ANATOMY OF THE COMMON FROG. 475 



in front is the tibialis anticus (fa). On the dorsal surface 

 of the thigh (Fig. 433, III) the glutmus (gl), the pyriformis 

 (p), the rectus anticus femorus (ret,), the vastus externus 

 (ve), the biceps (#), the semimembranosus (sm), lying deep 

 between the biceps and semimembranosus are seen the 

 femoral vessels and sciatic nerve ; the rectus anticus, vastus 

 interims and externus are known collectively as the triceps 

 femoris ; in the leg the gastrocnemius (g) and peroncsus (p). 



The sympathetic nerves can be seen as two cords, one on 

 either side of the vertebral column. The spinal nerves can 

 be seen as white threads on the dorsal surface of the body- 

 cavity. The brain (Fig. 373) may be dissected out by open- 

 ing the skull from above. The olfactory lobes of frogs and 

 toads are fused together, but separate in the tailed Batrachia. 

 The seventh, eighth, and ninth spinal nerves unite to 

 form the very large sciatic trunk ; the intercommunications 

 of these nerves form the lumbar plexus ; while the second 

 and third spinal nerves form the brachial plexus from which 

 arises the brachial nerve. (C. S. Minot.) 



Certain glands in the skin of some Batrachians secrete a 

 corrosive, or as in the European Salamandra maculosa, a nar- 

 cotic poison, which is poisonous to small animals. The 

 toads secrete in the parotid glands a bad-smelling fluid, 

 which applied to tender skins produces erysipelas. Lacerda 

 states that the poison of the Brazilian Bufo ictericus is a 

 milky humor from the glands on the sides of the neck. The 

 action of the poison is less fatal to small animals than that 

 of the European toad ; it gives a slight acid reaction and is 

 not soluble in alcohol, while that of the European toad is. 



Like fishes, the Batrachians assume high colors during 

 the breeding season. The males of the newts at this time 



Fig. 433. Anatomy of common Frog. My, mylohyoid ; sr, sternoradials ; th, 

 thyroid ; lu, lungs ; /, fat-body ; Te, testis ; St, stomach ; Sp, spleen ; R, rectum ; 

 a, adductor longus; mvi, vastus interims ; ms, sartorius; n', rectus interims 

 major; ta, tibialis anticus ; g, gastrocnemius; ri", rectus internus minor; a", ad- 

 ductor mafnus ; rob. rectus' abdominalis ; B, bladder ; vd, vas deferens ; &, gall- 

 bladder; Ki, kidney ; pv, portal vein ; Li, liver ; F, vena cava inferior ; Ao, aorta ; 

 8, vocal sac-, or croaking-bag. 



II. Origin of the arterial trunks. /, arteria ingualis ; eg, carotid gland, which is 

 merely a rete mirabile ; cr, carotid artery ; Ao< aortic arch: Pa, pulmonary artery. 



III. Dorsal view of muscles of hind leg. ql, glntseiw ; ra, rectus anterior ; p, pyri- 

 formis ; ve, vastus externus ; sm, semi-menibranosus ; b, biceps ; g, gastrocneraius ; 

 per, peronreus. Drawn by C. S. Minot. 



