Dissection and Structure of Pigeon | Zoology

In this article we will discuss about the dissection and structure of pigeon (Columba).

1. Hyoid Apparatus of Pigeon:

Columba sp.:

The hyoid apparatus occupies the same relative position as in Calotes. The components of the hyoid apparatus are bony for the most part.

Preparation:

Expose the basihyal in the floor of the mouth cavity. Anteriorly it reaches the base of the tongue. Posterolaterally, trace the two small ceratohyals (hyoid cornu). Follow the first and second basi-branchials, posteromedian to basihyal. On other side expose the ceratobranchial, articulated with the epibranchial which ends near the glottis.

Follow the technique adopted for Calotes:

Structure:

(Fig. 29.11)

i. Basihyal:

Median, arrow-shaped, bony except the tip.

ii.Ceratohyals (Hyoid cornu):

Short paired bones with cartilaginous tip and directed posteroventrally from the base of the basihyal.

iii. First basibranchial:

A median bone posterior to basihyal.

iv. Second basibranchial:

A median bone with a narrow cartilaginous tip, posterior to the first branchial.

v. Ceratobranchials:

Paired bones, run posterolaterally from the junction of the two basi-branchials.

vi. Epibranchials:

Paired, continuous with the ceratobranchials, curved posteriorly and gradually narrow down. Cartilaginous at the tip.

2. Syrinx of Pigeon:

Syrinx or voice box is the characteristic of birds.

Preparation:

Expose the trachea and the two bronchi in the body cavity. Syrinx is a slightly dilated chamber at the junction of the trachea and the two bronchi. Cut the trachea at about 6 to 8 mm anterior to the syrinx, and the bronchi close to the lungs. Carefully detach the external muscles and the syrinx is free.

Put the syrinx in water in a paraffin lined petri dish. Fix it on the dish with the dorsal surface directed upwards by driving pins through the sides of the trachea and the bronchi. Starting from the tracheal end cut the dorsal wall of the syrinx, close to its junction with the bronchi. Push the cut borders of the syrinx laterally and examine the structures in the voice box.

Structure:

(Fig. 29.12)

i. Syrinx is a small, cartilaginous chamber.

ii. The mucous membrane of the chamber forms a cushion-like thickening on each side.

iii. Pessulus, a cartilaginous bar, extends dorsoventrally at the junction of the bronchi.

iv. Pessulus supports a small membrana semilunaris (semilunar membrane).

v. Paired, intrinsic syringeal muscles run from the trachea to the syrinx.

3. Pecten of Pigeon:

Pecten is supposed to be an organ helping the bird in long distance vision.

Preparation:

Remove an eye-ball and cut it into two equal halves by giving an incision in the equa­torial plane with a pair of fine scissors. The posterior half contains the pecten at the point of entry of the optic nerve into the eye-ball. Separate the pecten from the eye-ball with a pair of fine scissors. Mount in glycerine.

Structure:

(Fig. 29.13)

i. Nearly square in outline.

ii. Heavily black pigmented.

iii. A membranous structure with close set longitudinal folds.

4. Down Feather of Pigeon:

Down feathers are present in between the contour feathers.

Preparation:

Pluck the contour feathers of a small area from the breast of a pigeon. Both the filo plumes and down feathers are exposed. The former is distinguished from the latter by its elongated axis and a few barbs at the tip.

Pluck one down feather from the skin by holding the calamus or the axis at its base with a pair of fine forceps and dip it in 50% glycerol in a watch glass. Take out the feather from the watch glass holding the calamus and put it on a glass slide. Carefully separate the barbs from one another as far as practicable with a fine needle. Cover it with a cover slip and examine under low magnification of a microscope.

Structure:

(Fig. 29.14)

i. The calamus is short, whitish and soft.

ii. The barbs are narrow, very delicate and project from the calamus outward and forward. Barbs are more crowded towards the distal end.

iii. Barbs are provided with barbules.