98 GENERAL PRINCIPLES OF ZOOLOGY. 



Classification of Tissues. 7. According to function and struc- 

 ture (1) epithelia, (2) connective tissue, (3) muscular tissue, (4) 

 nervous tissue are distinguished. 



8. The physiological character of epithelia is determined by the 

 fact that they cover the surfaces of the body, their morphological 

 character in that they consist of closely compressed cells united 

 only by a cementing substance. 



9. According to their further functional character epithelia 

 are divided into glandular epithelia (unicellular and multicellular 

 glands), sensory, germinal, and protective epithelia. 



10. According to the structure are distinguished simple (cubi- 

 cal, cylindrical, squamous epithelia) and stratified epithelia, 

 ciliated and flagellated epithelia, epithelia with or without cuticle. 



11. The physiological characteristic of the connective tissues is 

 that they fill up spaces between other tissues in the interior of the 

 body. 



12. The morphological distinction depends upon the presence 

 of the intercellular substance. 



13. According to the quantity and the structure of the inter- 

 cellular substance the connective substances are divided into (1) 

 cellular (scanty intercellular substance); (2) homogeneous; (3) 

 fibrous connective tissue; (4) cartilage; (5) bone. 



14. The physiological character of muscular tissue is its 

 increased capacity for contraction. 



15. The morphological characteristic is the fact that the cells 

 have secreted muscle-substance. 



16. According to the nature of the muscle-substance are dis- 

 tinguished smooth and cross-striated muscle-fibres. 



17. According to the character and origin of the cells (muscle- 

 corpuscles) the muscles are divided into epithelial (epithelial 

 muscle-cells, primary bundles) and connective-tisue muscle-cells 

 (contractile fibre-cells). 



18. The physiological distinction of nervous tissue rests upon 

 the transmission of sensory stimuli and voluntary impulses, and 

 upon the co-ordination of these into unified psychic activity. 



19. The conduction takes place by means of nerve-fibres (non- 

 medullated and medullated fibrils and bundles of fibrils); the 

 co-ordination of stimuli by means of ganglion-cells (bipolar, 

 multipolar ganglion-cells). 



20. Blood and lymph are proteid-containing fluids; rarely 

 without cells, they may contain only colorless amoeboid cells (white 



