1398 



HUMAN ANATOMY. 



Fig. 1 162. 



Mouth 

 of gland 



Duct 



Alveoli 



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 

 are wanting. The periphery 

 of the alveolus is occupied by a 

 single, or incompletely double, 

 layer of flattened and imper- 

 fectly defined basal cells, that 

 restimmediately upon themem- 

 brana propria and are distin- 

 guished by their dark 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. 

 structures (glandulae sudoriferae), 



Carium 







Sebaceou.s glands from skin co\ering nose. X 60. 



Cells from alveoli of sebaceous gland, 

 showing reticulated protoplasm (Jue to 

 presence of oil droplets. X 700. 



These structures (glandulae sudoriferae), also 

 called the sudoi'iparoiis glands, are the most important 

 representatives of the coiled glands (glandulae glomi- 

 formes) 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 iioo 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 

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

 place, and the excretory duct (ductus sudoriferus) which opens on the surface of the 

 skin, exceptionally into a hair-follicle, by a minute orifice, the sweat pore (porus 

 sudoriferus), often distinguishable with the unaided eye. 



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

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

 monly occupies the deeper part of the corium, but sometimes, as in the palm and 



