396 MUSCLES. 



tween the sternal and costal portion on each side, there is a 

 triangular fissure filled with fatty cellular tissue, which some- 

 times leaves an opening for hernia. I have seen a case of the 

 kind, in which the transverse part of the colon was the subject 

 of protrusion into the thorax. It is probable that the great dis- 

 placement of the abdominal viscera into the thorax, which some- 

 times occurs, may have a congenital origin in this very fissure, 

 and is subsequently, when the parts are accommodated to their 

 unnatural situation, thought to be a lusus naturae. The portion 

 described is called the Greater Muscle of the Diaphragm. 



Besides these origins, the diaphragm has several from the 

 vertebrae of the loins, constituting its crura; there being four 

 on each side of the foramen for the aorta. The first pair, en- 

 tirely tendinous, comes from the front of the body of the third 

 vertebra of the loins, and is prevented from being very distinct 

 in its origin, in consequence of running into the ligament in front 

 of the bodies of all the vertebrae or the Anterior Vertebral Li- 

 gament as it is called. The second pair of heads is on the out- 

 side of the first, and arises, tendinous, from the intervertebral li- 

 gament, between the second and third vertebrae. The third pair 

 of heads arises tendinous from the upper part of the lateral face 

 of the second lumbar vertebra. And the fourth pair of heads 

 comes also tendinous, from the fore part of the root of the 

 transverse process of the second lumbar vertebra. These ten- 

 dinous heads terminate in what is called the Lesser Muscle of 

 the Diaphragm, which is inserted into the notch of the cordi- 

 form tendon. It will now be understood that the aorta passes 

 between the two sides of the lesser muscle, and that the oeso- 

 phagus has a hole in the upper part of its belly.* 



The origin of the diaphragm is completed between its great- 

 er and lesser muscle, by a tense ligament, the Ligamentum Ar- 

 cuatum, which passes from the root of the transverse process 

 of the first lumbar vertebra to the inferior part of the middle 



* This origin of the lesser muscle of the diaphragm is given by Albinus, but 

 it is difficult to make out fairly; for the most part it would be much more correct 

 to say that it arises tendinous, from the first, second, and third vertebrae in front, 

 and the corresponding intervertebral matter. The heads are generally much 

 smaller on one side, the left, than the other. From which cause a large fascicu- 

 lus of muscle passes from the right to the left side in ascending, and separates 

 the hole for the aorta, from that for the oesophagus. 



