=General Pressure on the Encephalon=, whether through fracture of the cranium and depression of bone, by acute congestion, by blood extravasation, by inflammatory exudation, or by acute abscess, will cause pain, spasms, nausea, dullness, blindness, stupor and coma. After expulsion of the cerebro-spinal fluid from the cranial cavity, the increasing pressure compresses the blood vessels, reduces or interrupts the circulation and abolishes the functions in the parts deprived of blood. Thus congestion of one portion of the encephalon is usually associated with diminished circulation in another portion. Disorder in the first may occur from hyperæmia and irritation and in another part from a consequent anæmia. =Destructive Lesions of Cortex of One Cerebral Hemisphere= may or may not cause permanent symptoms, as shown by the passage of a crowbar through the front of the left hemisphere, yet the man survived for 13 years and showed no loss of intelligence, his disposition and character alone having changed for the worse. The one hemisphere may by itself sufficiently control mental acts, while the other lies dormant or may even have undergone degeneration. =Diagnosis of Encephalic and Spinal Lesions.= The following may be taken as guiding principles: =Encephalic=: Hemiplegic or bilaterally hemiplegic grouping of symptoms. =Spinal=: Paraplegic grouping of symptoms. =Encephalic=: Frequent contracture or spasms of paretic muscles. =Spinal=: Paralysis more perfect and continuous. =Encephalic=: Reflexes in affected muscles increased: Cerebral inhibition absent. =Spinal=: Reflex abolished or reduced in parts the seat of the lesion. =Encephalic=: Spasms in areas of distribution of cranial nerves (not spinal.) =Spinal=: Spasms and paralysis follow distribution of spinal nerves. =Encephalic=: Head symptoms frequent (vertigo, apoplexy, epilepsy, dementia, coma). =Spinal=: Relative absence of head symptoms. =Encephalic=: Comparative absence of marked muscle atrophy. =Spinal=: Atrophy in special muscular groups. =Encephalic=: Little tendency to form bed sores. =Spinal=: Tendency to form sloughs and bed sores. Sensory (Æsthesodic) and Motor (Kinesodic) Tracts in Encephalon. In the crus and above, the sensory tract lies dorso-laterad of the motor tract, forming about one-fifth of the crus, and extending upward through a white layer bending inward to form an angle and finally diverging to the different cortical convolutions. The motor tract is mainly contained in the inferior pyramids of the bulb, and constitutes the median two fifths and basal two fifths of the crus. Without entering farther into this subject it will be observed that lesions of the outer layer of the crus and its radiating fibres may cause hemianæsthesia of body or head, including the eye, while lesions of the median and basal layers and radiating fibres induce hemiplegia of the head, tongue, fore limb, hind limb, trunk, etc.