HISTOLOGY 



105 



capsule, from which septa project into the parenchyma and divide it into 

 irregular areas. The cells are arranged in cords and spherical groups 



(Fig. 45)- 



Neuroglia cells with long stellate processes form a reticular framework 

 for the cell cords. Some of the cells of the cords have compact, small, 

 round, dark staining nuclei and homogeneous cytoplasm. Others have 

 indistinct cell outline and possess large, pale staining, oval nuclei with finely 



Acervulus 



Capsule 



Fig. 45. 



-Pineal body. (X200.) 



distributed chromatin granules. Sand granules (acervuli) are present in 

 old animals, situated beneath the capsule or in the center of cell groups. 

 The blood supply is rich and small capillaries form a dense network around 

 the glandular cells. 



Skin and Hair 



The skin. — The skin is composed of two parts, the epidermis which is a 

 stratified squamous epithelium, and the corium or dermis, the underlying 

 connective tissue. The epidermis of the mouse is very thin at all surfaces 

 where hair covers and protects the animal. At areas where the hair is 

 thin or absent (as at the anus, around the nipples, tail, feet, etc.) the 

 epidermis is considerably thicker. 



Around the nipple the epidermis consists of about ten to twelve layers of 

 epithelial cells. The cells of the basal layer which are next to the corium 

 are columnar in shape and are placed perpendicularly to the skin surface. 

 They have large oval nuclei and frequently show mitotic figures. The next 

 few layers of cells are polyhedral or flattened squamous cells. These cells 



