Hippocrates (460–377 BC) postulated that the imbalance or excess of four fluids (called humors) within the body play a role in ones emotional and physical state. The chart below shows the four humors (row 1), the condition created by too much of each (row 2), and their respective emotions (row 3):


The Hippocratic theory of personality popularized the practice of bloodletting — opening a vein or applying leeches to "drain off" excessive amounts of the troublesome humor. In medieval Europe, it was common for barber-surgeons (whose professional practice relied on sharp instruments like knives and razors) to advertise their bloodletting services by posting a sign depicting a pale human arm traced with a crimson spiral of blood. (Remember that a ...

You guessed it! The tufted ground squirrel (Rheithrosciurus macrotis), also known as the vampire squirrel.

Check out what may be the first video of the remarkable and rare animal. This species of squirrel is twice the size of most tree squirrels, reputedly has a taste for blood, and has the bushiest tail of any mammal compared with its body size with its tail being 30 percent larger than its body.

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According to a new study published in the journal PLOS One, it was found that identical twins are equally attractive to mosquitoes than fraternal - or non-identical - twins. This correlation lead researchers to conclude that mosquitoes might be making preferential choices based on differences in our DNA.

What causes this preferences? While it may be nice to believe that that mosquitoes are attracted to "sweeter blood", it's not true at all. Female mosquitoes - the ones that bite, in order to get protein necessary for egg development - are actually drawn to us by chemical signals related to body odour. ...

The blood orange is a variety of orange (Citrus × sinensis) with crimson, almost-blood-colored flesh. The fruit is smaller than an average orange; its skin is usually pitted, but can be smooth.

The distinctive dark flesh color is due to the presence of anthocyanins, a family of antioxidant pigments common to many flowers and fruit, but uncommon in citrus fruits. The flesh develops its characteristic maroon color when the fruit develops with low temperatures during the night.

Hemocyanins are proteins that transport oxygen throughout the bodies of some invertebrate animals. These metalloproteins contain two copper atoms that reversibly bind a single oxygen molecule (O2). They are second only to hemoglobin in frequency of use as an oxygen transport molecule. Unlike the hemoglobin in red blood cells found in vertebrates, hemocyanins are not bound to blood cells but are instead suspended directly in the hemolymph. Oxygenation causes a color change between the colorless Cu(I) deoxygenated form and the blue Cu(II) oxygenated form. ...

Many people believe that if you eat certain foods, it can cause your blood to become more alkaline or acidic. Medical research studies have clearly shown that breathing and blood carbon dioxide and bicarbonate ions levels are more significant factors in blood-pH control. Alveolar hyperventilation that is common in the sick reduces cell oxygenation, increases resting blood lactate levels, intensifies production of free radicals due to tissue hypoxia (cells are deprived of oxygen), causes diabetic ketoacidosis in the genetically predisposed patients, and suppresses the immune system and main blood-pH buffer systems of the human organism. ...

Just one


A scanning electron microscope image of a single red blood cell on the tip of a needle.