Page 52 - The Miracle of Hormones

Pituitary
gland

Hypothalamus

Artery

Veins

Posterior
pituitary gland Anterior
pituitary gland

Capillaries

Artery Capillaries

If it were left to a human being to measure the amount of fluid in his blood and to
take measures according to the result, he would need the most advanced laboratory.
And he would have to observe what was happening in the blood night and day with-
out taking a break. A human being would encounter countless difficulties in carrying
out this duty (if he could even do it), but tiny cells manage it expertly.

If you had no training in biology, it may not enter your mind to puri-
fy the water molecules in the urine and send them back to the blood.
Even if such an idea came to your mind, you would not know how to
achieve this.
At the moment the sensor cells in the hypothalamus detect a fall in
the fluid level of the blood, they react with great ingenuity. They make
use of a very special messenger hormone (the antidiuretic hormone,

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