Protoplasm 



313 



constantly in process of change, it seems in all essential ways to 

 be similar in all plants, in all animals, and in man. 



Protoplasm not only has the same appearance in man, animals, 

 and plants, but it also has the same chemical com- 

 position and the same characteristics. It is com- 

 posed of the elements oxygen, hydrogen, nitrogen, 

 carbon, sulphur, and phosphorus. 



Among the properties of protoplasm are response 

 to influences outside itself, ability to move, to breathe, 

 to take in, digest, and assimilate food, to excrete 

 waste material, and reproduce itself. 



Protoplasm may be observed with the compound 

 microscope in the stinging hairs of the common net- 

 tle, in the eggs of the starfish, in the cells of young 

 plant shoots, and in the cells of the leaves of certain 

 water plants. 



Protoplasm makes up the living part of all or- 

 ganisms. Nearly every organism contains lifeless as 

 well as living matter. There is no protoplasm in life- 

 less matter, such as the mineral matter of our bones, 

 the outer layers of our skin, the skeletons of sponges 

 and corals, the feathers, claws, and beaks of birds, 

 the outer covering of insects, and the outer bark of 

 trees. 



Huxley called protoplasm 

 the physical basis of life and 

 there has been no better def- 

 inition. That it is the physi- 

 cal basis of life is proved by the fact that 

 life is found only where protoplasm exists. 

 Cells. We all know that bodies are 

 made up of organs. These organs are com- 

 posed of tissues, and tissues are composed 

 of collections of similar cells. A cell is a tiny amount of protoplasm 

 which may or may not be enclosed in a membrane. It can be 

 seen only with the aid of the compound microscope, and when 

 thus observed will usually show at or near the center a minute 



A PLANT 

 CELL 



A magnified 

 stinging hair 

 of a nettle. 

 Arrows indi- 

 cate the direc- 

 tion the proto- 

 plasm moves. 



AN AMCEBA 



N. Nucleus. 

 P. Protoplasm. 



