538 HUMAN ANATOMY. 



tenderness in the umbilical region. The reflected pain of ovaritis may be beneath 

 the costal margin or along the crural branch of the genito-crural nerve, where super- 

 ficial tenderness may be elicited, whereas the deep pain is in the ovary itself (Mayo 

 Robson). 



3. Pain due to abdominal disease has been described in connection with the 

 various viscera (page 1756). 



4. Much information may be elicited by percussion, as the dulness in the flanks 

 (movable on change of position) due to ascites, or the localized tympany due to 

 volvulus or to the escape of gas from a ruptured appendix into a surrounding abscess ; 

 or by auscultation, as the absence of the usual intestinal sounds when a general peri- 

 tonitis has arrested peristalsis ; or by inflation of the stomach, as on distinguishing 

 between a growth of that viscus and a retroperitoneal tumor, or of the colon {vide 

 supra), which will then lie below and perhaps behind an enlarged gall-bladder and 

 in front and probably to the inner side of an enlarged kidney. 



These and other procedures are too technical to be described here in detail, but 

 are mentioned that they may be associated with the anatomical relations on which 

 they depend. 



It should be noted that Treves and Keith state that the ileo-caecal valve corre- 

 sponds to the spino-umbilical line, that the region of the valve in a normal person 

 is usually tender to pressure, and that the root of the appendix is placed more than 

 one inch lower and perhaps more internally. This statement if confirmed will have 

 a most important bearing on the value of certain symptoms thought to indicate the 

 existence of appendicitis (page 1683). 



THE THORACIC MUSCLES. 



{a) THE RECTUS MUSCLES. 



The rectus abdominis, being supplied by the lower intercostal nerves, is evi- 

 dently a derivative of the thoracic myotomes. That portion of the rectus group 

 of muscles which should be derived from the upper thoracic myotomes is normally 

 unrepresented, although the occasional extension of the rectus abdominis to the upper 

 costal cartilages or even to the clavicle is probably an indication of it. 



{b) THE OBLIQUUS MUSCLES. 



1. Intercostales externi. 4. Levatores costarum. 



2. Intercostales interni. 5. Serratus posticus superior. 



3. Triangularis sterni. 6. Serratus posticus inferior. 



Here, again, a considerable portion of the obliqui and transversalis abdominis 

 is derived from thoracic myotomes. In addition, however, a number of muscles 

 belonging to the group occur in connection with the ribs. 



I. Intercostales Externi (Fig. 537). 



Attachments. — The external intercostal muscles are eleven in number, 

 stretching across all the intercostal spaces from the lower border of one rib to the 

 upper border of the next. The fibres, which are largely interspersed with strands of 

 connective tissue, are directed downward and forward, and form in each intercostal 

 space a sheet which extends in the upper spaces from the tubercle of the rib to the 

 junction of the rib with its costal cartilage and in the lower spaces is continued upon 

 the cartilages. The interval between the medial borders of the upper muscles and 

 the border of the sternum is occupied by a sheet of connective tissue known as the 

 external intercostal fascia or aiiterior ijitcrcostal aponeurosis. 



Nerve-Supply. — By the anterior divisions (intercostal nerves) of the thoracic 

 nerves. 



Action. — To draw the ribs upward. 



