THE SKIN 25 



10. Do all mammals have hair? 



11. What habit is common to no other vertebrates except mammals? 



12. Give two points of dilTerence between the two subclasses of Mammalia. 



13. Name the orders of Eutheria and give an example of each. 



14. Which orders derive their names from the habits of the animals? 



15. Which orders derive their names from anatomic features? 



16. Which orders are aquatic? 



17. What is the ultimate syllable of all family names? 



18. Explain what is meant by binomial nomenclature. 



19. Name three families of Carnivora. 



20. Examine specimens and determine where in the teeth of Canidae differ 

 from those of Felidae. 



21. What two rank names constitute the scientific name of an animal? 



22. Give the scientific name of five Carnivora, two Ungulata, and two 

 Primates. 



23. Define organ, system, tissue, and cell. 



24. Name two organs belonging to each system. 



25. How do the elements of the four kinds of tissue differ? 



THE SKIN AND ITS APPENDAGES 



The skin invests the body completely and is continuous with 

 the lining of the digestive and urogenital canals. It varies in 

 thickness in different regions, being very thin on the lips, ears, 

 and eyelids, and exceedingly thick on the pads of the feet and 

 on the ventral neck region, where, in contest with an enemy, 

 it is most likely to be seized. A fibrous connective tissue binds 

 the skin to the subjacent structures. In some places the union 

 is very firm, as on the distal parts of the limbs and the head, 

 while in other regions it is loose, as on the lateral aspect of the 

 trunk. 



The skin consists of an external layer, the epidermis, and 

 beneath this, the dermis or true skin, designated the corium. 

 The epidermis is composed of numerous strata of epithelial 

 cells. Those on or near the surface are much flattened while 

 the deeper ones are more or less cubical. As the superficial 

 layer desquamates in minute fragments, forming what is com- 

 monly called dandruff, it is replaced by cells developed from 

 the deeper layers. 



