30 CHEMICAL AND PHYSICAL PROPERTIES 



called pseudopods or false feet, a phenomenon characteristic 

 of the amebse. This is a pushing out or budding of a portion 

 of the cell wall into which the cytoplasm of the protozoon 

 flows, enlarging the false foot until it embraces all the con- 

 tents of the cell. The space formerly occupied by the proto- 

 zoon is vacated, the cell having moved to a position directed 

 by the pseudopod. In some protozoa a portion of the body 

 has muscular power and drives the organism. Again, a por- 

 tion of the cell wall may be fitted with a sucking apparatus, 

 serving either to drive the protozoon or to attach it to another 

 body. Protozoa gain their food by simple absorption through 

 the wall or by possessing definite vacuoles or openings for 

 this purpose. Excretion takes place the same way. 



Reproduction may occur by simple division as in bacteria. 

 Protozoa may divide by simple budding with breaking off of 

 the smaller piece similar to the first stages of the pseudopod. 

 The higher protozoa go through a complicated process of 

 division such as is seen in the higher animal cells, or there 

 may be male and female elements with conjugation. 



CHEMICAL AND PHYSICAL PROPERTIES. 



Bacteria. Chemically the bacterial body is composed 

 chiefly of water (80 to 90 per cent.), the remaining part 

 being made up of protein (see below), fatty matters, includ- 

 ing waxes, a trace of the carbohydrates (sugars and starches), 

 and inorganic material. The cellulose supposed to be charac- 

 teristic of vegetable cells is present in very small quantities, 

 if at all. The largest part of the solid matter is comparable 

 to the organic substances which form the most important 

 foodstuff for animals, the proteins. Chlorides and phos- 

 phates of the lighter metals form the inorganic salts. 



The wall of the bacterial cell permits the passage of fluids 

 containing foodstuff, and is therefore comparable to the 

 wall of other vegetable and animal cells. 



