The circulating fluids of the body are the blood, the lymph, and the chyle.
The Blood
An opaque, viscous fluid, salty to taste, with an alkaline reaction and peculiar odor. Its temperature is generally around 100° F, though it varies slightly in different parts of the body. It is bright red or scarlet from the arteries, and dark red or purple from the veins.
It is composed of a faintly yellow fluid (plasma or liquor sanguinis) with suspended particles (the blood corpuscles), the majority of which are colored and give blood its tint.
The blood corpuscles are mainly of two kinds: The colored corpuscles (Erythrocytes) and the colorless corpuscles (Leucocytes). A third variety, the blood platelets, are contained within the blood as well.
Colored or Red Corpuscles are shaped as biconcave circular disks. They have no nucleus but the indentation causes the appearance of a nucleus as the central part appears sometimes light and sometimes dark, and it is to these groupings that the blood owes its hue. Their size varies within a single drop of blood, but the average diameter is about 1/3200 of an inch, while their thickness is about 1/12000 of an inch. There are also smaller corpuscles (about a half to a third of that size), especially in disease. The smaller ones are scarce, however, and called microcytes.
There are between 4,000,000 and 5,000,000 colored corpuscles in a cubic millimeter of blood. Each red corpuscle is composed of a colorless elastic spongework or stroma, condensed at the edges to form a membrane, and the colored contents are uniformly diffused within this.
The stroma is made mainly of nucleo-proteid and the fatty substances lecithin and cholesterin, and the colored material is mostly composed of hemoglobin (a respiratory proteid that contains iron as well as the ordinary elements of a proteid).
Hemoglobin, when removed from the body, crystallizes easily in certain circumstances, and the hemoglobin in blood will dissolve in water.
In a body, blood flows continuously, and corpuscles don’t stick to each other or the wall of the vessel, but when blood is drawn and placed on a slide without reagents, the corpuscles often collect into heaps. It is surmised that this is because of a difference in surface tension.
Red corpuscles can change their shape under pressure to adapt to vessels of various sizes, but are highly elastic and return to the original shape when the pressure is removed.
They are quickly affected by the medium they are placed in and its gravity or weight. In water they swell, lose their shape, and become spherical. Then the hemoglobin dissolves out, and the envelope becomes simply a faint circular outline.
In solutions of salt or sugar, which are more dense, they gain a stellate or crenated appearance. However, when the solution is dilluted to the same gravity as the plasma, they return to their normal shape.
An electric shock can initially produce a crenated outline, and then, if strong enough, rupture the envelope. A solution of salt or sugar with the same gravity as the plasma will separate the blood corpuscles without changing their shape.
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