A system of medicine, by many writers; . does not, ho\vever, explain thedegenerated fibres in the oculo-motor nerve, because he has shown thatthese contain no muscle spindles, and they degenerate comi^etcly whenthe nerve to the muscle is divided. A consideration of the anatomical distribution of the degeneration TABES DORS A LIS 107 shows that it is especially an affection of the afferent projection systemby -which the central nervous system, spinal cord, cerebrum, and cerebellum,are gradually and progressively deprived of normal peripheral stinnili. The nature of the deg^eneration.—IMicroscop
A system of medicine, by many writers; . does not, ho\vever, explain thedegenerated fibres in the oculo-motor nerve, because he has shown thatthese contain no muscle spindles, and they degenerate comi^etcly whenthe nerve to the muscle is divided. A consideration of the anatomical distribution of the degeneration TABES DORS A LIS 107 shows that it is especially an affection of the afferent projection systemby -which the central nervous system, spinal cord, cerebrum, and cerebellum,are gradually and progressively deprived of normal peripheral stinnili. The nature of the deg^eneration.—IMicroscopical examination of thespinal cord shows the myelin sheath of the nerve-fibres diminished ordestroyed; the axis-cylinder process may be swollen in one place, attenu-ated in another, and generally irregular in thickness or completelyatrophied; the neuroglia is increased at the expense of the parenchyma,and a large number of Deiters cells are visiljle. Nearly the wholeof the posterior columns in the lumbo-sacral region may be destroyed,. Fig. 5.—Cervical tabes after Marinpsco. Section at the level of the 5th cervical. The same asjnnmetryof degeueratiou is observed iu the posterior external columns, and Golls column is intact. leaving only the cornu commissural and oval areas of endogenous vessels are often thickened in the sclerosed area, and not elsewhere;this change is secondary to the degeneration, not causal. The walls ofthe arteries are often thickened, and there is hyaline degeneration ofthe media; sometimes the vessels are so much thickened by thisdegenerative process as to become almost obliterated, especially when thesclerosis is advanced. The pia arachnoid membrane is also thickened, andoften presents the appearances of chronic inflammation. That tabes is awidespread process of degeneration, primary in origin, and not secondaryto vascular change, is shown by the fact that the vessels of the retina areunaltered, even in advanced gray atrophy. Atrophy and d
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