310 Profs. Percy Frankland and Marshall Ward. 



In p 7 and p8 the very faint outlines of the letters were also 

 showing. 



On the 12th, at 8.30 a.m., the gelatine plates had begun to run, and 

 although the M of p 1 was still intacb, and very well marked, p 2 had 

 liquefied completely, so that the H was a clear patch with blurred 

 outlines in the centre, p 3 still showed the outlines of the B, but it 

 was impossible to keep it longer. 



The main point was definitely established, however, and the treat- 

 ment of the plates proves conclusively that the spores are not killed 

 by high or low temperatures, but"by the direct solar rays. 



These experiments are being continued in order to answer some 

 other questions in this connexion. 



The gelatine and agar after such exposures as have been described 

 are still capable of supporting a growth of JB. anthracis if fresh spores 

 are sown on them, whence the effects described are not merely due to 

 the sub-strata being spoilt as food material. 



That the action of the light is direct on the spore, and not due to 

 any reaction from the medium, I have recently shown by the follow- 

 ing new method : — 



A thin layer of dried spores only, spread on glass without food 

 materials, shows the letter as in the experiments on pp. 305 — 306, if 

 a slab of solidified agar is placed on the film, of spores after exposure, and 

 the whole incubated ; whereas the reciprocal treatment — where the 

 agar alone is exposed, and then laid on a film of spores — yields negative 

 results, the spores germinate equally well all over.* 



Conclusions to Part II. 



The following conclusions are to be drawn from the results of the 

 experiments recorded in this Part II of the Report : — 



1. Thames water, like all open waters, contains a variable number 

 of bacteria at all times (pp. 244 — 256). 



2. The actual numbers of these bacteria are not great, but compari- 

 sons show that there are more in the Thames in December than in 

 March, and fewer still in June (pp. 246, 252, 254). 



3. There are no reasons for supposing any of these water bacteria 

 to be pathogenic, and some of them have been recognised as known 

 saprophytes (pp. 247, 280, 285—290). 



4. In agreement with the universal experience of those observers 



* This proof that the action of the light is direct on the spores is opposed to 

 Roux's conclusions ('Ann. Inst. Pasteur,' 1887, pp. 445 — 452), and in support of 

 those of Arloing (' Compt. Rend.,' vol. 104, 1887), and of Janowski ('Centralbl. 

 fur Bakteriol.,' 1890, Nos. 6 — 8) . These authors worked with less perfect methods, 

 however, and Janowski's results concern typhoid only. I have given more 

 extensive results in the paper read to the Royal Society on February 16, 1893. 



