140 CLINICAL APPLIED ANATOMY. 



attached to the sides of the bodies of the last thoracic and all the 

 lumbar vertebrae. When the lower -thoracic or the lumbar centra 

 become infected with tubercle, and caseation or suppuration 

 occurs, the tuberculous material is prevented from passing 

 forward by the anterior common spinal ligament, is hindered 

 from invading the spinal canal by the posterior common liga- 

 ment, and therefore tracks laterally, and enters the substance of 

 the psoas muscle. The muscular tissue gradually becomes dis- 

 placed or absorbed, and the sheath filled with the tuberculous 

 material. This is then conducted by the sheath downwards along 

 the brim of the pelvis, behind Poupart's ligament to point in 

 Scarpa's triangle not far from the insertion of the muscle into the 

 lesser trochanter. 



When such a collection of caseous matter is opened in the 

 lumbar region, and the finger introduced, it is often found that the 

 cords of the lumbar nervous plexus have been dissected out, and 

 remain stretched across the cavity. 



Injuries of Muscles. Laceration of muscular fibres is a very 

 common accident. A muscular belly may be completely ruptured 

 within the sheath. The sheath of a muscle may be lacerated 

 without the contained muscular fibres being torn, in which case a 

 protrusion, or hernia, of the fibres may occur. A muscle and its 

 sheath may both be ruptured simultaneously. Certain muscles 

 from their attachments, position or functions are more liable to 

 injury than others. Thus it is that some of those muscles which 

 have their attachments widely separated and are subjected to 

 sudden and violent strain, are often the site of laceration or rup- 

 ture. The great stretching which the sterno-mastoid from its 

 position must necessarily undergo during the birth of the after- 

 coming head, by no means infrequently leads to some laceration, 

 resulting in the formation of a hsematoma, which constitutes the 

 so-called tumour or gumma of the sterno-mastoid. Torticollis 

 may result from the subsequent contraction. 



The physiological action of the rectus abdominis in parturition, 

 or even def aecation, may occasion some laceration of its fibres, and 

 the consequent extravasation of blood which occurs within its 



