torn away. The power of accommodation remained. More- 

 over, the ciliary processes being laid bare to view, it was seen that dm'- 

 ing the act of accommodation they did not touch the lens, which, as it 

 were, of itself took a more convex shape. Dr. Jeffries next described 

 the ciliary muscle first spoken of as such, by Dr. Clay Wallace of New 

 York, afterwards simultaneously studied by Professor Bowman of 

 London and Professor Briicke of Vienna ; also by Professor Arlt 

 and Heinrich Miiller, who discovered a set of circular fibres close 

 to its attachment to the sclerotic. This is a true muscle, freely supplied 

 with nerves from the lenticular ganglion and the nasal branch of the 

 ophthalmic division of the fifth nerve. In the act of accommodation we 

 have a sensation of muscular effort. Dr. Jeffries thought the chano;e in 

 the lens was produced by the action of this muscle drawing forward 

 the choroid and ciliary processes, and thus slacking up the hgament 

 of the lens by which it is suspended, and so allowing it to take its (as 

 it were) natural, more convex form: i.e., to become thicker antero- 

 posteriorly. This it does when removed from the eye. The ciliary 

 ligament, by its tension, keeps the lens flattened ; the action of the mus- 

 cle slacks up this tension and the lens assumes its more spherical 

 shape. Dr. Jeffries exhibited dissections of the eyes of the seal, horse- 

 mackerel and sword-fish in illustration of the anatomy of the lens, its 

 capsule and ligament, and a model in imitation of one of Professor Lud- 

 wig's of Vienna, to show the action of the ciliary muscle and the change 

 of shape of the lens. Dr. Jeffries said, as old age came on the lens 

 grew harder, the muscle less powerful, and we therefore had to supply 

 this deficiency by a convex glass before the eye. He gave some illustra- 

 tions of the importance of this muscle and a proper appreciation of its 

 action, as through it we gained distinct vision of near objects, and 

 when it failed the causes must be thoroughly understood to enable the 

 ocuhst to assist his patient. He described the action of atropine 

 and the calabar bean upon this muscle and the iris; these two 

 substances being opposed to each other in their influence upon 

 the ciliary muscle. 



Mr. S. H. Scudder exhibited diagrams illustrative of the 

 structure of the wings in the two fossil insects fi-om carbonife- 



