_Lesions._ These are like those in the larger animals, being to a large extent determined by the cause and nature of the lesion, concussion, sprain, fracture, pyæmic, septicæmic, or other infection. The implication of the myel to the exclusion of the meninges is very frequent and the lumbar enlargement is the most common seat of disease. Localization in the brachial enlargement or in one lateral half of the cord is uncommon. The gray matter towards the extremity of the horn is the most commonly involved, reflecting a yellowish, grayish red or deep red color, and breaking down into a pultaceous mass on the slightest pressure. At an advanced stage the altered coloring matter gives to the tissue a brownish yellow color without altering its consistency. The still vital and vascular area around the centre of softening may be slightly swollen and abnormally firm. The neuroglia is the seat of leucocytosis, and minute (usually punctiform) extravasations of blood. The red globules are crenated or otherwise distorted and the white are granular and opaque. The neurons are swollen, granular and opaque and the nerve fibres are more or less diffluent, moniliform and in their substance show no clear outline of white substance and axis cylinder. Interruptions by granule masses and vacuoles are common. In old standing or chronic cases the liquid exudate and granular debris have been largely absorbed and the thickening of the neuroglia by fibrous neoplasm, has restored the firmness or even approximated the part to a condition of sclerosis. In case the meninges are involved there is thickening by exudation into their substance or on their surface, there may be adhesion between the outer and inner layers of the arachnoid and a serous fluid, red, milky or clear, distends the arachnoid or subarachnoid space. The false membranes, here as elsewhere, are usually red if recent, and increase in pallor with age.