But the most singular of osteophytic pro ductions is certainly that which forms in inembraniform patches between the cranium and dura-mater of a certain (as yet unsettled) proportion of pregnant wotnen. The natural history of this production (of which a beauti ful specimen lies before us) has been unravelled with great sagacity by M. Ducresti- Exuda tion matter soft; pulpy, and reddish, forms the matrix of the future osteophyte; it soon becomes sandy to the feel ; subsequently hard particles of some size are felt, and these form eventually one, more or less perfectly, contin uous plate. The frontal regions are its chosen seat, and M. Ducrest shows that its formation occurs symmetrically. Its thick ness does not exceed a sixth of an inch, and is generally much less ; the specimen before us (irregular thickness from point to point gives this a lace-like appearance) forms a coating for the entire base and upper arch of the skull ; but its superfical extent is very rarely so considerable. When fresh it is of red colour ; twice (in jaundiced women) M. Ducrest found it yellow. This production, which entails no symptoms, is more prone to appear in young than in more aged women.
(d) °steams. By osteonm we understand a growth composed of bone, and either (a) altogether free from, or (b) having but very slight, connection with any part of the skele ton. Tumours of the fornier kind (a) are of excessive rarity-, and are perhaps only met with as results of bony infiltration of a pre existing plastic mass, either of the serous cavities or of the parenchymata; it seems un necessary to insist upon the greater frequency of calcification than of true ossification of such masses. Tumours of the latter kind (b) are best exemplified by growths front bone, gene rally termed pedunculated exostoses, in which the peduncle may be so small, and the body of the growth comparatively so large, that a centre of ossification distinct from the original bone appears to exist. Such produc
tions are not very unfrequent about the pha langes of the toes ; their texture is generally loose, but may be eburniform from density.
(e) Osteoid.— Under the names of osteoid or ossify ing fungous tumour, Miller de scribes a growth of slow or rapid course, generally springing from the surface of bones, sometimes acquiring great bulk, composed of porous or close osseous texture, and of a greyish white, vascular, nodulated substance, of the consistence of fibro-cartilage, the latter lying in the interstices of the former. The softer substance furnishes neither glutin nor chondrin by boiling, and exhibits a dense fibrous rete under the microscope, containing a few nucleated cells in its nieshes. The for mation of osteoid growths seems dependent on a peculiar diathesis ; they generally appear at first on one bone, but may eventually in vade several bones and certain soft parts — the lungs, great vessels, Sze. The removal of a primary growth by amputation does not pre vent the development of others internally-. Cruveilhier's osteochondrophyte (Anat. Path. livrais. 34.), is a production of this class ; this writer calls the soft part of the tumour carti lage, but gives no proof of its being so.
(f) Bone formation in the interior of new products (exclusive of osteopbytes springing from some part of the skeleton) is very rare. We have never seen such bone in cancer or in fibroma ; but there is sufficient evidence that it has, in sorne rare instances, been ob served.