The _venous return_ is through the frontal, temporal, and occipital veins. These have free communications, through the _emissary veins_, with the intra-cranial sinuses, and by these routes infective conditions of the scalp may readily be transmitted to the interior of the skull. The most important of the emissary veins are: the _mastoid_, _condyloid_, and _occipital_, passing to the transverse (lateral) sinus; the _parietal_, which enters the superior sagittal (longitudinal) sinus; and a branch from the nose which traverses the foramen cæcum and enters the anterior end of the superior sagittal sinus. The supra-trochlear, supra-orbital and auriculo-temporal branches of the trigeminal nerve, together with the greater and lesser occipital nerves, supply the scalp with sensation, while the muscles are supplied from the facial nerve. The _lymph vessels_ pass to the parotid, occipital, mastoid, and submaxillary groups of glands, the different areas of drainage being ill-defined. INJURIES OF THE SCALP #Subcutaneous Injuries.#--_In simple contusion_ of the superficial layers, owing to the density of the tissues, the blood effused is small in quantity and remains confined to the area directly injured, which is firm and tender to the touch, swollen and discoloured. The disappearance of the swelling may be hastened by elastic pressure and massage. _Hæmatoma of the scalp_ results when lacerated vessels bleed into the sub-aponeurotic space. Owing to the laxity of the connective tissue in this area, the effused blood tends to diffuse itself widely, and, according to the position assumed by the patient, gravitates to the region of the eyebrow, the occiput, or the zygoma. When a large artery is torn the swelling may pulsate. A hæmatoma of the scalp may readily be mistaken for a depressed fracture of the skull, owing to the fact that the margins of the effusion are often raised and of a firm resistant character. A differential diagnosis can usually be made by observing that the swelling is on a higher level than the rest of the skull; that the raised margin can to a large extent be dispersed by making firm, steady pressure over it with the finger; and that, on doing so, the smooth and intact surface of the skull can be recognised. When a fracture exists, the finger sinks into the depression and the irregular edge of the bone can be felt. In doubtful cases, if cerebral symptoms are present, an exploratory incision should be made. Even a large hæmatoma is usually completely absorbed, but the dispersion of the clot may be hastened by massage and elastic pressure. Any excoriation or wound of the skin must be disinfected. Sometimes a blood-cyst, consisting of a connective-tissue capsule filled with a yellowish-red fluid, remains, and may require to be emptied with a hollow needle.