282 THE BIOLOGY OF THE FROG chap. 



from the lymph sacs. The lymph hearts are furnished with 

 a muscular coat composed of a network of bundles of striated 

 muscle fibers. 



The beating of the lymph hearts may readily be observed 

 in a recently killed frog. Often the pulsations of the pos- 

 terior lymph hearts may be seen beneath the skin, but they 

 are easily demonstrable in a very satisfactory manner by 

 removing the integument on each side of the end of the 

 urostyle. Their pulsations have no relation to those of the 

 heart, nor is there unison between the beats of the lymph 

 hearts on the two sides of the body. 



REFERENCES 



Briicke, E. Beitrage zur vergleichenden Anatomie unci Physi- 

 ologic des Gefasssystems, I. Ueber die Mechanik des Kreislaufes bei 

 den Amphibien. Denkskr. d. k. Akad. Wiss. math.-wiss. CI., Bd. 3, 

 Wien, 1852. 



Dekhuysen, M. C. Ueber das Blut der Amphibien. Verh. Anat., 

 Ges., 6 Vers., 1892. 



Fuchs, E. Beitrag zur Kentniss des Froschblutes und der Frosch- 

 lymphe. Virchow's Archiv, Bd. 71, 1877. 



Gaule, J. Beobachtungen iiber die farblosen Elemente des Frosch- 

 blutes. Arch. Anat. u. Phys., phys. Abth., 1880. 



Macallum. Studies on the Blood of Amphibia. Trans. Canadian 

 Inst., Vol. 2, 1892. 



Marquis, C. Das Knochenmark der Amphibien in den verschie, 

 denen Jahreszeiten. Inaug. Diss., Dorpat, 1892. 



Neumann, E. Hamatologische Studien, 1. Ueber die Blutbildung 

 von Froschen. Virch >w's Archiv, Bk. 143, 1896. 



Sabatier, A. Etudes sur le cceur et la circulation centrale dans la 

 serie des Vertebres. Ann. Sci. Nat. (5), T. 18, 1873. 



Torok, L. Die Theilung der rothen Blutzellen bei Amphibien. 

 Arch. f. mik. Anat., Bd. 32, 1888. 



