of the villus. At the time of contraction, the lymphatic capillary is compressed and shortened, and its contents forced onward into the true lymphatic. When the muscular fibers relax, regurgitation is prevented by the closure of the valve in the lymphatic at the base of the villus.

As the walls of the lymphatic vessels contain muscular fibers, when they become distended, these fibers contract and assist materially in the onward movement of the fluid.

The contraction of the general muscular masses in all parts of the body, by exerting an intermittent pressure upon the lymphatics, also hastens the current onward; regurgitation is prevented by the closure of valves which everywhere line the interior of the vessels.

The respiratory movements aid the general flow of both lymph and chyle from the thoracic duct into the venous blood. During the time of an inspiratory movement, the pressure within the thorax, but outside the lungs, undergoes a diminution in proportion to the extent of the movement; as a result, the fluid in the thoracic duct outside of the thorax, being under a higher pressure, flows more rapidly into the venous system. At the time of an expiration, the pressure rises and the flow is temporarily impeded, only to begin again at the next inspiration.

BLOOD.

The Blood is a nutritive fluid containing all the elements necessary for the repair of the tissues; it also contains principles of waste absorbed from the tissues, which are conveyed to the various excretory organs and by them eliminated from the body.

The total amount of blood in the body is estimated to be about one-eighth of the body weight; from 16 to 18 pounds in an individual of average physical development. The quantity varies during the 24 hours; the maximum being reached in the afternoon, the minimum in the early morning hours.

Blood is a heterogeneous, opaque, red fluid, having an alkaline reaction, a saline taste, and a specific gravity of 1.055.

The opacity is due to the refraction of the rays of light by the elements of which the blood is composed. The color varies in hue, from a bright scarlet in the arteries to a deep purple in the veins, due to the presence of a coloring matter, hemoglobin, in different degrees of oxidation.

The alkalinity is constant, and depends upon the presence of the alkaline sodium phosphate, Na,HPO.

The saline taste is due to the amount of sodium chlorid present.

The specific gravity ranges within the limits of health, from 1.045 to 1.075. The odor of the blood is characteristic, and varies with the animal from which it is drawn, due to the presence of caproic acid.

The temperature of the blood ranges from 98° Fahr. at the surface to 107° Fahr. in the hepatic vein; it loses heat by radiation and evaporation as it approaches the extremities, and as it passes through the lungs.

Blood Consists of Two Portions :

1. The liquor sanguinis or plasma, a transparent, colorless fluid, in which are floating

2. Red and white corpuscles; these constituting by weight less than onehalf, 40 per cent., of the entire amount of blood.

Water acts as a solvent for the inorganic matters and holds in suspension the corpuscular elements.

Albumin is the nutritious principle of the blood; it is absorbed by the tissues to repair their waste and is transformed into the organic basis characteristic of each structure.

Paraglobin or fibrinoplastin is a soft amorphous substance precipitated by sodium chlorid in excess, or by passing a stream of carbonic acid through dilute serum.

Fibrinogen can also be obtained by strongly diluting the serum and passing carbonic acid through it for a long time, when it is precipitated as a viscous deposit.

Fatty matter exists in small proportion, except in pathological conditions and after the ingestion of food rich in oleaginous matters; it soon disappears, undergoing oxidation, generating heat and force, or is deposited as adipose tissue.

Sugar is represented by glucose, a product of the digestion of saccharin matter and starches in the alimentary canal; glycogenic matter is derived from the liver.