SCIENCE-GOSSIP. 



141 



combining the advantages of the hibernating 

 dormouse and the rolled-up hedge-hog. Spores 

 may remain unaltered for years and then come to 

 life again. Thus, as they have a high resistance 

 to heat, cold and chemical substances, they play a 

 great part in the history of the life-struggle of each 

 particular species. 



It would be too long a task to attempt to describe 

 the various methods employed in studying bacteria, 

 and I shall consequently not do more than indicate 

 just the outlines of these procedures. The first 

 step is to discover upon what substance the germ 

 will best flourish — no easy task, for their appetites 

 are as variable and fastidious as those of chronic 

 dyspeptics. Some grow best on milk, others on 

 broth or beef tea, on clotted blood, or on jelly 

 made from nutrient gelatine or sea-weed. Slices 

 of potato, bread, white of egg, and other luxuries 

 too numerous to mention, are all utilized. What- 

 ever is used is carefully boiled first to destroy any 

 other micro-organisms that may chance to be 

 present, and every instrument and piece of appara- 

 tus is similarly treated, this process being called 

 " sterilization." Whatever be the medium chosen, 

 the germ or substance to be examined is now 

 mixed with it in a test tube, which is promptly 

 sealed to exclude all air-borne species. The par- 

 ticular temperature at which each germ will grow 

 best has to be found by many tedious trials. Most 

 grow well at the temperature of the blood, 98° 

 Fahr., and consequently inoculated tubes are 

 generally put into ovens or incubators kept at 

 that temperature. In these incubators the tubes 

 are kept until there is some evidence of growth, 

 which growth closely resembles that of mould on 

 any damp surface. A portion of the growth is 

 then picked off with a needle, mounted on a glass 

 slide and examined under the microscope. To 

 obtain further information, the specimen is usually 

 stained with one of the aniline dyes, in order to 

 bring into greater prominence minute variations of 

 structure. 



In a world so thickly populated as the World of 

 Germs, we should, I think, expect to find good and 

 evil pretty generally mixed. So indeed it is, there 

 being no more reason for saying that all germs are 

 evil than there would be for making the same 

 remark about mankind. Classifying according to 

 their works, we may speak of microbes as those 

 forming Pigment, those exciting Putrefaction and 

 Fermentation, and those Causing Diseases in men, 

 animals or plants. There is this advantage in the 

 world of germs, each individual sticks to his own 

 business. One never finds a microbe of putrefac- 

 tion trying to cause sickness, or a germ of fermen- 

 tation attempting to manufacture pigment. Each 

 is content to do its best in its own sphere, and 

 possibly Nature intends us to read a lesson from 

 these facts. 



The remarkable power of manufacturing colours 

 from colourless materials possessed by our first 

 series of germs has attracted much attention. As 

 a rule the organisms themselves are colourless, but 

 digesting the medium in which they lie they alter 

 entirely its chemical constitution, and new coloured 

 bodies arise — reds, blues and greens being common, 

 also various shades of yellow or orange. One 

 pigment-forming bacillus grows almost exclusively 

 in bread, with the formation of a brilliant scarlet 

 colour. Every now and then this bacillus invades 

 a country, and the householder finds his daily loaf 

 mottled with blood-red spots. Its last recorded 

 appearance was in Germany five or six years ago. 

 During the middle ages, when superstition was 

 rife, the occurrence of "bloody-bread," as it was 

 called, was, especially if the sacramental bread 

 was affected, regarded as an omen of the very 

 worst kind, and gave rise to the wildest excitement. 

 More than once it was thought that the bread had 

 been tampered with by religious opponents, and 

 bitter persecutions at once arose. Another air- 

 borne microbe has the power of giving a black 

 colour to rain, the water collected, in spite of 

 precautions taken for the cleanliness of vessels or 

 roofs, being as black as ink. The consternation 

 and fright of the people in a country-side so invaded 

 may be more easily imagined than described. A 

 case of this kind was recorded in Science-Gossip 

 (N.S. vol. ii. p. 294) by Mr. W. F. de V. Kane, in 

 Ireland. Milk is often coloured by the action of 

 bacteria. Yellow, buff, red, or blue milk is not 

 uncommon, apart altogether from the manipulation 

 it sometimes receives at the hands of some not too 

 honest retailers. Not infrequently the discharges 

 from wounds receive a yellow, green, or blue 

 coloration from the presence of bacteria. Coloured 

 snow is from time to time recorded. Such, then, 

 are a few of the phenomena connected with colour- 

 producing bacilli. With a wider knowledge of 

 bacterial methods of growth these powers will, I 

 have no doubt, be utilized for commercial purposes, 

 such as calico-printing, dyeing, etc. ; providing the 

 fugitive tendency of some of these colours can be 



arrested. 



(To be continued.) 



The new observatory at Heidelberg was opened 

 on June 20th. Professor Valentine will have 

 charge of the astrometric department, and also 

 attend to the determination of time and its com- 

 munication to railways, etc. There is a 6-inch 

 Repsold meridian circle. The astro-physical 

 department is in charge of Professor Max Wolf, 

 who has been so successful in celestial photo- 

 graphy. The equatoreal is mounted in a dome 

 eighteen feet in diameter, which can be rotated 

 completely in eight seconds. Another dome, twenty 

 feet in diameter, is for the astro-photographic 

 instrument being constructed by Brashear, and 

 provided by the liberality of Miss Catherine 

 Bruce. 



