1. Fowl paralysis (neurolymphomatosis gallinarum) is a disease entity, with characteristic clinical and pathological features.

2. The disease occurs in all parts of the United States, Holland, Austria and probably South America.

3. The disease appears to be endemic in certain foci. Having once appeared, the disease tends to persist through successive years.

4. It occurs with about equal frequency in both sexes; all common breeds may be affected.

5. Symptoms appear between the 3rd and 18th months. Typical clinical cases have not been observed outside of these limits.

6. The conspicuous symptoms are (a) asymmetrical, partial and progressive paralysis of the wings and both legs, and rarely of neck muscles; (b) occasional grey discoloration of iris, with blindness. Nutrition is usually preserved.

7. The duration is variable; the outcome is usually fatal, but spontaneous recovery may rarely occur.

8. The principal pathological changes are found in the nervous system. In the peripheral nerves, the essential feature is an intense infiltration of lymphoid, plasma cells, and large mononuclears. This is accompanied by a myelin degeneration in the more advanced lesions, but the cellular infiltrations appear to precede the degenerative changes. In brain, cord and meninges, there are similar infiltrations predominantly perivascular.

Infiltrations of the iris with lymphoid and plasma cells are found in the cases showing gross discoloration of the iris.

Visceral lymphomata, originating usually in the ovary, are associated in a certain percentage of the cases. Evidence is presented in favor of the view that this association is not accidental, and that the lymphomata are a manifestation of the disease.

9. Infiltrations of the spinal cord and brain, rarely of the peripheral nerves, are frequently present in birds showing no clinical symptoms. These are interpreted as mild cases of the same disease.

10. No microorganisms of etiological significance have been demonstrated in the tissues or by cultural methods.

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