454 NATURE'S TEACHINGS. 



Then some people leave their machines untouched for days, or 

 even weeks, and then wonder that they work stiffly. Every 

 day the machine should be worked, if only for a few seconds, 

 and then it will seldom stiffen. It is just the same with steamers. 

 When they are in harbour, though the fires be out, and they 

 are not meant to move for weeks, the engines are always turned 

 round at least once daily. 



BOTH these rules hold good in the animal kingdom. 



To every joint there are attached certain glands that supply 

 a kind of oily substance technically named "synovia," which 

 acts exactly the same part as the oil or grease of machinery. 

 If these glands do not do their duty, and the supply of synovia 

 be defective, the joints become stiff, painful, and crackle when 

 they are moved. 



Then, exactly as the joints of a machine become stiff frcfm 

 non-usage, so do those of a human being. "We will take, for 

 example, the Indian Fakirs who vow that they will not move 

 some limb from a definite posture. At first the exertion is 

 trying and painful, but by degrees the disused joints lose their 

 faculty of motion, and, even if their owner wished to move a 

 limb, he could not do it. 



The right-hand figure of the illustration represents the 

 lubrication of an ordinary sewing machine, and the left-hand 

 figure is a section of the human knee-joint, showing the gland 

 which supplies the synovia. 



PERHAPS some of my readers may think that such a subject as 

 the "Lazy -tongs" is too trivial for a work which deals, however 

 lightly, with science. But there may be some who know the 

 inestimable benefit of Lazy -tongs under certain conditions. 



There are many cases where a severe injury has occurred, or 

 where rheumatism has fixed its tiger-claws in the joints, so 

 that movement is all but impossible. There may be no one in 

 the room to help the invalid, and even to stretch the arm over 

 the table is as impossible as to jump over the house. 



Then it is that the real value of the Lazy-tongs becomes 

 manifested, and that it shows itself in the light of a supple- 

 mentary limb. With a mere movement of the fingers it can 

 be stretched across any table which is likely to be placed before 



