1398 



HUMAN ANATOMY. 





Duct 





Alveoli 



Sebaceous glands from skin covering nose. X 60. 



into the ducts and alveoli of the sebaceous glands is directly prolonged from the 



outer root-sheath of the epidermis, where associated with the hair-follicles, or from 



the epidermis where the hairs 



FIG. 1162. are wanting. The periphery 



of the alveolus is occupied by a 

 single, or incompletely double, 

 layer of flattened and imper- 

 fectly denned basal cells, that 

 rest immediately upon the mem- 

 brana propria and are distin- 

 guished by theirdark cytoplasm 

 and outwardly displaced oval 

 nuclei. Passing towards the 

 centre of the alveolus, the next 

 cells contain a number of small 

 oil drops which, with each suc- 

 cessive row of cells, become 

 larger and appropriate more 

 and more space at the expense 

 of the protoplasmic reticulum 

 in which they are lodged. In 

 consequence, the cells occupy- 

 ing the axis of the alveoli, which 

 are completely filled and with- 

 out a lumen, contain little more 

 than fat. As the cells are 

 escaping from the glands they 

 lose their nuclei and individual 

 outlines and, finally, are merged 



as debris into the secretion, or sebum, with which the hairs and skin are anointed. 



The necessity for new cells, created by the continual destruction of the glandular 



elements that attends the activity of the sebaceous 



glands, is met by the elements recruited from the FIG- 1163. 



proliferating basal cells, which in turn pass towards 



the centre of the alveolus and so displace the 



accumulating secretion. 



THE SWEAT GLANDS. 



These structures (glandulae sudoriferae), also 

 called the sudoriparous glands, are the most important 

 representatives of the coiled glands (glandulae gloini- 

 fornies) often regarded as constituting one of the two 

 groups (the sebaceous glands being the other) into 

 which the cutaneous glands are divided. They 

 occur within the integument of all parts of the body, 

 with the exception of that covering the red margins of 

 the lips, the inner surface of the prepuce and the glans 

 penis. They are especially numerous in the palms and soles, in the former locality 

 numbering more than uoo to the square centimetre (Horschelmann), and fewest on 

 the back and buttocks, where their number is reduced to about 60 to the square 

 centimetre ; their usual quota for the same area is between two and three hundred. 



Modified simple tubular in type, each gland consists of two chief divisions, the 



' (corpus) or gland-coil, the tortuously wound tube in which secretion takes 

 place, and the c.\-i-n-tnry duct (dtictus sudorifenis ) which opens on the surface of the 

 skin, exceptionally into a hair-follicle, by a minute orifice, the sweat poit i poms 

 siulnrifiTiis . often distinguishable with the unaided eye. 



The body of the gland, irregularly spherical or tlattened in form and yellowish 

 red in color, consists of the windings of a single, or rarely branched, tube and com- 

 monly occupies the deeper part of the curium, hut sometimes, as in the palm and 



Cells from alveoli of sebaceous eland, 

 slum-in.^ ictiru'au-il protoplasm due to 

 invsrm-e of oil droplets. X 700. 



