In the atlantal extremities, the terms are taken from the names of the two bones that compose the lore arm, and from the positions of the elbow and the palm of the hand. Thus the aspect of those parts that are next the radius is radial, that of those next the ulna is ulna'', while those which look towards the elbow are said to have an anconal, and those which look towards the palm of the hand (with the exception of the palm itself, to which the term volar is applied,) are said to have a thenal aspect. In the sacral extremities the terms arc taken in a similar manner from the tibia and fibula, and from the positions of the barn (poples,) and the knee pan, (rotula ;) those parts that look towards the tibia being tibial, those towards the fibula, fibular, while those that look to the ham, have a polditeal aspect, and those which look towards the rotula a rotular aspect. The term plantar, is here confined to the sole of the foot, as was volar to the palm of the hand.
In general, every part of the body is supposed to have six aspects. Thus every part of the head has an inial, a glabellar, a coronal, a basilar, a dextral, and a sinistral aspect; every part of the trunk has an atlantal, a sacral, a sternal, a dorsal, a dextral, and a sinistral aspect ; every part of the atlantal extremities has a pro einial, distal, radial, ulnur, anconal, and Mena/ a,pec.t ; and eve ry part of the sacral extremities a pro., wail, distal, tibial, fibular, rotula•, ul aspect.
These terms, as they here stand, are adjectives, re ferring only to po.s•irion and asp( c1 ; but they may he converted into ge neral adjectives, by changing toe ter mination from a/ or ar, into en. Titus ru L.ca, uln en, fibulen,rcrer to something belonging to dn, radius, ulna, tibia, or fibula.
By another change on the termination, viz. substitut ing- d for l or r, the adjectives may be converted into ad verbs, expressing direction, like upward, downward, backward, f,rward, outward, inward, sideways, he. but in a more definite manner. Thus, by one or other of the lour straight muscles of the eye, the ball may he moved coronad, basqlati, meduzd, or lute-rad ; the head may be drawn airmail, or dorsad, he. Some other terms are introduced by Dr Barclay, and sonic other modes of employing them are mentioned ; but for these we must refer to the work itself, where plates illustrat ing the terms are given.
With respect to this nomenclature, we may remark in general, that it is simple, clear, and founded on fixed principles ; and though some of the terms may appear harsh and singular, few of them are new except in their terminations. The new term of me•iul is particularly useful, and those of atlantal and sacral, sternal and dor sal, peripheral and central being equally applicable to all the vertebral animals, as to man, render the com parative anatomy of those animals, more explicit in its phraseology, and therefore more easily understood.
In fact, when these terms become familiar, anti, like many terms in common language, exchange their origi nal signification for one more arbitrary, they may be ex tended to all animals. Just as the word candlestick signifies any thing that holds a candle, and the word ink horn any thing that holds ink ; so these terms, by a natu cal transition, arc applicable to inverts oral animals. Thus the atlantal aspect, will denote that aspect. which points towards the head ; the sacral aspect, that which points towards the opposite extremity ; though in these animals there be neither atlas nor sacrum. In insects and worms, for instance, these terms will denote parts corresponding in relative positions, to those parts in ver tebral animals, from which the terms arc originally de rived. In short, the principle on which this nomencla ture is constructed, is so obvious, and the application of it so natural and easy, that even the youngest student at tending a course of anatomical lectures may become master of it in less than an hour.
Dr Barclay has himself pointed out the application of these terms in his valuable work on the Muscular Motions of the human Body , and we shall occasionally follow his example in the present article.
For a fuller account of the history of anatomy, we refer our readers to Le Clerc's " Histoire de la Medi cine ;" Hunter's Introductory Lectures ;" Haller's Bi bliotheca .4natomica ;" Portal's " Histoirr d' .1natomir ct. dc Chirurgie," and a German work on the history of medicine, by Sprengel.