BY W. J. McKAY. 943 



The interspinales arise from the anterior border of the neural 

 spine, and run forwards and slightly outwards to be inserted on 

 each side of the posterior borders of the spine immediately in 

 front, and slightly into the laminae leading up to the spine. 



Hoffmann has described this muscle ; but in the figures attached 

 to his paper he has described as interspinales the postzygapo- 

 physes spinales. 



M. LONGISSIMUS DORSI. 



J/, semispinalisy Hoffmann ; Der laiige, ahsteigende Muskel 

 zwischen den Gelenk- und Dornforlsdtzen^ D'Alton ; Halhdorn- 

 muskel^ Meckel ; Longissimus dor si, Owen, Jones. 



The longissimus dorsi arises by tendons from the processes of 

 the anterior zygapophyses. The tendons of origin are blended 

 together, so that a vertical aponeurosis is formed which stretches 

 between the zygapophyses, separating the longissimus from the 

 spinalis group, and at the same time helping to give origin to the 

 semispinalis. As the tendons run upwards and forwards they 

 pass into muscular bundles, which are arranged in a laminated 

 position, the posterior overlapping the anterior. 



Thus a column of muscle is formed which gives off two sets of 

 tendons, an inner and an outer. The inner set runs towards the 

 neural spines, and joins the tendons of the spinalis, helping by this 

 means to form the median aponeurosis described above. The 

 outer set serves to give origin to the sacro-lumbalis muscle, and as 

 in the case of tendons of origin an aponeurosis was formed, so now 

 these outer tendons are joined together, and a partition is by this 

 means formed between the longissimus and the sacro-lumbalis. 

 This aponeurosis reaches down to the ribs where it is attached, and 

 so the muscle gets an insertion by this means. 



The muscle by its inner tendons acts as a semispinalis ; while its 

 outer tendons can act as retractors of the ribs. 



We are at a loss to understand on what ground Hoffmann and 

 Meckel could consider this muscle as a semispinalis. 



The muscle is supplied by the external division of the spinal 

 nerves. 



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