. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. and radiating to- Fig. 375. wards the circum- ference of these bones, it follows that the angles will be incomplete when the rest of the bone is formed. On this account it is that, at the four angles of each pa- rietal bone, there is a membranous spot which the ossific matter has not reached, when, in other parts, it is joined to the surrounding bones. These spaces are called fontanelles; two of them are situated on the median line and superiorly ; and two others inferiorly and in each lateral region. The posterior super
. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. and radiating to- Fig. 375. wards the circum- ference of these bones, it follows that the angles will be incomplete when the rest of the bone is formed. On this account it is that, at the four angles of each pa- rietal bone, there is a membranous spot which the ossific matter has not reached, when, in other parts, it is joined to the surrounding bones. These spaces are called fontanelles; two of them are situated on the median line and superiorly ; and two others inferiorly and in each lateral region. The posterior superior fontanelle is triangular, and is found between the superior angle of the occipital bone, and the occipital angles of the two parietal. The anterior superior fontanelle (a, Jig. 376), by reason of the frontal bone being formed in two parts, is of a lozenge shape; and it is between those two parts and the frontal an- gles of the parietal bones that it occurs. These two fontanelles are conse- quently at the extremities of the sagittal suture. The inferior fontanelles are found, the anterior (a, fig. 375) between the spinous angle of the parietal, and the great wing of the sphenoid bone; the posterior (b, fig. 375) between the mastoid angle of the first-named bone and the mastoid process of the temporal. These two fontanelles are, therefore, situated at the extremities of the squamous suture. Fig. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Todd, Robert Bentley, 1809-1860. London, Sherwood, Gilbert, and Piper
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