136 Proceedings of the Royal Physical Society. 



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 differences 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 



