48 THE FROG 



tive tissue, contains considerable pigment especially next to 

 the Malpighian layer. Between and above the branched 

 cells containing black pigment observe the golden pigment 

 cells, which are oval granular cells containing, in life, the 

 yellow pigment which gives the golden color to the skin. 



The glands are mainly confined to this layer. Each gland 

 is flask-shaped and its body is lined by a layer of thick se- 

 creting epithelial cells. If the section is cut near the middle 

 O'f the gland the neck may be seen extending through the 

 epidermis to the surface; the cells of the neck are flattened 

 but they form a layer continuous with the secreting cells of 

 the gland. The glands are of two kinds, the numerous small 

 mucus glands, and the large poison glands, much fewer 

 in number. The poison glands are distinguished by their 

 granular contents. 



(b) The inner layer is composed mainly of a compact 

 mass of connective tissue fibers which run in a wavy course 

 parallel to the surface of the skin. At intervals, transverse 

 bands of connective tissue fibers cross this layer and extend 

 into the outer layer. Both outer and inner layers are occa- 

 sionally traversed by small bundles of non-striated muscle 

 fibers extending between the glands. 



Sketch a cross-section of the skin, selecting for this pur- 

 pose a portion that shows clearly as many of the above 

 features as possible. Be sure to include a mucus gland, if 

 possible one showing the neck extending through the epi- 

 dermis. 



D. Connective tissue forms the deeper layers of the 

 skin, binds together muscle fibers, and forms tendons and 

 ligaments; in general it serves to unite the various elements 

 of an organ. There are several varieties of connective tissue, 



