OSS A 1NNOMINATA. 101 



and in the adult it is fused completely into the crus of the 

 pubes, so that very faint marks of their primitive separation 

 are left. The anterior margin of the crus has, for the origin 

 of the crus penis and the erector penis muscle, an excavation 

 continuous with that on the crus of the pubes. 



In examining the general features of the os innominatum, it 

 will be observed, that its outline is in some degree like the 

 figure 8; the narrowing in its centre being produced by the 

 sciatic notch below, and by the deep concavity above, between 

 the anterior superior spinous process and the symphysis of the 

 pubes. The regularly rounded margin of the ilium above, and 

 of the ischium below, contribute to the resemblance, but the 

 angle of the pu-bes interrupts it. The narrowest part of the 

 bone, or its neck, is between the top of the sciatic notch and 

 the fossa below the anterior inferior spinous process. It will 

 also be remarked, that the posterior margin of the sciatic notch 

 is formed by the ilium, and the anterior by the ischium. 



The acetabulurn, or the cotyloid cavity, (camli cotyloide,) is 

 placed immediately on the outside of the neck of the os inno- 

 minatum. In infancy one-fifth of it is seen to be made by the 

 pubes, two-fifths by the ilium, and two-fifths by the ischium. 

 It is a very deep hemispherical depression, having a sharp ele- 

 vated margin all around, particularly at its superior part. 

 The inferior margin, amounting to one-eighth of the whole 

 circumference, is comparatively shallow, and is, indeed, con- 

 verted into a notch, sunk much below the general surface of 

 the brim. The greater part of the acctabulum is smooth, and 

 incrusted with cartilage wherever the head of the os femoris 

 is applied to the support of the trunk; but the very bottom, 

 with the intervening surface continuous with the notch, 

 amounting to rather more than one-fourth of the whole cavity, 

 is rough, sunk below the general concavity, and is occupied 

 by a soft vascular fat. 



In the fore part of the innominatum a large deficiency, called 

 the thyroid foramen, (foramen thyroideum,) exists between the 

 pubes and ischium. In the male subject it is triangular, with 

 the angles rounded ; but in the female it is rather oval. Lead- 

 ing from the plane of the ischium is a groove, which goes 

 along the superior end of the foramen, and appears externally 



9* 



