DESIGNATION OF RELATIVE POSITION. 35 



§ 66. OMique lines lie in one plane, but are not iDerpendicular to either 

 of the other planes ; neither do tliey coincide with the intersection of two of 

 the body planes, or of planes parallel thereto. They are comparable with 

 the diagonal of a iJarallelogram. Such lines are EC ; ME ; BH. 



§ 67. Designation of Direct Lines. — This requires a term of two 

 words, of which one indicates the point of departure and the other the point 

 of approach. 



On the figure of the model, the line ABC is a cephalo-caudal line, or 

 extends cephalo-caudad ; or the order may be reversed by saying that it is a 

 caudo-cepMUc line, or extends caudo-cephalad. The line CFK is a dorso- 

 ventral or ve7itro-dorsal line, and the line IFS is dextro-sinistral or sinistro- 

 dextral. 



§ 68. Designation of the Relative Positions of Points upon 

 Direct Lines. — This requires a term of but one word, adverbial in form, 

 and indicating a point of approach. 



In Fig. 5, C is cephalad of B, and dorsad of F ; A is caudad of B ; H is 

 ventrad of M, but dorsad of L. 



In the body, the sternum is ventrad of the heart, the Columna vertebralis 

 is dorsad, and the diaphragm is caudad of the same organ. 



In man, the sternum would be said to be before, or in front of, or anterior 

 to the heart ; but in animals it might be described as below, under or inferior 

 to the same organ. 



It should be kept in mind that these terms are relative, not absolute. 

 The diaphragm, for example, lies cephalad of the stomach, but caudad of the 

 heart. 



§ 69. Designation of Oblique Lines. — This requires a term of two 

 words, both of which indicate j)oints of approach. The points of departure 

 are usually apparent from the context. Thus, the line E, C, extends both 

 towfird the head and the back ; hence it is called a cephalo-dorscd line, or 

 described as passing cephalo-dorsad. The same line could be described as 

 caudo-ventral, or as extending caudo-ventrad. 



In man, such a line would be described as extending forward (ventrad) 

 and doivnivard (caudad). In comparative anatomy, it might be said to pass 

 dowmoard (ventrad) and backward (caudad). 



§ 70. Designation of the Relative Position of Points upon 

 Oblique Lines. — This requires a term of two words, in the adverbial form. 



On the line CE, C is cephalo-dorsad of E, while E lies caudo-ventrad 

 of C. 



In man, C would be said to be above and behind; in animals, in front 

 and above. 



§ 71. Designation of Diagonal Lines not in Either of the Three 

 Planes. — This requires a term of three words, all of which indicate points 

 of approach ; the order of the words is immaterial. 



