Royal Irish Academy. 599 



and observations, and -what is particularly -worthy of being noticed, 

 an analysis of its history." 



March 16, 1841 (Stated Meeting).— Mr. J. M. Ferrall drew the 

 attention of the Academy to several drawings, and a preparation, exhi- 

 biting a new and beautiful mechanism belonging to the human eye, and 

 discovered by him in April last, while engaged in researches on cer- 

 tain 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, facilitating its movements, and separating it 

 from all the surrounding tissues. 



The anatomy of the schools, and of the best authors, from the ear- 

 liest 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 sub- 

 stance on which it was supposed to be cushioned. It was difficult to 

 conceive, however, why the eye did not manifest any of the sym- 

 ptoms incidental to pressure suddenly endured, whenever those mus- 

 cles were brought into action, since there appeared to be no provi- 

 sion for its protection. That pressure, suddenly made on the globe 

 of the eye, produces the sensation of a spark or flash of light, is fa- 

 miliarly known as the consequence of a slight blow on the eye. 



The act of sneezing is frequently followed by a similar phaenome- 

 non, and Sir Charles Bell has shown, in a paper published in the 

 Philosophical Transactions, that it is occasioned by the sudden pres- 

 sure on the ball of the eye, by the orbicularis palpebrarum or princi- 

 pal muscle of the eyelids, which is suddenly brought into action by 

 the respiratory nerves. The four recti muscles, which move the eye 

 in difterent directions, being favourably placed (according to the re- 

 ceived anatomy) for exercising such a pressure, it might have been 

 expected that a similar phsenomenon would have resulted; but no such 

 coruscations have ever been observed to follow their most rapid actions. 



The discovery of this tunic, which Mr. Ferrall has ventured to 

 term the tunica vaginalis oculi, at once explains the absence of 

 those phsenomena, by showing that a protective provision has always 

 existed to prevent them. 



Mr. Ferrall went on to state, that the most beautiful portion of 

 this mechanism remained to be described. It was one of those ex- 

 quisite manifestations of design which abound in the animal frame. 



In the anterior portion of this tunic were to be found six diflerent 

 well-defined openings, through which the tendons of the muscles 

 pass to their insertion in the sclerotic coat of the eye, and over which 

 they play as over pulleys in their progress. 



Wood engravings, executed from original drawings made in April 

 1840, for Mr. Ferrall's clinical lectures in St. Vincent's Hospital, 

 and displaying this conformation faithfully, are given in No. 28 of 

 the Proceedings of the Academy. 



The first shows the tendon of the internal rectus emerging from 

 behind the tunic, and passing through its pulley to be inserted in 

 the eyeball. 



The second figure represents the eyeball drawn downwards, in 



