in their Structure and Functions. 407 



The vegetable lymphatics, or veins, which arise from the 

 . '^pongioles, are extremely fine tubes. They ascend through 

 the stem, and convey the nutritious materials from the roots 

 to the leaves, where they terminate. In many instances they 

 pass through glands ; as, for example, in the gramineous 

 plants, the stems of which have placed upon them, at certain 

 spaces, knots or joints ; which, in their structure, are very 

 analogous to the absorbent glands of the animal system. It 

 has long been a subject of enquiry among physiologists, to 

 ascertain upon what principle the contents of the absorbents 

 effect their entrance into these vessels. Some have sup- 

 posed that they enter on the principle of capillary attrac- 

 tion ; others, that they enter by the operation of the vital 

 power: some, by filtration, or imbibition through the coats of 

 the vessels ; and others, again, by the pressure of the atmo- 

 spheric air. Dutrochet, however, ascribes absorption to a 

 new principle, which he calls endosmose. It is difficult to 

 decide which of these theories is the most correct. That of 

 Dutrochet appears to me to be the least objectionable. I may 

 remark, however, that, upon whatever principle we explain 

 the entrance of substances into the mouths of the lacteals, the 

 lymphatics, and the veins, belonging to the animal body ; on 

 the same we can account for the ingress of substances into 

 the orifices of the absorbents and veins of plants. '^i. 



'^^' From absorption, we pass on to the function o^ circulation, 

 jiA.s soon as the chyle, the decayed corpuscles of the system^ 

 and the various substances brought in contact with the surface, 

 have entered within the orifices of the absorbents and veins, 

 they are carried along the minute ramifications of these ves- 

 sels into their larger branches. At length they are all poured, 

 by one or two large trunks, into a vein situate at the left side 

 of the neck. In this vein they are mixed with the whole mass 

 of blood, and conveyed along with it, to the right side of the 

 heart. The venous blood, now replenished with new materials, 

 is propelled from the right cavity of the heart, into the puW 

 *&onary artery. By the branches of this vessel it is conveyed 

 ' tlirough the lungs, where it is exposed to the vivifying influ- 

 ence of the atmospheric air. After it has been duly elaborated 

 in the lungs, it is returned, by appropriate vessels, to the left 

 side of the heart, the contractile power of which forces it 

 'into a hirge artery called the aorta; whose numerous ramifi- 

 ''cations convey it to every part of the body, furnishing ma- 

 ' tei'ials for growth, for nutrition, and for the supply of all the 

 "."^'aHous secretions. After serving these purposes, the blood 

 *^^s deprived of its nutritive properties, and, being mixed with 



B'Wdra clpt'bartic4es, it becomes def^ifio4^ate<iyHBrjtf Enable to 



