(_b_) Lesions of the spinal pyramidal tract (of fasciculi 10 and 11) are followed by motor symptoms only—viz. paralysis and contracture—or, in other words, by a spastic paralysis. Sensibility is unaffected; the bladder, rectum, and truncal muscles are not distinctly paralyzed; the reflexes are much increased, and ankle-clonus is often present. The electrical reactions of the paralyzed muscles are normal, qualitatively at least. The diagnosis of localization may be pushed still farther by the following considerations: (1) When the condition of spastic paralysis is unilateral, of hemiplegic distribution, and follows an attack of cerebral disease of some sort, we may feel sure that both the crossed and the direct fasciculi of the pyramidal (10 and 11) belonging to one cerebral motor tract are degenerated throughout the length of the spinal cord, the crossed fasciculus on the paralyzed side and the direct on the healthy side (same side as injured hemisphere). It would thus appear that lesion of the direct pyramidal fasciculus (11) produces no symptoms,[4] except, of course, in those rare cases in which it is larger than its associated crossed fasciculus. [Footnote 4: Unless it be the increase of reflexes which is so often observed on the non-paralyzed side in hemiplegics.] (2) The above symptoms may be bilateral, as observed in children as a congenital or early-acquired condition. In such cases the four fasciculi of the motor tract are degenerated or undeveloped, in correspondence with a symmetrical bilateral lesion of the motor area of the cerebrum—imperfect development or early destruction. (3) When the legs alone are the seat of spastic paralysis, with increased reflexes, spastic or tetanoid gait, without sensory symptoms, the diagnosis of a primary sclerosis of both lateral columns (inclusive of 10) of the spinal cord is justified. (_c_) Lesions of antero-lateral columns of the cord (8 and 12), primary and independent of lesions of the anterior horns or of the crossed {74} pyramidal fasciculus, cannot now be diagnosticated during life. These large masses of fibres include fasciculi whose functions are probably motor; others (especially in 12) whose functions, according to recent experiments, may be sensory; and still others which are associating or commissural.