ABDOMEiN^. 153 



MYOLOGY. 



The muscles of the abdomen are supported exter- 

 nally by the abdominal tunic. They nnite on the medi- 

 an plane forming the white line, and are four in num- 

 ber. 



1. Tunica abdominalis. — A vast expansion of yel- 

 low elastic tissue, spread over the external muscles, 

 thick near the pubis and along the wliite line, and be- 

 coming tliinner towards its circumference. Posteriorly 

 it becomes lost in the inguinal region, and gives origin 

 to the testicular envelope known as the dartos. Ac- 

 tion : assists the abdominal muscles in supporting the 

 intestinal mass. 



2. White line. — Linea alba. Formed by the inter- 

 crossing of the aponeurosis of the abdominal muscles, 

 it extends from the xyplioid cartilage of the sternum 

 to tlie anterior border of the pubis. 



3. Great or external oblique of the abdomen. — 

 Synonyms : Costo-abdominalis, (G). Qbliqus externus 

 abdominis, (P). Structure : fleshy and aponeurotic por- 

 tions. Attachments : fleshy portion, on tlie external 

 face of the thirteenth or fourteenth last ribs, on the 

 aponeurosis of the great dorsal muscle ; by its internal 

 border it gives origin to its aponeurosis ; aponeui-otic 

 portion, on the linea alba, the anterior border of the 



