Part 76

The lymph vessels of the head accompany the branches of the jugular vein, collecting the lymph from the structures of the head and the neck.

The lymphatic vessels communicate at the anterior and posterior oblique anastomosing vessels. At the lower part of the neck each trunk receives a vessel, which accompanies the carotid arteries. Further on they are provided with a lymph gland which rests on the jugular vein.

THE BLOOD AND ITS FUNCTIONS

The special function of the blood is to nourish all the tissues of the body, and in this way to aid growth and repair. It furnishes material for the purpose of the elaboration of body secretions; it supplies the organism with oxygen; and it carries away carbon dioxid and other effete material. Blood is constantly in circulation.

Blood is red, opaque, and is, in the fowl, quite viscid. The exact tint of the blood depends on whether it is drawn from an artery or from a vein. Blood from a vein has a purplish tinge while that from an artery is a bright scarlet. The color of blood is largely due to pigment in the erythrocyte, called hemoglobin.

The reaction of the blood is alkaline, due to the phosphate and the bicarbonate of soda. The alkalinity of the blood is reduced by work. This is due to the formation of sarcolactic acid in the muscle. The odor of blood is due to volatile fatty acids. Each kind of fowl has its own peculiar odor. The taste of the blood is saltish, due to a small amount of sodium chlorid it contains.

The blood consists of the following substances:

First, the unorganized part, or fluid, the liquor sanguinis or plasma. It contains in solution proteids, extractives, mineral matter, and gases. The gases are held in loose chemical union.

The liquor sanguinis constitutes fully 66 per cent. of the volume of the blood. It is albuminous in nature and contains a small amount of coloring matter of a fatty nature. It holds in solution three proteids—fibrinogen, serum globulin, and serum albumin.

Second, the organized parts, or the cellular structure (Fig. 74, Nos. 1 to 21). The cells float in the plasma and consist of three groups: the erythrocytes, or red blood cells, the leucocytes, or white blood cells, and the thrombocytes.

=Erythrocytes.=—The average number of red cells (Fig. 74, No. 21) of the domestic fowl range between 3,000,000 and 4,000,000 per cubic millimeter. The red blood cells are flattened and elliptical in shape, and possess an oval elliptical nucleus. The average length is ¹⁄₂₁₀₀ inch and the diameter ¹⁄₃₈₀₀ inch, or 7 to 8 micra in diameter and 12 to 13 micra in length. However the diameters vary in different kinds of birds. The cytoplasm is yellow and glassy, and the nucleus takes basic stains and appears somewhat picnotic.

=Thrombocytes.=—The thrombocyte (Fig. 74, No. 19) is of about the same length as the erythrocyte but somewhat narrower. The nucleus is round, stains purple with the Wright’s stain, and the chromatin material is somewhat diffused. The diameter of the nucleus is nearly equal to that of the cell. The cytoplasm is pale and may show vacuoles near the nucleus. They may contain small circumscribed red structures. They vary somewhat in size and shape. There are in the domestic fowl between 45,000 and 55,000 per cubic millimeter.

=Leucocytes.=—There are, in the blood of the hen, 28,000 to 35,000 leucocytes per cubic millimeter. The leucocytes may be divided into five distinct types. These are as follows:

Polymorphonuclear leucocytes with eosinophilic rods (Fig. 74, No. 2) are round and have a diameter about equal to the length of the erythrocyte. The nucleus is polymorphous; that is, it has two or more lobes. The nucleus stains a pale blue, and the chromatin is diffused. The cytoplasm is colorless with bright red staining spindle-shaped rods. There are 28 to 32 per cent. of this type of cell in the blood of the hen.

