THE WORKERS OF THE BODY. 139 



of the stomach make, from the blood, gastric juice. 

 Again, we see a change of duty as we pass to a dif- 

 ferent set of cells. The cells of the liver compose that 

 large organ, and discharge its multifarious duties. They 

 are the living units of which the liver is composed, and 

 are thus part and parcel of the living colony we term our 

 body. The cells of the sweetbread make the digestive 

 juice of that gland another change of duty and another 

 race of cells. The brain-cells guide and direct the body's 

 highest acts equally with lower nervous operations. 



Cells in the skin repair our wounds and throw off 

 other cells which are cast away as the outer skin wears. 

 The bone-cells renew and repair that dense structure, 

 and build up the solid portions of the frame. In a 

 word, every act of life is performed by the cells : each 

 group of which remains distinct as a colony of workers 

 charged with the performance of a specific duty. Truly, 

 then, it may be held that our life is a divided existence 

 physically ; while from another point of view it is an 

 harmonious existence, because of the perfect co-opera- 

 tion of these wonderful workers of the body the living 

 cells. 



