336 



NORMAL HISTOLOGY. 



homogeneous zone, sometimes described as a cuticle, next the lumen. 

 On entering the epidermis, the duct not only loses its fibrous sheath and 

 membrana propria, but the epithelial constituents of its wall are soon 

 lost among the cells of the stratum germinativum, so that its lumen is 

 continued to the surface as a spiral cleft bounded only by the cornified cells 

 of the cuticle. 



Apart from mere variations in size, certain glands the circumanal, the 

 ciliary, and the ceruminous depart sufficiently from the typical form of the 

 coiled glands to entitle them to brief notice. The circumanal glands y 

 lodged chiefly within a zone from 12-15 mm. wide and about the same dis- 



Muscle-cell 

 Secreting-cells 



Parts of duct 



Parts of coiled 



secreting 



segment 



Muscle-cells 



FIG. 382. Section of coiled portion of sweat-gland. X 325. 



tance from the anus, are not all the same, but include, according to Huber, 

 four varieties. In addition to (i) the usual sweat-glands and (2) some 

 (Gay's) of exceptional size, (3) others have relatively straight ducts that 

 end in expanded saccules, from which secondary alveoli arise; finally (4) 

 branched glands of the tubo-alveolar type are present. The ciliary glands 

 (Molls' s} of the eyelid are not typical coiled structures, but belong to the 

 branched tubo-alveolar groups. The ceruminous glands, distinguished 

 by the large amount of oil and pigment mingled with their secretion, are 

 likewise referable to the branched tubo-alveolar type. 



The blood-vessels of the sweat-glands include arterial twigs given off 

 from the cutaneous rete, a capillary network outside the membrana propria, 

 best developed within the coiled portion of the tube, and the veins that join 

 the deeper plexus within the corium. 



The nerves are especially numerous and consist of nonmedullated 

 sympathetic fibres that traverse the fibrous sheath and form a close epilem- 



