Department of Anatomy, Nippon Medical Schoo
Measurements were taken from three directions to determine the sites of the prominent points of the semicircular canals in 26 half-crania of 13 individuals using methods directly applicable clinically to gain exposure. The four standard planes used in the measurements were the horizontal Frankfort (O. A. E.), coronal porion (P. F. E.), porion sagittal (P. S. E.) and median sagittal plane (M. S. E.). The results are as follows.
1. The prominent points of the lateral and superior semicircular canals lie on almost the same coronal plane passing through the point suprameatal spine, although the plane on which the prominent point of the lateral semicircular canal lies, is on an average a little more than 1mm before that of the superior semicircular canal.
2. The prominent point of the lateral semicircular canal is approximately 15mm medial to the suprameatal spine and a little over 3mm the horizontal plane through the suprameatal spine.
3. The prominent point of the superior semicircular canal lies approximately 19mm medial to the suprameatal spine and about 10mm above the horizontal plane through that point
4. The prominent point of the posterior semicircular canal lies on the coronal plane 4mm behind the suprameatal spine and is 17mm medial, 2mm above the horizontal plane through that point.
5. Regarding the position of the suprameatal spine to the plane O. A. E., the three prominent points of the semicircular canals are situated rather superiorly when the position of the suprameatal spine is above the plane O. A. E. The sites of the prominent points do not appear to bear any relation to the anterior or medial position of the supremeatal spine.
6. In the triangular plane formed by connecting the three prominent points of the semicircular canals, the distance between the points of the posterior and superior semicircular canals is the greatest.
7. The triangular plane formed by connecting the three prominent points transects the horizontal plane in a lateral and slightly posterior direction and forms an outer angle of 114°45' on the average.
8. For determining the three prominent points of the semicircular canals clinically, the line oonnecting the more stable prominent points of lateral and posterior semicircular canals may be taken as the base line and the prominent point of the superior semicircular canal can be fixed at a position about 9mm above the plane O. A. E. and 1mm posterior, 10mm superior and 19mm medial to the suprameatal spine at an angle of 114° medial and slightly anterior to the base line.
9. The prominent point of the superior semicircular canal is found to be higher than the lowest part of the bulge of the tegmen tympani in specimens when the suprameatal spine is above the plane O. A. E., and the distance from the operative site to the anterior wall of the sigmoid sinus is less than 5mm. Consequently, the temporal bone in such instances would be considered as dangerous for operative procedures.
10. The floor of the internal auditory meatus and the internal auditory foramen lie approximately on the horizontal plane passing through the prominent points of the lateral and posterior semicircular canals. They are situated also in a relatively higher position when the suprameatal spine is above the plane O. A. E.
11. The anterior small portion of the jugular foramen lies on the coronal plane that passes through the prominents of the lateral and superior semicircular canals and the posterior large portion on the coronal plane that passes through that of the posterior semicircular canal. Those portions also situated somewhat higher when the suprameatal spine is above the plane O. A. E. and the diameter of the foramen is greater.

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1. The material consists of 5 early human embryos ranging from 4.5 to 10mm in length. Three specimens (4.5, 5 and 7mm) among them are in the developmental stage of Streeter's horizon XIV, the other two (7 [F] and 10mm (F.)) are in that of horizon XV.
2. In all these embryos the pleuropericardial canals are yet open.
3. The cranial surface of the liver is covered with the mesenchymal tissue of septum transversum and pleuroperitoneale of both sides, only a small lateral area is of peritoneal covering.
4. Dorsal to the septum transversum and between both sides septum pleuroperitonealis of the liver, there is mesocardium a little rightward, to the left of it mesogastrium ventrale. In the mesocardium the sinus venosus of the heart goes on to the ductus venosus of the liver, the mesogastrium ventrale adheres to the dorsal and caudal surfacc of the liver.
5. In the younger 4 specimens among them the right and left side peritoneal surface are separated completely by the adhesion of the mesogastrium ventrale on the liver, while they are continuous dorsal to the V. umbilicalis in the eldest 10mm long embryo.
6. This continuation of the peritoneal surface of both sides dorsal to the V. umbilicalis on the liver occurs on the gall bladder.
7. Dorsocaudal to the mesocardium and at right of the mesogastrium ventrale there is a peritoneal surface of the liver which belongs to bursa omentalis. The bursa omentalis opens to the right candalward. The right wall of this bursa is the caudal mesenchymal continuation of the surrounding the right lung bud tissue. This continuation is the Broman's socalled mesolaterale.
8. The ductus venosus in the liver runs at first left and ventralward to the central part, then turns ventrocaudal and it becomes V. umbilicalis a little leftward inclined. In the middle of the liver branches V. portae dorsal rightward which runs through the right lobe to its medial surface. After a little continuation on the medial surface of the right lobe it turns into the mesogastrium ventrale and then caudalward dorsal to the duodenum.
9. At this beginning of the development of the liver the righl lobe is larger than the left. This separation of the sides can be identified by the furrow of the adhesion of the mesogastrium ventrale.

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