BBCTS. 171,172,173.] ORGANS OF RESPIRATION. 375 



Tr tns., 1S52, i. p. 295. Structure and Use of the Spleen, Lond., 1854. Fk. 

 Fuhrer, ia Arch.f.ph. Heilkunde, 1854., p. 149, and 1856, p. 105. Stinstra, 

 De Funct. Lienis, Diss. Groning, 1854. Huxley, On the Structure of the Mal- 

 \ian Bodies, in Microsc. Journal, ii. p. 74. Kolliker, On the Function of 

 thi' Spleen, Wwrzb. Trains., vol. vii. Billroth, in Mull. Arch., 1357, p. 104. 

 \. Sasse, De Milt, Besch. in hare Structuur, etc., Anast., 1855. Schonfeld, 

 Diss. Phys. de Funct. Lienis, Gron., 1855. E. Crisp, Treatise on the Structure 

 and Use of the Spleen, Loud., 1857. 



OF THE ORGANS OF RESPIRATION. 



§ 171. In the respiratory organs are usually enumerated the 

 larynx, trachea, and lungs. In this connexion, however, it will be 

 proper to describe also the thyroid and the thymus glands, two 

 organs which, at their origin, are related to the ' branchial arches ' 

 of the embryo, and which retain, perhaps, some physiological re- 

 lation to the lungs. 



•& 1 - 



Of the Lungs. 



§ 172. The lungs consist of a structure exactly similar to that 

 of a compound racemose gland, the lobes, lobules, and air-cells 

 constituting the proper parenchyma; whilst the bronchia, trachea, 

 and larynx represent the excretory apparatus. Considered as such 

 a gland, the lung presents peculiarities both in function and struc- 

 ture : in function, since the process in the cells is one of absorption 

 as well as excretion, and affects the entire mass of the blood ; in 

 structure, since the peculiar nature of the contents of the cells 

 requires a special structure, firm and at the same time elastic. 



§ 173. The larynx is the most complex part of the air-passages, 

 and consists, firstly, of a firm framework, the laryngeal cartilages 

 with their ligaments ; secondly, of numerous small muscles attached 

 to these ; and lastly, of a mucous membrane full of glands, which 

 lines its interior. 



The cartilages of the larynx are not all alike in their structure, 

 seeing that some consist of ordinary cartilaginous tissue, others of 

 fibro- cartilage, and a third sort, again, are composed of the so- 

 called reticulated or yellow cartilage. To the first kind belong the 

 thyroid, cricoid, and arytenoid cartilages, all of which possess a 

 homogeneous, hyaline matrix, with cartilage cells scattered through 

 it (fig. 157). The affinities of these cartilages are especially with 



