442 ELEMENTS OF BIOLOGY 



Book lungs. The chief respiratory organ of the spider. They are es- 

 sentially modified gills housed in chambers in the ventral body 

 wall. 



Botany. The science of plant life. 



Breathing. The process of intake of a supply of oxygen from the en- 

 vironment and the expulsion of carbon dioxide by the animal body. 



Bronchus. One of the tubes in vertebrates that lead from the trachea 

 into the lungs. 



Buffer. The term is employed by the chemist to include substances 

 that release OH ions in the presence of an acid and H ions in the 

 presence of an alkali, thus acting to neutralize both and to main- 

 tain a constant acid-alkali balance. 



Cadaver. The body of a dead animal. 



Calorimeter. A device employed to measure the heat produced by a 

 reaction. 



Cancer. An abnormal structure composed of cells occurring in ani- 

 mals. If the cells differentiate into a tissue it is known as a benign 

 cancer or tumor; if there is no differentiation and the cells con- 

 tinue to divide it is known as a malignant cancer. 



Carbohydrate. An organic substance containing carbon, and also hy- 

 drogen and oxygen in the same proportions as in water. 



Cartilage bones. Bones that pass through a cartilage stage in their de- 

 velopment; phylogenetically derived from the primitive cartilage 

 endoskeleton. 



Catabolism. Metabolic processes essentially destructive in nature. 



Catalyst. A substance that causes chemical reactions to occur, or speeds 

 up chemical reactions without being itself used up in the reaction. 



Cell. A mass of protoplasm which constitutes the structural and func- 

 tional unit of living organisms. It always contains a nucleus or 

 nuclear material and is usually set off from other cells by a boundary 

 membrane of some sort. 



Cell wall. Non-living covering of the cell. 



Cellulose. A complex carbohydrate formed by plant metabolism that 

 commonly forms the cell walls of plant cells. 



Cementum. a layer of substance that binds the tooth to its socket. 



Centrosome. a small body just outside the nucleus of the cell. The first 

 observable step in mitosis is its division and the migration of the 

 two resulting centrosomes to opposite poles of the nucleus. 



Centrosphere. Modified protoplasm in the vicinity of the centrosome. 



