556 INTEGUMENTARY SYSTEM 



2) Development of the contour feather 



a) Formation of barbs during the primary or early phase of contour-feather 

 formation 



b) Secondary phase of contour-feather formation 



c) Formation of the barbules and the feather vane 



d) Later development of the feather shaft 



3) Formation of the after feather 



4) Development of the later down and filoplumous feathers 

 5. Mammals 



a. Characteristics of the mammalian skin 



b. Development of the skin 



1 ) Development of the skin in general 



2) Development of accessory structures associated with the skin 



a) Development of the hair 



b) Structure of the mature hair and the hair follicle 



3) Development of nails, claws, and hoofs 



4) Development of horns 



5) Development of the skin glands 



a) Sebaceous glands 



b) Sudoriferous glands 



c) Mammary glands 



C. Coloration and pigmentation of the vertebrate skin and accessory structures 



1. Factors concerned with skin color 



2. Color patterns 



3. Manner of color-pattern production 



a. Role of chromatophores in producing skin-color effects 



b. Activities of other substances and structures in producing color effects of the 

 skin 



c. Genie control of chromatophoric activity 



d. Examples of hormonal control of chromatophoric activity 



e. Environmental control of chromatophoric activity 



A. Introduction 



1. Definition and General Structure of the Vertebrate 

 Integument or Skin 



The word integument means a cover. The word appHes specifically to the 

 external layer of the body which forms a covering for the underlying structures. 

 The integument also includes the associated structures developed therefrom, 

 such as hair, feathers, scales, claws, hoofs, etc. The latter are important fea- 

 tures of the body covering. The skin is continuous with the digestive and 

 urogenital tracts by means of mucocutaneous junctions at the lips, anus, and 

 external genitalia. 



The integument is composed of two main parts, an outer epidermis and 

 an underlying corium or dermis. Below the latter is a third layer of connective 

 tissue which connects or binds the corium to the underlying body tissues. This 

 third layer forms the superficial fascia (tela subcutanea or hypodermis). The 

 superficial fascia is continuous with the deep fascia or the connective tissue 



