7o6 



THE POPULAR SCIENCE MONTHLY. 



carried out, will not be far greater in 

 the long-run than its benetits. 



The many American friends of Mr, 

 Herbert Spencer will be pleased to 

 learn that he contemplates visiting this 

 country next year. He has long wished 

 to do so, but has been deterred from 

 seriously thinking about it by the state 

 of his health, which forbade the vent- 

 ure of an Atlantic voyage. But he is 

 now so much better that this difficulty 

 is removed, and he hopes to come over 

 some time next summer. 



LITERARY NOTICES. 



The Bacteria. By Dr. Antoine Magnin, 

 Translated by George M. Sternberg, 

 M. D., Surgeon United States Army. 

 Boston : Little & Brown. Pp. 227. 

 Price, 2.50. 



The readers of "The Popular Gcience 

 Monthly" have been from time to time 

 informed concerning the progress of inquiry 

 in relation to those lowest, minute, and cu- 

 rious organisms now known under the gen- 

 eral name of "Bacteria." The first observ- 

 er who perceived them was the father of 

 microscopy, the Dutchman Lceuwenhoek, 

 as early as 16*75. lie was examming with 

 his magnifying-glasses a drop of putrid 

 water, when he remarked with profound 

 astonishment that it contained a multitude 

 of little globules which moved with agility. 

 In 1773 they were studied by 0. F. Miiller, 

 and classified as a group of the Infusoria. 

 They soon began to occupy a good deal of 

 the attention of raicroscopists, and there 

 was much conflict of opinion about their 

 nature, as was inevitable from the novelty 

 of the research and the imperfection of in- 

 struments. At one time they were consid- 

 ered as animals, and at another they were 

 taken for plants ; were now ranked as Al(/(e, 

 and again as fungi. But it is only in the 

 present generation that our knowledge of 

 them has become so perfect as to lead to a 

 larpre amount of aoireemcnt amoncr observ- 

 ers respecting their nature, varieties, and 

 clcssification. It is now recognized that 

 they are the lowest organisms, standing 



upon the limit of the two kingdoms, ani- 

 mal and vegetable, and are thus defined by 

 the botanists who have most recently stud- 

 ied them: "Cells deprived of chlorophvl, 

 of globular, oblong, or cylindrical form, 

 sometimes sinuous and twisted, reproduc- 

 ing themselves exclusively by transverse 

 division, living isolated or in cellular fami- 

 lies, and having affinities which approach 

 them to the Alffce, and especially to the Os- 

 cillatorice.^^ There has been, as our read- 

 ers are aware, a long and intense struggle 

 over the question of their spontaneous gen- 

 eration, but the great preponderance of 

 opinion is now against that mode of origin. 

 They vary much in form and dimensions, but 

 are regarded as the smallest of all micro- 

 scopical beings. Some of them are motion- 

 less, but they are generally remarkable for 

 the movements they exhibit. These are thus 

 described by the eminent observer Cohn : 



In certain conditions they are excessively mo- 

 bile ; and, when they swarm in a drop of water, 

 they present an attractive spectacle, similar to 

 that of a swarm of gnats, or an ant-hill. The 

 bacteria advance, swimming, then retreat with- 

 out turning about, or even describe circular lines. 

 At one time they advance with the rapidity of 

 an arrow, at another they turn upon themselves 

 like a top ; sometimes they remain motionless 

 for a long time, and then dart off like a Jiash. 

 The long rod bacteria twist their bodies in swim- 

 ming, sometimes slowly, sometimes with address 

 and agility, as if they tried to force for themselves 

 a passage through obstacles. It is thus that the 

 fish seeks its way through aquatic plants. They 

 remain sometimes quiet, as if to repose an in- 

 stant : suddenly the little rod commences to os- 

 cillate, and then to swim briskly backward, to 

 again throw itself forward some instants after. 

 All of these movements are accompanied by a 

 second movement analogous to that of a screw 

 which moves in a nut. When the vibrios, in 

 the shape of a gimlet, turn rapidly round their 

 axis, they produce a singular illusion : one would 

 believe that they twisted like an eel, although 

 they are extremely rigid. 



An order of beings so amazingly minute 

 that the various kinds of them are just barely 

 revealed by the utmost powers of the micro- 

 scope, might seem of little importance, at 

 least, practically, in this world's concerns. 

 But this is not so. The bacteria are at the 

 foundations of life, and it is now admitted 

 that they have a grand office in relation to 

 the general preservation and continuance of 

 life. Exactly in what way is perhaps not 

 yet determined ; but they are in some way 



