Never Mind the Bullocks, Here's the Science by Karl Kruszelnicki Read Free Book Online

bloodstream, it just passes through until it leaves the ‘other end’. And, all the time, the victim is losing water and electrolytes that desperately need to be replaced.
Gut Absorption
Human beings are approximately 45-75% water. One of the body’s major ‘water pumping stations’ is the small intestine.
Surprisingly, the small intestine is not short. It makes up about 70% of the gut. It is called ‘small’ because it is narrow, with an internal diameter of about 2.5-3.0 cm. It has a massive surface, thanks to all the folds on its inner surface – 250 square metres, instead of just 0.5 square metres if it were a smooth tube.
The small intestine begins at the end of the stomach and finishes before the large intestine. (The word ‘stomach’ does not mean ‘all that stuff between the bottom of the ribs and the top of the legs’. Instead, I use the word ‘stomach’ in its anatomical sense, as the organ between the oesophagus and the small intestine.)
It absorbs water and nutrients through the cells that line it, sending them to the bloodstream.
However, under certain circumstances, the small intestine can stop absorbing.
Each day, you take in about 1.5 litres of fluid. Your gut secretes a further 7 litres or more, giving a total of 8-9 litres per day.
Your small intestine normally absorbs about 7 litres each day, leaving 1.5 litres to enter the colon. But, if required, your small intestine can absorb about 20 litres or more each day (as well as lots of nutrients). And your large intestine can absorb even more water (but virtually no nutrients). Overall, absorption is greater, leading to relatively dry faeces.
However, in diarrhoea, the normal balance is upset, with a combination of increased secretion from the gut wall and/or reduced absorption from the gut wall.
Either way, diarrhoea is defined by the World Health Organization as ‘passage of loose or watery stools at least three times in a 24-hour period’. But their definition also emphasises the importance of change in stool consistency.
    The first scientific approach to the problem of cholera deaths occurred in 1831. At the age of just 22, Dr William Brooke O’Shaughnessy, an Irish doctor, scientist and inventor, read out to the Westminster Medical Society the results of his analysis of the blood of cholera victims in India. He discussed how dehydrated the ‘thick, cold, black blood of cholera’ was, and said that this might be reversed by injecting suitable fluids directly into the veins. He published his observations in The Lancet in December that year. (Dr O’Shaughnessy also introduced medical uses of marijuana to Western medicine and received a knighthood for his later work on electric telegraph systems.) In June 1832, Dr Thomas Latta, following on from Dr O’Shaughnessy’s work, published in The Lancet a recounting of the first successful use of intravenous (IV) rehydration to treat the diarrhoea of cholera.
    The principle was simple: a needle was inserted into a patient’s vein, and large quantities of sterile water gradually dripped into the vein. But still, it did not always work. Why? Because in many cases the treatment was not aggressive enough—too little fluid was entering the patients’ veins. In addition, the fluids themselves were often unsterile, chemically impure and not formulated to the same ‘saltiness’ as blood.
    But even if the IV fluids were sterile and pure, and given in large enough quantities, they were still very expensive. So even today, IV treatments are not really suitable for the mass treatment of cholera diarrhoea.
Cholera Resistance
Surprisingly, a person can be somewhat resistant to cholera. There are at least two factors – blood type and the inherited disease cystic fibrosis.
We do not fully understand why, but there appears to be a spectrum of resistance to cholera based on blood type – AB being most resistant, followed by Type A, then Type B, with Type 0 the most susceptible.
We partially understand the