Question

The Scottish Society of the History of Medicine extended knowledge of osmosis. In his textbook, Elements of chemistry, there are eight pages on osmosis and he clearly indicated its probable importance in biolog;y Extracts of this section were quoted at length in many of the textbooks of physiology, widely read by medical students and doctors at times when great cholera epidemics were raging The failure of the medical and chemical establishments to link together cholera and osmosis seems in retrospect a remarkable failure in constructive thinking. Had the two imaginative men, Dutrochet and O'Shaughnessy, met by chance in 1832 in Paris or London, their conversation over a bottle of wine might have led to the means of saving many millions of lives THE ONE HUNDRED AND SECOND ORDINARY MEETING This meeting took place in University Hall, St Andrews, on 19 June 1982, when two papers were presented. The first, by Professor Ian A. D. Bouchier, was entitled WHALES AND WHALING: CONTRIBUTIONS BY THE MEDICAL PROFESSION There is a rich heritage of literature related to the whaling industry. Much of it is documentary, natural history, and of a scientific nature; but at least one great work of art, Moby Dick, has emerged. Remarkably little has been contributed by the medical profession; remarkable because from the seventeenth century, each British whaler carried a surgeon, and he would have been the one man aboard with the requisite education and scientific training to observe and record events occurring during the voyage. The surgeon lived in the cabin and messed with the captain and mate. Very often, he had just taken his degree and had not yet settled into his practice. The reasons for doctors to undertake these voyages were varied: financial, love of adventure, and a desire to see new and unexplored parts of the globe, initially the Arctic, then the Pacific and South Seas, and, from the early part of this century, the Antarctic. John Lyell (1807-74) Lyell is the first of our medical authors. Born at Newburgh, Fife, he was a Licentiate of the Royal College of Surgeons of Edinburgh (1829) and later MD of St Andrews (1850). He kept a careful diary1 of his voyage as surgeon on the whaler The Ranger from 1829 to 1833. The diary, located in the Perth Museum, has never been published. It is of considerable interest both as a record of whaling life and of travel and contains charming and accurate watercolour illustrations of islands, fauna and flora, and whaling artefacts. Ranger fished in the Pacific, both north and south of the Equator, and towards the end of the voyage, life was quite uncomfortable. Lyell relates how he had to sleep atop Diary of John Lyell, ship surgeon. Written on a voyage to the Southern Arctic Seas, 1829-33. 1 am grateful to the Curator of the Perth Museum for access to Lyell's diary 182

4. It might be logical to assume that if a patient was suffering from diarrhea and dehydration, that rehydration with water that is hypotonic or isotonic to normal cells would aid the patient. Explain why this is not the case and why Rodgers treatment in 1908, with a hypertonic solution, is an effective treatment of cholera. Answer this question in terms of osmosis and tonicity.

Answer 1

Diarrhea is characterised by mild dehydration, so by administering hypotonic or isotonic solution can replace the losts water and electrolytes in the plasma.

But Cholera is a disease charaterised by severe diarrohea. Certain pathophysiological conditions block the absorption of sodium and chloride by the microvilli of teh small intestine and promotes the secretion of chloride and water by the crypt cells.

In this condition electrolytes are severely lost and the ECF becomes hypotonic to ICF and the fluid starts moving into the ICF by osmosis. Homeostasis is disturbed by loss of water on both sides, either releasing into the lumen of the intestine or entering the cell.

By treating the patient with hyeprtonic solution results in normalising the osamolarity of the plasma. When hypertonic solution is released into plasma, automatically water moves from ICF to ECF and the homestasis is attained.

ICF= Intra cellular fluid

ECF= Extra cellular fluid