162 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. 1 



141. The lungs (/g), 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.fiy, 6*<r.) until the 

 following structures are laid bare : 



144. The trachea (tr) y 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 : 

 sHt open the pericardium, and cut off the apex of the ventricle ( 197). 

 When the bleeding has stopped, pu h a cannula through the \\ ound 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 Caroline, 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. 



