The degree to which the promontory projects, of course, varies considerably. The distortion is occasionally so great as not even to leave an inch of antero-posterior diameter. This excessive deformity, however, is more frequently the result of mollities ossium coming on after puberty, for we seldom find children live through this critical period where it has been the result of rickets. The brim of a deformed pelvis varies considerably in shape: "sometimes it has the form of a kidney, or that of the figure eight ([Symbol: infinity]); sometimes it is triangular or heart-shaped, the sides being curved inwards, from the acetabula having been pressed backwards or inwards, the ossa pubis are bent forwards and outwards, and form at their symphysis a sort of beak-like process, which is the apex of the heart: in this species of deformed pelvis, which is usually the result of mollities ossium, the outlet also is usually much distorted: this arises from the tubera ischii being forced nearer to each other, thus contracting the pubic arch." (Naegelé's _Lehrbuch_, 2te Ausgabe, p. 247.) [Illustration: _From_ Naegelé.] [Illustration] _Malacosteon_, or _mollities ossium_. An arthritic, rheumatic, or gouty diathesis is a morbid state, in which softening of the bones may take place at a much later period of life, and to a most extraordinary extent. In almost all the cases of extreme pelvic deformity which have been recorded, the distortion has been owing to this disease, and not to rickets in early life: in a pathological point of view there is a considerable analogy between these two diseases. From a variety of causes there is a superabundant formation of acid in the system, which its excreting organs are unable to throw off. The effects of this condition will vary according to circumstances; among them the softened state of the bones from a deficiency of insoluble bone earth is not the least remarkable. Mollities ossium seldom attacks women who have had no children: sometimes it begins shortly after delivery, and very frequently during pregnancy, during the progress of which it continues to increase. Hence, it occasionally happens, that a woman has given birth to several healthy living children without any unusual difficulty in her labours, and where, after this, the pelvis has gradually become so deformed from mollities ossium, as to render delivery impossible by the natural passages, and, therefore, to require the Cæsarean operation. Pelves of this sort, may be easily distinguished from those which have been deformed in early life by rickets; they have evidently attained their full adult growth before the process of softening had commenced: the ilia, for instance, are of the natural size, but bent across, as if they had been folded like wet pasteboard; whereas, the bones of the ricketty pelvis have not attained their full development, they are stunted in growth as well as distorted in shape, the two processes, viz. of growth and distortion,