RESPIRATORY APPARATUS IN MAMMALIA. 



Fig. 311. 



of the various cartilages (Figs. 312, 314). 4. Prepare the muscles in conformity with the 

 indications furnished by a glance at Fig. 314. 5. Remove a larynx as carefully as possible, 

 80 as not to injure the walls of the pharynx, in order to study the interior of the organ, and 

 especially its pharyngeal opening (Fig. 315). 



Form — Situation. — The larynx forms a veiy short canal, which gives admis' 



sion to the air during respiration, and is at the same time the organ of the voice. 



It is a cartilaginous box, flattened on each side, and open from one end to 



the other : the anterior orifice being situated at the bottom of the pharyngeal 



cavity, and the posterior continuous with the trachea. 



This apparatus, situated in the intra-maxillary space, is suspended between 



the two cornua of the os hyoides, and 

 fixed to the extremities of these append- 

 ages by one of its constituent pieces. It 

 supports the pharynx, and by means of 

 the walls of the latter is attached to the 

 circumference of the posterior openings 

 of the nasal cavities. 



In order to facilitate description, this 

 brief notice of its form, situation, general 

 relations, and mode of attachment will be 

 followed by a notice of its structure ; 

 afterwards, the study of its external and 

 internal surfaces will receive attention. 



Structuee of the Larynx. — It 

 comprises in^its structure : 1. A cartila- 

 ginous framework, composed of five pieces. 

 2. Muscles, which move these pieces. 3. 

 A mucous membrane spread over the inner 

 surface of the organ. 4. Vessels and 

 nerves. 



1. Cartilaginous fratneivorh of the 

 larynx. — In this we find : three single 

 median cartilages — the cricoid, thyroid, 

 and epiglottis ; and two lateral cartilages, 

 the arytcenoid. All are movable, one upon 

 the other. 



Cricoid Cartilage (Fig. 311, c). 

 — This cartilage, as its name indicates 

 (xptKos, cTSos, " hke a ring "), is exactly 

 like a ring with a bezel placed upwards. 

 Depressed on each side, but all the less as 

 the animal has its respiratory apparatus 

 well developed, this ring offers ttvo faces, and ttvo borders or circumferences. The 

 internal face is smooth, and covered by mucous membrane. The external face is 

 provided, in the middle of the widened portion forming the bezel, with a little 

 eminence more or less prominent, elongated in the form of a crest, and separating 

 the two posterior crico-arytaenoid muscles (to which it gives attachment) from 

 each other. On the sides of this bezel are two small, articular, concave facets, 

 which coiTespond to the branches of the thyroid cartilage. Nothing remarkable 

 is to be noted for the remainder of the extent of this face. The superior circum- 



CARTILAGES OF THE LARYNX DIS- 

 ARTICULATED. 



C, Anterior surface of the cricoid: 1, facet 

 for the arytaenoid ; 2, facet for the thyroid. 

 A, External surface of the arytcenoid. a', 

 ibid., internal surface: 3, facet for the 

 cricoid. T, Thyroid, seen from above: 4, 

 4, posterior extremities of its wings; 5, 

 appendages for the hyoid cornua ; 6, body of 

 the thyroid. F, Epiglottis, supero-posterior 

 surface: 7, 7, prolongations forming the 

 supposed superior vocal cords. 



