In this group of cases patches of atrophy, semi-transparent and grayish in color, focal or diffused, are clearly perceptible to the naked eye. As a rule, the atrophy is unilateral, and sensibly affects the entire half of the cord. In some cases of paraplegia, however, there is a bilateral, symmetrical shrinkage of the entire lumbar cord, which has been reduced to the size of a quill.
The atrophy involves, first and most markedly, one or both anterior cornua; second, the anterior nerve-roots arising from them; third, the antero-lateral columns.
In both the latter localities the microscope will often find individual nerve-tubes wasted and deprived of their myeline. The atrophied patches are generally sclerosed as the seat of a proliferated neuroglia, coloring deeply with carmine. In Laborde's cases, published at the very beginning of what may be called the anatomical period, the atrophy and sclerosis were said to be limited to the antero-lateral columns and the nerve-roots, while the cornua remained intact. In all more recent observations, however, the lesion of the white columns and roots has been found strictly proportioned to that of the gray horns. The sclerosis extended into the latter, constituted by a reticulum of connective-tissue fibres, sometimes fine, sometimes so matted together as to form a dense felt-like substance, sometimes offering the ordinary aspect of sclerosis.
Amyloid corpuscles have been found infiltrated in great numbers through both the gray and white substance in these old cases (case by Cornil),102 seeming to replace the infiltration with exudation corpuscles observed in the more recent ones.103 When the lesion is distinctly circumscribed the focus is often surrounded by a zone of embryonic cells, seeming to indicate a reactive proliferation on the periphery.104
102 Loc. cit., Soc. Biol.,1863.
103 Seguin (loc. cit.) observes that the opinion is gaining ground which ascribes these to a transformation of the neuroglia corpuscles.
104 Case by Schultze, loc. cit.
As in the relatively fresh cases, the circumstance which has attracted the most attention is the atrophy of the ganglionic cells from the sclerosed patches of the anterior cornua. The completeness with which these have disappeared in any focus seems to be proportioned to the completeness of the paralysis in the corresponding limb. Partial atrophy or disappearance of spinal groups of cells from the cornua may sometimes be correlated with paralysis of special muscles.105
105 Thus in Schultze's case, already quoted, the external group of cells had disappeared from the focus in one gray horn, and the extensors of the foot were alone paralyzed. This seems to confirm the opinion advanced by Spitzka, that this external group of motor-cells corresponds to the extensor, the internal groups to the flexor muscles.
Study of the pathology of infantile paralysis is not completed when the above series of spinal lesions has been enumerated. Most various interpretations have been made of these lesions as they have been successively discovered. Thus, after the theory of congestion came the theory of primary sclerosis, built upon Laborde's two autopsies;106 then the theory of primary atrophy of ganglionic cells;107 then the theory of myelitis;108 finally, a theory of complex and variable lesion.109