422 CHYLIFEROUS SYSTEM. 



opened lacteals, we perceive that they are still destitute of 

 the internal folds, which form the valves throughout their 

 whole course in higher classes, they already present a sac- 

 culated or beaded appearance when injected, from numerous 

 small constrictions like rudimentary valves. Two or three 

 small lenticular glandular bodies, seen in some fishes as far 

 forward as the oesophagus, appear more analogous to a 

 thymus than to chyliferous glands. 



The trunks of the chyliferous vessels communicate with 

 the trunks of the lymphatics, as the lymphatics communicate 

 with the trunks of veins, or as the ducts of chylopoietic 

 glands communicate with the alimentary canal ; but the dis- 

 similarity of function is equally obvious in the several parts 

 thus connected with each other. The lacteals from the in- 

 testine, and the lymphatics from the posterior parts of the 

 body, generally unite to form two great trunks before they 

 enter the receptaculum, and this reservoir formed by their 

 union, whether single or double, is comparatively very large 

 in fishes. The two thoracic ducts, before entering the inter- 

 nal jugular veins, receive the lymphatic trunks from the head 

 and fore part of the body, and they form several loops and 

 plexuses by their frequent anastomoses in this place ; and 

 indeed the two thoracic ducts, whether they originate from a 

 single or double receptaculum, communicate with each other 

 in the freest manner, by lateral unions, throughout their whole 

 course. The capillary lacteals exceed in diameter the capil- 

 laries of the blood-vessels, and in the frequency of their anas- 

 tomoses throughout their course they much exceed the veins, 

 which surpass the arteries in this character. 



In the amphibious animals the chyliferous system is nearly 

 in the same condition of development as in fishes, being still 

 destitute of valves and mesenteric glands, and conveying only 

 a thin limpid chyle, like the fluid of lymphatics, from the 

 intestine to the blood. They appear to have a similar origin 

 and distribution on the intestine ; they follow closely the 

 C3urse of the blood-vessels, and form the same anastomoses 

 and plexuses on the expanded mesentery of these animals, as 

 in fishes. Their wide reservoir formed by the union of their 

 trunks, sends forw r ard two thoracic ducts, to terminate in the 

 jugular veins, with the trunks from the anterior pair of lym- 

 phatic hearts. Although the lymphatic pulsating cavities. 



