IN THE HUMAN FRAME. 55 



the first necessity to action, if not to life, but of a nature 

 so delicate and tender, so susceptible and so impatient of 

 injury, as that any unusual pressure upon it, or any consid- 

 erable obstruction of its course, is followed by paralysis or 

 death. Now the spine was not only to famish the main 

 trunk for the passage of the medullary substance from the 

 bi-ain, but to give out, in the course of its progress, small 

 pipes therefrom, which, being afterwards indefinitely sub- 

 divided, might, under the name of nerves, distribute this 

 exquisite supply to every part of the body. The same 

 spine was also to serve another use not less wanted than 

 the preceding, viz. to aflTord a fulcrum, stay, or basis (or 

 more properly speaking a series of these) for the insertion 

 of the muscles which are spread over the trunk of the 

 body ; in which trunk there are not, as in the limbs, cylin- 

 drical bones to which they can be fastened, and likewise, 

 which is a similar use, to furnish a support for the ends of 

 the ribs to rest upon. 



Bespeak of a workman a piece of mechanism which 

 shall comprise all these purposes, and let him set about to 

 contrive it ; let him try his skill upon it ; let him feel the 

 difficulty of accomplishing the task, before he be told how 

 the same thing is effected in the animal frame. Nothing 

 will enable him to judge so well of the wisdom which has 

 been employed; nothing will dispose him to think of it so 

 truly. First, for the firmness, yet flexibility, of the spine, 

 it is composed of a great number of bones (in the human 

 subject of twenty-four) joined to one another, and compact- 

 ed together, by broad bases. The breadth of the bases 

 upon which the parts severally rest, and the closeness of 

 the junction, give to the chain its firmness and stability ; 

 the number of parts, and consequent frequency of joints, 

 its flexibility. Which flexibility, we may also observe, 

 varies in different parts of the chain : is least in the back, 

 where strength more than flexure is wanted ; greater in the 

 joins, which it is necessary should be more supple than the 

 back ; and greatest of all in the neck, for the free motion 

 of the head. Then, secondly, in order to afford a passage 

 for the descent of the medullary substance, each of these 

 bones is bored through the middle in such a manner, 

 as that, when put together, the hole in one bone falls into 

 a line, and corresponds with the holes in the two bones 

 4Jontiguous to it. By which means, the perforated pieces, 

 when joined, form an entire, close, uninterrupted channel : 

 ni leaat whilst the spi^ie is upright and at rest. But, as a 



