194 BAOTEEIA. 



wafer placed over night in the moist and bacteria-laden 

 air of the church edifice would in the morning be found 

 to be besprinkled with bright red drops. What could it 

 be but blood? No human hand could have come near 

 the place, and so what else could be believed but that it 

 was the hand of God ? It was one of those early miracles 

 in which both priest and layman could share alike in be- 

 lieving with perfect honesty. The divine finger pointed, 

 but to what ? — it was the office of the priest to say. 



How many lives were sacrificed and homes destroyed 

 through that most honest of ecclesiastical delusions, the 

 miracle of the bleeding Host, it were useless now even to 

 conjecture." 



Some bacteria cause the phosphorescence seen in de- 

 caying fish, and tubes of these have been photographed 

 by their own light. 



I have no time to mention here some of even the more 

 important peculiarities of very many interesting species 

 among the saprophytes, as I wish to speak later on of 

 some of the microbes which cause disease. We owe to 

 Koch, the great German bacteriologist, the easy and effi- 

 cient method of separating species, known as the plate 

 method. If I have a mixed culture in a tube, and wish 

 to separate the species, I melt the gelatine in three tubes 

 by putting them in warm water, then with a needle I 

 put a little — very little — of the mixed culture in the first 

 tube and stir with the needle to mix them thoroughly 

 through the gelatine, then transfer a little of this first 

 dilution to tube number two and mix as before. The 

 probabilities are that tube number two will still contain 

 a great many more bacteria than I want, so I repeat the 

 process and inoculate tube number three from number 

 two. When the contents of tube number three are 

 poured out on a sterilized glass plate they will contain 

 few microbes, and these will be widely separated the one 

 from the other. The gelatine immediately solidifies and 



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