on the Structure, Distribution, and Functions of the Nerves. 355 



that in sleep, faintness, and insensibility, the eye-ball is given 

 up to the one, and in watchfulness, and the full exercise of 

 the organ, it is given up to the influence of the other class of 

 muscles : and finally, that the consideration of these natural 

 conditions of the eye explains its changes as symptomatic of 

 disease, or as expressive of passion." 



This first part, therefore, is taken up by a number of experi- 

 ments and observations which confirm these views, and afford 

 the author secure ground for establishing an arrangement of the 

 nerves of the eye, whilst they at the same time enable him to 

 distinguish them according to their uses. 



The recti and obliqui form the two natural classes of mus- 

 cles attached to the eye-ball; the four recti are strictly volun- 

 tary, and the two obliqui are involuntary: hence, according 

 to the author's experiments upon the eye of the monkey, the 

 division of the latter does not in any degree affect the volun- 

 tary motions which direct the eye to objects. This cannot, 

 however, be said of the involuntary winking motions of the 

 eyes; in those, in winking to avoid injury, the oblique muscles 

 are in operation, as likewise in that peculiar and invariable 

 elevation of the cornea, which takes place during sleep, or 

 when the eye-lids are closed. The same experiments and ob- 

 servations have moreover led the author to conclude, that 

 whilst the control and direction of the eye to objects belong 

 entirely to the voluntary or recti muscles, the preservation of 

 the organ itself, either by withdrawing the surface from in- 

 jury, or by the removal of what is offensive to it, belongs, 

 more especially, to the two obliqui. 



In illustration of the necessity and importance of this classi- 

 fication of the muscles of the eye, we wish to bring forward 

 some of the author's remarks upon the expression of the eye, 

 and of the actions of its involuntary or oblique muscles in dis- 

 ease. 



" If, as I have alledged, the uses of the oblique muscles of 

 the eye have been misunderstood, and if, as I hope presently 

 to prove, the distinctions of the nerves have been neglected, 

 the symptoms of disease, and the sources of expression in the 

 eye, must remain to be explained. 



" During sleep, in oppression of the brain, in faintness, in 

 debility after fever, in hydrocephalus, and on the approach of 

 death, the pupils of the eyes are elevated. If we open the 

 eye-lids of a person during sleep or insensibility, the pupils 

 will be found elevated. Whatever be the cause of this, it will 

 be found that it is also the cause of the expression in sick- 

 ness, and pain, and exhaustion, whether of body or mind: for 

 then the rye-lids are relaxed and fallen, and the pupils ele- 



V y 2 vat* (I 



