74 INTRODUCTION. 



bone of each finger is united to its corresponding metacarpal, by a 

 simple articulation, which only admits of the hinge-like motion of 

 flexion and return. To this first row succeeds a second, consisting of 

 smaller bones, but of a like character and mode of articulation. Next 

 follows the third row, consisting of still smaller bones, similarly arti- 

 culated, but less independent, and more limited in the degree of motion 

 allotted to them. 



Little or no difference characterizes the bones of each finger, separately 

 viewed, excepting that of relative magnitude. Those of the middle finger, 

 as it is termed, being the longest and largest ; those of the fore finger, 

 next in thickness, but not in length, the bones of the third finger being 

 rather longer : the little finger has the shortest and most slender bones. 



The thumb is situated obliquely, with respect to the fingers ; i. e. 

 neither directly opposite to, nor on the same plane with them, but is 

 capable of being brought to antagonize with all or each separately. This 

 counteracting agency, which the thumb maintains against the fingers, 

 requires that its bones should be thick and strong, in proportion to their 

 length : they are two in number, excluding the metacarpal bone, which 

 is articulated with the trapezium of the carpus, the union being such as 

 to allow of a more free (but still limited) action than is possessed by 

 the metacarpal bone of ,any of the fingers ; a degree of motion need- 

 ful, inasmuch as, without it, the thumb could not act the part of an 

 antagonist to the fingers with requisite facility. The first true phalangal 

 bone of the thumb is stout and short, with a large base hollowed into an 

 oblong cavity, in order to its resting securely upon its metacarpal bone ; 

 the joint, thus formed, is especially strong and well knit ; but more con- 

 fined, and less expeditious, than hinge-like joints in general. The ulti- 

 mate bone of the thumb proceeds, also, from a basal portion, of great 

 extent, hollowed into two concavities, for the reception of two pulley-like 

 projections of the bone, to which it is articulated. The hinge of this joint, 

 thus contrived, is very secure, while it possesses tolerable freedom. 



This elaborate mechanism is provided with a system of muscles fully 

 adequate to its active employment, in the various simple and combined 

 movements of which it is organically susceptible. The hand, therefore, 

 while possessing sufficient solidity for the performance of such of its 

 offices as require considerable strength and powers of resistance, is 

 enabled, by its wonderful mobility, to execute an endless multitude of the 

 most precise and delicate operations ; to modify its shape according to the 

 differences of form in external objects, and to move upon and feel them, 

 at a number of different points, with degrees of pressure infinitely variable. 



As an organ of touch, the perfection of the human hand is owing, in a 

 great measure, to its admirable structure as an instrument of prehension. 

 Other parts of the surface of the body are capable of receiving impres- 



