136 Proceedings of the Royal Physical Bociety. 
attached to the posterior margin of the inferior horn of the 
thyroid cartilage. The inferior laryngeal nerve passes under 
it, and the kerato- cricoid ligament crosses it at nearly a right 
angle. The entire muscle is about 3-4'" long. Its action, 
which certainly cannot be important, is to fix the lower horn 
backwards and downwards ; it opposes in some measure the 
part of the crico-thyroid muscle connected to the anterior 
margin of the horn." (Pp. 132, 133.) 
My attention having been directed some months ago by 
Professor Goodsir to this description of Dr Merkel, I have 
since that time carefully examined the larynx in almost all the 
subjects received into the dissecting-rooms of the University, 
and have thus been enabled to supplement the account of Dr 
Merkel with some additional particulars, as well as to correct 
an error into which he has fallen. Thirty-two specimens have 
been dissected by me, and amongst these the muscle existed 
in seven cases, being in the ratio of 21*8 per cent. In four of 
these it was on the right side only, in two on the left, and in 
one on both sides. Thus, the statement of Merkel, that the 
muscle exists only on one side," is not absolutely correct ; 
and although it is undoubtedly true as a general rule, yet, 
like most general rules, it admits of occasional exceptions. I 
have had a drawing made of the larynx, which was from a 
male subject, in which this double muscle was found, an en- 
graving of which is here subjoined. 
The kerato-cricoid muscle is not confined to the larynx of 
one sex, as I have found it both in the male and female. The 
majority of cases in which it was present were certainly in the 
male, but I do not feel disposed to attach much importance 
to this circumstance, as the examination of a larger number 
of instances might perhaps alter the proportion, and render 
it equal in the two sexes. 
The muscle exhibits considerable difi'erences in breadth ; 
thus I have found it as much as one-eighth of an inch broad 
in one larynx (that being the broadest one I have yet seen), 
and a mere thread in another, — other specimens furnishing 
examples between these two extremes. In length it corre- 
sponds to the distance between its origin on the cricoid and 
its insertion into the inferior cornu of the thyroid, — a few 
