Tin-: /;/>T//M ///> APPABATUS i.\ /;//;//>. c;. 



The thyimig ijliiinl in young Ruminants is more voluminous than in the Foal, and is 

 situated higher up in tlirccrvif.il region. In the ( arnivorii. it is divided intu two lira; 

 l>nt il is .-mall, and completely lodged between the layers of tin- anterior mediastinum. 

 It pei-i-u tor some time after birth, aud seldom disappears in Us* tbau a year.) 



S OF THE GLANDIFOKM BODIES ANNEXED TO THE RESPIBATOUY APPAKATI S IN 

 MAN WITH THOSE OF ANIMALS. 



In Man the two lobes of the thyroid body are connected by an isthmus, and the upper 

 extremity of the lobe is carried up to the side of the thyroid curtilage. The i-tlnniis 

 ufteii gives origin to a process of variable length and size, called tin: /;(///;'</ or third 

 lot*-, which is generally sitoated to the left A muscle is sometimes found conn, .-t-d 

 with the isthmus or pyramid, and is attached above to the body of the os hyoides or to 

 the thyroid cartilage ; it has been named the hvntor ijlnmlnl-' tlyr- . 



The tl,yutn* ijlnnd is composed of two lobes, a right and left, only joined by 

 ci'imeetive t. --ne. and having no structural communication. There is a cervical and u 

 thonicic jNirtion, the whole extending from the fourth rib as high as the thyroid gland. 

 Alter birth it continues to enlarge until the cud of the second year, and begins to 

 diminish between the eighth and twelfth years.) 



CHAPTER II. 



THE RESPIRATORY APPARATUS IN BIRDS. 



THE organs composing the respiratory apparatus of birds, offer conditions altogether 

 s| < ial. and which l.uve a remarkable influence on the mechanism of respiration. The 

 modifications imp- > d upon the performance of this function will be indicated after an 

 examination of the tabular ujifMratu*, which carries the air into the lung, and the 

 characters of that organ, as well as the air reservoirs (or sacs} annexed to it. 



THE TUBVLAB APPARATUS. AVhen this apparatus is compared witii that of Mammals, 



. sensible differences are observed at least in domesticated birds. 

 The nostrils, pierced through the upper mandible of the beak, bave no membranous 

 and movable wings, and the natal fossas open into the pharynx by a long, narrow slit 

 In-hind the bony palate. A transverse row of small, horny papilla?, placed at the 

 anterior extremity of this aperture, represents the soft palate. 



Tlie luryiuc has no epiglottis : a defect which does not prevent the complete occlusion 

 of the glottis during the pa--a_'e of food, as the laiyngeal orifice in ciicnm.-criU-d h\ two 

 lateral lips which then meet in the most exact manner. 



The trd'lt'ii is oompowd of complete cartilaginous rings and not simple a.-- 1 

 j-on.'-l'irds. tin- last riii--' is a second larynx, the real organ which produces the modulated 



eat nre.-; it onlv exists in a rudimentary condition in jKmltry, ho\\ 



the hi-t tiaeh--:d pi-'', in them In ing slightly dilated, and showing at the origin of the 



luiiiifhi a membranous lajvr, from whose vibration results cries or crowing. Other 



.lir jM-culiarities belonging to the trucln a deserve to U- de-i-nl.. .1 1,< re, if they 



.ot the .-xe.n-ive appanage of some wild fowl. We are content t> im ntiou tlio 



!(-e of the bony drum found at the terminal extremity of the trachea in the 



\shi-tling duck, and the remarkable convolutions that tube forms in the breast-bone of 



< 1 in, de Swans. 



The 1,,-nnrl,; only show incomplete rings in their structure. They pass into the lung 

 }>y it- inferior face, towaidl the union of its anterior and t\\o |<'.-t. ri.T thinU. \S 



ibing this organ, their mode of ramificuitiou, and the nature of the relations tin \ 

 Jn-ar to it- pi-"per ti.--iie will IKJ considered. 



Tn I ^1 ^appey, iii the remarkable memoir published by him in 1847, has 



iU-d them as follow.- : - The lun-_'s of l.ird.- are situated on the laU-ral jxirts 

 vertebnc of the back which .- j-nate them, and lying against the arch of the th 

 ea\iiy, to which they ndhere. Their m-y colour resembles that pi.-.nt<d by these 

 - in Man and the Mammalia during uterine life, and for s"ine time after birth ; 



!y remarkable f,. r their r. -trietid volume, which scarcely r. | 



part of the thoracic capacity. Their rontii;nrat:"n i- t'ar r. m..\il tn-m the 

 I foim <>f the Inn-- in Mamm: !-. and the oval torm of the same organs in n-ptili .- 

 th. \ aie .-< mi-elliptical, and if the two lungs of a Mammal w i. i-o to base, 





