Commentary: two views of cholera.

Edmund Parkes was a well-qualified choice to provide a critical assessment 1 of John Snow's second edition of the Mode of Communication of Cholera 2 in the British and Foreign Medico-Chirurgical Review. A former military surgeon, Parkes had extensive experience of cholera in Asia. His monograph, Researches into the Pathology and Treatment of the Algide or Asiatic Cholera, 3 had been published in London 8 years previously, and was dedicated, we might note, to the editor of the Review, his good friend John Forbes. Parkes' book was built around 47 autopsies of cholera victims conducted during cholera epidemics in Burma and Madras in the 1840s. Working in a military hospital, Parkes tended to see patients in the advanced stages of disease, and was more impressed by the cold, clammy appearance of his cholera patients (algide ¼ cold) than by their copious diarrhoea, which several of his patients no longer had by the time he saw them. Although Parkes was aware of the marked thickening of the blood in cholera patients , unlike Snow he did not attribute it to dehydration from diarrhoea. 4 For Parkes, the most important pathological finding was pulmonary vascular congestion , which we might now recognize as a reflection of dehydration and shock, whereas for Snow the key pathological event was the massive intestinal fluid loss. As to the communicability of cholera, Parkes asserted in 1847 'I have never observed any indication of contagion'. Snow's major clinical experience of cholera was as a teenage apprentice assigned to the Newcastle coal mines in 1832–33. He thus saw cholera at the front lines, and it is tempting to see here the difference in perspective between the primary care practitioner and the hospital specialist that still permeates modern medicine. Parkes thus came to Snow's book with some strongly fixed views, especially on pathology and communicability. In the book, Snow described with almost eerie exactness the pathophysiology of chol-era—understanding, even then, that cholera kills via massive fluid loss from the intestines. This coherence with modern understanding, we must acknowledge, allows us to be drawn easily into to Snow's argument on the mode of communication, which depends entirely on viewing cholera as a disease of the gut. Fecal-oral transmission made no sense to someone like Parkes who saw cholera as centrally a disease of the heart and lungs. Parkes was as meticulous a dissector of arguments as of bodies, and he …