Part 295

Ellenberger found, as the result of extensive observations (8000 subjects), that about 2 to 3 per cent. of mares have erupted canines in both jaws; that 6 to 7 per cent. have them in the upper jaw; while 20 to 30 per cent. have them in the lower jaw.

Footnote 82:

It is interesting to notice that vestigial canines are not at all uncommon in mares, especially in the lower jaw. They are very small, and do not usually erupt; their presence is indicated in the latter case by a prominence of the gum. This is in conformity with the fact that they were present in both sexes in Eocene and Miocene ancestors of existing equidæ.

Footnote 83:

It is common in veterinary works to call all the cheek teeth molars, since, in the horse particularly, the premolars are molariform, i. e., do not differ materially from the true molars in size or form. The term cheek teeth conveniently includes the premolars and molars.

Footnote 84:

The student is advised to amplify these very general statements by the examination of heads of subjects of varying ages. It may also be noted that the position of the septum between the two divisions of the sinus varies much.

Footnote 85:

Careful observations (especially on frozen subjects and those in which the organs have been hardened in situ) show that there is no abdominal part of the œsophagus in the strict sense of the term. The stomach here lies directly on the diaphragm, so that the last inch or so of the œsophagus is placed obliquely in the hiatus œsophageus, and is partly covered by the pleura, but not by peritoneum. In soft subjects the weight of the stomach, or traction on it, draws part of the œsophagus into the abdomen, inclosed in a collar of peritoneum.

Footnote 86:

The potential lumen is difficult to determine at all accurately. When distended, its diameter (according to Rubeli) varies from 5.7 cm. at its origin to 4 cm. at its cardiac end. The thickness of the wall varies (inversely as the lumen) from 4 mm. to 1.2 cm. or more.

Footnote 87:

At the origin of the tube muscular bundles arise on the raphé pharyngis and blend with the crico-pharyngeus. Ventrally fibers come from the depression between the cricoid and arytenoid cartilages. Bundles of striped fibers may be continued in the superficial part of the muscular coat as far as the cardia.

Footnote 88:

This method of division, although long in use, is of very little value for accurate description. It is mentioned here chiefly because agreement on a more useful topographic method has not been arrived at.

Footnote 89:

Only a general account of the arrangement of the peritoneum is given in this section, since a detailed description cannot be understood without a knowledge of the viscera concerned.

Footnote 90:

This is the position in the expiratory phase as usually seen in the dead subject. In inspiration the saccus cæcus lies under the upper parts of the sixteenth and seventeenth ribs.

Footnote 91:

This occlusion is usually so complete that distention of the stomach by air or fluid forced in through the pylorus may be carried far enough to rupture the stomach without ligating the œsophagus.

Footnote 92:

No natural line of demarcation exists, but there is a marked increase of the thickness of the wall toward the terminal part. Other differences will be noted in the further description.

Footnote 93:

It will be noticed that the mesoduodenum is not continuous with the great mesentery, but ends by a free edge. The mesentery begins on the opposite surface of the end of the duodenum, so that the bowel is attached by two peritoneal folds at this point.

Footnote 94:

Abnormal displacement, e. g., torsion of the left parts, is not rare, and is liable to produce death if not promptly reduced.

Footnote 95: