466 



ZOOLOGY 



SECT. 



the right anterior intercostal (i.cs.), and the rir/ht anterior epigastric 

 or internal mammary also open into it. The h^ft precaval receives 

 a series of veins similar to those forming the right, except that 

 there is no azygos on the left side. 



The postcaval vein {ptc.) is formed in the hinder part of the 

 abdominal cavity by the union of the internal iliacs (i. il. v.), 

 bringing the blood from the back of the thighs. Shortly after 

 its origin it receives the two external iliacs (e.il.v.) bringing the 

 blood from the hind-limb. In front of this a pair of ilio-lumhar 

 (i.l.) veins join it ; a little farther forward a pair of spermatic {spm.) 

 or ovarian veins ; and opposite the kidneys a pair of rc%«Z veins (r.). 

 From the liver the blood is carried to the postcaval by the hepatic 

 veins {h.v.). A pair of small p)Osterior p)hr€nic veins {p>-ph.) bring the 

 blood from the diaphragm and open into the postcaval as it passes 

 through the substance of the latter. 



The hepatic portal system consists, as in other Vertebrates, of a 

 system of veins conveying blood from the various parts of the 

 alimentary canal to the liver, the trunks of the system uniting to 

 form the single large /'orto/ it />i (Fig. 1089, ^j.'V.). The principal 

 veins of the portal system are the I ieno- gastric, duodenal, anterior 

 mesentric, and posterior mesenteric. There is no trace of a renal 

 portal system. The red blood corpuscles are circular, biconcave, 

 non-nucleated discs. 



Respiratory Organs. — The larynx (Fig. 1092) is a chamber 

 with walls supported by cartilage, lying below and somewhat 



behind the pharynx, with 

 ep 



th 

 sanT 



fir 7, 



"^ 



cr 



which it communicates 

 through a slit-like aperture. 

 The cartilages of the larynx 

 are, in addition to the epi- 

 glottis, which has been al- 

 ready referred to (p. 460), 

 the large thyroid (th), which 

 forms the ventral and lateral 

 walls, the ring-like cricoid 

 (cr.), the two small aryte- 

 noids (ary.), and a pair of 

 small nodules, the cartilages 

 of Santorini (sant.), situated at the apices of the arytenoids. The 

 vocal cords extend across the cavity from the thyroid below to 

 the arytenoids above. Leading backwards from the larynx is 

 the trachea, or wind-pipe (Fig. 1088, tr.), a long tube the wall 

 of which is supported by cartilaginous rings which are incom- 

 plete dorsally. The trachea enters the cavity of the thorax, 

 and there divides into the two Ironchi, one passing to the root 

 of each lung. 



The lungs (Fig. 1093) are enclosed in the lateral parts of the 



Fig. 10;i2.— Lepus cuniculus. Larj-nx. A, 

 ventral view ; B, dorsal view. ai-y. arytenoid ; 

 cr. cricoid ; ep. epiglottis ; sant. cartilage of San- 

 torini ; th. thyroid ; tr. trachea. (From Krause, 

 after Schneider.) 



