SECTION V. 



LYMPH. 



As THE blood circulates through the capillaries, it is continually 

 losing a portion of its fluid constituents through transudation, carrying 

 with the water of the blood various salts, gases, and organic matters 

 in solution. This fluid, which is termed the lymph, bathes all the ulti- 

 mate tissue elements and supplies them directly with materials necessary 

 for their nutrition, at the same time removing the soluble effete matters 

 which result from cellular activity. This fluid, thus resulting from trans- 

 udation from the blood-vessels, not only fills all the intercellular chinks 

 of the different tissues, but also finds its waj r from the extra-vascular 

 spaces and large lymph-spaces (as the lacunae of the connective tissue 

 and great serous sacs) through the minute radicals of the lymphatic 

 vessels to the lymphatic glands, and from there through the large lym- 

 phatic trunks again enters the blood-vessels (veins in the neighbor- 

 hood of the heart). 



From its origin it is evident that the lymph must have a compo- 

 sition closely similar to that of the liquor sanguinis ; but since different 

 organs take from the lymph different substances needed by their nutri- 

 tive demands, and yield effete matters of varying composition, its com- 

 position must vary according to the region from which it is taken and 

 the stage of activity of the organs contributing to it. This contrast of 

 lymph, drawn from different localities, is most marked in the lymph 

 taken from the tymphatics of the mesentery during the period of diges- 

 tion when compared with that drawn from other localities. Lymph 

 drawn from the so-called lacteals during the digestion of fat is termed 

 chyle, and is of a milky appearance from the large quantities of minute 

 fat-globules which it holds in suspension. The characters of the chyle 

 have been already considered. 



Lymph may be obtained by inserting a cannula into the thoracic duct of an 

 anaesthetized animal where it empties into the junction of the large veins at the 

 root of the neck ; or in large animals, such as the horse and ox, it maybe collected 

 by a similar process from the lymphatics which accompany the carotid artery. 



The amount of tymph which may be obtained by such a process varies 

 under different circumstances. It is increased by active or passive move- 

 ments, by venous obstructions, and by poisoning with curare. It is 

 diminished by decrease in blood pressure. 



(463) 



