171 



THE RESriRATORY Al'I'MiM 1'ti IN MAM MA 1. 1 I 



Interim!!;/, the human larynx has no snbepiglottio r,r nnbarytcm.id .sinus like tl at of 

 S.lipcils, though it has lateral, or Morgagni's, ventricles Hint aset ml n little to the ont.si.le. 

 i.t'tlic .superior vocal cords. 



2. Tracftea. 3. Brondn. There is little dill', rem-e. to 1x5 remarked in tli.-e. The 

 tnirhi'a is about fonr inches long and alxjnt one inrh \\ide, and is compo.-ed of ulmtit 

 twenty C-shapo<l rings, which are closely united. n.s in animals. It in Mtual. .1 in tin- 

 median plane, in the up{x:r part of tho luck, when- it is embraced l>y tlie lubes of the 

 thyroid gland; at its entrance into the chest it deviates slightly to the right, '['he t\\o 

 short canals between its lower extremity and the lungs are the /</</<</// .- the right 

 l>ronchns is the shortest and widest, and has an almost horizontal direction, entering 

 tlie right lung at the fourth dorsal vertebra; the left is longer and kv-s voluminous, ami 

 reaches the corresponding lung at the fifth vertebra. 



4. Lung*. The lungs weigh about forty ounces. As in all animals, the right is 

 more voluminous than the left, and is divide.! into three lobes; the hitter has only t\\o. 

 The inferior vena cava is not surrounded by pulmonary tissue; the principal lobes an- 

 partitioned into lobules, which are visible on the surface, and on the limits of which 

 are deposited, only in the adult, a notable quantity of pigmentary matter, that u r iv< s th.- 

 lungs the appearance of a chess-board. There is nothing to be said respecting their 

 internal conformation and structure. 



Fig. 243. 



THE GLANDIFORM BODIES CONNECTED WITH THE EE8PIBATOBY APPARATUS. 



1. Thyroid Body (or Gland). 



The thyroid gland, or body, is composed of two oval lobes of a reddish- 

 brown colour, and is situated close to, and behind, the larynx, beside the two 

 first rings of the trachea. 



These two lobes, distinguished as right and left, appear at first sight to 

 be perfectly independent ; but a less superficial examination shows thorn to 

 be united by an intermediate portion (the isthmus), which passes across the 

 anterior face of the trachea. 



Each lobe of the thyroid body corresponds, inwardly, to that tube ; 

 outwardly, it is covered by the subscapulo-hyoid muscle. 



STRUCTURE. The thyroid body 

 is composed of a fibrous envelope, 

 and a proper tissue or parenchyma. 

 The fibrous envelope is composed 

 of slender, but strong connective 

 tissue; it sends from its inner 

 face a large number of thin nu- 

 cleated laminaa that intersect each 

 other, forming spaces in which the 

 proper tissue is contained. 



The parenchyma is divided into 

 lobules, whoso presence is mani- 

 fested on the surface of the organ. 

 They are composed of vesicles, the 

 shape and contents of which vary 

 considerably with age and situa- 

 tion. In the foetus, or very young 

 animal, they arc round or ellip- 

 tical, and constituted by a thin 

 amorphous membrane, lined by 

 polygonal colls with a large nu- 

 cleus, and containing a granular 

 fluid. In the adult, these vesicles 

 are deformed, and, after being distended, several arc confounded together ; 



OKOUP OF GLAND VESICLES FROM THE THYROID 

 BODY OF A YOUNG SUBJECT. 



", Connective tissue ; b, Basement membrane of 

 the vesicles; c, Epithelial cells. 



