10 



GENERAL PRINCIPLES APPLICABLE TO 



to the species. They are apportioned to the regions of the trunk and limbs 

 just mentioned, in the manner indicated in the following table : 



ARTICLE II. GENERAL PRINCIPLES APPLICABLE TO THE STUDY OF ALL 



THE BONES. 



The description of any bone comprises its name, situation, direction, 

 conformation, structure, and mode of development. 



Name. 



The nomenclature of osteology does not rest on any basis capable of 

 conferring upon it a methodic form. Consequently, we find bones which 

 derive their name from their shape, (example : the fibula) ; others from 

 their resemblance to known objects (the tibia and vomer). Some owe it 

 to their position (cotes, sides or ribs), or their uses (the axis and parietal 

 bones). Several attempts have been made to submit the nomenclature of 

 the bones to more precise and uniform rules, but the new designations 

 proposed have not been sanctioned by custom. 



Situation. 



The situation of a bone should be viewed in two ways : 1st, Relative to 

 the median plane of the body ; 2nd, Relative to the oilier portions of the skeleton. 



A. Situation relative to the median plane of the body. The designation 

 of median plane, or improperly median line, is given to an imaginary vertical 

 plane, passing through the middle of the skeleton which it divides, from 

 before to behind, into two equal portions. The bones may be situated 

 on the median plane, in which case there is only one of each kind, and 

 they are called single; they are also named symmetrical bones, because 

 the median plane divides them into two equal lateral halves exactly alike. 

 The bones disposed in a double and regular manner on the sides of the 

 median plane bear, for this reason, the name of pairs ; they are also called 

 asymmetrical bones, because their form does not admit of their being 

 separated in any sense into two similar portions. On the contrary, a bone 

 of this kind always oners the most perfect symmetry with its fellow on the 

 opposite side. 



1 One lumbar vertebra less is found in the ass, and sometimes also in the mule. 



2 The os penis has not been included. 



8 The sacrum is reckoned as a single bone, and the number of coccygeal vertebrae at 

 an average of 12 for the Horse, 16 for the Ox, 14 for the Pig, and 15 for the Dog. 

 4 The os hyoides comprises, and is reckoned as, a single bone. 



