290 



.MAMMALIA. 



Srd 



.h 



finally on the intercostal arteries and the iliac veins of the Dolphin. 



A renal-portal system is always absent. 



The lymphatic system is provided with numerous lymphatic 



glands, and its main trunk (dt ictus t-horacicus), which is placed on 



the left, opens into the 

 superior vena cava. 



Of the so-called vascular 

 glands the spleen, the thy- 

 mus, and the thyroid, which 

 is especially developed in the 

 young, are very generally 

 present (fig. 675). 



The paired lungs (tig. 675) 

 are freely suspended in the 

 thoracic cavity, and are dis- 

 tinguished by the numerous 

 ramifications of the bronchial 

 tubes, the finest branches of 

 which end with conical, fun- 

 nel -shaped dilatations (///- 

 fundibula), which are pro- 

 vided on their lateral surfaces 

 with swellings. Respiration 

 is mainly effected by the 

 movements of the diaphragm, 

 which forms a complete, 

 usually transversely placed, 



Fi. >. G7C. -Circulatory apparatus of Man (from Owen septum between the thoracic 



after Alien Thomson). TV, Right Ventricle ; T' S , and abdominal cavities : by 



left Ventricle ; Ad, right Auricle ; As, left Auricle ; 



A o, Aortic arch;, 4 o<Z, descending Aorta; Cd, right the Contraction of its mUS- 



Carotid; C,, left Carotid; Sd, right subclavian 1{U . tg it actg ^ an in _ 



Artrry ; .SV, left subclavian Artery ; -V, Meseuteric 



Artery; Jl, common Iliac Artery; Va, inferior spiratory muscle ; that IS, it 



Vena Cava; TV, superior Vena Cava ; J7' common dilateg the thoracic Cavity. 



Iliac vein ; T ji, Vena portSe ; Jd, right Jugular _ * 



J.s, left Jugular ; Svd, right subclavian Vein The elevation and depression 



Svs, left subclavian ; Ap, pulmonary Artery ; T> f , ., , , pflfpct 



. ATT m i -n T> i 7> OI DJie 11US ttlaU lltLVo ctll clltr^u 



pulmonary Vein ; Tr, Trachea ; Sr, Bronchi ; I' 



Lungs ; L, .Liver ; N, Kidney ; D, Intestine. in dilating the thorax. The 



trachea is, as a rule, straight, without coils, and divides at its lower 

 end into two bronchi leading to the lungs. There may be, in addition, 

 a small accessory bronchus on the right side. The trachea is supported 

 by cartilaginous half-rings which are open behind, and only excep- 

 tionally by complete rings of cartilage. The first part of the trachea, 



