July 12, 1894] 



NA TURE 



257 



composition was started in a few hours if some of the germs 

 collected from the air were added to it. 



If a pot of ordinary paste, after being used, is placed on a 

 shelf for a few days, the surface will be found coated with a fine 

 crop of mould or mildew. On examining this mould under the 

 microscope, it will be seen to somewhat resemble a bed of 

 rushes ; after a few more days, some of these. rush-like filaments 

 will have developed little pods, not unlike poppy-heads, and 

 after the lapse of another week the pods will have split open, 

 and myriads of seeds or germs will have poured forth into the 

 air to carry on nature's cleansing work, for these germs possess 

 the power of setting up the process of decay, by which the 

 waste matter derived from vegetable sources is once again 

 resolved into the water vapour and carbon dioxide used by 

 nature as the foundation of all organic creations. 



Decay and putrefaction are the great fac'ors of change which 

 nature utilises for removing the waste products of animal and 

 vegetable life, and for once more bringing them into a con- 

 dition in which living things can again assimilate, and use 

 them for building up their tissues and carrying on their 

 functions. Without decay, the dead animal and vegetable 

 matter would remain choking the face of nature, and life would 

 be impossible, because the food of life would be cut off; and it 

 IS the almcist imperceptible germs floating in the air which 

 start this marvellous natural action, germs so minute that it 

 requires the sirongest microscope to detect them, yet so potent 

 that the whole balance of life hangs on their existence. 



These facts show us that not only has dust a most marvellous 

 hi-tary. but that in it nature has disguised her most important 

 factor for cleaning the face of the earth from waste matter 

 of both mineral and vegetable origin. 



The surface soil when mixed with water gives the mud which 

 dirties our hoots, and forms clois on the train of our skirts ; but 

 this, as well as the dust which has settled in our living rooms, 

 and merely clings mechanically to the surfaces upon which it 

 has deposited, may be removed by such simple physical means 

 as the duster and brush. When dust has found its way into a 

 fabric such as a carpet, it requires considerable force to again 

 'iislodge it, and this is applied by means of the broom, but in 



J Tous sweeping we find that the largest proportion of the 



si is driven up into the air, only to resettle once again on other 

 nrlaces, so that although we can make the nuisance "move 

 1 ," we do not in this way remove it, and experience has 



ight our servants that wet tea-leaves scattered on the carpet 



i.)re sweeping lessen this evil In some cases, instead of 

 -iiig this method, it has been argued that it must be the 

 iii"isiure which acts in preventing the raising of the dust, and 

 ilii- carpet has been sprinkled with water. This converts the 

 dust into mud, which remains fixed in the fabric whilst the 

 ■weeping is going on, but as soon as the water has evaporated 

 'iiiiu it, again reasserts its right of rising as dust. 



When, however, wet tea-leaves, damp sawdust, or even 

 moistened sand is scattered over the surface to be swept, the 

 du-t when dislodged adheres to the moistened substance and is 

 removed. In choosing moist bodies for this purpose, the only 

 points to consider are that they must have no staining action 

 on the carpet, must not be too wei, and must not be so finely 

 grained as to sink into the fabric, nor so clinging as to resist 

 easy removal by the broom. 



It is manifest, however, that the mechanically held dirt which 

 we have been considering, difiers very considerably from the 

 dirt on our skins, and on linen in contact with our bodies, 

 which although derived from the same sources <is the dust on 

 the furniture, resists any ordinary mechanical process for its 

 removal, and rinsing dirty hands or linen in cold water has but 

 lillle cleaning effect, whilst if the hands are afterwards dried in 

 the usual way, a transfer of a portion of dirt to the towel takes 

 place. 



If we carefully notice the portions of our skin and shirt 

 which become most soiled, we at once observe that it is where 

 the skin is exposed to air, whilst the linen, which is in contact 

 with both air and skin, becomes dirty more quickly than when 

 exposed to either alone. 



The part played by the atmosphere is made clear by the facts 

 which we have already been considering, but the action of the 

 skin introduces a new and most important factor. For the 

 healthy carrying on of the functions of life, nothing exceeds 

 in importance the skin with which our body is covered. We 

 may live for days without giving our stomach any work to do, 

 the liver may cease action for several days before death ensues, 



NO. 1289, VOL. 50] 



but it is impossible to survive for the same length of time if the 

 functions of the skin are entirely stopped. 



