CHAMBERS'S INFORMATION FOR THE PEOPLE. 



noxious air diffused by these means through the 

 narrow streets and confined dwellings would tend 

 to the most fatal effects. In old drains there is 

 generated a gas sulphuretted hydrogen which 

 is calculated to produce dreadful consequences in 

 those exposed to its inhalation. It has lately been 

 discovered that it is the presence of this gas, 

 arising from the shores, river deltas, and man- 

 grove jungle of tropical Africa, which causes the 

 peculiar unhealthiness of that region. It is ascer- 

 tained that small animals, such as birds, die when 

 the air they breathe contains one-fifteen-hundredth 

 part of sulphuretted hydrogen, and that an infusion 

 six times greater will kill a horse. It follows 

 that we can scarcely attach too much importance 

 to measures for cleaning and improving the sewer- 

 age of cities. There are as yet no large towns in 

 Britain kept in a state so clean as is desirable for 

 the welfare of their inhabitants ; nor will they be 

 so till the measures now in agitation for improved 

 modes of construction, for adequate supplies of 

 pure water, and for thorough scavengering and 

 sewerage, be adopted. 



The human subject tends to vitiate the atmos- 

 phere for itself, by the effect which it produces on 

 the air which is breathed. Our breath, when we 

 draw it in, consists of the ingredients formerly 

 mentioned, but it is in a very different state when 

 we part with it. On passing into our lungs, the 

 oxygen, forming the lesser ingredient, enters into 

 combination with the carbon of the venous blood 

 or blood which has already performed its round 

 through the body : in this process about two-fifths 

 of the oxygen is abstracted and sent into the blood, 

 only the remaining three-fifths being expired along 

 with the nitrogen nearly as it was before. In 

 place of the oxygen consumed, there is expired 

 an equal volume of carbonic acid gas, such gas 

 being a result of the process of combination just 

 alluded to. Now, carbonic acid gas in a larger 

 proportion than that in which it is found in the 

 atmosphere, is noxious. The volume of it expired 

 by the lungs, if free to mingle with the air at 

 large, will do no harm ; but if breathed out into 

 a close room, it will render the air unfit for being 

 again breathed. Suppose an individual to be shut 

 up in an air-tight box ; each breath he emits 

 throws a certain quantity of carbonic acid gas into 

 the air filling the box ; the air is thus vitiated, and 

 every successive inspiration is composed of worse 

 and worse materials, till at length the oxygen is 

 so much exhausted that it is insufficient for the 

 support of life. He would then be sensible of a 

 great difficulty in breathing, and in a little time 

 longer he would die. 



Most rooms in which human beings live are not 

 strictly close. The chimney and the chinks of the 

 door and windows generally allow of a communi- 

 cation to a certain extent with the outer air, 

 so that it rarely happens that great immediate 

 inconvenience is experienced in ordinary apart- 

 ments from want of fresh air. But it is at the 

 same time quite certain that in all ordinary apart- 

 ments where human beings are assembled, the air 

 unavoidably becomes considerably vitiated; for 

 in such a situation there cannot be a sufficiently 

 ready or copious supply of oxygen to make up for 

 that which has been consumed the carbonic acid 

 gas will be constantly accumulating, and there 

 is also putrefying organic matter in the vapour 

 of the breath. This is particularly the case in 



7M 



bed-chambers, and in theatres, assembly-rooms, 

 churches, and schools. An extreme case was that 

 of the celebrated Black Hole of Calcutta, where 

 146 persons were confined for a night in a room 

 eighteen feet square with two small windows. 

 Here the oxygen, scarcely sufficient for the healthy 

 supply of one person, was called upon to support 

 a large number. The unfortunate prisoners found 

 themselves in a state of unheard-of suffering ; and 

 in the morning all were dead but twenty-three, 

 some of whom afterwards sunk under putrid fever, 

 brought on by breathing so long a tainted atmos- 

 phere. 



Although the vitiation of the air in ordinary 

 apartments and places of public assembly does not 

 generally excite much attention, it nevertheless 

 exercises a certain unfavourable influence on health 

 in all the degrees in which it exists. Perhaps it is 

 in bedrooms that most harm is done. These are 

 generally smaller than other rooms, and they are 

 usually kept close during the whole night. The 

 result of sleeping in such a room is very injurious. 

 A common fire, from the draught which it pro- 

 duces, is very serviceable in ventilating rooms, but 

 it is at best a defective means of doing so. The 

 draught which it creates generally sweeps along 

 near the floor between the door and the fire, leav- 

 ing all above the level of the chimney-piece un- 

 purified. Yet scarcely any other arrangement is 

 anywhere made for the purpose of changing the 

 air in ordinary apartments. To open the window 

 is a plan occasionally resorted to, but it is not 

 always agreeable in our climate, and sometimes it 

 produces bad consequences of a different kind. 



A plan, to a considerable extent serviceable, 

 though not perfect, for producing a draught from 

 a room possessing a fire-place, was suggested by 

 the philanthropic Dr Arnott. It is only necessary 

 to make an aperture into the flue, near the ceiling 

 of the room, and insert therein a tin tube, with a 

 valve at the exterior, capable of opening inwards, 

 but closing when at rest, or when a draught is sent 

 the contrary way. The draught produced by the 

 fire in the flue causes a constant flow of air out of 

 the upper part of the room (where most vitiated) ; 

 and the valve is a more or less effectual protection 

 against back-smoke. This plan can be applied to 

 any existing house at a mere trifle of expense. (For 

 various modes of ventilation, see No. 31.) 



FOOD. 



The second requisite for the preservation 

 health is a sufficiency of nutritious food. 



Organic bodies are constituted as explaine 

 under PHYSIOLOGY upon the principle of a con- 

 tinual waste of substance supplied by continual 

 nutrition. The nutritive system of animals, with 

 the exception of the very lowest animal organisms 

 (see ZOOLOGY, vol. i. 129), comprehends an alimen- 

 tary tube or cavity, into which food is received, 

 and from which, after undergoing certain changes, 

 it is diffused by means of smaller vessels through- 

 out the whole structure. In the form of this tube, 

 and in the other apparatus connected with the 

 taking of food, there are in different animals 

 varieties of structure, all of which are respectively 

 in conformity with peculiarities in the quality and 

 amount of food which the particular animals " 

 designed to take. 





