GENERAL CONSIDERATIONS ON THE STRIPED MUSCLES. 229 



is either vprtiraJ, Iwrizontal , or oblique — expressions which caiTj their own definition 

 and require no explanation. 



c. If the direction of tlie muscles be compared with that of the bones they 

 surround and move, it will be found that they are either parallel to these levers, 

 or form with them angles more or less acute. The proper direction of the bones 

 being known, it is sufficient to indicate that of the nuiscles to clearly establish 

 this comparison. For instance, in saying that the majority of the muscles of 

 the shoulder are oblique from above to below, and from before to behind, it is 

 understood that these muscles are parallel to the scapula, and that their incidence 

 on the humerus takes place at a right angle. 



E. Attachments or Insertions. — This is undou})tedly the most essential 

 part of the study of the muscles ; for with a knowledge of their insertions, we 

 may determine their extent and direction, and even their relations and uses. 



By the term attachment, fixed insertion, or origin, is meant the point of the 

 muscle which usually remains fixed while the muscle itself contracts ; the attach- 

 ment, movable insertion, or termination is the name given to that portion which 

 is fixed to the lever displaced by the muscular contraction. Muscles are fre- 

 quently met with the two insertions of which are alternately fixed or movable ; 

 and in such cases care is taken not to give these insertions one or other of the 

 designations. 



The fixeA insertion is often confounded with that of other muscles ; the 

 movable insertion is generally free and independent. 



The muscles are sometimes directly attached to the bones by the ends of their 

 fleshy fibres ; but most frequently they are fixed to these inert levers through the 

 medium of a tendon or an aponeurosis, the volume of which is less considerable 

 than that of the fibres. But for this aiTangement, the surface of the skeleton 

 would not be sufficiently extensive to give insertion to all the external muscles. 



F. Relations. — The indication of the relations of the muscles completes the 

 idea of their situation, and is of great importance from a surgical point of view. 

 They should, therefore, be studied with all the precision possible. 



The muscles entertain relations either with the skin, the bones, other muscles, 

 or with vessels and nerves. 



a. It is only, properly speaking, the subcutaneous muscles— such as the 

 panniculus carnosus and the muscles of the face — which are really in immediate 

 contact with the skin. The others are separated from it by the aponeurotic 

 fascia, which will be described as the appendage of the muscular system. 



b. The sujx^rficial muscles are only related to the bones by their extremities. 

 Those which are deeply situated are immediately appUed by their bodies against 

 the bones of the skeleton. 



c. The muscles are related to each other in a more or less intimate manner. 

 Sometimes they adhere closely to one another ; and at other times they are 

 separated by interstices filled with fat or connective tissue, and which are generally 

 traA'ersed by vessels and nerves. 



d. The connections of the muscles with the latter organs sometimes assume 

 a remarkable character ; this is when one of them accompanies, like a satellite, 

 the vascular and nervous trunks concealed beneath its deep face. There is in this 

 circumstance an important fact with regard to surgical anatomy. The borders of 

 these muscles are usually visible on the surface of the region, and for this reason 

 may become valuable guides in seeking for important organs in their vicinity. 



G. Nomenclature. — a. Before the time of Sylvius, the muscles had not 



