818 THE NERVOUS fii'STEM. 



site nuclei being normal. Oppenheimer describes a similar case of tabes 

 "with laryngeal crises in which there were pronounced degenerative changes 

 in the pneuniogastric nucleus and in the ascending root of the glosso- 

 pharyugeal. Changes have been described in the cells of the cerebral 

 cortex. They are similar to those found in dementia paralytica, but 

 less marked. 



Although various hypotheses have been advanced iu explanation of the tabetic 

 lesion, and especially iu reference to "the fairly constant selection of certain groups of 

 neurones, doubt still exists as to the origin and essential nature of the process. Earlier 

 writers looked upon the lesion as a primary sclerosis of the posterior columns, probably 

 of vascular origin. Flechsig ' and Trepinski ' 2 describe the posterior columns as made up 

 of several distinct systems of fibres, each system distinguishable from the others by its 

 period of ripening or myelinization. They assert that the tabetic process affects these 

 different systems successively. As the systems overlap one another, this would explain 

 the admixture at certain stages of tabes of normal and abnormal fibres. Present 

 knowledge favors the view that tabes is a primary degeneration of the peripheral sen- 

 sory system of neurones, the degeneration affecting the entire neurone, and that the 

 picture presented ^by the tabes cord varies with the particular neurones affected. The 

 cell bodies of these neurones are in the spinal ganglia and their cranial analogues. 

 Thorough examinations of spinal ganglion cells have as yet been made in too few cases 

 to warrant any general conclusions. Degeneration of spinal ganglion cells in tabes has 

 been reported even in cases dying early in the disease. Such degenerations are best 

 shown by the method of Nissl, the general application of which is comparatively 

 recent. Certain it is that a degeneration which affects both peripheral and central proc- 

 esses of the neurone, and yet is most pronounced in those parts of the neurone farthest 

 removed from its nutritive centre, is most easily explained on the basis of some agent 

 affecting the general metabolism of the neurone. A majority of the cases of tabes give 

 a syphilitic history. Our knowledge of the effects of toxins upon neurones is certainly 

 not opposed to the consideration of such a toxin as the etiological factor in tabes. 



COMBINED SYSTEM DEGENERATION ATAXIC PARAPLEGIA. This is 

 a disease of uncertain etiology, in which there are degenerative changes 

 in both motor and sensory neurone systems (Fig. 535). The tracts usu- 

 ally involved are those of Burdach and of Goll, the direct cerebellar 

 tracts, and the crossed pyramidal tracts. Less commonly the degenera- 

 tion extends to the tracts of Gowers and to the direct pyramidal tracts. 

 It seems probable that the lesion in the cord is not always the expression 

 of the samejpathological process, and that in many cases it is not the 

 result of a true systemic degeneration. In perhaps the minority of cases 

 the lesion corresponds to the tract systems of the cord and probably 

 represents a combined sensory-motor degeneration. Such are those rare 

 cases in which the degeneration affects all of the above-mentioned tracts. 



According to Dejerine, the appearance of a combined system disease may be 

 induced by the chronic meningitis, which exists over the posterior columns in tabes, 

 extending forward over the direct cerebellar tract, the productive inflammation finally 

 spreading to this tract and to the crossed pyramidal. In these cases that part of the 

 latter tract which lies deepest, i.e., close to the gray matter, usually remains unin- 



1 Flechsig, "Die Leitungsbahnen im Gehirn und Rilckenmark," Leipsic, 1878. "1st 

 die Tabes Dorsalis eine System-Erkrankung? " Neur. Cent,, Bd. ix. 



2 Trcpinski, " Die embryonalen Fasersysteme in den Hinterstrangen und ihre Degen- 

 eration bei der Tabes Dorsalis." Arch. f. Psych, und Nerv., Bd. xxx., 1897. 



