NA TURE 



637 



THURSDAY, OCTOBER 17, 1878 



ON THE SCIENCE OF EASY CHAIRS 



THERE is a reason for everything, if we can only 

 find it out, but it is sometimes very hard to dis- 

 cover the reasons of even the very simplest things. 

 Every one who has travelled much, and even those who 

 have merely looked through books of travels, must have 

 been struck by the variety of attitudes assumed by the 

 people of different countries. The Hindoo sits down on 

 the ground with his knees drawn up close to his body, so 

 that his chin will almost rest upon them ; the Turk squats 

 down cross-legged ; the European sits on a chair ; while 

 the American often raises his legs to a level with his 

 head. Nor are the postures assumed by the same people 

 under varying circumstances less diverse. Climate or 

 season, for example, will cause considerable alteration in 

 the posture assumed, as was well shown by Alma 

 Tadema, in his pictures of the four seasons exhibited 

 in the Academy a year ago. In his representation of 

 summer he painted a woman leaning backwards on a ledge, 

 with one leg loosely hanging down, while the other was 

 drawn up so that the foot was on a level with the body. 

 In the picture of Winter, on the other hand, we saw a 

 figure with the legs drawn up in front of the belly. The 

 reason for these different postures has been explained by 

 Rosenthal. The temperature of the body, as is well known, 

 is kept up and regulated by the circulation of the blood 

 through it, and a great proportion of the blood contained in 

 the whole body circulates in the vessels of the intestines. 

 Now the intestines are only separated from the external 

 air by the thin abdominal walls, and therefore any change 

 of temperature in the atmosphere will readily act upon 

 them, unless they be guarded by some additional protec- 

 tion. The Hindoos are well aware of this, and they 

 habitually protect the belly by means of a thick shawl or 

 cummerbund, thus guarding themselves against any sudden 

 change of temperature. This precaution is also frequently 

 adopted by Europeans resident in hot climates, and is 

 even retained by them after returning to England. But 

 the function of the cummerbund may, to a certain extent 

 be fulfilled by change of posture alone. When the legs 

 are drawn up, as in the picture of Winter already referred 

 to, the thighs partially cover the abdomen, and taking 

 the place of additional clothing, aid the abdominal walls 

 in protecting the intestines and the blood they contain 

 from the cooling influence of the external air. 



Thus it is that in cold weather, when the quantity of 

 covering in bed is insufficient, persons naturally draw up 

 their legs towards the abdomen, so as to retain as much 

 heat as possible before going to sleep. In hot weather, 

 on the contrary, they wish tp expose the abdomen as 

 much as possible to the cooling influence of the atmo- 

 sphere. The posture depicted by Alma Tadema is the 

 most efficient for this purpose. It no doubt answers the 

 purpose to lie down flat on one's back, but in this posi- 

 tion the abdominal walls are more or less tight, whereas, 

 when one of the legs is drawn up as in the painting just 

 alluded to, the walls are relaxed, and, the intestines not 

 being subject to any pressure, the blood in them will cii"- 

 culate more rapidly, and the cooling process be carried 

 Vol. xviii. — No. 468 



on more effectually. In this attitude also the thighs are 

 completely separated and loss of heat allowed from their 

 whole surface. 



Varying conditions of fatigue also alter the postures 

 which people assume. When slightly tired one is con- 

 tent to sit down in an ordinary chair in the position of 

 the letter N 'with the middle limb horizontal. As we get 

 more and more fatigued we usually assume positions in 

 which the limbs of the N become more and more 

 oblique, the trunk leaning backwards and the legs 

 extending forwards. If we lie down in bed on our back 

 the legs will probably become straight, but if we rest 

 upon our side they will be more or less bent. The 

 straightness of the legs in the supine position is simply 

 due to their weight, which is then supported at every 

 point by the bed, but when we lie on our sides the 

 genuflexion of the legs is most agreeable, because not 

 only are the muscles more perfectly relaxed, but, as the 

 late Prof. Goodsir pointed out, the bones which form 

 the knee-joint are slightly removed one from another, 

 and thus the joint itself, as well as the muscles, passes 

 into a state of rest. Some of the bamboo easy chairs 

 manufactured in India allow us to obtain the advantages 

 of both positions. These chairs are made in the form of 

 a somewhat irregular straggling V\/> and in them one can 

 lie on one's back with every part of the body thoroughly 

 supported, and the knees bent in the same way as they 

 would be if one lay upon one's side. 



Thus simple inaction, the relaxation of muscles, and 

 the laxity of joints, are some of the factors necessary for 

 complete rest, and an easy chair, to be perfect, must 

 secure them all. 



But it is possible for an easy chair to secure all these,, 

 and yet be imperfect. We have just said that usually, 

 as the fatigue becomes greater and greater, the tendency 

 is to assvuTie the position of the N with the limbs at a more 

 or less obtuse angle, but when sitting in an ordinary chair 

 we find relief from raising the feet by means of a foot- 

 stool, although this tends to make the angles of the fsj 

 more acute instead of more obtuse. Still more relief, how- 

 ever, do we obtain when the legs are raised up on a level 

 with the body by being placed upon another chair, or by 

 being rested on the Indian bamboo seat already described, 

 if, in addition to this, the legs are gently shampooed up- 

 wards, the sensation is perfectly delightful, and the feel- 

 ings of fatigue are greatly lessened. To understand how 

 this can be, it is necessary for us to have some idea as 

 to the cause of fatigue. Any muscular exertion can be 

 performed for a considerable time by a man in average 

 health, without the least feeling of fatigue, but by and by 

 the muscles become weary, and do not respond to the 

 will of their owner so readily as before; and if the 

 exertion be too great, or be continued for too long a 

 time, they will ultimately entirely refuse to perform their 

 functions. The muscle, like a steam-engine, derives the 

 energy which it expends in mechanical work from the 

 combustion going on within it, and this combustion, in 

 both cases, would come to a standstill if its waste products 

 or ashes were not removed. It is these Avaste products of 

 the muscle which, accumulating within it, cause fatigue, and 

 ultimately paralyse it. This has been very neatly shown by 

 Kronecker, who caused a frog's muscle, separated from 

 the body, to contract until it entirely ceased to respond 



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