It follows from the preceding statements that in cases of limited atrophic paralysis with De R. the diagnosis between a central lesion (destruction of ganglion cells of the anterior horns of the cord) and a strictly peripheral (or neural) lesion is to be chiefly based upon two considerations: (1) The distribution of the paralysis, which in the first case affects muscles which are physiologically grouped or associated, while in the second case the simple law of anatomical associations or grouping is observed; (2) by the state of sensibility, which is normal in disease of the anterior horns of the cord, and is frequently impaired or abolished in nerve lesions. Lesions affecting the cauda equina cause all the above-mentioned symptoms of peripheral lesions in a limited (partial) paraplegic distribution. If the lesion or injury be in the sacro-coccygeal region, the symptoms will, as a rule, be found confined to parts below the knee, occasionally also involving the muscles on the posterior aspect of the thigh (flexors of the leg). Below the knees we find an atrophic paralysis with De R., anæsthesia of the foot and part of the leg, loss of plantar and achillis reflexes, and the sphincter ani will be paralyzed. The patellar reflex is {69} preserved or exaggerated. In case the lesion be in the lumbar region, below the first lumbar vertebræ, the symptoms will be found to extend as high as the groin, involving also the buttocks and sphincter ani; state of the bladder variable. All reflexes will be lost in the paralyzed extremities, except in some cases the cremasteric reflex. Strange as it may appear, physicians do not always remember that there is practically no lumbar spinal cord (vide Fig. 2), and that injuries, etc. of the lumbar vertebræ and dura tend to affect nerves, and not a nervous centre. II. Localization of Lesions in the Spinal Cord. Diseases of the spinal cord are distinguished by the following general characters, positive and negative: Positive Characters.—Tendency to primary bilateral or paraplegic distribution of all the symptoms. In the majority of cases preservation of electro-muscular excitability, and in one well-defined group of cases De R. more or less typically developed in the paralyzed parts. Frequent vesical and rectal paralysis, either of the retaining or of the ejecting apparatus. Pains and other paræsthesiæ in the extremities, the pains often possessing the electric or fulgurating character. Anæsthesia of paraplegic distribution. Sensations of constriction or cincture about a limb or about the body at various levels. Occurrence of ataxia without paralysis. Progressive muscular atrophy without actual paralysis. Easy production of eschars (bed-sores).