I2S 



NA TURE 



[June ii, 1903 



mous number of bacteria present at times in ice-creams 

 — one of the highest records being seven millions in 

 one cub. cm. The sources of danger in ice-creams are 

 obvious, as they come from the spoons and vessels, and 

 the persons and dwellings of the street vendors. 



Laboratory experiments have confirmed the conclu- 

 sion that a freezing process is not necessarily fatal 

 to bacterial life. We have instances of bacteria multi- 

 pl^'ing at zero, and of their survival after a six months' 

 exposure to the temperature of liquid air. It is not 

 therefore surprising that the American observers were 

 unable to secure a complete sterilisation of bacterial 

 cultures by the freezing methods they employed. The 

 question became therefore a relative one. What u'as 

 the probability or likelihood of infection through ice 

 in the case of typhoid fever? It would appear that 

 abolit 90 per cent, of the Ordinary water bacteria are 

 eliminated by the process of freezing. The authors 

 find that, in the case of a specific pathogenic organism 

 such as the Bacillus typhosus, less than one per cent, 

 survive simple freezing for a period of fourteen days. 

 Complete sterility did hot occur even at the end of 

 three months, whilst a process of alternate thawing 

 and freezing, if on the whole more fatal to the typhoid 

 germs than a simple freezing, was equally unsuccess- 

 ful in effecting an absolute sterilisation of the infected 

 water. The reduction in the number of typhoid bacilli 

 in chilled water was approximately as great as occurred 

 in ice. The process of destruction proved to be a con- 

 tinuous one, whether it occurred above or below the 

 freezing-point, and whether the experiments were made 

 in water or in soil. A progressive reduction in the 

 number of organisms occurred to the extent of about 

 99 per cent., and proceeded pari passu with the dura- 

 tion of the experiment. Cold exercises a disinfecting 

 action as regards the typhoid bacillus, and in natural 

 ice there is a supplementary purifying influence to be 

 taken into account, as, at the time of freezing, 90 per 

 cent, of the germs are thrown out by a process of 

 physical exclusion. These are the main conclusions 

 arrived at, and the authors find that they are in ac- 

 cord with the general result of experience, namely, 

 that natural ice can very rarely be a vehicle of typhoid 

 fever. 



The research may perhaps fairly be described as a 

 study of the death-rate of typhoid bacilli under adverse 

 conditions, as furnished by cold. The percentage 

 mortality, as a matter of fact, is such as might occur 

 under the influence of light, a poor food supply, 

 and disinfectant agents generally. It is therefore per- 

 missible to think that the danger of infection in the 

 case of ice, if it is minimised, is not by any means 

 abolished. A certain number of typhoid bacilli, as the 

 experiments show, do remain alive, and these may, on 

 rethawing, undergo a rapid multiplication outside as 

 well as inside the human body. And it has likewise to 

 be remembered that it is notoriously difficult to trace 

 the exact channels of infection in sporadic cases of 

 typhoid fever. The infection has at times occurred 

 from the most unexpected quarters. 



Prof. Sedgwick and Mr. Winslow have rightly drawn 

 attention to the unfavourable conditions furnished by 

 natural ice for the propagation of the typhoid 

 organism. It is at the same time feasible to assume 

 that ice may likewise act as a conserving agent, inas- 

 muchas the cold, whilst inhibiting the growth of the 

 typhoid bacillus, will equally prevent the multiplica- 

 tion of other competitive , forms of life. 



The experiments do not affect the general question 

 of the persistence of life at low temperatures. If the 

 temperature be sufficiently low to produce a complete 

 anaesthesia of the cells, cold tends to act as a conserving 

 agent on the typhoid bacillus and allied forms. 



It only remains to commend the memoir of Prof. 

 NO. 1754, VOL. 68] 



Sedgwick and Mr. Winslow to the attention of all 

 who are interested in the epidemiological questions 

 involved. Allan Macfadyen. 



NOTE ON THE PROBABLE OCCASIONAL 

 INSTABILITY OF ALL MATTER. 



A S a summary of my remarks at the discussion on 

 ^*- Prof. Rutherford's most Interesting communica- 

 tion on the subject of radio-activity to the Physical 

 Society of London on Friday last, June 5, I beg U) 

 communicate the following : — 



Consider an electron or other particle, of mass »; 

 and of negative charge e, revolving at speed u round 

 the much more massive rest of an atom possessing an 

 equal positive charge. The centripetal force between 

 them Is 



mit!^ _ e"^ 

 r Kr- 



where the first r strictly Is measured to the centre 

 of gravity of the two bodies, and the second r is the 

 distance between their centres ; but taking these as 

 usual practically equal for the lighter body, we get 

 Kepler's law for the case 



Kw 



(I) 



Larmor has shown (" /Ether and Matter," p. 227) 

 that an electric charge subject to acceleration radlate> 

 some of its kinetic energy, though the radiation be- 

 comes of prominent amount only when the acceler- 

 ation is great; as, for instance, when kathode ray> 

 are suddenly stopped by a target. The " power " of 

 the radiation, or the energy lost per unit time, is 



R = '^^' (2) 



where u is the acceleration of the electric charge e, and 

 -c Is the velocity of light. 



In the case of steady circular motion, the only 

 acceleration is normal or centripetal, viz. 



(3- 



but that Is just as effective for radiation purposes as 

 the tangential variety. 



Hence, combining the three equations, we get, for 

 the radiating power, 



2 /W\2 «8 

 ^=>-(^)-^' ^^' 



that Is, a constant multiplied by the eighth power ot 

 the velocity of the rapidly moving particle : an ex- 

 pression which corresponds with what for ordinary 

 molecular motions Is known as Stefan's law, connect- 

 ing radiation with temperature, i.e. with square 0/ 

 molecular velocity. 



Now the radiation loss is equivalent to a resisting 

 medium, and accordingly the revolving particle tends 

 to move inwards towards its centre, and its speed to 

 increase in accordance with equation (i). A slight 

 increase In speed brings about a great increase in 

 radiating power, as Is shown by equation (4) ; where- 

 fore the change, once appreciably begun, may be ex- 

 pected to go on rapidly, until presently the speed 

 approaches the velocity' of light. On the electric 

 theory of matter, radiation or loss of energy must occur 

 from every atom, and therefore it is only a question of 

 time how long an atom shall last before it reaches this 

 stage. 



Directly this stage is reached another effect super- 

 venes ; the rapidlv moving portion of the mass begins 

 rapidly to rise In value, according to a complicated 

 expression not yet quite fully worked out. This effect 



