QO ELEMENTS OF HISTOLOGY. [Chap. xi. 



corpuscles, and other solid particles, are readily taken 

 up by the stomata (see Fig. 20) and brought into 

 the lymphatics. Here the respiratory movements of 

 the intercostal muscles, of the diaphragm, and of 

 the lungs produce the result of the action of a 

 pump. 



118. There is a definite relation between the 

 lymphatics and the epithelium which covers the 

 mucous membranes and lines the various glands and 

 also between the endothelium covering serous mem- 

 branes and that lining vessels and lymph cavities 

 viz., the albuminous semifluid cement substance (see 

 former chapters) between the epithelial or endothelial 

 cells is the medium by which fluid and formed matter 

 pass between the surfaces and the lymph-canalicular 

 system, i.e., the rootlets of the lymphatics. 



119. Lympli taken from the lymphatics of dif- 

 ferent regions differs in composition and structure. 

 That from the thoracic duct contains a large amount 

 of colourless or white corpuscles (lymph corpuscles), 

 each of which is a protoplasmic nucleated cell 

 similar in structure to a white blood corpuscle. 

 They are of various sizes, according to the stage of 

 ripeness. The smaller contain one, some of the larger 

 contain two and three, nuclei. The latter show more 

 pronounced amo3boid movement than the small ones. 

 A few red corpuscles are also met with. Granular 

 and fatty matter is present in large quantities during 

 and after digestion. 



In the frog (and also in other lower vertebrates, 

 e.g., reptiles) there exist certain small vesicular lymph 

 cavities, about an eighth of an inch in diameter, 

 which show rhythmic pulsation ; they are called lymph 

 Jiearts. On each side of the os coccygis and under- 

 neath the skin is a pulsating posterior lymph heart. 

 The anterior lymph heart is oval, and situated on 

 each side of the processus transversus of the third 



