CHAPTER EIGHT 



OBSERVATION 



" Knowledge comes from noticing resemblances and 

 recurrences in the events that happen around us." 



— Wilfred Trotter 



Illustrations 



PASTEUR was curious to know how anthrax persists endemi- 

 cally, recurring in the same fields, sometimes at intervals 

 of several years. He was able to isolate the organisms from soil 

 around the graves in which sheep dead of the disease had been 

 buried as long as 1 2 years before. He was puzzled as to how the 

 organism could resist sunlight and other adverse influences so 

 long. One day while walking in the fields he noticed a patch of 

 soil of different colour from the rest and asked the farmer the 

 reason. He was told that sheep dead of anthrax had been buried 

 there the previous year. 



" Pasteur, who always examined things closely, noticed on the 

 surface of the soil a large number of worm castings. The idea 

 then came to him that in their repeated travelling from the 

 depth to the surface, the worms carried to the surface the earth 

 rich in humus around the carcase, and with it the anthrax spores 

 it contained. Pasteur never stopped at ideas but passed straight 

 to the experiment. This justified his forecast. Earth contained 

 in a worm, inoculated into a guinea-pig produced anthrax."^* 



This is a fine example of the value of direct personal observation. 

 Had Pasteur done his thinking in an armchair it is unlikely that 

 he would have cleared up this interesting bit of epidemiology. 



When some rabbits from the market were brought into Claude 

 Bernard's laboratory one day, he noticed that the urine which 

 they passed on the table was clear and acid instead of turbid and 

 alkaline as is usual with herbivorous animals. Bernard reasoned 

 that perhaps they were in the nutritional condition of carnivora 

 from having fasted and drawn on their own tissues for susten- 



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