THE NATURE AND MOVEMENTS OF LYMPH. 315 



thence along the lymph-channels, or both, may be either increased or 

 diminished. 



The Characters of Lymph. 



248. As it slowly flows from its origin in the tissues to the mouth of 

 the thoracic duct (we may for simplicity's sake omit the right lymphatic 

 trunk) the lymph is subjected to the influence of the lymphatic glands, and 

 is possibly affected by the walls of the lymph-vessels. Moreover, the lymph 

 coming from one tissue differs more or less in certain characters from the 

 lymph arising in another tissue, just as the venous blood of one organ differs 

 from the venous blood of another organ ; and these differences may be exag- 

 gerated by the activity of theone or other tissue. Of these differences by 

 far the most striking is that between the lymph coming from the alimentary 

 canal during active digestion and known as chyle, and the lymph coming 

 from other parts of the body. When digestion is not going on, and when, 

 consequently, no considerable absorption of material from the alimen- 

 tary canal into the lacteals is taking place, the fluid flowing along the 

 lacteals is lymph, not differing from the lymph of other regions to any 

 marked degree. 



The food, accordingly, which flows along the thoracic duct in an animal 

 which has not been fed for some considerable time may be taken as illustrat- 

 ing the general characters of lymph. The contents of the thoracic duct 

 may be obtained by laying bare the junction of the subclavian and jugular 

 (in the dog the junction of the axillary and jugular) veins, and introdu- 

 cing a canula into the duct as it enters into the venous system at that point. 

 The operation is not unattended with difficulties. 



Lymph, so obtained, is a clear transparent or slightly opalescent fluid 

 which left to itself soon clots. The clotting is not so pronounced as that of 

 blood, but clotting is caused as in blood by the appearance of fibrin. The 

 fibrin which is formed, though scanty (0.5 per cent.), is identical apparently 

 with that of blood, and, as far as we know, all that has been said previously, 

 ( 14-23), concerning the nature of clotting blood applies equally well to 

 lymph. 



Examined with the microscope lymph contains a number of corpuscles, 

 lymph-corpuscles, which in all their characters as far as is at present known 

 are identical with white blood-corpuscles ; they vary in size from 5// to 15/Jt, 

 and the smaller corpuscles are much more abundant in lymph than in 

 blood. Like the white corpuscles of blood they exhibit amoeboid move- 

 ments. Their number varies in different animals, and, apparently, in the 

 same animal, according to circumstances ; on the whole perhaps it may be 

 said that lymph-corpuscles are about as numerous in lymph as white cor- 

 puscles in blood. Even when every care is taken to avoid admixture with 

 blood, lymph, and especially chyle, not unfrequently contains a certain 

 number of red blood-corpuscles ; sometimes these are sufficient to give 

 the lymph (or chyle) a reddish tinge. They have been observed within 

 the living lymphatic vessels, even within small ones, and have probably 

 in some manner or other made their way from the blood into the lymph 

 channels. 



249. The chemical composition of lymph, even when taken in each 

 case from the thoracic duct, varies a good deal. The total solids are 

 much less than in blood, amounting in general to not more than 5 or 6 

 per cent. Hence the venous blood of a vascular area contains rather 

 more solids than the arterial blood of the same area, since the blood in 

 giving rise to the lymph during its passage through the capillaries from the 

 arteries to the veins has parted with relatively more water than solid matter. 