The skin not only plays an important part in throwing off 

 and getting rid of waste matter from the system, but it is also 

 credited with being an important auxiliary to our lungs, .md 

 experiments have clearly shown that if tire skin of animals be 

 coated in such a way as to completely stop its action, a very few 

 hours will bring about death. Indeed the experiment has been 

 once accidentally tried on a human being, a child gilded all 

 over to represent a statue having died in a few hours ; 

 all the symptoms pointing to suftocation as being the cause of 

 deaih. 



If we examine the structure of the skin, we find that it is 

 built up of two distinct layers, an outer skin called the cuticle 

 or epidermis, and an inner termed the cutis or dermis. .\ third 

 layer intermediate between these two, used to be looked upon 

 as a third skin, but more recently has been recognised as being 

 only a transition form of the ou'er skin. 



The cuticle or outer skin consists of several fine layers of 

 scales which gradually assume a more rounded and granular 

 form the deeper one gets into the cuticle. These rounded 

 granules form the middle skin of the old observers, and as the 

 outer portion of the cuticle roughens and scales off as scurf, 

 these granules gradually flatten and form the new surf.ace to 

 the outer skin, and we difi'er therefore from other scaly reptiles 

 by being continually in a condition of renewing our skin, whilst 

 most reptiles and fish cast their scaly covering in on 

 operation. 



No nerves or blood-vessels find their way into this outer skin, 

 ,is may be seen when it becomes detached from the inner skin 

 in the formation of a blister, the outer portion of which is 

 devoid of sensation. 



The lower or true skin varies in thickness, being thicker in 

 the palm of the hand and sole of the foot, where most resistance 

 is needed. 



When we look at the skin of the hand, we notice delicate 

 grooves in it, which examined through a magnifying glass are 

 seen to be pierced with small orifices, and if the hand be 

 warm, minute shining drops of perspiration will be seen issuing 

 from them. 



The glands for the secretion of the perspiration are set in the 

 lower side of the inner skin, and are in connection with the 

 capillary network of blood-vessels, which cover the surface of 

 the body. The gland or duct which conducts the perspiration 

 to the surface of the skin is about a quarter of an inch in length, 

 and is straight in the true skin, but becomes spiral whilst 

 traversing the outer skin. Over 3500 of these small ducts have 

 been found to exist in a single square inch of the skin, and it 

 has been computed that the aggregate length of the sudoriferous 

 ducts in the body of an ordinary-sized man is about twenty-eight 

 miles. 



These little glands and duels perform the important function 

 of throwing off the moisture produced during the combustion of 

 waste tissue, by the blood-borne oxygen of the body, and 

 secrete about 23 ounces of perspiration in the twenty-four hours, 

 which under ordinary conditions evaporates, without our 

 noticing it, into the air, but under conditions of considerable 

 exertion or unusual heat, accumulates as beads of perspiration. 



The throwing off of the perspiration and its evaporation on 

 the skin, is a beautiful natural contrivance for regulating 

 the temperature of the body, as the conversion of the perspira- 

 tion into vapour renders latent an enormous amount of heat, 

 which being principally derived from the body keeps it in a 

 comparative state of coolness, even when subjected to high 

 temperatures. 



That this is so, is proved by the fact that a bath heated to 

 120° F. ( = 49 C.) is almost unbearable, because the evaporation 

 from the surface of the skin is checked, whilst it is perfectly 

 possible for a person with the skin fully exposed to go into an 

 oven and remain there for some time at a temperature of 325" F. 

 or 162'S C, at which temperature a beefsteak can be cooked, 

 and it can be clearly noticed in a Turkish bath, that although 

 there is a feeling of oppression at first, the temperature of the 

 hot room can readily be borne as soon as perspiration begins 

 to flow. 



In the 23 ounces of liquid so secreted in the course of the 

 twenty-four hours, there will be found rather more than an 

 ounce of solid matter, which is left when the liquid portion of 

 the perspiration evaporates, and tends to clog the pores of the 

 skin, and it is the removal of this by the morning tub and 



