Part 296

There is no natural line of demarcation between the small colon and rectum: the plane of the pelvic inlet is selected for convenience of description.

Footnote 96:

The anterior part of the rectum is very variable in position and relations. It is not often median, but may be deflected either to right or left. Most often it is pushed to the left by the pelvic flexure of the colon. In other cases—especially when empty—it may lie against the right wall, and the space to the left is occupied by the small colon. The amount covered by peritoneum dorsally and laterally is very variable, and appears to be in inverse proportion to the fullness of the bowel.

Footnote 97:

A descriptive method based on that in use in human anatomy cannot be applied with clearness to the organ in the horse.

Footnote 98:

These impressions are not evident on the soft organ. In hardened material they are clearly mapped out, although of course variable in size, in conformity with the degree of fullness of the various hollow viscera. The cæcal impression may not be evident if, as often happens in old horses, the right lobe of the liver is much atrophied.

Footnote 99:

Flower and Ruge describe the mammalian liver as being primarily divided by the umbilical fissure into two parts, the right and left lobes. Secondary fissures on either side may subdivide each of these primary lobes. On this basis we may recognize in the liver of the horse right lateral, right central, left central, and left lateral lobes. In the young foal these four lobes are distinctly recognizable. The two central lobes would correspond to the middle lobe of the foregoing description, and the right central lobe would be the equivalent of the quadrate lobe of man.

Footnote 100:

In the young foal the interlobular tissue is more abundant and the lobulation correspondingly distinct.

Footnote 101:

The hepatic veins may be recognized on section from the fact that they remain open, being connected closely with the parenchyma.

Footnote 102:

The ductless glands are organs which elaborate substances which pass directly into the veins or lymphatics, instead of being conveyed away by ducts. This process is termed internal secretion. The ductless glands include the lymph glands, which are described with the organs of circulation; the thyroid and thymus bodies, described usually with the respiratory organs; the adrenal or suprarenal bodies, described with the urinary organs; the pineal and pituitary bodies, described with the brain; and the spleen, described with the digestive system as a matter of convenience. The spleen is not, strictly speaking, a gland at all: it is not epithelial in origin or structure, but is mesenchymatous.

Footnote 103:

The student is strongly recommended to study the peritoneum of a foal or other small subject when the opportunity occurs, as in these the viscera are easily handled, and the course of the peritoneum can be followed without difficulty.

Footnote 104:

The passage is subject to a good deal of variation in caliber and is sometimes completely occluded.

Footnote 105:

In dissecting-room subjects (which are usually aged) the omentum often exhibits pathological changes, such as adhesions, rents, tumors, formation of twisted strands, etc.

Footnote 106:

The student will note here the difference between the structure and behavior of the brachydont (short-crowned) incisors of the ox and the hypsodont (long-crowned) type of the horse.

Footnote 107:

In popular language these are conveniently regarded as so many stomachs, and termed accordingly “first,” “second,” etc. Other names are in common use, e. g., paunch, honeycomb, manifold or manyplies, and rennet or true stomach.

Footnote 108:

It has been customary to term the sacs left and right respectively, but these do not represent the relations as they exist in situ and as they are presented on frozen sections.

Footnote 109: