COMPARATIVE ANATOMY 33 



brates, where greater support is needed, almost all myomeres 

 are so modified that the original segmental arrangement of the 

 muscles is no longer recognizable. 



Muscles of the Cat 



A cat will be supplied that has been embalmed in such a way 

 that it does not need to be immersed in a preserving fluid. It 

 must be kept in its container, however, with the cover on tight, 

 when not in use. This is important. The cat will remain 

 in good condition throughout the semester if properly cared 

 for. 



Skin your own cat. Before proceeding ask the instructor for 

 directions. It is preferable, though not essential, to skin the 

 cat a day or two before using it for muscle dissection to allow 

 the excess embalming fluid to drain off. During the skinning 

 notice that the skin is held to the muscular wall underneath by a 

 loose fibrous tissue, the superficial fascia. Observe also that 

 certain muscles, particularly in the thoracic region, have their 

 insertions in the skin. If your cat Is a female, the mammary 

 glands will be noticeable; in some cases milk may be present. 



In speaking of the muscular system reference is made to the 

 voluntary muscles only. Each muscle is attached at each end 

 to some other structure, most commonly, though not always, to 

 bone. The less movable end of a muscle is known as the origin; 

 the more movable end, as the insertion. A muscle may have 

 more than one point of origin or insertion. Attachment of a 

 muscle is frequently made by means of a white fibrous cord called 

 a tendon. A broad flat tendon is known as an aponeurosis. 

 Occasionally part of a tendon ossifies, forming a sesamoid bone. 

 (The patella is a good example.) 



Surrounding each muscle, and also groups of muscles and 

 the musculature of the body as a whole, are sheets of connective 

 tissue known as fasciae. Dissection of muscles consists almost 

 wholly of tearing and separating these. Fascia frequently serves 

 also as the origin or Insertion of a muscle. 



Muscles are often described by their actions. In this con- 

 nection the following terms are important: 



Flexor, a muscle which bends a joint. 



Extensor, a muscle which straightens a joint. 



