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AN ELEMENTARY TEXT-BOOK OF BIOLOGY. 



The mouth-cavity passes behind into a short, wide gullet or 

 oesophagus, and this merges without sensible demarcation into a 

 narrower tube, the stomach. This passes backwards, gradually 

 narrowing as it does so. The lining of both oesophagus and 

 stomach is raised into longitudinal ridges. At the posterior or 

 pyloric end of the latter there is a well-marked constriction 



Fig. 51. SIDE-DISSECTION or MALE FROG. 2, 3, 4, 5, Digits; to, tongue; 

 st, stomach, upon which are blood-vessels; py, pylorus; d, duodenum; 

 i, rest of small intestine ; Li, large intestine ; cl, cloaca, opened ; r.l, and 

 l.l, right and left liver-lobes; g, gall-bladder; x, opening of bile-duct, 

 which is represented by the black line ; p, pancreas, s.v, Sinus venosus, 

 near which is cut end of right precaval ; r. a, right auricle, above which 

 are the cut ends of carotid arch, systemic arch, and cutaneous artery, 

 while the pulmonary artery is seen running along lung ; v. ventricle ; 

 t.a, truncus arteriosus. gl, Glottis; Ig, right lung. A:, Right kidney, 

 the dark space above which represents the subvertebral lymph-sinus ; 

 u-g, right urinogenital duct, which opens on a papilla in the cloaca 

 (just above the I in cl) ; bl, bladder (its opening is seen just below I in 

 cl). t, Spermary (testis) above which the vasa efferentia are seen 

 running in the mesorchium; v.s, vesicula seminalis. ol, Right ol- 

 factory lobe, from which right olfactory nerve is seen running forwards ; 

 c h, right cerebral hemisphere ; o. I, right optic lobe, passing below and 

 in front into optic tract and nerve ; cb, cerebellum ; m.o, medulla 

 oblongata; sp, spinal cord, na, Right nasal sac. 



marking the position of the pylorus or point at which the cavity 

 of the stomach communicates with that of the small intestine. 

 This is a narrow thin-walled tube, the first part of which, the 

 duodenum, forms, together with the stomach, a U-shaped loop, 



