PHYSIOLOGY OF THE EYE OF THE HORSE. 517 
below must continue their path to the upper part. It is habit 
and the exercise of judgment which sets all this right in the 
mind. It is in the same way that, out of two retinal paintings, 
differing more or less from each other, the mind is conscious of 
only one perfect one. If the eyes are alternately closed we shall 
sometimes be surprised at the different pictures painted on each 
retina. It is by a rapid intellectual amalgamation that they become 
one consistent and perfect one. The question of the decussation 
of the fibres of the optic nerve has nothing to do with this expla¬ 
nation ; it is purely an affair of the mind. 
When either eye is pushed a little from its axis, or the Irish¬ 
man (I am one) drinks a little too much whisky, and the judg¬ 
ment begins to be impaired, this amalgamation no longer takes 
place, but we have a double vision, as curious as it is perfect. 
How the eye adjusts itself to the distance of the object of vision, 
has caused an endless theme for argument. 
I consider that it is effected by the muscles, particularly the 
recti, assisted, doubtless, by the retractor and the palpebres, which 
compress the globe and alter the actual distance between the 
cornea and the retina. There is a wonderful mechanism for 
effecting this in birds. In persons under the influence of fear, 
the eyes are open, and the eye is protruded, which is performed 
by the trochlearis muscle. We observe, on the other hand, that 
near-sighted persons close the lids and compress the eye, in order 
to obtain a correct view of the object. Thus we perceive in this 
admirable organ a power by w’hich it can act as a telescope and 
a microscope, as circumstances may require, a degree of perfec¬ 
tion to which no instrument of human construction has ever yet 
been brought. 
TOXICOLOGY; 
On thk Efi'icacy of the Hydrate of the Peroxide 
OF Iron as an Antidote for Arsenic. 
Bij M. Bou LEY, Jun. M,V., Paris. 
A VACUA RLE Report, drawn up by this gentleman, of the 
poisoning of seven horses by means of the arseniate of potash, a 
preparation of arsenic, extensively used in the preparation of that 
beautiful pigment “ Sc/teele’s green ,was inserted in our last 
Number. Soon after these unfortunate cases, the antidote for 
arsenic, |)roposcd by M. Bunzen, began to be spoken of. ft may 
be readily supposed that M. Bouley was one of the first to put it to 
the test; and, as many chemists and medical men were experi- 
