254 MANUAL OF HISTOLOGY. 



The inferior thyro-arytenoid ligaments, or true weal cords, 

 are made up almost entirely of yellow elastic fibres stretched 

 across from the thyroid cartilage in front, to the vocal processes 

 and adjacent anterior borders of the arytenoids behind. The 

 elastic bundles originate, anteriorly, in a mass of connective 

 tissue which occupies the angle of the thyroid. Posteriorly, 

 many of the fibres are prolonged into the arytenoid cartilage, 

 converting that part of it into reticular tissue. These liga- 

 ments are continuous below with the lateral crico-thyroid mem- 

 branes, and are described by some anatomists ' as their superior 

 borders. 



The innermost fibres of the internal thyro-arytenoid mus- 

 cle mingle with the outer fibres of this ligament, some ending 

 in or taking their origin from them. The intimate relation be- 

 tween the muscle and the ligament can be seen in a vertical sec- 

 tion through the larynx. 



Of the laryngeal cartilages, the three larger are of the 

 hyaline variety. Horizontal sections show a broad central area 

 with two zones between it and either the outer or inner sur- 

 face. The appearance of the zones or bands is thus described 

 by Rheiner : a " 1. A thin peripheral portion, appearing to the 

 naked eye as a narrow, bluish, opalescent band, which con- 

 sists of a transparent and longitudinally striated matrix with 

 elongated cartilage- cells arranged parallel to the surface. 2. 

 The intermediate layer, a narrow, whitish, opaque band, con- 

 sisting of a dull yellowish ground-substance with numerous 

 large mother-cells containing fatty daughter-cells. 3. The 

 broad central layer, with a perfectly transparent homogeneous 

 matrix and few cells. The intercellular substance increases, 

 relatively to the contained cells, from without inward, and, in 

 the interior, presents numerous large spaces in which no cells 

 are found. In the thyroid and cricoid cartilages the outer 

 peripheral zone is thicker arid more easily distinguished than 

 the inner." 



The following peculiarities are to be noted : the central por- 

 tion of the thyroid, viz., that part which forms the anterior 

 projection or angle, is distinguished by the great number and 

 small size of its cells. It is penetrated by numerous fibres 



1 Quain's Anatomy, eighth edition, Vol. II. , p. 284. 



2 Quoted by Merkel in Anatomic u. Phys. des mensch. Stimm- u. Sprach-Organs. 

 Leipzig, 1863, S. 166. 



