44 THE STORY OF THE BIRDS 



within the limits we have assigned to our treat- 

 ment of the subject. The Muscular, Nervous, 

 and Digestive Systems of a bird each require the 

 fullest treatment to render the study comprehen- 

 sive, and any attempt w^ould be more or less 

 futile to condense it in the limited space 

 at our disposal or to bring it at all into pro- 

 portion with the purely introductory character 

 of the present little treatise. Suffice it then to 

 say, that the muscles of a bird constitute what 

 is popularly known as flesh, and consist of a 

 series of fibres, arranged with their long axes 

 in the direction of the muscles' action, each 

 being in connection with a nerve-cell, the ex- 

 citement of which causes contraction and the 

 drawing together of the parts to which the 

 whole muscle is attached. Muscles are of two 

 kinds. First, involuntary or unstriped muscles, 

 usually of slow and rhythmical action, belong- 

 ing to the viscera and the skin : second, volun- 

 tary or striped muscles ; whilst the cardiac 

 muscles are to some extent intermediate between 

 the two. The Nervous System of a bird consists 

 of two portions, a Central portion made up of 

 the Spinal Marrow or Cord and the Brain, and 

 a Peripheral portion containing the Cranial and 

 Spinal Nerves with all that relates to the 



