ECOLOGY AND BIOLOGY OF THE PACIFIC WALRUS 53 



Fig. 35. Diagrammatic representa- 

 tion of the relative thickness of 

 the cornified and Malpighian 

 layers of epidermis on the ante- 

 rior parts of the face of a Pacific 

 walrus. 



are abundant there in the subepidermal tissues, suggesting that these also are 

 particularly sensitive areas. 



Pilosebaceous Units 



Each pilosebaceous unit on the body usually comprises a single hair with sev- 

 eral sebaceous glands and one apocrine sweat gland (Sokolov 1960). The 

 sebaceous glands are compound, and each empties into the hair canal through a 

 separate duct. Well-developed sweat and sebaceous glands were present in the 

 skin of fetal walruses in their first (lanugo) pelage, some 6 months before birth. 

 In those specimens, the opening of the sweat duct into the pilary canal always 

 was distal to the openings of the sebaceous ducts. 



The sweat glands of adult walruses taken in autumn and winter were of small 

 diameter and apparently inactive. Atrophy of the sweat glands in autumn was 

 recognized earlier by Sokolov (1960). In all of the calves and older animals taken 

 during the spring and summer, the sweat glands were capacious and apparently 

 productive. In most of my specimens, the ducts entered the hair canal at the 

 same level as or somewhat distal to the entrance of the slightly convoluted sweat 

 duct; in a few, the sweat duct was slightly more distal. 



Some of the largest sweat glands, with a capacity at least twice that of glands 

 on the body surface, were found in the anterior surface of the snout, where they 

 were associated with groups of small hairs in the spaces between the mystacial 

 vibrissae. Conceivably, these larger glands function in the production of scent 

 that is important in olfactory recognition during the nose-to-nose greeting 

 between mother and calf and between older animals (see Miller 1976). Sweat 

 and sebaceous glands were absent from the hairless skin of the fore and hind 



