62 ANIMAI, HEAT. 



are suspended in it (emulsion). The basis of the fluid found in 

 the lacteals is lymph, and it is only during digestion that the lymph 

 in the visceral lacteals becomes chylous. 



What is the character of lymph ? 



It is a limpid, watery fluid, which differs from blood-plasma only 

 in that it is somewhat more watery. Like plasma, the lymph co- 

 agulates or clots on exposure to the air, but the clot is not so firm, 

 and the clotting is due to the presence of fibrinogen and globulin. 

 Chyle is lymph in which there is present an increased amount of 

 fatty and proteid material. 



What conditions favor the absorption of food ? 



To be absorbed by the blood-vessels or lacteals we must have 

 substances in (1) a fluid state, and the more dilute in solution the 

 more ready the absorption ; insoluble substances are not apprecia- 

 bly affected by this process, nor are any dense solutions readily 

 taken up. (2) The rapid removal of the absorbed matter and the 

 renewal of fresh blood in the capillaries is of importance. Thus, 

 if the portal circulation is obstructed, so that the blood is circulat- 

 ing slowly or the capillaries are tense from intravascular pressure, 

 the absorption will be slow. 



What is the quantity of chyle which is taken into the system 



daily ? 



This is somewhat problematical, but it is estimated to be about 

 one-half to two-thirds of the volume of the blood. 



How is lymph propelled in the lymphatic vessels ? 



In the villi are bands of unstriped muscle (musculi mucosse), 

 which act to propel it into the larger channels ; muscular pressure 

 upon the lymph-vessels and intrinsic contractile power of the vessel- 

 walls help it along ; while the pumping force of the respiratory 

 movements and the " negative pressure " in the great veins are of 

 great value in maintaining the circulation. 



ANIMAL HEAT. 

 What is the normal temperature of the body ? 



98.5 F. (37 C.). This temperature is not invariable, but in 

 the superficial cavities, mouth, and axilla, which are convenient for 

 ascertaining the body-temperature, this is nearly exact. In the in- 



