urity 

 urpose 



SCIENTIFIC SIDE-LIGHTS 



566 



bacteria in the air, as there is in water. 

 The open air possibly averages about 250 

 per cubic meter. On the seacoast this num- 

 ber would fall to less than half; in houses 

 and towns it would rise according to cir- 

 cumstances, and frequently in dry weather 

 reach thousands per cubic meter. When it 

 is remembered that air possesses no pabulum 

 for bacteria, as do water and milk, it will 

 be understood that bacteria do not live in 

 the air. They are only driven by air-cur- 

 rents from one dry surface to another. 

 Hence the quality and quantity of air or- 

 ganisms depend entirely upon environment 

 and physical conditions. In some researches 

 which the writer made into the air of work- 

 shops in Soho in 1896, it was instructive 

 to observe that fewer bacteria were isolated 

 by Sedgwick's sugar-tube in premises which 

 appeared to the naked eye polluted in a 

 large degree than in other premises appar- 

 ently less contaminated. In the workroom 

 of a certain skin-curer the air was densely 

 impregnated with particles from the skin, 

 yet scarcely a single bacterium was isolated. 

 In the polishing-room of a well-known hat 

 firm, in which the air appeared to the naked 

 eye to be pure, and in which there was am- 

 ple ventilation, there were found four or five 

 species of saprophytic bacteria. NEWMAN 

 Bacteria, ch. 3, p. 107. (G. P. P., 1899.) 



2793. PURITY IS SAFETY Qermless 

 Air Produces No Putrefaction nor Disease. 

 During the ten years extending from 1859 

 to 1869 researches on radiant heat in its 

 relations to the gaseous form of matter oc- 

 cupied my continual attention. When air 

 was experimented on I had to cleanse it 

 effectually of floating matter, and while 

 doing so I was surprised to notice that, at 

 the ordinary rate of transfer, such matter 

 passed freely through alkalis, acids, alco- 

 hols, and ethers. The eye being kept sensi- 

 tive by darkness, a concentrated beam of 

 light was found to be a most searching test 

 for suspended matter both in water and in 

 air a test, indeed, indefinitely more search- 

 ing and severe than that furnished by the 

 most powerful microscope. With the aid of 

 such a beam I examined air filtered by cot- 

 ton-wool, air long kept free from agitation, 

 so as to allow the floating matter to sub- 

 side; calcined air and air filtered by the 

 deeper cells of the human lungs. In all 

 cases the correspondence between my experi- 

 ments and those of Schwann, Schroeder, Pas- 

 teur, and Lister in regard to spontaneous 

 generation was perfect. The air which they 

 found inoperative was proved by the lumi- 

 nous beam to be optically pure and there- 

 fore germless. TYNDALL Floating Matter of 

 the Air, essay 5, p. 288. (A., 1895.) 



2794. PURITY, RELATIVE, OF ANI- 

 MAL FOOD Meat Rarely Contains Bacteria. 

 Parasites are occasionally found in meat, 

 but bacteria are comparatively rare. Not 

 that they do not occur in the bodies of ani- 

 mals used for human consumption, for in 



the glands, mesenteries, and other organs 

 they are common. But in those portions of 

 the carcass which are used by man, namely, 

 the muscles, bacteria are rare. The reasons 

 alleged for this are the acid reaction (sar- 

 colactic acid) and the more or less constant 

 movement during life. A bacterial disease 

 which, perhaps more than any other, might 

 be expected to be conveyed by meat is tuber- 

 cle. Yet the recent Royal Commission on 

 Tuberculosis has again emphasized the ab- 

 sence of bacilli in the meat substance. 

 NEWMAN Bacteria, ch. 6, p. 234. (G. P. P., 

 1S99.) 



2795. PURPOSE, APPARENT, IN RE- 

 FLEX ACTION The Brainless Frog. In ob- 

 serving the effects, and in reading accounts 

 of the effects, of what is called " reflex ac- 

 tion " in the animal economy, and before I 

 had submitted the phrase to strict analysis, 

 I had long felt that sense of confusion which 

 results from the presentation to the mind 

 of false analogies, of incompetent descrip- 

 tion, and of formulae of expression which, 

 pretending to be scientific, are in reality 

 nothing but the wilful shutting-out of knowl- 

 edge. It is, however, most satisfactory to 

 find that in one of the latest and best text- 

 books of physiology, that of Professor Fors- 

 ter of Cambridge, there is a full confession 

 of the incompetency of such words as " re- 

 flex action " to describe the relation between 

 the stimulus of an " afferent " nerve and the 

 " efferent " movements which are carried 

 into responsive preadjusted action. The 

 two classes of impulse and of resulting 

 movement are justly described as really " in- 

 commensurate." And whilst the purely me- 

 chanical or physical relation of mere bending 

 or turning is thus condemned not only as an 

 inadequate, but as essentially a false image 

 of the real relation which subsists between 

 the antecedent and the consequent phenom- 

 ena, that real relation is described and ad- 

 mitted in the following remarkable passage : 

 " In the more complex reflex actions of the 

 brainless frog, and in other cases, the rela- 

 tion is of such a kind as that the resulting 

 movement bears an adaptation to the stimu- 

 lus; the foot is withdrawn from the stimu- 

 lus, or the movement is calculated to push 

 or wipe away the stimulus. In other words, 

 a certain purpose is evident in the reflex 

 action." ARGYLL Unity of Nature, ch. 8, 

 p. 302. (Burt.) 



2796. PURPOSE IN NATURE Beauty 

 and Utility of Dust. Let us now briefly 

 summarize what we owe to the universality 

 of dust, and especially to that most finely 

 divided portion of it which is constantly 

 present in the atmosphere up to the height 

 of many miles. First of all, it gives us the 

 pure blue of the sky, one of the most ex- 

 quisitely beautiful colors in Nature. It gives 

 us also the glories of the sunset and the 

 sunrise, and all those brilliant hues seen in 

 high mountain regions. Half the beauty of 

 the world would vanish with the absence 



