Makch G, 1SS5.] 



♦ KNOWLEDGE ♦ 



193 



of the hole through the wood lieing sninllrr than the wire, 

 enables us to tix the reel with the aid of friction. 



The bow is the next thing to bj dealt with. Procure a 

 piece of bamboo or cane — preferably the former — about 

 2 f t G in. long, and jj in. in diameter. At a distance of 

 4 in. from the end 15 of the cane, A C B (Fig. l.'i), cut with 

 a saw about half-way through the cane ; then, with a sharp 

 knife, split it from the end. A, to the bottom of the 

 saw-cut. Then, from the sawcut, taprr otT (on the cut 

 side of the cane) to the end A, at which end cut a small 

 groove. About ^ in. from the saw-cut (towards the end 

 B), bore a small hole through the cane. 



Obtain a piece of gut, ^^^ in. thick, and about I ft. long (A D 

 B). Tie one end round the groove at A, and pass the other 

 end through the hole bored near B, and wind that portion 

 which is drawn through round the end of the cane forming 

 a handle, the last turn of the gut being fastened by a slip- 

 knot. The length of the gut left between A and the 

 htmdle must depend upon the length and rigidity of the 

 cane. Two things must be borne in mind. The gut must 

 be sufficiently taut to impart by friction the necessary 

 power to drive the drill-stock. At the same time it must 

 not be so taut as to cause the drill-stock to fly when the 

 drill is released from the work. 



The function of the breastplate is to aflford a convenient 

 means for supporting the drill-stock during its rotation. It 

 consists of a sheet of metal, A F (Fig. 14), bent on the under 

 side, so as to fit the breast against which it is placed during 

 the process of drilling. Two s-lots, C D, are cut near the 

 ends of the plate, and through these a jiiece of tape, gut, 

 string, itc, is fastened to keej) the plate in position, or for 

 the purpose of suspension. Upon the front of the plate, 

 between the slots, is screwed or riveted: a steel-plate or 

 strap, in the middle of which is bored a conical hole. As 

 the point of the drill stock rotates in this hole, it is essential 

 that the steel strap in the vicinity of the hole should be 

 hardened. 



Ex. XXXV. It will be found necessary to give the drill 

 a start. This is done with the aid of a centre punch 

 (Fig. 15), which consists of a piece of steel about a quarter of 



Fig. 15. 



an inch in diameter and two inches long, pointed at one end. 

 This point, which should be conical, requires hardening and 

 tempering. To use it, simply place the point over the 

 place where the hole is to be bored, and give a slight blow 

 with a hammer. The small puncture thus made becomes 

 the starting-point for the drill. 



OUR TWO BRAINS. 

 By Richard A. Proctor. 



SUGGESTIONS FOR THE PRACTICAL APPLICATION 



OF THE THEORY. 



{Continued from p. 142.) 



IT would seem, then, that to the left brain we must 

 assign the chief control over speech, writing, and 

 gesture — the methods, that is, of expressing ideas. This 

 side, also, seems piincipally concerned in the process of 

 reasoning ; and besides these special functions, we must 

 assign to the left side of the brain the principal control over 

 the motions and organs of the right side of the body. 



The right side of the brain in turn possesses its special 

 functions. It serves chiefly to the emotional manifesta- 

 tions, including those calkd hytteriea), and also to the 



needs of the body as respects nutrition.* It also, of course, 

 possesses a function correpponding to the control of the loft 

 side of the brain over the bodily organs, the right side 

 having principal control over the movements and organs of 

 the left side of the body. 



These facts seem to have their practical application. 



If the dillerencc which exiats between the two sides of 

 the brain depended on a radical dillerenco in their structure, 

 it would, of course, be impossible to bring aliout any 

 change. The facts I have cited would bo interesting, but 

 they would have no practical application, however 

 thoroughly they might bo demonstrated. We recognise 

 clearly the dill'erence between the functions of the eye and 

 those of the ear, between the otlice of the legs and that of 

 the arms ; but we do not inquire whether both the eye and 

 the ear might be trained to perform the same duties, nor 

 do we practise walking on our hands, or grasping objects 

 with our feet. But it is manifest that a useful purpose 

 might be served by calling to any person's attention the 

 fact, if such it should lie, that he Ufes one or other eye 

 more frequently than the other, or for different purposes, 

 and that his general powers of sight would be improved if 

 he accustomed both eyes to the same amount and kind of 

 work.t Similarly of the ears. Again some persons are 

 loo right-handed (I question, indeed, whether one-handcd- 

 ness, whether riglit or left be chiefly employed, does not in 

 all cases involve a loss of power). In all such cases it is 

 probable that careful tiaining, especially if begun in early 

 life, by tending to equalise the work of each member of 

 each pair of organs, might add considerably to the general 

 powers of the body. It is something of this sort that 

 Brown-Sequard hopes to attain for the brain ; in fact, it is 



* The evidence adduced by Dr. Brown-Seqnard respecting the 

 special function of the right side of the brain is chiefly derived 

 from his medical experience, and would therefore not be altogether 

 suitable to these pages — or rather, its force would not be so clearly 

 recognised as that of the evidence relating to language and gesture. 

 It appears that ulceration of the lungs or liver, haemorrhage and 

 sudden inflammation, may result more or less directly from irrita- 

 tion, and that in such capes it has chiefly been the right side of the 

 brain which has been affected. Among 121 cases of paralysis, 

 caused by hysteria, 07 were found associated with disease of the 

 right side of the brain, and only 2t with disease of the left side. 

 It is also well kncwn that paralysis is more common on the left 

 side of the body than on the right side, which corresponds to the 

 fact that the right side of the brain is more commonly diseased in 

 the manner which results in paralysis. He cites other medical 

 evidence in support of the theory that the right side of the brain is 

 chiefly concerned in the nutrition of the various organs of the 

 body. 



t Perhaps in some instances the reverse may be the case — 

 though we question whether many would care to have one eye 

 specially suited for one kind of work, and the other eye for a 

 different kind. This is not an imaginary case. It is much more 

 common than many suppose, for the two eyes to differ in focal- 

 length ; and if the difference is not early noticed, it is apt to 

 increase, each eye being used for the work to which it is best suited. 

 I suppose that a marked difference between my own eyes attained 

 its present extent in this way, though the difference was prob.ibly 

 considerable in childhood. It is now so great that my left eye is 

 scarcely used at all (and is almost useless for ordinary vision), being 

 very near-sighted, but is almost microscopic for near objects; 

 while the right eye is not used at all on examining minute objects, 

 and very little in reading, but is of average power for distant 

 objects. To use both has become impossible, and may have always 

 been so. I did not notice the difference, however, until I was about 

 18 years of age. That it existed in boyhood to a marked degree, I 

 consider to be proved by the difficulty I experienced in acquiring 

 skill in such games as cricket, rackets, fives, billiards, Ac, where 

 ready and exact judgment of distances is required. I believe that 

 in almost every instance when a boy shows .a marked want of skill 

 in such games — while apt in others — it will be fiinnd that one eye 

 differs so much in focal length from the other as to be little used. 

 By recognising this early we may be able to correct the defect.- 

 Latcr, correction is generally impossible. 



