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Mr. J. M. Ferrall drew the attention of the Academy to 

 several drawings, and a preparation, exhibiting a new and 

 beautiful mechanism belonging to the human eye, and 

 discovered by him in April last, while engaged in researches 

 on certain diseases of the orbit, which the received anatomy 

 of those parts did not appear to him to explain. 



The new structures consisted of a distinct fibrous tunic, 

 investing the globe of the eye, facihtating its movements, 

 and separating it from all the surrounding tissues. 



The anatomy of the schools, and of the best authors, 

 from the earhest time to the present, teaches that the ball of 

 the eye is in contact with its muscles, and, between them, 

 with a quantity of adipose substance on which it was sup- 

 posed to be cushioned. It was difficult to conceive, how- 

 ever, why the eye did not manifest any of the symptoms 

 incidental to pressure suddenly endured, whenever those 

 muscles were brought into action, since there appeared to 

 be no provision for its protection. That pressure, sud- 

 denly made on the globe of tlie eye, produces the sensation 

 of a spark or flash of light, is familiarly known as the con- 

 sequence of a slight blow on the eye. 



The act of sneezing is frequently followed by a similar 

 phenomenon, and Sir Charles Bell has shown, in a paper 

 published in the Philosophical Transactions, that it is occa- 

 sioned by the sudden pressure on the ball of the eye, by the 

 orbicularis palpebrarum or principal muscle of the eyelids, 

 which is suddenly brought into action by the respiratory 

 nerves. The four recti muscles, which move the eye in dif- 

 ferent directions, being favourably placed, (according to the 

 received anatomy), for exercising such a pressure, it might 

 have been expected that a similar phenomenon would have re- 

 sulted ; but no such coruscations have ever been observed 

 to follow their most rapid actions. 



The discovery of this tunic, which Mr. Ferrall has ven- 

 tured to term the tunica vaginalis oculi, at once explains 



