12. A boy, aged fifteen years. Double optic neuritis, headache, and vomiting. Recovery. (Two and a half years.) 13. A woman, aged twenty-one years. Double optic neuritis, much swelling of the disks, headache, and vomiting. Complete recovery with normal vision. (Four and three-quarter years.) 14. A girl, aged fifteen years. Double optic neuritis, headache, and vomiting. Recovery with good vision. (Five and a quarter years.) 15. A boy, aged twelve years. Double optic neuritis, headache, and vomiting; slight internal strabismus of the right eye. Recovery with good vision. (Four years.) 16. A man, aged forty years. Double optic neuritis, headache, and vomiting. Recovery, but with complete blindness. (Eighteen months.) 17. A youth, aged seventeen years. Double optic neuritis, headache, and vomiting. Recovery, but with total blindness. (Five years.) 18. A woman, aged twenty-two years. Double optic neuritis, headache, and vomiting. Recovery, but with total blindness. (Two and three-quarter years.) 19. A girl, aged fourteen years. Double optic neuritis, headache, and vomiting; internal strabismus (left) for fourteen days. Recovery, with normal vision. (Two years.) The following are brief notes of the cases in Group IX.: 20. A girl, aged twelve years. Headache, vomiting, and double optic neuritis in December, 1893. Recovery in twelve months, but vision was much impaired. She remained well with the exception of occasional headache until December, 1899. Then the severe headache returned. She became ataxic and optic neuritis reappeared. In April, 1900, the headache was much less and the patient felt much better, but she was completely blind. (Six and a half years.) 21. A young woman, aged seventeen years. Headache, vomiting, and double optic neuritis. Vision was impaired. Vomiting ceased; the headache continued for over two years, but recently disappeared after lumbar puncture. (Two and a quarter years.)