w 



ks structure is the same as that of the lymphatics, and its inner part is 

 furnished with valvular folds. Its increase of size is not progressive, as 

 it approaches towards its termination; on the contrary, there are. seen, 

 here and there, dilatations of diffeient sizes, separated by proportionate 

 contractions. Sometimes, it divides into several vessels which ioosculate 

 and form lymphatic plexuses. The opening at which the thoracic duct 

 enters the subclavian vein, is furnished with a valve, better calculated to 

 prevent the flow of blood into the lymphatic system, than to moderate the 

 too rapid flow of the lymph into the torrent of circulation. Compres- 

 sion of the thoracic duct, in aneurism of the heart and aorta, gives rise to 

 several kinds of dropsy, a disease always depending on the loss of equi- 

 librium, between the processes of inhalation and exhalation, either from 

 increased action of the exhalants, or from the absorbents refusing to take 

 up the lymph, in consequence of obstruction in the glands, or 01 com- 

 pression of the duct. 



XL VIII. The nature of the lymph is far from being as well under- 

 stood, as that of the vessels along which it circulates. Haller considers 

 it as very analogous to the serum of the blood, and says, that this sub- 

 stance, to which he frequently gives the name of lymph, is like the fluid 

 contained in the absorbents, slightly viscous and saltish; that heat, alco- 

 hol, and the acids coagulate it; in short, that it possesses all the qualities 

 of the albuminous fluids. The serum of the blood exhaled, throughout 

 the extent of the internal surfaces, and even, within the substance of our 

 organs, by the capillary arteries, is absorbed by the lymphatics, and is 

 one of the principal sources of the lymph, which resembles it much. It 

 may be conceived, however, that the nature of the lymph must be much 

 more compound than that of the serum of the blood, since the lymphatic 

 which absorb, almost indiscriminately, every kind of substance, take up 

 what comes off from our organs, and the recrementitious parts of our 

 fluids; and these are sometimes recognizable in the absorbents, when 

 marked by striking qualities, as fat by its not mixing with aqueous fluids, 

 and bile by its deep yellow colour. 



The chyle, which is necessarily affected by the various kinds of food 

 which we use, has different appearances in the same persons, varying 

 according to the quality of the different substances on which we feed ; 

 indigo gives it a blue colour; it is reddened by madder and beet root, 

 and is changed to 'green, by the colouring matter of several vegetables, 

 Sec. In a great number of experiments performed on living animals, it 

 has always appeared to me, such at it is described by authors, white, 

 with a slight viscidity, and very like milk, containing a very small quan- 

 tity of flour. It is easy to collect a certain quantity of chyle, by tying the 

 thoracic duct of a large dog, of a sheep, or even of a horse, as was done 

 several times at the veterinary school at Alfort. This fluid, when ex- 

 posed to the air, on cooling, separates into two parts; the one, forming 

 a kind of gelatinous coagulum, very thin and not unlike the buffy coat of 

 inflammatory blood; the other, in greater quantity and liquid, rising 

 above the coagulum, on its being detached from the sides of the cup to 

 which it adheres. The coagulated mass is semi-transparent, of a light 



is, however, the most subject to deviations of any in the animal economy. Author's 

 Note. 



The fact referred in the above note also explains the appearance of certain sub- 

 stances in the blood, after the thoracic duct has been tied. Godman. 



S 



