MOVEMENTS OF THE LYMPH AND CHYLE. 303 



minishes progressively from the smaller to the larger vessels, on account 

 of the constant admixture of lymph. The size of the granules is pretty 

 uniformly ^fg-g- to ysiur o * an * nch (1 to 2 /*). They are much smaller 

 and more uniform in size in the lacteals than in the cavity of the 

 intestine. Their constitution is not constant; and they are composed of 

 the different varieties of fat which are taken as food, mixed with each 

 other in various proportions. The ordinary corpuscular elements of the 

 lymph, leucocytes and globulins, are also found in variable quantity in the 

 chyle. 



MOVEMENTS OF THE LYMPH AND THE CHYLE. 



Compared with the current of blood, the movements of the lymph and 

 chyle are feeble and irregular ; and the character of these movements is such 

 that they are evidently due to a variety of causes. As regards those constitu- 

 ents which are derived directly from the blood, the lymph may be said to un- 

 dergo a true circulation ; inasmuch as there is a constant transudation at the 

 peripheral portion of the vascular system, of fluids which are returned to the 

 circulating blood by the communications of the lymphatic system with the 

 great veins. The constituents of the lymph, however, are not derived entirely 

 from the blood, a considerable portion resulting from interstitial absorption 

 in the general lymphatic system ; and the chyle contains certain nutritive 

 matters absorbed by the lacteal vessels. These are, physiologically, the most 

 important constituents of the lymph and chyle ; and they are taken up sim- 

 ply to be carried to the blood and do not pass again from the general vascular 

 system into the lymphatics. 



As far as the mode of origin of the lymph and chyle has any bearing upon 

 the movements of these fluids in the lymphatic vessels, there is no difference 

 between the imbibition of new matters from the tissues or from the intestinal 

 canal and the transudation of the liquid portions of the blood ; for the 

 mechanism of the passage of liquids from the blood-vessels is such that the 

 motive power of the blood can not be felt. An illustration of this is in the 

 mechanism of the transudation of the liquid portions of the secretions. The 

 force with which fluids are discharged into the ducts of the glands is very 

 great and is independent of the action of the heart, being due entirely to the 

 processes of transudation and secretion. This is combined with the force of 

 imbibition, and with it forms one of the important agents in the movements 

 of the lymph and chyle. These movements are studied with great difficulty. 

 One of the first peculiarities to be observed is that under normal conditions, 

 the vessels are seldom distended, and the quantity of fluid which they con- 

 tain is subject to considerable variation. As far as the flow in the vessels of 

 medium size is concerned, the movement is probably continuous, subject only 

 to certain momentary obstructions or accelerations from various causes ; but 

 in the large vessels situated near the thorax and in those within the chest, the 

 movements are in a marked degree remittent, or they may even be intermit- 

 tent. All experimenters who have observed the flow of lymph or chyle from 

 a fistula into the thoracic duct have noted a constant acceleration with each 



