CHAP, i.] TISSUES AND MECHANISMS OF DIGESTION. 49' 



The Characters of Lymph. 



295. As it slowly Hows 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 exaggerated by the activity of the one 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 alimentary 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 fluid accordingly which flows along the thoracic duct in 

 an animal which has not been fed for some considerable time 

 may be taken as illustrating 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 introducing a cannula 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, 

 '05 p.c., 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 in 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 p to 15 //,, and the smaller corpuscles 

 are much more abundant in lymph than in blood. Like the 

 white blood 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 corpuscles 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 



F. 32 



