Dean D. Lewis . 183 



met with wliich will explain the different orientation of cartilage cells 

 adjacent to the process, and the significance of the wedge-shaped carti- 

 lage described by the investigator. 



Eambaud and Eenault/' in discussing the development of the thyroid 

 cartilage, say that the laminae of the thyroid cartilage are united by means 

 of a circumscribed median cartilage — " le cartilage vocal." It may be 

 distinguished by its transparency. This cartilage is well-marked in young 

 subjects. In the adult, however, the cartilage may not be present, but 

 is represented by an indistinct point of ossification. It is lozenge-shaped, 

 and its borders unite with the lamina of the thyroid cartilage. 



Henle " states that horizontal sections through the thyroid cartilage 

 show that its laminas are separated more or less distinctly from a middle 

 piece by a condensed layer of interstitial substance, curved so that the 

 convexity is directed mediad. This middle piece of the thyroid carti- 

 lage is the lamina mediana cartilaginis thyreoideffi of Halbertsma. In 

 this piece the cartilage nests are smaller and more closely grouped than 

 in the laminae. The ligamenta thvreo-arytasnoidea inferioria and their 

 corresponding muscles arise from this part, or a connective tissue mass, 

 connected with it. The fibers from the mass pass a short way into the 

 middle piece, so that this tissue immediately posterior to the hyaline 

 cartilage resembles in structure fibro-cartilage. 



Nicolas '"' states that immediately after birth there is found in the 

 median line of the thyroid cartilage, at the level of the vocal cords, a 

 special arrangement of the cartilage cells, corresponding to the position 

 of the lamina mediana. In the adult this middle portion of the thyroid 

 cartilage can be distinguished from its laminae only by the different 

 orientation of its cells. 



The embryology of the thyroid cartilage explains the different orienta- 

 tion of the cartilage cells adjacent to the median process, and in it. I 

 have sectioned the larynges of young dogs, and have found, occupying 

 the space between the laminae of the thyroid cartilage, the wedge- 

 shaped cartilage which Katzenstein states is comparable to the median 

 process described by Gerhardt in man. I consider it to be the lamina 

 mediana which fuses later in the lower animals than in man. 



Friedrich's description of the median process is correct, with the 

 exception of that of the perichondria! relation. The perichondrium does 

 not i)ass between the hyaline substance of the thyroid cartilage and the 



"Rambaud et Renault: Origin et devellopement des os. Paris, 1864. 



"Henle: Handb. der Eingeweidelehre des Menschen; p. 243. 



""Nicolas: Poirier et Charpy's Traite d'Anatomie humaine. T. 4, p. 447. 



