OP THE ABSORBENT VESSELS. 2G5 



larger part of the thoracic or PECQUETIAN duct is 

 distinguished. 



429. This duct is* a membranous canal, slender, 

 strong, more or less tortuous, subject to great varieties 

 in its course and division/)- destitute of muscular fibre 

 and nerves, and possessing here and there valves. At 

 about the lowest cervical vertebra, after passing the 

 subclavian vein, it turns back again, $ and is inserted 

 into it, being furnished with a peculiar valve at the 

 point of insertion. 



430. The motion of the chyle throughout its course 

 is to be ascribed to the contractility of its containing 

 vessels, to their valves, and the vis-a-tergo. 



431. The use of the valve placed at the opening of 

 the thoracic duct, is probably not so much to prevent 

 the influx of blood, as to modify the entrance of the 

 chyle into the vein, to cause it to enter by drops. 



By this contrivance, such a portion of fresh chyle 

 cannot have access to the blood as would stimulate the 

 cavities of the heart too violently and be imperfectly 

 and difficultly assimilated ; for fresh chyle consists of 

 very heterogeneous elements, brought not only from 

 the primae viae by the lacteals, but from every part of 

 the body by the lymphatics. 



432. These lymphatics, which constitute the third 



* See Haller, Observations de ductu thoracico in tkeatro Got tingcnsi fact &. 

 Getting. 1741. 4to. 



B. S. Albinus, Tabula vasis chylifcri. LB. 1757. large folio ; Mascagni, 

 tab. xix. 



f- v. J. C. Bohl, Vug lactete. c. h. historia naturalis. Rcgiom. 1741. 4to. 



Summering, Commentaf. Soc. Sclent. Gottingens. T. xiii. p. 111. 



J v. Haller, Opera Minor a. Vol. i. tab. xii. 



Consult, ^jnong others already and hereafter quoted, J. F. Mcckel, De 



va.fi> 



