Adult dogs maintained on an artificial, balanced ration adequate in all dietary essentials as far as is known except water-soluble, heat-stable vitamin B2 (G) developed, after a sufficient time, a slowly progressive disease characterized by loss of weight, persistent vomiting and diarrhea, and marked muscular weakness, which ended fatally in from 200 to over 300 days.

The clinical features of this condition, as pointed out in the discussion, are quite different from those characterizing the canine disease known as black tongue.

The anatomic changes in this condition consist of marked demyelination of the peripheral nerves, including the vagus; degeneration of the medullary sheaths and replacement by gliosis of the posterior columns of the spinal cord, particularly the fasciculi graciles; degeneration of the medullary sheaths of the posterior and less often of the anterior nerve roots of the cord; occasionally slight degenerative changes in most of the other fiber tracts of the cord.

Attention is called to the fact that degenerative lesions in the central nervous system similar or identical with these have frequently been described in pellagra in man.

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