430 
ME. E. A. SCHAFEE OX THE MINUTE STEUCTUKE OF 
into this, and finally terminating near its middle in an enlarged knobbed extremity, 
which appears as a minute dark dot. Consequently each of the bodies we are now 
considering, and which from their form may be denominated muscle-rods * , may be 
described as consisting of a cylindrical middle part or shaft , which is imbedded in the 
substance of the dim stripe, and of two enlarged extremities or heads , which are 
found near the middle of the bright stripe. It further follows that there are as many 
series of muscle-rods as disks of dim substance in the fibre. Moreover each rod of any 
one series corresponds exactly with one in the next following series, their enlarged 
extremities almost meeting in the middle of the bright substance ; this arrangement 
causes the appearance of a double row of dots (c) running transversely across each 
bright stripef . 
It must be observed, however, that in such a preparation as is here spoken of, the 
appearance represented in the figure, although very common, is by no means the only 
one that presents itself. All the variations, however, that are met with are accompanied 
and, as will be hereafter shown, in all probability caused by variations either in the 
relative position or in the form of the muscle-rods. Thus we not unfrequently find 
fibres in which the rod-heads of contiguous series, instead of being in more or less close 
apposition in the middle of the bright disk, are separated by a distinct bright interval ; 
this is more especially the case when the muscular fibre happens to be somewhat 
stretched. 
Sometimes a greater or less number of the rods of neighbouring series are shifted 
abruptly upon the rest in a longitudinal direction, so much so that their heads may 
come to be opposite the middle of the shafts of the remainder (see fig. 1). In such 
cases the transverse striae also become correspondingly shifted. This fact would of itself 
almost preclude the conception of the existence of continuous membranes extending 
across the fibre, an idea which has been largely prevalent of late years. 
The variations which occur in the form of the muscle-rods are chiefly, if not entirely, 
dependent upon the relation in size which subsists between the shafts and the ends, 
these seeming to be in inverse ratio with one another. Thus the shafts are not unfre- 
quently increased in length, the heads at the same time becoming smaller and closer 
to those of the next series, so that a double row of dots is no longer seen in the middle 
* A word here seems due to explain why the use of the term “ sarcous elements” — which was applied 
by Mr. Bowman (“ On the Structure and Movements of Voluntary Muscle,” Phil. Trans. 1840) to the 
minute particles of which he conceived a muscular fibre to be composed, and which has been very 
generally applied by subsequent observers, both here and on the Continent, to the rod-like bodies which are 
commonly described in the muscles of insects — has been omitted throughout the present communication. The 
reason is simply this — that the term is ordinarily understood to imply that the bodies to which it is applied 
form the essential contractile constituent of muscle, wherea s it will be seen from what follows that this is 
probably not the case with the structures here denominated muscle-rods. It should, however, be distinctly 
understood that the latter term is employed to signify simply the form, without reference to tho naturo of the 
material of which the particles in question are composed. 
t Compare Stbickee, ‘ Handbuch der Gewcbelehre,’ p. 1225. 
