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The liquid portion of the blood is called the plasma; the small bodies are known as corpuscles. Other round particles, smaller than the corpuscles, may also be seen under favorable conditions. These latter are known as blood platelets. Each one consists of a little mass of protoplasm, called the stroma, which contains a substance having a red color, known as hemoglobin.
The stroma, which forms only about one tenth of the solid matter of the corpuscles, serves as a contrivance for holding the hemoglobin. *Disappearance and Origin of Red Corpuscles.*—The red corpuscles, being cells without nuclei, are necessarily short-lived.
The attraction of the oxygen and the hemoglobin is sufficient to cause them to unite where the oxygen pressure is more than one half pound to the square inch, but it is not sufficiently strong to cause them to unite or to prevent their separation, if already united, where the oxygen pressure is less than one half pound to the square inch.
The separation of the oxygen from the hemoglobin at the tissues appears to be due to two causes: first, to the weakness of the chemical attraction between the atoms of oxygen and the atoms that make up the hemoglobin molecule; and second, to a difference in the so-called oxygen pressure at the lungs and at the tissues.
The free oxygen is transported from the lungs to the cells by means of the hemoglobin of the red corpuscles, while the combined oxygen in carbon dioxide and other compounds from the cells is carried mainly by the plasma. The limited supply of free oxygen in the body at any time makes necessary its continuous introduction into the body. *Exercises.*—1. Describe the properties of oxygen.
But it was tricky stuff; one part in ten-million would destroy the chlorophyll in plants in about twenty hours, or the hemoglobin in blood in about fifteen minutes. It was practically a universal poison. Hal started for the door, then stopped. He glanced around the room, turned back to me, and suddenly let out a healthy bellow of seeming amusement. Jenny's laugh was right in harmony.
The blood is sea water, to which has been added hemoglobin as a pigment for carrying oxygen to the cells not in direct contact with the atmosphere, nutrients to take the place of the prey our marine ancestors gobbled up frankly and directly, and white cells to act as the first line of defense.
When the oxygen comes in contact with the blood, it unites with the hemoglobin of the blood and is carried to every cell, tissue, muscle and organ, which it invigorates and strengthens, replacing the worn out cells and tissue by new materials which Nature converts to her use. Arterial blood, properly exposed to the air, contains about 25 per cent of free oxygen.
They had hoofs, single hoofs, not cloven. They were not like any Earth animal. But horns and hoofs will appear in any system of parallel evolution. It would seem even more certain that proteins and amino acids and such compounds as hemoglobin and fat and muscle-tissue should be identical as a matter of chemical inevitability. These creatures had teeth and they were herbivorous.
The hemoglobin or red coloring matter forms crystals and the variations of these crystals both in form and molecular construction are such that they set apart every species of animal from every other, and even the races of men perhaps may even set apart individuals. Here, Walter, we have sample of human blood crystals." I looked through the microscope as he directed.
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