If the ophthalmic branch is not involved, neither it nor the ganglion should be interfered with; the maxillary and mandibular divisions should be divided within the skull, and the foramen rotundum and foramen ovale obliterated.

CHAPTER XVII

THE SKIN AND SUBCUTANEOUS TISSUE

Structure of skin—­Blisters—­<
i>Callosities—­Corns—­Chilblains
    —­Boils—­
Carbuncle—­Abscess—­Veldt sores—­Tuberculosis of
    skin:  Inoculation tubercle—­Lupus:  Varieties—­Sporotrichosis
    —­Elephantiasis—­Sebaceous cysts or wens—­Moles—­Horns—­New growths: 
    Fibroma; Papilloma; Adenoma; Epithelioma; Rodent cancer;
    Melanotic cancer; Sarcoma—­AFFECTIONS OF CICATRICES—­Varieties
    of scars—­Keloid—­Tumours—­AFFECTIONS OF NAILS.

#Structure of Skin.#—­The skin is composed of a superficial cellular layer—­the epidermis, and the corium or true skin.  The epidermis is differentiated from without inwards into the stratum corneum, the stratum lucidum, the stratum granulosum, and the rete Malpighii or germinal layer, from which all the others are developed.  The corium or true skin consists of connective tissue, in which ramify the blood vessels, lymphatics, and nerves.  That part of the corium immediately adjoining the epidermis is known as the papillary portion, and contains the terminal loops of the cutaneous blood vessels and the terminations of the cutaneous nerves.  The deeper portion of the true skin is known as the reticular portion, and is largely composed of adipose tissue.

#Blisters# result from the exudation of serous fluid beneath the horny layer of the epidermis.  The fluid may be clear, as in the blisters of a recent burn, or blood-stained, as in the blisters commonly accompanying fractures of the leg.  It may become purulent as a result of infection, and this may be the starting-point of lymphangitis or cellulitis.

The skin should be disinfected and the blisters punctured.  When infected, the separated horny layer must be cut away with scissors to allow of the necessary purification.

#Callosities# are prominent, indurated masses of the horny layer of the epidermis, where it has been exposed to prolonged friction and pressure.  They occur on the fingers and hand as a result of certain occupations and sports, but are most common under the balls of the toes or heel.  A bursa may form beneath a callosity, and if it becomes inflamed may cause considerable suffering; if suppuration ensues, a sinus may form, resembling a perforating ulcer of the foot.

The treatment of callosities on the foot consists in removing pressure by wearing properly fitting boots, and in applying a ring pad around the callosity; another method is to fit a sock of spongiopilene with a hole cut out opposite the callosity.  After soaking in hot water, the overgrown horny layer is pared away, and the part painted daily with a saturated solution of salicylic acid in flexile collodion.