x] of the Nervous System. 273 



the following argument. " The following three things are 

 " especially essential requisites for the maintenance of a flame. 

 " In the first place a free and continuous access of air must be 

 " allowed to the flame so soon as it is lighted. In the second 

 " place the flame must enjoy a constant supply of sulphureous 

 " (combustible) material. In the third place the products of 

 " the flame whether gaseous or solid must be continually 

 "removed." All these conditions are met with in the body. 

 Fresh air is supplied by breathing, sulphureous material is 

 furnished by the food, and the products of the flame in the 

 blood are removed by excretion through the skin. 



He naturally finds a difficulty in the fact that the flame of 

 the blood is not visible ; but this difficulty is not insuperable. 



"But indeed the blood might be actually in flames and yet 

 " the light of it, on account of its tenuity, might not be visible 

 "to our eyes. We know that in the clear light of day we 

 " can see neither red-hot iron nor fireflies, nor ignes fatui nor 

 " (phosphorescent) rotting wood, nor many other things which are 

 " visible at night. Why then should not the vital fire, much 

 " lighter than any of the above, escape our vision ? Moreover 

 " sometimes warm-blooded animals are wont to emit a visible 

 " flame or fire at night only. For instance we have known 

 " certain folk endowed with a warm and vaporous blood who 

 "in the evening when on going to bed they take off their 

 " underclothing near a fire or a candle, have emitted a very 

 "delicate and shining flame which lit up all the lower parts 

 " of their body. The cause of the above seems to be the same 

 "as that by which a torch just put out and still smoking is 

 " relighted by the merest trifle, shewing that a kind of flame, 

 "the root of the one outside, lay hid in the torch. For the 

 " same reason again the coats of horses, mules, cats and other 

 " warm-blooded animals, when rubbed give rise to sparks which 

 " in the dark may amount to a really conspicuous light." And 

 he goes on to quote the case of "an ingenious man with an 

 " active brain who said that after an extra good bout of wine 

 "he could see to read print clearly on a very dark night." 



Willis, as the above shews, had no great critical power in 

 judging the value of evidence, and he was led to this idea of 



F. L. 18 



