96 COMPARATIVE ZOOLOGY. 



The lacteals are only a special part of the great lym- 

 phatic system, which absorbs and carries to the thoracic 



duct matter from all parts 

 of the body." The lymph 

 is a transparent fluid having 

 I* many white blood corpus- 

 cles. It is, in fact, blood, 

 minus the red corpuscles, 

 while chyle is the same fluid 

 rendered milky by numer- 

 ous fat - globules. During 

 the intervals of digestion, 

 the lacteals carry ordinary 

 lymph. This fluid is the 

 overflow of the blood the 

 plasma and white corpus- 

 cles which escape from the 

 blood capillaries, and carry 

 nutriment to, and waste from, 

 those parts of the various 

 tissues which are not in con- 

 tact with the blood capilla- 

 ries. This surplus overflow 

 is returned to the blood by 



PIG. 61. Principal Lymphatics of the Hu- f; ne lymphatics. The Current 

 man Body: a, uuion of left jugular and J r 



subclavian veins; &, thoracic duct; , IS kept lip by the movements 

 receptaculum chyli. The oval bodies . . . . , . 



are glands. of the body, and in many 



Vertebrates, as Frogs and Fishes, by lymph hearts. 



Like the roots of Plants, the absorbent vessels do not 

 commence with open mouths ; but the fluid which enters 

 them must traverse the membrane which covers their mi- 

 nute extremities. This membrane is, however, porous, 

 and the fluids pass through it by the forces of filtration 

 and diffusion. 58 How the fat gets into the lacteals is not 

 yet well understood, but the lacteals are themselves rhyth- 

 mically contractile, and force the absorbed chyle towards 



