70 THE VOYAGE OF H.M.S. CHALLENGER. 



of the rib behind. They are very closely related to the accessory intercostal muscles 

 which arise from the uncinate processes. 



Relations. — These muscles occupy the whole of the interval between any two 

 vertebral ribs extending from the vertebral column above to the junction of the vertebral 

 with the corresponding sternal ribs below. They do not occupy the intervals between 

 the sternal ribs. 



Nerve supjily. — Branches of the intercostal nerves. 



5. Accessory external intercostal muscles. 



Attachments. — These muscles are superficially placed with reference to the external 

 intercostals, to which they may be regarded as accessories. Each arises from the whole 

 length of the posterior border of an uncinate process, and passing obliquely backwards 

 and downwards, is inserted into the outer surface of the vertebral rib next behind that to 

 which the uncinate process belongs. These slips correspond in number to the uncinate 

 processes, and are therefore absent in the case of the first and last ribs. 



Action. — These muscles elevate the ribs into which they are inserted, and are there- 

 fore muscles of inspiration. 



Relations. — The accessory muscles rest upon the external intercostal muscles, from 

 the anterior fibres of which they can scarcely be separated. 



Nerve supply. — Twigs from the intercostal nerves. 



Remarks. — In connection with these muscles, it may be as well to refer to a number 

 of aponeurotic slips which attach the uncinate processes to the corresponding ribs. 

 Each of these consists of a stout aponeurotic plate, triangular in form, which is attached 

 by its apex to the anterior border and free extremity of the uncinate process, while its 

 base is attached to the posterior border of the vertebral rib to which the process belongs. 

 These aponeurotic slips overlap each other from behind forwards, and serve to strengthen 

 the articulation between the rib and its uncinate process. By thus fixing the uncinate 

 process they aSbrd a point d'appui from which the accessory intercostal muscles may act 

 in raising the ribs during inspiration. 



6. Internal intercostal muscles. 



Les muscles intercostaux, Vicq d'Azyr, 1774, p. 520, No. 1. 

 Die inne)-e Zioisclienripp&n-Muskeln, Tiedemann, p. 301, No. 7. 

 Intercostaux internes, Meckel, vol. vi. p. 17, No. 3. 

 Intercostaux internes, Cuvler, vol. i. j). 219. 

 Intercostales intemi, Selenka, vol. vi. p. 104, No. 28. 

 Muscles intercostaux, Gervais and Alix, p. 13. 



Attachments. — These muscles occupy the intervals between the sternal ribs, and extend 



