fissura

When two are present, they are generally situated one above the other, the upper being the larger; the second piece has seldom more than one; the third, fourth, and fifth pieces are often formed from two centers placed laterally, the irregular union of which explains the rare occurrence of the sternal foramen (Fig. 121), or of the vertical fissure which occasionally intersects this part of the bone constituting the malformation known as fissura sterni; these conditions are further explained by the manner in which the cartilaginous sternum is formed.

II. Osteology. 4a. The Sternum 1918

The Posterior Median Fissure (fissura mediana posterior; dorsal or dorsomedian fissure) is a narrow groove; and exists only in the closed part of the medulla oblongata; it becomes gradually shallower from below upward, and finally ends about the middle of the medulla oblongata, where the central canal expands into the cavity of the fourth ventricle.

IX. Neurology. 4a. The Hind-brain or Rhombencephalon 1918

The Longitudinal Cerebral Fissure (fissura cerebri longitudinalis; great longitudinal fissure) contains a sickle-shaped process of dura mater, the falx cerebri.

IX. Neurology. 4c. The Fore-brain or Prosencephalon 1918

The Calcarine Fissure (fissura calcarina) (Fig. 727) is on the medial surface of the hemisphere.

IX. Neurology. 4c. The Fore-brain or Prosencephalon 1918

The Hippocampal Fissure (fissura hippocampi; dentate fissure) begins immediately behind the splenium of the corpus callosum, and runs forward between the hippocampal and dentate gyri to end in the uncus.

IX. Neurology. 4c. The Fore-brain or Prosencephalon 1918

The Anterior Median Fissure (fissura mediana anterior; ventral or ventromedian fissure) contains a fold of pia mater, and extends along the entire length of the medulla oblongata: it ends at the lower border of the pons in a small triangular expansion, termed the foramen cecum.

IX. Neurology. 4a. The Hind-brain or Rhombencephalon 1918

The inferior orbital fissure (fissura orbitalis inferior; sphenomaxillary fissure), horizontal in direction, opens into the lateral and back part of the orbit.

II. Osteology. 5c. The Exterior of the Skull 1918

At the front part of the auricula, where the helix bends upward, is a small projection of cartilage, called the spina helicis, while in the lower part of the helix the cartilage is prolonged downward as a tail-like process, the cauda helicis; this is separated from the antihelix by a fissure, the fissura antitragohelicina.

X. The Organs of the Senses and the Common Integument. 1d. 1. The External Ear 1918

The petrotympanic fissure (fissura petrotympanica; Glaserian fissure) opens just above and in front of the ring of bone into which the tympanic membrane is inserted; in this situation it is a mere slit about 2 mm. in length.

X. The Organs of the Senses and the Common Integument. 1d. 2. The Middle Ear or Tympanic Cavity 1918

The best marked of the early fissures are: (a) the fissura prima between the developing culmen and declive, and (b) the fissura secunda between the future pyramid and uvula.

IX. Neurology. 2. Development of the Nervous System 1918