36 IXTRODUCTIOX. 



In Fig. 5 the line HK may be described as having a dorso-sinistro-caiidal 

 direction. In man, it would be said to extend lackward (dorsad), to the left 

 (sinistrad), and downward (caudad). But with an animal it would be 

 described as passing upward, to the left, and liachward. 



§ 72. Designation of the Relative Position of Points upon 

 Diagonal Lines not in Either of the Planes. — A term of three words 

 is needed, with the adverbial termination. Thus H is dorso-sinistro-caudad 

 of K ; or K is veiitro-meso-cephalad of H. 



§ 73. In all these cases, it is sometimes more cpnyenient, and equally 

 intelligible, to substitute for the more specific terms dextral and sinistral, 

 the more general terms mesal and lateral. The line ME, for example, might 

 be called dorso-lateral instead of dorso-sinistral; or it might be called ventro- 

 inesal, and the context would show which side was referred to. If, while 

 dissecting upon the left side, the student were directed to cut mesad for 

 2 cm., he would cut towards the right, that is dextrad. 



§ 74. Designation of Direction and Relative Position upon the 

 Limbs. — The various terms are employed and combined as for the soma, 

 excepting that in place of mesal and lateral, or dextral and sinistral, there 

 are used the terms proximal and distal. 



§ 75. Ectal and Ental, and their Derivatives. — The general signifi- 

 cance and uses of these terms have been indicated in § 46. Other examples 

 will be given in connection with Eig. 7. 



A special employment of the two words in combination is for the sake of 

 designating the direction of an incision. Ordinarily incisions are carried 

 from the surface inward, that is ecto-entad; sometimes, however, it is desir- 

 able to divide parts, especially the skin and abdominal parietes, by an 

 incision in the opposite direction — ento-ectad. 



§ 76. Figure 6 is intended to show certain features of the cat, regarded 

 as a Mammal, and not simply as a Vertebrate, as in Figures 2, 3, 

 and 4. 



As in Fig. 2, the body is ventricumbent, so as to expose the dorsal 

 aspect. 



The limbs (arms and legs) are extended at each side at right angles with 

 the axis of the soma, in what is commonly regarded as their normal position. 

 The principal divisions of the body are named in the Table on p. 39. 

 § 77. The Soma and its Divisions. — The lai-gest division of the 

 soma is the trunk. The tail forms an extension in one direction, while the 

 other end is continued as the neck and head. The neck is narrower than 

 the head or trunk, and the head itself consists of the cranium and 

 the face. 



§ 78. The Trunk and its Divisions. — There are readily distinguished 

 three regions of the trunk. The intermediate region or abdomen has only 

 fleshy sides, while the more caudal — pelvis — has the Os innominatum on 



