FIJ3RES OP THE INTERNAL CAPSULE OP THE BONNET MONKEY. 
G7 
i.e., along the middle line of the cerebrum by a narrow (1-2 mm. wide) strip of 
inexcitable tissue. (? Septum lucidiun and anterior perforated spot, grey mattei'.) 
Summary and Application of the Anatomical Facts. 
It remains to connect these anatomical data with the facts observed upon 
excitation. 
In the first place discrimination must be made between the effects of exciting- 
fibres in their continuity and on their transverse section respectively, since it is 
plain that the identity of result might otherwise lead to an undesirably extended 
view of the limits of the efferent tract. 
Reference to fig. 1 and to Table I. shows thaf some of the efilferent excital^le fibres 
which partly compose the anterior limb in Group I. are rapidly concentrated in the 
posterior limb as we descend to Group III. These fibres are those for the move¬ 
ments of opening the mouth and protrusion of the tongue, as is shown by a glance 
at fig. 1, C and F. 
At Group IV., fig. 1, it is evident that a further change now occurs Apparently 
owing to the appearance of the second or middle zone of the lenticular nucleus, that 
part of the anterior limb which is opposite this second zone is found ti> be excitable, 
whereas the rest, which really exactly corresponds with the whole anterior limb of 
Group III., is inexcitable as in that Group. 
It is to be observed (fig. 1) that this excitability of the posterior part of the 
anterior limb again diminishes until we arrive at Group VII., where, upon the further 
appearance of the third or innermost zone, the hinder end of this limb is seen to be 
excitable. 
To speak next of the inexcitable fibres of the anterior limb, we have in the fore¬ 
going pages referred to the views of those who have treated the subject, and we only 
would express our belief that these fibres of the anterior limb are for the most part 
horizontal, and that they pass backwards through the genu to the thalamic region. 
A point of equal interest is the arrangement of excitable and inexcitable fibres in 
the posterior limb of the capsule. 
In Groups I. and II., fig. 1, the posterior limb is excitable in its whole length, 
but, in Group III., the hindermost part {i.e., for the last yfoths) is inexcitable. This 
inexcitable portion steadily increases as we pass downwards (see fig. 1), so that in 
Groups VI., VII., and VIII., the excitable part terminates posteriorly at the hinder 
limit of the middle zone. 
The classical dictum,"" that the sensory fibres are contained in tlie posterior third 
of the hinder limb of the capsule only holds good for the lowest levels. The gradual 
character of the development of this inexcitable (afferent) part of the capsule is 
interesting by way of contrast with the variable arrangement of the excitable fibres 
in the anterior limb just discussed, 
* Carvillb and Duret, Charcot, loc . cit , 
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