REPTILIA. 



301 



direction transverse, whilst in the latter the 

 canals are smaller, and their course longitudi- 

 nal. 



In the small intestine, likewise, there are 

 two layers of lacteal vessels, one superficial 

 (the peritoneal), and the other deep-seated. 

 There is, moreover, a third stratum, composed 

 of very fine lymphatics, which penetrate as 

 far as the villi of the mucous membrane of 

 the intestine. In the stomach they are com- 

 paratively few in number. 



The lymphatics of the lungs form a net- 

 work, the meshes of which are scattered and 

 are irregular ; upon the heart they are very 

 numerous, inclosing rhomboidal spaces. 



In the green lizard the lymphatics form a 

 beautiful plexus around the corpus caver- 

 nosum, and a complicated net-work upon the 

 cloaca ; but it is remarkable that Panizza was 

 not able to inject the lymphatics of the limbs, 

 nor those of the testicles or kidneys. 



In Ophidian reptiles, the whole extent of 

 the alimentary canal, with the exception of 

 the oesophagus, is covered with lymphatic 

 vessels, which are disposed in two layers, one 

 deep-seated, made up of very delicate tubes, 



the other superficial, the vessels of which are 

 larger. 



The kidneys also are very rich in lym- 

 phatics. 



The central parts of the lymphatic system 

 of reptiles, corresponding with the reccptacu- 

 lum chyli and thoracic duct of mammalia, are 

 extraordinarily capacious. They resemble, in 

 fact, great serous cavities which are never 

 entirely filled with lymph, but which establish 

 a communication between the lymphatics of 

 the viscera and other organs, and the veins 

 situated in front of the heart. These reser- 

 voirs embrace the principal arteries, and even 

 the veins that they encounter in their passage, 

 covering them as with a sheath (fg. 219, c.). 

 The lymphatics from the different organs, as 

 they run towards these receptacles, form 

 plexicose chains or detached brandies, which 

 are more or less knotty in their calibre. 



In the Chelonian reptiles, according to 

 Hewson, all the lymphatics derived from the 

 hinder part of the body terminate in a plexus 

 which surrounds the right aorta, and from 

 thence open into a reservoir situated further 

 forward beneath the left aorta. This latter 



Fig. 219. 



Viscera of the European Tortoise in situ, seen from behind, 



E, the trachea ; C C, great central reservoirs of the lymphatic system surrounding the principal arterial 

 and venous trunks; F F, subcluvian vessels divided; bb, hh, ii, trunks of the large vessels derived from 

 the arches of the aorta; i i, lateral margins of the liver; z z, the lungs; o o, the kidneys; N, external 

 iliac artery; u r, lateral supplementary bladders; v v, urinary bladder dilated transversely; H, the penis 

 retracted into the cloaca ; R, termination of the urethral groove. {After Bo j anus.) 



