1 62 ZOOTOMY. 



139. The heart (v, r.au, l.au), situated a short distance 

 in front of the liver and enclosed in a delicate membrane, the 

 pericardium. (For the characters of the heart see §§197 

 — 200.) 



140. The postcaval vein {pt.c), a large vessel, usually- 

 gorged with blood, passing from the anterior border of the 

 liver forwards to the right side of the heart.' 



141. The lungs {Ig), two transparent, thin- walled sacs 

 lying one on each side of the postcaval vein between the 

 heart and the liver (see § 213). 



142. More or less of the reproductive organs can 

 usually be seen even without moving the intestines : by 

 turning the latter aside the testes of the male (§ 166) and 

 the ovaries (§ 169) and oviducts (§ 170) of the female, 

 are displayed. 



143. A large vein is also seen, by turning aside the 

 intestines, lying between the testes or ovaries, and passing 

 forwards to the postero-dorsal region of the liver ; this is the 

 hinder part of the postcaval {pt.c). 



XVII. Dissect away the mylo-hyoid {m.hy) and under- 

 lying muscles {c.mn, o.hy, s.hy, d^r.) until the 

 following structures are laid bare : 

 r44. The trachea (tr), an annulated tube lying in the 

 middle ventral line of the throat. 



1 The injection of the lizard's vascular system is conveniently done 

 as follows : Render the animal insensible with chloroform : lay bare the 

 heart as directed (§ XVI), taking care not to injure the epigastric vein : 

 slit open the pericardium, and cut oif the apex of the ventricle (§ 197). 

 When the bleeding has stopped, pu h a cannula through the wound into 

 the cavity of the ventricle and thence into the right aorta (§ 199), and tie 

 it in place by a ligature round the base of the ventricle. A warm 

 solution of gelatine coloured with carmine, vermilion, or French blue 

 (ultramarine) is the best injecting medium ; it is firm enough to pass 

 through capillaries, so that the whole vascular system, with the excep- 

 tion of the pulmonary vessels, can be injected at one operation. 



