168 BJEPTILIA. 



collected together into a receptaculum chyli ; one or several thoracic 

 ducts convey the lymph and chyle into the anterior venae cavae. 



The pulsating lymphatic hearts, which have been discovered 

 chiefly in the ischiadic region of the Frogs, Salamanders, Serpents, 

 Tortoises, and Crocodiles, constitute one of the most remarkable 

 peculiarities of the present system in Reptiles. They are provided 

 with muscular walls, the fibres composing which exhibit under the 

 microscope the peculiar transverse striae characteristic of the 

 voluntary muscular tissue. The posterior pair of these hearts may 

 be seen externally pulsating very distinctly immediately beneath 

 the integument covering the ischiadic region in the Frog ; they 

 discharge their contents into a branch of the ischiadic vein ; situated 

 more deeply above the third cervical vertebra, lie the anterior 

 lymphatic hearts in the same animal, and they appear to impel 

 their contained fluid into a branch that opens into the jugular 

 vein. These organs appear to be largest in the Chelonia, where, 

 placed invariably behind the superior extremity of the iliac bones 

 upon the origin of the semitendinosus muscle, they measure an inch 

 in diameter, and receive lymphatic vessels of the thickness of a 

 quill ; they pour their lymph into a vein that forms a twig of the 

 reno-portal vein. 



If the results be correct (for some degree of uncertainty always 

 attends them) that have been obtained by injections of the vascular 

 system of Reptiles with mercury, it would appear that their blood- 

 vessels are surrounded, to wit, in the Serpents and Tortoises, in a 

 sheath-like manner by very large and broad lymphatic vessels, and 

 that plexuses of the latter cover all the viscera, and are moreover 

 attached by ligamentous filaments to the arteries. A very large 

 reservoir of lymph is usually situated in the lower part of the belly, 

 and from its bifurcation the thoracic ducts take their rise ; in the Frog 

 several such reservoirs .are met with. A more direct passage into 

 the venous branches is never met with. 



The relative size and form of the Blood-corpuscules in the present 

 class is most remarkable ; in all the naked Amphibia, as the Frogs, 

 Tritons, and Salamanders, they are large and oval in shape, but it 

 is in the Ichthyodea, as in Proteus, that they attain the greatest size 

 in the whole animal kingdom, being from eight to twelve times longer 

 than in man. The corpuscules are smaller, but invariably oval in 

 all the Squamigerous Reptiles, even in the Crocodiles, and resemble 

 in figure and diameter those of Birds. The rounded lymph-corpus- 

 cules are always smaller and more irregular. 



