Normally, the larger the animal, the higher is its blood pressure. This can clearly be seen in eels, sharks and other fish whose sizes vary considerably. The longer the eel or shark, the higher is its blood pressure. There are, however, many exceptions to this rule, one of which is a cock whose blood pressure is the same as that of a horse.

There is no doubt that the heart of a great blue whale weighing 600 to 700 kilograms, even if it does not function normally, will do much more work than the heart of a coal tit weighing about 5 thousand million times less, i. e. only 0.15 gram. For a correct estimation, a comparison is made between the work done by one gram of cardiac muscle. In this case man also has nothing to boast about. Each gram of our heart does work equal to 4000 gram-centimetres per minute, about the same as the heart of a snail. A frog’s heart works three times as hard, a rabbit’s five times as hard, whilst that of a white mouse works twelve times as hard.

Most of the earth-dwelling animals are horizontal. Their brain and heart, the two most important organs, are on the same level. This is very convenient since no additional effort is required on the part of the animal’s heart to supply the brain with blood. It is quite different for man whose brain is on a much higher level than-his heart. The same applies to a six-metre giraffe whose heart is situated 2 to 3 metres lower than his brain. All the creatures, following the same general plan (man, the cock, the giraffe), have high blood pressure.

The heart of typically horizontal animals is unable to supply the brain with blood when they take up an unnatural position. If a rabbit or a snake is placed in a vertical position, they will soon ‘faint’ because of brain anaemia. Nor are such animals very comfortable when placed with their head much lower than the heart since the supply of blood to the brain is confused owing to a disrupted outflow. However, the animal kingdom abounds with virtuosi acrobats. An obvious example are bats who do not care very much in what position their body is.

April 23, 2010 at 11:22 am by admin
Category: blood pressure
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