316 ANATOMY OF THE DOMESTIC FOWL 



Isolated granules are frequently scattered throughout the lower sec- 

 tion of the corium. Barrows concludes that the lower bodies of pig- 

 ment play little or no part in the color of the external shank, as they 

 lie far below the opaque connective tissue. Melanin pigment gran- 

 ules are always contained in the pigment cells. When found in the 

 Malpighian layer, the pigment cells are of an oval form. 



Immediately below the epidermis in the shank skin, extends a 

 space less in width than the row of columnar cells, which is devoid 

 of pigment. The brown pigment is melanin, which in large quanti- 

 ties takes on a black hue. 



White skin does not contain superficial pigment. Melanin has 

 been observed in the study of white shank skin, but it lay at con- 

 siderable depth or in quantities insufficient to be noticeable. In 

 some breeds of fowls, as the Mottled Houdan, there are areas in 

 which much melanin is irregularly deposited, which circumstance 

 gives the leg its mottled appearance. 



The yellow color is the result of a deposit of the yellow pigment 

 in the fat of the shank. This may be deposited in both layers of the 

 skin, or in the corium alone. When present it is diffused throughout 

 the entire cell as well as throughout the intercellular substance. 

 In young birds the Malpighian layer contains much yellow pigment. 

 Old hens have only small quantities in the corneum. In breeds 

 with normal yellow shanks old hens that have never laid eggs show 

 a deep orange color in both the dermis and epidermis. 



In blue shanked birds melanin is present only in the corium. The 

 black pigment is seen through the semi-transparent Malpighian 

 stratum, making it appear bluish instead of brown or black. 



The black shank color results when melanin appears in the epi- 

 dermis. Two forms of black pigment occur in the epidermis: 

 granules in both layers and pigment cells in the rete Malpighii. 



The green shank is produced where there is pigment in the epi- 

 dermis and numerous melanin pigment cells in the upper corium. 

 It is an optical effect due to melanin lying under the semi-transparent 

 yellow epidermis. There is no melanin in the epidermis. 



In the beak the corium of the skin is represented by a thin layer 

 located between the periosteum and the stratum Malpighii. 

 Numerous blood-vessels pass into it, and in the soft horn-like skin, 

 occur sensory nerve fibers. 



The nails originate from the epidermis, of which they are a 

 modification. The nails of the toes are bent downward. They 



