THE ECONOMY OF THE MUSCULAR COVERING. 73 



the tongue, which it retracts ; descending along the front of the neck to 

 the shoulder, it is for the greater part of its length, covered by other 

 muscles. The principal depressor muscle of the head, called sterno-max- 

 illaris, (n,) partly covers the last named. It rises from the upper part of 

 the point of the breast, (sternum) ^ covers the lower front of the neck, 

 proceeds upward by the side of the retracting muscle of the tongue, and 

 is inserted by a flat tendon into the rear angle of the lower jaw. It is 

 not a large muscle, since it requires but little force to depress the head. 



Extending from the back of the head and upper part of the neck, 

 along the front of the shoulder, to the top of the fore leg, and beyond 

 the sterno-maxillaris^ is a long and important muscle (levator humeri, 

 or deltoides) page 69 (o) having a double function to perform. The head 

 being held up by its own proper muscles, it then becomes the fixed point 

 from which the levator humeri raises the shoulder. But its action can be 

 reversed. With the shoulder as a fixed point, the head can be depressed 

 l)y means of a small slip of the muscle being carried forward to the 

 point of the breast bone to bear the head in that direction. In conclu- 

 sion, it may be stated that the muscles are all arranged in pairs, some- 

 times, but rarely, in contact ; so that in speaking of them in the singular, 

 their i)ositi()u and function is to be understood as applying to each side 

 of the animal. 



III. Muscles of the Shoulder and Back. 



In every science the use of Latin has generally been adopted in nam- 

 ing the several parts and objects. The reason of this is that the true and 

 exact meaning of the names is thus preserved with scientific accuracy, 

 which could not always be the case if these terms were loosely translated 

 from and into the various languages of the earth. In English and in 

 other languages there are several names for one and the same oljject 

 Once named in scientific nomenclature the object remains fixed and clearly 

 defined by its scientific name as long as the science lasts. Sometimes 

 it would take many words to express the same meaning, and when neces- 

 sary the meaning of the scientific term is explained. Sometimes thers 

 is no common name, and hence we are obliged to depend upon the Latin 

 name. For instance the trapezius is the muscle whose office it is to raise 

 and support the shoulders, assisted by another important nmscle, (serratus 

 major) (g,) a muscle that is hardly visible externally, since it is situated 

 between the ribs and shoulder blades, and forms the main connection 

 between them. Hence in explaining the illustrations we use these terms, 

 explaining them, so far as may be necessary, in the body of the text. 



