6 IXTRODUCTIOX. 



longitudinal axis of the trunk, as previously stated, the similarity lietween the 

 cephalic and caudal imrts is of a different and only a remote kind : that, viz., which 

 is involved in the repetition in series of vertebral elements, wliich, though funda- 

 mentally similar, yet differ greatly in the form and development of their parts. 



Descriptive Terms. — In the description of parts so numerous, so various in 

 form, and so complex in their connections as those composing the human body, 

 there is difficulty m finding terms which shall indicate with sufficient precision 

 their actual position and their relation to the rest of the organism. This diffi- 

 culty is farther increased by the exceptional erect attitude in which the trunk of 

 the human body is placed as compared with the horizontal position in animals. 

 Hence, a number of terms have long been in use in human anatomy which are 

 understood in a technical or restricted sense. The mesial j^Iruic, for example, 

 already referred to, is that by which the body might be divided into right and 

 left lateral halves, and the middle or median line is that in which the mesial plane 

 meets the surface of the body. The words internal and external are used to 

 denote relative nearness to and distance from the mesial plane towards either 

 side, and might therefore be replaced by mesial and lateral. The words anterior 

 and 27osterior, superior and 'infrrior. and several others indicating position, are 

 employed in human anatomy strictly with reference to the erect posture of the 

 body. But now that the more extended study of comi^arative anatomy and 

 embryonic development is largely applied to the elucidation of the human struc- 

 ture, it is very desirable that descrij^tive tenns should be sought which may 

 without ambiguity indicate position and relation in the organism at once in man 

 and animals. 



Such terms as dorsal and ventral, neural and visceral, cephalic and caudal, 

 central and peripheral, proximal and distal, a.rial and appendicular, 2>rea,rial and 

 2)ostaxial. are of this kmd. and ought, whenever this may be done consistently 

 with sufficient clearness of description, to take the i^lace of those which are only 

 applicable to the peculiar attitude of the hmnan body, so as to bring the 

 language of human and comparative anatomy as much as possible into confor- 

 mity. In many instances, also, precision may be obtained by reference to certain 

 fixed relations of parts, such as the rertehral and sternal aspects, the radial or 

 tilnar, and the tibial or Jihular borders, the flexor or extensor surfaces of the 

 limbs, and similarly in other parts of the body. 



DIVISIONS OF DESCEIPTIVE ANATOMY. 



The systems and organs of the body to l3e described in this work 

 may conveniently be brought under the following divisions, viz. : — 



1. Osteolog}^ the Bones. 



2. Arthrology, the Joints. 



3. ]\Iyology, the Voluntary Muscles, with the Fascia3 and Apo- 



neuroses. 



4. Angeiology, the Distribution of the Blood-vessels and Lym- 



phatics. 



5. Neurology, the Distribution of the Nerves. 



6. Splanchnology, the Viscera, including — 



a. The Brain and Spinal Cord. 

 h. The Organs of the Senses. 



c. The Heart. 



d. The Lungs and Organs of Respiration. 



e. The Organs of Digestion with the Accessory Glands. 

 /. The Urinary Organs. 



(J. The Organs of Reproduction. 



The integuments -will be described in the part on General Anatomy. 



