792 ORGANIC 
consentaneous action between the branches of 
the third nerve supplied to the internal recti 
muscles, and it is only by a considerable effort 
that they can be made to act together; whilst 
the branches of the same nerve supplied to the 
levatores palpebrarum, which for the most part 
act consentaneously, may by a very slight effort 
of the will be made to act separately; but few 
persons experience any difficulty in opening 
one eye while the other is closed. Again, the 
tendency to consentaneous action between the 
internal rectus supplied by the third nerve and 
the external rectus supplied by the sixth nerve, 
as well as between the inferior oblique supplied 
by the third nerve and the superior oblique by the 
fourth, is as irresistible as that between the supe- 
rior and inferior recti of the two eyes. We see 
then that all the muscles supplied by corres- 
ponding branches of the third nerve have not 
this tendency to consensual action, and two 
muscles supplied by the third nerve act con- 
sentaneously with two other muscles supplied 
by the fourth and the sixth nerves respectively. 
For the maintenance of the parallelism 
between the axes of the two eyes, it is evidently 
necessary there should be a consentaneous 
action of the superior recti as well as of the in- 
ferior recti; it is also necessary that the internal 
tectus and the inferior oblique of one eye should 
act with the external rectus and the superior 
oblique of the other; but it is by no means 
evident why it is necessary, in order to effect 
this, that the external rectus and the superior 
oblique should each have a nerve specially 
provided for them. We must not suppose we 
are explaining the necessity for this arrange- 
ment by asserting that “ if in place of the sixth 
nerves, the external recti muscles had received 
each a branch of the third nerve, it would have 
been impossible to make one of these muscles 
act without the other,” because, as we have 
seen, there is no such irresistible innate ten- 
dency in all the corresponding branches of the 
third nerve to consentaneous action. Assuming 
that the use of the oblique muscles is such as 
we have mentioned, it is certainly curious to 
observe that when corresponding muscles of the 
two eyes are intended to act together, as the 
superior rectus of one eye with the superior 
rectus of the other, and the same with the infe- 
rior recti, both muscles are supplied by the 
third nerve, but the external rectus which acts 
consentaneously with the internal rectus of the 
opposite eye has a separate nerve, the sixth, and 
the superior oblique, which acts with the infe- 
rior of the opposite eye, has the fourth nerve 
entirely devoted to it. 
There is one other phenomenon to which we 
may briefly allude, namely, the adaptation of the 
eye to distances. This will be found fully dis- 
cussed under the article Visron ; but it deserves 
a ing notice in this place, since one hypo- 
thesis by which an aticinos has been ete Ae 
explain it is that a change is effected in the form 
of the eye by the action of its external muscles, 
some writers attributing the influence in ques- 
tion to the recti muscles, and others to the 
obliqui. It seems by no means improbable 
that the action of both sets of muscles at the 
ANALYSIS. 
same time might have the effect of increasi 
the antero-posterior diameter of the eye ; 
and thereby of adapting it for vision at small 
distances. The following experiment seems to. 
favour the notion that there 1s some muscular 
action in the adaptation of the eye to vision at 
es : small distances. at? 
lace a printed page closer to the eyes than 
the natural focal distance, and merely look 
upon the letters without making any effort to — 
read them; they appear confused and indis- — 
tinct; then by a considerable voluntary effort 
which cannot be long sustained, and which is — 
attended with some pain, we may so adjust the — 
eyes that the letters appear perfectly distinet 
and legible. This subject is attended with 
great difficulties, indeed it is scarcely possible — 
to determine the precise mode in whee eda 
tation is effected; the hypothesis we have now — 
mentioned appears at least as provaliets ny 
other ; it is, however, open to objections. 
state of adaptation of the eye is often entire 
changed in a very short time by the local action 
of narcotics, which at the same time dilate the 
pupil, and this change is effected without any 
apparent influence over the voluntary contrac- 
tions of the muscles. Most observers state that 
the eye is rendered long-sighted (presbyopic), 
while others have experienced an opposite 
result, Miiller has recorded the results of the 
application of belladonna to his own eye; the 
general effect was to render the eye presbyopie, 
but the capability of adaptation was not de 
stroyed by it. When the solution of b 
was applied to one eye both eyes were affeete 
but in different degrees, so that both eyes ¢ 
not be adapted to distinct vision of the - 
object at the same moment. These effects we 
attended with great dilatation of the pupil, 
inasmuch as they were probably in some w 
dependent on this, they are opposed to the hyp 
thesis that adaptation is effected by any acti 
of the external muscles. at 
(G. Johnson.) 
ORGANIC ANALYSIS.—Under thet 
organic analysis are included the various 
thods of discovering the constituent parts 
substances, formed either directly by 
actions of organized beings, or indirectly 
subjecting the products of such actions to 
further operation of re-agents. To treat 
subject in its full extent would, howe 
foreign to the purpose of the present art 
in which I shall confine myself to the an 
of the products of animal life, and part 
of those combinations liable to be met 
the human frame. 4 
In this analysis two distinct objects pp 
themselves : the first consists in the det 
ation of the proximate principles which 
into the constitution off the substance 
analyzed, and the second in the discov 
the elementary composition of the dif 
proximate principles. ' = 
I shall therefore in the first place deser 
the various means by which we recognize 
occurrence of the more important proxi 
animal principles, and determine as 
adc 