FIG. 74.—Blood cells of the fowl. Wright’s stain. From a S. C. Rhode Island Red cockerel. 1, Basophile (mast cell) with lilac staining spherical granules. 2, Eosinophile with rod-shaped acidophile bodies. 3 and 4, Eosinophiles with acidophile staining round granules. 5, Eosinophile ruptured. 6, Mononuclear leucocyte with vacuoles in the cytoplasm. 7 and 9, Transitional leucocytes (first stage). 8, Mononuclear leucocyte. 10, 11, and 12, Small lymphocytes. 13 and 14, Large lymphocytes. 15, A lymphocyte. 16, Lymphocyte (nucleus centrally located). 17 and 18, Transitional leucocyte. 19, Thrombocyte. 20, Neutrophile (polymorphonuclear). 21, Erythrocytes. ]

Polymorphonuclear leucocytes with eosinophilic granules (Fig. 74, No. 3 and 4) are of about the same shape and size as the preceding. The nucleus is similar to the former except that it may appear slightly picnotic. The cytoplasm stains not at all or faintly blue; it contains round or spherical granules which stain a dull red. There is from 4 to 6 per cent. of this type of eosinophiles found in the domestic fowl.

Lymphocytes are round in shape and of about the diameter of the width of a thrombocyte (Fig. 74, No. 11). The nucleus is round, staining somewhat purple, and contains a diffused chromatin material. The cytoplasm exists in only small amounts; it lies to the side of the nucleus and stains a pale blue. This is the small lymphocyte. A similar cell but much larger also exists. This is the large lymphocyte (Fig. 74, No. 13). There is from 40 to 44 per cent. of the lymphocytes in the blood of the fowl. The small lymphocytes are most abundant.

Large mononuclear cells (Fig. 74, No. 6) either round or oval, in shape, whose diameter may be about that of an erythrocyte and at times much larger. The nucleus may be round, oval, or irregular, and at times rather crescent or U-shaped (Fig. 74, No. 17). The cytoplasm is abundant and completely surrounds the nucleus. The cytoplasm stains a paler blue than the nucleus. Both taking the basic stain as do the lymphocytes. These constitute 18 to 20 per cent. of the cells of the blood.

Mast cells or basophiles (Fig. 74, No. 1) are of about the same size and shape as the eosinophiles. The nucleus is round or oval, and stains a very pale blue. The cytoplasm is colorless, mostly to one side of the nucleus, and contains round or spherical purple staining granules. This type of cell constitutes from 2 to 4 per cent. of the white cells of the blood.

=Structure of the Red Blood Cell.=—The red blood cell is composed of a spongy stroma holding in its meshes the red coloring matter. The stroma, or framework, of the erythrocyte consists principally of nucleo-albumin; it contains lecithin, cholesterin, and salts. The red matter consists of an albuminous crystalline substance called hemoglobin, which forms about 90 per cent. of the total solid matter of the dried corpuscle. Each red cell offers a certain absorbing surface for oxygen. As the blood circulates through the delicate walls of the lungs and the air-sacs, it takes up oxygen; the blood at the same time delivers to the air carbon dioxid which has been brought from the tissues where active cell metabolism has been going on. This oxygen taken up by the erythrocyte forms a loose chemical union and is known as oxy-hemoglobin. In this form it is carried to the tissues of the body where it is given up by the erythrocyte to the tissues where oxidation is going on.

Hemoglobin is a crystallizable proteid substance containing carbon, hydrogen, oxygen, nitrogen, sulphur, and iron.

=Formation of the Cells of the Blood.=—The red blood cells are formed in the red marrow of the bone.

Polymorphonuclear leucocytes are formed in the red marrow of the bones, and the lymphocytes in the lymph glands and lymph follicles.

The bird carries a normal body temperature of 105° to 107° F. The average temperature of 50 mature hens and cocks was 106.8° F. The blood is of a deep red color.

=Composition of the Blood.=—The average composition of the blood of the domestic fowl as given by Owen, is as follows:

Whole shed blood: Water 780 parts Clot 157 parts Albumin and salts 63 parts ————— 1000 parts

Moist blood cells: Average total weight 456.69 Water 342.52 Solid matter 97.50

Plasma: Total weight 543.30 parts Water 495.72 parts Solid matter 30.72 parts