(_a_) Lesions of the cauda equina (by tumors, caries, or fracture of the bones, etc.) produce paralysis, anæsthesia, atrophy of muscles, with De R., in the range of distribution of the sciatic nerves mainly. The sphincter ani is paralyzed and relaxed, while the bladder remains normal as a rule. In all essential respects this paraplegiform, but not paraplegic, affection resembles that following injury to mixed nerve-trunks. It is in reality an intra-spinal peripheral paralysis. The more exact location of the lesion, in the absence of external physical signs (fracture, etc.), may be {75} approximately determined by a study of the distribution of the symptoms and their relation to nerve-supply. (_b_) Lesions of the lower end of the lumbar enlargement, or conus medullaris, behind the first lumbar vertebra, will give rise to the same symptoms as (_a_). The expression, lumbar part of the spinal cord, should be more carefully used than it is at present in the discussion of spinal injuries and spinal-cord diseases, disease of the lumbar enlargement being common enough, but disease of the lumbar part of the cord very rare. In the discussion of railway cases, more especially, it is often forgotten that the spinal cord practically ends behind the first lumbar vertebra. (_c_) Lesions of the middle and upper parts (segments) of the lumbar enlargement are evidenced by true paraplegia, without paralysis of the abdominal muscles. In some cases the quadriceps group, supplied by the crural nerve, is not paralyzed. The constriction and the limit of anæsthesia are about the knees, at mid-thigh, or near the groin in different cases. The paralyzed muscles, as a rule, retain their irritability and show normal electrical reactions; the cutaneous and tendinous reflexes are preserved or increased. The sphincter is usually paralyzed, while the bladder is relatively unaffected. (_d_) Transverse lesion of the dorsal spinal cord produces the classical type of paraplegia—_i.e._ paralysis and anæsthesia of all parts caudad of the lesion. The limit of anæsthesia and the constriction band are nearly horizontal, and their exact level varies with the height of the lesion, from the hypogastric region to above the nipples. Below the level of anæsthesia, which indicates by the number of the dorsal nerve the upper limit of the cord lesion, there are complete paralysis, retention of urine, constipation with relaxed sphincter ani, greatly exaggerated reflexes in the lower extremities, even to spinal epilepsy; the muscles preserve their volume fairly well, and their electrical reactions are normal—sensibility in all its modes is abolished; bed-sores are easily provoked. Retention of urine is an early symptom in lesion of the middle dorsal region of the cord—sometimes, in our experience, preceding symptoms in the legs.