io8 BIOLOGY OF THE LABORATORY MOUSE 



Vincent (94) this is much shrunken in prepared sections, but in expanded 

 state surrounds the foUicle entirely and fills in the space between the walls. 

 The root sheath shows two slight enlargements forming the superior and 

 inferior swellings. Vincent stated that many nerve fibers have their 

 terminations here. 



Striated muscle fibers surround the connective tissue sheath. The con- 

 traction of the muscles around the opening of the follicle permits the hair to 

 vibrate freely. Muscle fibers connect the walls of adjacent foUicles and 

 are responsible for the uniform, almost continuous movement of these hairs. 



Hibernating, Lacrimal and Harderian Glands 



Hibernating glands. — Some of the adipose tissue differs from the usual 

 white fat and has a characteristic light brown color which is due to the 

 presence of pigment. It is divided into lobules by loose fibrous connective 

 tissue and was considered to be a gland of internal secretion by the early 

 investigators. Many different names were suggested for it, among them 

 hibernating gland, interscapular gland, multilocular adipose tissue, oil 

 gland, etc. It is present as a large bilobed mass between the scapulae, in 

 the superior mediastinum about the thymus, in the cervical region, in each 

 axillary fossa, and in the abdominal cavity as perirenal lobes (80). 



The fat cells have large, round, centrally located nuclei with fine chroma- 

 tin granules. The distribution of fat is multilocular, being present in the 

 form of numerous small droplets. The abundant granular cytoplasm con- 

 tains small spherical vacuoles (dissolved fat droplets), the outline of which 

 stains intensely with eosin. Groups of cells are supported by reticular fibers 

 which also surround the capillaries. The blood supply is rich. 



According to Rasmussen (80), "The structural differences such as the 

 more granular character of the cytoplasm of the cells . . . are not sufficient 

 evidence to warrant the conclusion that the structure under consideration is 

 of any endocrine significance." 



Lacrimal glands. — The exorbital lacrimal glands are situated slightly 

 below and in front of the ears. The gland is tubulo-alveolar and is composed 

 of small lobes, which are enveloped and divided into lobules by fibrous con- 

 nective tissue (Fig. 47). Structurally the gland resembles the parotid 

 gland. It differs from it in that its intra-lobular ducts are lined by low 

 cuboidal epithelial cells, which lack basal striations. The alveoli are 

 slightly larger and more loosely arranged than the similar structures of the 

 parotid gland. 



