INGUINAL HERNIA. 



•79 



Hence, in the operation for hernia, the following layers are cut 

 through : — 



Skin, superficial fascia, cremaster mvscle, transversalis fascia^ 

 and the hernial sac. 



In the dissection of a hernial sac, we will find alterations in thick- 

 ness and colour, the consideration of which properly belongs to the 

 surgical part of this work. 



Direct or ventro-ingui7ial hernia consists of a protrusion directly 

 at the external abdominal ring, and of course does not pass through 

 the canal. The coverings are the skin, superficial fascia, the com- 

 mon tendon of the internal oblique and transversalis muscles, trans- 

 versalis fascia, and hernial sac. 



This variety is not of so frequent occurrence, on account of the 

 insertion of the tendon of the internal oblique and transversalis into 

 the pubes immediately behind the external abdominal ring, which 

 protects this opening, and therefore it must be ruptured or expanded 

 when a protrusion takes place at this ring ; when it is ruptured, of 

 course this covering of the sac does not exist. 



Diaphragma. — This muscle forms the septum between the thorax 

 and abdomen ; it consists of two parts, a greater and lesser muscle. 

 The greai^er*^^ muscle 



arises from the ensi- Fig. 61. 



form cartilage, and 

 from six inferior ribs ; 

 the fibres converge to 

 the cordiform tendon, 

 which is in the cen- 

 tre. The lesser^ ^° 

 muscle consists of two 

 bellies, which are 

 called crura, the right 

 of which is the larger. 

 Origin, from the 

 second, third, and 

 fourth lumbar verte- 

 brae. Insertion, into 

 the cordiform tendon. 



There are three 

 openings in the dia- 

 phragm ; one in the 

 tendinous centre, ^^ 

 called foramen quadratum, which transmits the ascending vena 

 cava; another, an elliptical muscular opening,*- called foramen ceso- 

 phageum, through which passes the oesophagus and the par vagum 

 nerves ; and the third, the hiatus aorticus,^^ which is between the 

 crura, and in front of the vertebra ; through it passes the aorta, the 



