7 6 



NA TURE 



[May 24. 1883 



left, where the sky as indicated does not appear to be a 

 very luminous one. 



142. "... these Yellow Sands," John Brett, A. In 

 this admirable picture, in which the sea and sky are quite 

 perfect, Mr. Brett has attempted some difficult effects. 

 More transparent water has never been seen on a canvas, 

 and the colour of the yellow sand at its bottom is beauti- 

 fully mingled with the light reflected from its surface. 



626. " Sounding for Shallows at Low Nile," Tristram 

 Ellis. A bold attempt at reflection in the Nile water, 

 but, as a matter of fact, the real colour is not so entirely 

 subordinated by reflection. 



Snowstorms 

 764. " The Joyless Winter Day," Joseph Farquharson. 

 The storm must have been very considerate to the artist. 

 In spite of the driving blast there is not a single snow- 

 flake to be seen in the first twenty yards. 



THE LIVING ORGANISMS OF THE 



A TMOSPHERE 



Les Organismes vivants de I 'Atmosphere. Par M. P. 



Miquel, Docteur es Sciences et Docteur en Mddecine, 



Chef du Service micrographique a l'Observatoire de 



Montsouris. (Paris: Gauthier-Villars, 18S3.) 

 TiLUS occidit aer guam gladuis, such is the main idea 

 contained and explained in M. Miquel' s very able 

 and interesting book. If the modern theories are true, it 

 must be certainly conceded that although the sword and 

 gun are very murderous tools, air is yet more so. But on 

 the other hand one may say of our atmosphere's mur- 

 derous propensities what a French writer said when he 

 was told that coffee was a poison : " Well, it may be a 

 poison to be sure, but it must be a very slow one ; I have 

 been indulging in it for over fifty years." In fact, if 

 Voltaire and many other men took too much of it, it 

 began to tell on them only very late. Taking it for 

 granted that coffee is murderous, it must be also granted 

 1 hat it is not always so. Such is also the case of the 

 atmosphere we live in. 



The influence of infinitely small organisms contained 

 in the air and water, as well as in the body of man and 

 animals, can no longer be denied, at least, in a general 

 manner. Certainly much remains to be done to bring 

 the Microbe Theory to the point it must attain ; many 

 inconsistencies and discrepancies yet interfere with its 

 general harmony ; but Davaine's and Pasteur's experi- 

 ments and discoveries have certainly opened new ways in 

 science. 



Now that it is granted that the organisms alluded to 

 are to be found and may thrive in the air, it is interesting 

 to know what these are, how abundantly they may be 

 found in the atmosphere, and by what means they may 

 be captured and experimented upon. To these im- 

 portant questions M. Miquel answers in a very precise 

 and interesting manner. 



It is not a difficult thing to detect the corpuscles con- 

 tained in the atmosphere ; a mere sunbeam in a room 

 shows hundreds of them dancing in the light. But it is 

 less easy to ascertain tbe nature of these little atoms ; 

 great skill is required to do that. Some are vegetable, 

 some are mineral, some are animal. 



M. G. Tissandier has established that a great quantity 



of mineral atoms is contained in the atmosphere ; the 

 most interesting of these are meteoric iron melted into 

 the form of little globules. Some infusoria are also to 

 be found, but bits of wool and silk, pollen and spores are 

 more abundant. As one may easily believe, all these 

 corpuscles are less abundant in the atmosphere after a 

 fall of rain. For instance, M. Tissandier finds in a cubic 

 metre of air 0023 gramme of dust after a rainless week ; 

 coo6 gramme the day after a heavy rain. 



The description given by M. Miquel of the numerous 

 instruments contrived by himself and by others to col- 

 lect the corpuscles contained in the air is good and 

 interesting, but is not easily condensed. Another very 

 important chapter of this book is that concerning the 

 nature and origin of the aerial corpuscles among which 

 pollen, flour, and spores are most abundant. For 

 instance, the number of spores to be found in a cubic 

 metre of air is about 14,200. But this number changes 

 very much according to the season. In winter the mean 

 number is 6200 ; in spring, it is 13,000; in summer, 

 2S,ooo ; in autumn, 9800. The reason of these variations 

 is easy to understand. 



However abundant spores and pollen, woollen and silk 

 threads may be in the air, that is a question of little im- 

 portance when compared with that of the presence of bac- 

 teria in the atmosphere. Bacteria are to be found, often in 

 great quantity, in the air. Generally speaking, according 

 to M. Miquel's experiments and observations, bacteria 

 are more abundant when the weather is dry ; the reverse 

 is to be observed concerning spores of inferior cryptogams. 

 The direction of the prevailing wind has much to do with 

 the number of bacteria found in the air. M. Miquel 

 shows, by means of a diagram, how the air having passed 

 through part of Paris, before coming to the Montsouris 

 Observatory, contains more bacteria than that which 

 passed only over the suburbs and country around the town. 

 South winds bring from 42 to 77 bacteria to a cubic 

 metre of air ; northern ones bring from 108 to 152. 

 Other experiments give the same results. M. Miquel 

 draws from his numerous experiments the conclusion that 

 the air in Paris contains nine or ten times more bacteria 

 than does that outside of the fortifications or close to 

 them. For instance, in the Rue de Rivoli, M. Miquel 

 finds an average number of 760 bacteria in autumn, 410 

 in winter, 940 in spring, and 920 in summer ; that is, a 

 mean annual number of 750 bacteria per cubic metre of 

 air. At Montsouris the mean annual number is 75. The 

 minimum number found by M. Miquel is 45 (winter 

 1882); the maximum is 3000 (summer 1881) bacteria per 

 cubic metre. 



In hospitals, the air contains a much greater quantity 

 of bacteria, as might be expected ; the cubic metre con- 

 tains an average of five or six thousand ! In some cases 

 M. Miquel has found ten, even sixteen, twenty-one, and 

 twenty-eight thousand bacteria per cubic metre of air. 

 These last numbers are stupendous. 



These bacteria in the air, liable every moment to 

 penetrate into our lungs and body, are of many sorts. 

 Some are spherical, — the sphero-bacteria ; they generally 

 have no power of locomotion : some are coloured red 

 or yellow. M. Miquel remarks that although some 

 of these bacteria must exert a pathogenetic action, 

 he has not been able to produce any disease in ani- 



