ANATOMY OF THE COMMON FROG. 473 



the cloaca, where it opens just in front of the ureter. At 

 the season of reproduction the oviduct is found very much 

 distended with ova. Its anterior end has a ciliated opening 

 into the body-cavity. In the neighborhood of the sexual 

 glands lies the fat-body (/). 



The lungs (lu) are two large sacs with very elastic walls, 

 richly supplied with blood-vessels. These vessels spring 

 from the pulmonary artery. From each division of the 

 truncus arteriosus are given off four branches (Fig. 433, II). 

 The first is the pulmonary aorta (Pa), which also gives off 

 a large cutaneous branch ; the second, the true aortic arch 

 (Ao), which, curving backwards, unites with its fellow just 

 in front of the kidneys and below the spinal column, to form 

 the descending aorta ; the third (cr), the carotid artery, run- 

 ning to the head, and bearing at its origin the singular caro- 

 tid gland (eg] ; the fourth, the lingual artery. The blood 

 is returned from the lungs by two veins, which empty into 

 the left auricle. 



The space of the lower jaw is covered over by a thin trans- 

 verse muscle (My), the mylohyoid. On either side behind 

 the posterior edge of this muscle lies a croaking bag or air- 

 sac (S). In the mouth are to be observed, 1st, the mus- 

 cular tongue, attached by its anterior end to the lower jaw, 

 and forked posteriorly ; 2d, the openings of the nasal cavi- 

 ties ; 3d, the recessus Eustachii, lying further back, and 

 leading into the tympanic cavity ; 4th, the opening of the 

 oesophagus ; and 5th, the slit-like epiglottis. 



The muscles are best dissected in alcoholic specimens. 

 The muscles of the hind limbs are as follows : On the ven- 

 tral surface, the cut ends of the recti abdominis (r. ##.); 

 on the ventral surface, 1, of the thigh, outwardly musculm 

 vastus internus (mvi), the adductor longus (a), the sar- 

 torius (ms), adductor magnus (a"), rectus internus minor 

 (ri") ; the rectus internus major (ri 1 ) ; a small part of the 

 adductor brevis can be seen close to the pubis between the 

 adductor magnus and the rectus internus major ; underneath 

 the rectus internus major lies the long and the semitendino- 

 sus with two -heads ; 2, of the leg (crus) gastrocnemius (g), 

 and between that muscle and the bone the tibialis posticus ; 



