BY W. J. McKAY. 963 



Mm. retrahentes costarum. 



Mm. retrahentes costarum longi, Hoffmann ; Innerer^ kleiner 

 Rilckwdrtszieher der Bippen, D'Alton ; Costales interni inferi(yres, 

 Hiibner ; Retrahentes costarum inferiores, Owen. 



The retrahentes costarum arise from the anterior border of the 

 ribs at the junction of the inner three-fifths with the outer two- 

 fifths. The flat quadrilateral bundles run forward and inwards, 

 passing over three ribs to be inserted into the fourth at the place 

 where the sternal cartilages join the ribs, at the same time giving 

 slips to the ribs passed over. The muscles are separated from the 

 external intercostals by large branches of the intercostal nerves ; 

 while they are also separated from the transversalis muscle proper 

 by branches from the intercostal nerves. 



These muscles most probably represent modified internal inter- 

 costals, combined with subcostals. 



M, RECTUS CAPITUS ANTICTJS. 



M. rectus capitis anticus tnajor et minor, Hoffmann ; Der grosse, 

 untere, und der klein^, g evade Kopfheuger, D'Alton ; Der gerade 

 Seitenmuskel des Kojyfes order Seitwdrtsheuger, Meckel ; Rectus 

 capitis inferior, Hiibner ; Longiis colli, Owen ; Transverso-spinalis 

 inferior, Jones. 



The rectus anticus is formed by the forward extension of the de- 

 pressores costarum. These muscles as they approach the head 

 divide into a superior and inferior layer. The inferior layer is 

 formed thus : — the various bundles instead of running outwards and 

 forwards to be inserted into the ribs, run inwards and forwards, 

 and coalesce to form a single column of muscle which is inserted 

 into the tubercle on the basioccipital bone close to the median line. 



The superior layer still continues to have its bundles inserted on 

 the ribs, until it reaches to the fourth vertebra, when the bundles 

 coalesce and a second column of muscle is formed similar to the 

 first, but runuiug outwards and forward to be inserted into the 

 lower tubercle of the exoccipital. 



