HISTOLOGY AND CHEMISTRY OF LYMPH. 189 



Histology of Lymph. Pure lymph is a colorless, watery 

 looking liquid; examined with a microscope it is seen to 

 contain numerous pale corpuscles exactly like those of the 

 blood. It contains none of the red corpuscles. 



Chemistry of Lymph. Lymph is not quite so heavy as 

 blood, though heavier than water. It may be described as 

 blood minus its red corpuscles and considerably diluted, 

 but of course in various parts of the body it will contain 

 minute quantities of substances derived from neighboring 

 tissues. 



Summary. To sum up: the blood and lymph pro- 

 vide a liquid in which the tissues of the body live; the 

 lymph is derived from the blood, and affords the immedi- 

 ate nourishment of the great majority of the living cells of 

 the body; the excess of it is finally returned to the blood, 

 which indirectly nourishes the cells by keeping up the 

 stock of lymph. The lymph itself moves but slowly, but 

 it is constantly renovated by interchanges with the blood, 

 which is kept in rapid movement by the heart, and which, 

 besides containing a store of new food-matters for the lymph, 

 absorbs the wastes which the various cells have poured into 

 the latter. 



What does lymph look like? What is seen when it is examined 

 with a microscope? 



How does lymph differ in density from blood and from water? 

 How may it be briefly described? What does it contain in various 

 regions of the bod}^? 



What do the blood and lymph provide? Whence is the lymph de- 

 rived? What does it afford? What becomes of its excess? How 

 does the blood play a part in nourishing the cells of the body? 

 Which moves faster, lymph or blood? How is the lymph renovated? 

 What keeps the blood in motion? What does the blood do besides 

 renewing the food-matters in the lymph? 



