458 
MR. BOWMAN ON THE MINUTE STRUCTURE AND 
the general correctness of this opinion, and to render more exact and ample the 
knowledge of its details ; secondly, to point out the existence and properties of new 
parts which, as far as I can ascertain, have not yet been described ; and thirdly, to 
elucidate the proximate cause of voluntary motion, by describing shortly the mecha- 
nism of certain movements performed by the elementary constituents of muscles. 
In speaking of the threads already mentioned, it becomes necessary to attach to 
them a term of definite meaning. The words fibre, Jibrilla, and Jilament, have been 
so much abused by indiscriminate application, that it would be confusing the subject 
to employ them in this sense ; and though the term primitive fasciculus, adopted by 
Fontana and some subsequent writers, will be shown in the sequel to be liable to 
considerable objections, as implying a composition by smaller fibrils, which can never 
be said to be a correct expression of the actual condition, yet I shall prefer its use to 
that of a new designation. The small component fibrils, into which the primitive fasci- 
culus may usually be split up, will be styled primitive Jibrillce, or simply Jibrillce. 
As even the configuration and bulk of the primitive fasciculi have not hitherto been 
fully ascertained, these points demand attention. Their shape may be briefly described 
as polygonal in all animals, though in some examples they approach very nearly to a 
cylindrical form. The examination may be conducted by obtaining either a longi- 
tudinal or transverse view' of the parts ; but the former, without precaution, is apt to 
lead to error. It is usual to place the recent fasciculi, moistened with water, between 
glasses, previous to inspection, whereby they become swollen from absorption of the 
fluid, and more or less altered towards a cylindrical figure. If this mode of exami- 
nation be desired, it is requisite, therefore, either not to wet the object, or to moisten 
it with a fluid which is not absorbed, such as thick syrup. It will then be seen that 
the cross markings, called transverse strise, with which every anatomist is familiar, 
as visible on the fasciculus, have not uniformly a straight direction across it, but are 
frequently all bent at an obtuse angle, along a certain line parallel to the margin, 
showing a sudden change in the aspect of the surface on which the strise are seen. 
This appearance was not unobserved by Fontana*, who in a figure of four fasciculi, 
has represented it more or less decidedly in all, and it has been observed by others. It 
is often so slight as at first to escape notice, and it is by no means constant. It is best 
seen when by an accident a fasciculus slopes from the observer, who, as he alters the 
focus, so as to bring different portions of it successively before the eye, gains partially 
such a view as would be presented by a transverse section. Now supposing the fas- 
ciculi to be polygonal, the frequent slightness or absence of this appearance may still 
consist with a uniformity of the configuration which occasions it, since if the fasci- 
culus lie flat, and the observer regard it perpendicularly, as is generally done, he would 
w'ant that perspective view which could alone disclose it. But besides this, it is easy 
to notice, as the object is being brought into focus, which part of it is first seen, as 
being the most prominent, and this is not always the central part. Moreover, as the 
* Fontana, Traits sur le Venin de la Vipere, tab. vi. fig. 6. 7. 
