PUTKEFACTION AND INFECTION. 127 



to the limits of the powers of the microscope, his 

 demonstration that the germs of monads survive in a 

 medium raised to a temperature which destroys the 

 adult, and that precipitated mastic particles like those 

 mentioned in § 16 of this paper are not to be discerned 

 by a magnifying-power of 15,000 diameters, constitute 

 a most interesting and important communication. 



Note I. Action of Bacteria upon a Beam of Light 



To trace the gradual growth and multiplication of the 

 Bacteria by their action on a beam of light, an infusion 

 of beef was prepared on the 5th of October, 1875, placed 

 in a globular flask of about 50 cubic inches capacity, 

 and put aside with its mouth open to the laboratory air. 

 On the 8th, 9th, 10th, 11th, and 12th similar flasks were 

 prepared and put aside in succession. On the 12th all the 

 flasks were examined by the concentrated electric light. 

 The freshest one showed the track of the beam as a richly- 

 coloured green cone. The green light was unaffected 

 by a Nicol's prism, which, however, quenched the ordi- 

 nary scattered light and augmented the purity and 

 vividness of the green. It was a case of fluorescence. 

 In the second flask, one day old, the fluorescent beam 

 was in great part masked by the scattered light ; the 

 latter, however, could be partially quenched by a Nicol's 

 prism, the purity of the fluorescence being thus in part 

 restored. Through the third flask, two days, and through 

 the fourth flask, three days old, the track of the beam 

 was still discernible ; through the fifth flask, four days 

 old, it was all but obliterated, while in the sixth flask, 

 seven days old, it was entirely shattered, the turbid 

 medium being filled uniformly with the laterally scat- 

 tered light. 



Two of these flasks were of a bright yellow-green 



