ix THE SKIN AND CUTANEOUS GLANDS 501 



largest are in the alae of the nose and the red margin of the lips 

 near the angle of the mouth. 



The sebaceous content of the glandular spaces is fluid, and 

 consolidates into a semi -soft yellowish mass during its passage 

 through the duct, so that it can sometimes be squeezed out, 

 particularly at the nasal pinnae, in the shape of a vermiculus. 

 The ceruininous glands of the external auditory meatus are coiled 

 glands. But there are also true sebaceous glands in connection 

 with the hairs of the auditory meatus, to which, exclusively, some 

 authors attribute the secretion which lubricates this duct. 



Under the microscope the sebaceous secretion shows innumer- 

 able fat-granules, cells in fatty degeneration, crystals of cholesterol, 

 and almost invariably microscopic acari (demodex folliculorum). 

 Chemical examination shows the presence more particularly of 

 neutral fats, soaps, fatty acids, cholesterol, a small quantity of 

 protein, casein, and extractives of an undetermined character. In 

 the minerals insoluble earthy phosphates, chlorides, and alkaline 

 phosphates predominate. 



The vernix caseosa which covers the skin of the foetus comes 

 from the accumulation of the sebaceous substance secreted during 

 intra-uterine life, mixed with detritus of macerated epidermal and 

 epitrichial cells. According to Liebreich and Buppel it contains 

 cholesterol, oleic and palmitic acid, and their respective glycerides. 

 It facilitates the progress of the foetus along the vagina in delivery. 



The smegma preputii is analogous to the foetal vernix caseosa, 

 and contains a specific compound of ammonia, on which the 

 odour peculiar to this secretion depends. The substance known 

 as castoreum is the secretion from the sacculated prepuce of the 

 beaver ; it has a characteristic odour, and is employed as a sedative 

 in medicine. It contains resinous substances, benzoic acid, and 

 other aromatic compounds. 



The wax or cerumen of the auditory meatus, in addition to 

 specific fats of a waxy consistency, contains a specific bitter 

 extractive. The secretion of the Meibowmian glands does not 

 differ from that of the cutaneous sebum, and lubricates the eye- 

 lashes. It tends to collect along with the tears in the inner angle 

 of the eye, where it is entirely or partly absorbed, and is carried 

 off with the former by the lachrymal duct. 



All these secretions have a protective function which is quite 

 distinct from that of perspiration. Their mechanism is also very 

 simple, and quite different from that of other secretions. The 

 ordinary secreting cells elaborate the material of their secretion 

 without being destroyed in the process ; the young cells of the 

 sebaceous glands, on the contrary, multiply incessantly by karyo- 

 kinesis (Bizzozero and Vassale), while the older cells undergo fatty 

 degeneration, until they drop off and mingle with the sebaceous 

 substance collected in the cavity of the gland. 



