Remarks on the Musculus Kerato-Cricoideus. 
135 
last might be changed for some other object. When the 
microscope was marked as above, an object might instantly 
be found and focussed at any future time by adjusting the 
microscope to " scratch No. 2," placing the nose and forehead 
as described, and the object required to be focussed in the 
fourth adjusted point, and screwing down the body of the 
microscope to " scratch No. 1." 
The author illustrated his method before the Society, by 
instantly placing and focussing several small objects under 
the microscope without looking through the eye-piece. 
III. Remarks on the Musculus Kerato-Cricoideus, a Muscle of the Larynx. 
{MerheVs Muscle). By Wm. Turner, M.B. (Lond.), M.R.C.S., Senior 
Demonstrator of Anatomy, University of Edinburgh. 
The muscular arrangements of the human body have been, 
during the last two or three centuries, so thoroughly examined, 
and carefully described, that it rarely falls to the lot of a 
modern anatomist to discover, merely by the aid of his un- 
assisted vision, a new muscle. To such a structure, however, 
the attention of anatomists has been recently directed by Dr 
Carl Merkel of Leipsic, in an elaborate treatise on the Ana- 
tomy and Physiology of the Organs of Voice and Speech 
(Stimm und Sprach Organs, 1857). In this work he has de- 
scribed a muscular slip occasionally extending between the 
posterior surface of the cricoid cartilage and the posterior 
margin of the inferior cornu of the thyroid, and thus forming 
one of the intrinsic muscles of the larynx. His account of 
the muscle is as follows : — 
" Musculus Kerato-cricoideus. Horn-Ringknorpelmuskel, 
— This small, hitherto undescribed muscle, is not found in every 
larynx, and when present, it exists only on one side, for which 
reason I have considered it as one of the unsymmetrical mus- 
cles of the larynx. It arises, about broad, close to the 
origin of the outer (or anterior) fibres of the musculus crico- 
arytenoideus posticus, so that it appears as an additional por- 
tion of the same, and probably has been hitherto so regarded by 
anatomists, or as such overlooked by them. It does not, how- 
ever, pass upwards with this last muscle, but extends ob- 
liquely upwards and outwards, and after a short course is 
