The malady has been described in horses, oxen, sheep, goats and dogs, attacking by preference the young, which are not yet inured to the unknown poison, and by preference in winter and spring, the periods of close stabling, dry feeding and shedding of the coat. In the absence of bacteriological data from the horse, it may be noted that in man cerebro-spinal meningitis, has been commonly found to be associated with the presence in the meningeal exudates of the _micrococcus pneumoniæ crouposæ_, (Micrococcus lanceolatus encapsulates). This is frequent in the mouths of healthy persons so that some additional accessory cause must be invoked to increase the susceptibility or lessen the protective power of the tissues. This has been thought to be found in the concurrent presence of other bacteria, the staphylococcus pyogenes aureus, pneumobaccillus of Friedländer and the streptococcus pyogenes. Mosny appears to have established this for the staphylococcus in the case of rabbits. With a given dose of the micrococcus pneumoniæ death was always delayed for a fortnight, while with the same dose thrown into one thigh, and the staphylococcus aureus in the other, the rabbit died in one day. This enhanced potency resulting from the presence of the golden staphylococcus has been invoked to account for the germ making its way from the mouth to the brain in cases of otitis, suppuration of the Eustachian tube, tonsilitis or nasal catarrh. These remarks are intended to be suggestive, rather than conclusive, as we have as yet no certainty that cerebro spinal meningitis in the horse is caused by the same germ as it is in man. _Lesions._ The lesions are usually those of leptomeningitis, or congestion of the brain and spinal cord and often effusion into the ventricles, with a serous exudation under the pia mater or into the arachnoid cavity. This may be transparent and yellowish, or grayish and turbid, or milky. In the sheep, Roloff has found purulent products under the pia mater, around the roots of the spinal nerves, and in the surface layers of cerebral gray matter. The marked hyperæmia on the surface of the gray matter is a striking feature, and circumscribed areas of necrotic nervous tissue and softening are not uncommon. Petechiæ are frequent on the meninges, the brain, heart, lungs and kidneys. Granular and fatty degenerations are also met with in these parenchymatous organs. The blood may be dark and liquid or diffluent. _Symptoms in the_ =Horse=. The mildest attacks are manifested by paresis, or loss of perfect control over the limbs, or loss of power over the tail, impairment of appetite and some difficulty of swallowing, together with some congestion or reddish brown discoloration of the orbital and nasal mucosæ. In other cases paralysis of one or more limbs may supervene but without marked fever or coma.