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Fear always increases the blood pressure. This is probably largely due to the peripheral contractions of the blood vessels and nervous chilling of the body. The venous pressure, after a long neglect, is now again being studied, and its determination is urged as of diagnostic and prognostic significance. Jour. Jour.
The arterial circulation consists of those channels which convey the blood supposed pure blood away from the heart to the different parts of the body, loaded with the life-giving principle of sustenance, invigoration and heat, while the veins or venous circulation conveys to the heart and lungs the impure blood, loaded many times with disease-breeding germs.
When the sputum almost from the first is tinged with venous blood, or even when the sputum is very bloody, of the prune-juice variety, the heart is in serious trouble, and the right ventricle has generally become weak and possibly dilated. The heart may have been diseased and therefore is unable to overcome the pressure in the lungs during the congestion and consolidation.
As the venous blood in this unchanged state is unfit to excite or sustain the action of the brain, the mental functions become impaired, and death speedily ensues, as in the case of a number of persons breathing a portion of confined air, or inhaling the fumes of charcoal.
It may be true, as Thomas Henderson says, that the intra-ocular pressure is influenced by changes in the general arterial or general venous pressures, whereby a rise in general arterial pressure induces a proportionate rise in the intra-ocular pressure, but it would seem that future investigations must confirm this statement before it can be entirely accepted, as well as his further statement that the effect of an increased general venous pressure is a direct one, producing millimeter for millimeter a corresponding increase in the intra-ocular pressure.
My idea is that the common air inspired enters into the venous blood entire, in a state of dissolution, carrying with it its subtle or ethereal part, which in ordinary cases of chemical change is given off; that it expels from the blood carbonic acid gas and azote; and that in the course of the circulation its ethereal part and its ponderable part undergo changes which belong to laws that cannot be considered as chemical the ethereal part probably producing animal heat and other effects, and the ponderable part contributing to form carbonic acid and other products.
The whole of the long tube that runs along the ventral side of the alimentary canal and contains venous blood may be called the "principal vein," and may be compared to the ventral vessel in the worms.
The blood starts on its arterial journey, bright red and rich, laden with life-giving qualities and properties. It returns by the venous route, poor, blue and dull, being laden down with the waste matter of the system. It goes out like a fresh stream from the mountains; it returns as a stream of sewer water. This foul stream goes to the right auricle of the heart.
When the heart's action is weak and the blood tension low the flow may appear to be continuous and not in jets. The blood from a divided artery at the bottom of a deep wound, escapes on the surface in a steady flow. Venous bleeding is not pulsatile, but occurs in a continuous stream, which, although both ends of the vessel may bleed, is more copious from the distal end.
This frequently takes place without the formation of a hæmatoma as the arterial blood finds its way into the vein and so does not escape into the tissues. Even if a hæmatoma forms it seldom assumes a great size. In time a swelling is recognised, with a palpable thrill and a systolic bruit, loudest at the level of the communication and accompanied by a continuous venous hum.
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