LYMPHATIC SYSTEM. 615 



pieces. In the frog the anterior pair are situate below the 

 posterior edge of the scapula, and above the broad transverse 

 processes of the third cervical vertebra, the posterior pair 

 on each side of the free end of the long coccygeal bone, quite 

 superficially near the sides of the anus ; they are seen pul- 

 sating, about sixty times in a minute, through the skin of 

 the entire animal without dissection, and they propel the 

 lymph collected from the anterior and posterior parts of the 

 body and extremities, into the neighbouring venous trunks. 

 They contain only the usual colourless lymph, and by dis- 

 tending them with air the lymphatics of the extremities 

 become inflated, and also the lymph spaces beneath the skin. 

 The anterior pair of these lymphatic hearts propel their con- 

 tents, on each side, into a branch of the jugular vein, which 

 becomes distended by each contraction of the sac, and the 

 posterior pair send their lymph on each side into a branch 

 of the ischiadic vein. The posterior pair of these pulsating 

 sacs are the more constant in their development, and have 

 been observed, where the anterior were imperceptible, in 

 salamanders, serpents, and saurian reptiles. They are pro- 

 vided with simple valvular folds at their orifices in the 

 python, where they send their lymph into branches of the 

 renal veins. 



The structure and distribution of the lymphatic system of 

 reptiles have been illustrated by the researches of Bojanus, 

 Panizza, and other anatomists, especially in the chelonia, 

 where they present great facilities for their investigation, 

 from their great size, their extensive distribution, and the 

 still imperfect development of their valves. The imperfect 

 development of the valves in the lymphatics of all the rep- 

 tiles, still allows injections to pass from the larger trunks of 

 these vessels towards their branches and capillaries, and 

 hence the convenience and the facility of illustrating their 

 distribution through the textures and organs, by preparations 

 from this class, especially from the vegetable eating chelo- 

 nian reptiles, where they are largest and most extensively 

 developed. They are always wide and dilatable vessels, and 

 they present a knotted or beaded appearance, most conspi- 

 cuous when filled, injected, or inflated, from the constric- 

 tions caused internally by the valves, and the dilatations of 

 the elastic parietes of the vessels between the valves. Sue- 



