30 Jl. LISSER 



TPIE CARTILAGES 



The cartilages of the larjaix, or better what become the carti- 

 lages of the laryiix, are at this stage but very imperfectly formed, 

 as is to be expected, since they reveal themselves for the first time 

 in a 10.5 mm. human embryo. Consequently their appearance 

 is introduced by condensations of mesenchyma, very well termed 

 "pre cartilage." No true cartilage formation, whatsoever, has 

 occurred at this time in any of the laryngeal cartilages, nor yet in 

 the hyoid bone and styloid process. I have investigated the 

 sections of 8, 8.5, 9, and 10 mm. embryos for earlier traces of these 

 structures, but have been consistently unsuccessful, so that I 

 place the first recognizable stage of the larynx skeleton (if one 

 may be permitted to use such an expression) at 10.5 mm. in man. 

 Of course, it is well known that all the structures of the larynx 

 have their ultimate foundation in the gill arches, and I refer those 

 interested in this very early stage of the subject to Frazaer's inter- 

 esting studies ; but I would be skeptical of finding, wdth the present 

 means of study at our disposal, actual structural status, as regards 

 separate cartilage and muscle masses, earlier* than 10.5 mm. in 

 man. 



The cricoid-cartilage. {Figs. 1-2.) Contrary to expectations, the 

 cricoid cartilage does not appear to develop from two lateral por- 

 tions of condensed mesenchyma, separate and independent of each 

 other, which later grow together ventrally and dorsally about the 

 lumen of the larynx; nor as one might be led to anticipate, form a 

 large area posterior or dorsal to the larnyx lumen (this portion 

 later becoming more prominent by far than the anterior arcus). 

 But at this stage, there is a predominance of condensed mesen- 

 chyma about the ventral portion or arcus, which fades ofT later- 

 ally, and then becomes more emphasized again, by greater com- 

 pactness and deeper stain, dorsal or posterior to the lumen, but not 

 so extensively nor so well marked as ventrally. This is true pro- 

 vided one considers the deeper staining, more strikingly isolated 

 portions of condensed mesenchyma, as the anlage. So that it 

 seems reasonable to assume that the cricoid cartilage originates 

 from an anlage primarily ventral in the position of what later be- 



