Besides those tumours which have been described, there is a number of others not of a malignant disposition, which are so various in their structure as to baffle all attempts to reduce them to a scientific classification. Some are composed of a homogeneous substance of almost cartilaginous consistence and a whitish colour; some consist of cartilaginous matter, mixed with substance of less density and of a different appearance; in some, fibrous matter is mixed with a homogeneous glandular-looking substance, partially softened. Some are almost entirely composed of osseous matter; others contain it in small proportion. It would be endless to enter into a minute detail of the structure of such tumours, for it may be said that their appearances vary with their number. In almost all tumours cysts are found, and the internal structure of some tumours consists almost entirely of cysts, or hydatids, as they have been called; in others, these only occupy certain parts, and compose but a minor feature in the structure. The sacs are generally lined with a delicate and smooth membrane, which is often vascular at various points; some contain a transparent and glairy fluid, albuminous or gelatinous; some bloody serum; some purulent, some curdy matter, or this mixed with a serous or purulent fluid; some pure blood; some a fluid like printer’s ink; and not a few are occupied by a dense elastic substance, which, on a section being made of the tumour, rises irregular and ragged above the cut surface. Some tumours are smooth; others lobulated or tuberculated. OF ENCEPHALOID TUMOURS.