( 35 ) 



The corpus of the iTiyolonic siu»\\s a kiicelikc iiillcclidii (liu. II A'), 

 which is alvvjiys situated nearei- the mi(i-\'eiilral line of tlic IkkU tliaii 

 the mid-dorsal line. In transverse section (along the line hl'\ lig. 11) 

 I'^ig- HI- the corpus of the myotome is rliomboidal, this 



rhond)us being more and more flattened towards 

 llie coi-nua ; consequently the cornua ajtpeai' in 

 transverse section as lamellae in jnxlaposition 

 (lig. Ill L.L.). These lamellae are slightly incin-\'e(l. 

 One side of the rhombus lies in the bod\ sur- 

 face (black in lig. \\). This surface is cylindrical 

 in the middle region of the body, the transverse 

 section being perfectly elliptical. The black-coloiu-ed 

 surface of the myotome, nuist therefore be con- 

 sidered as cut out of this cylindrical sui'face. 

 The opposite side of the j-hombus is turned 

 |>L towards the skeletal-axis and the abdominal cavity. 

 In general it has the same form as the outer side, 

 being oidv slighllv e\ca\ate(l bv the abdominal 



Traiisvei'sc section 

 thiouah the Iriink of 



Pctromyzoii: the inter- «^'^^vity, which in this part of the body is cylin- 

 segmental tissue being drical, the transverse section being a perfect circle. 

 ^^'^^^- Both the other sides of the rhombus are con- 



gruent and I)oiuid respectively, a more cranial and a more caudal 

 myotome. 



The position of the myotome as a whole in respect to the sagittal 

 plane, passing through the mid-lines of the body, is such, that the 

 corpus shows an inclijuition towards the caudal end of the body. 

 Seen in transverse section (along the line FF lig. 11) the longest 

 axis of the rhombus makes an acute angle with the sagittal axis of 

 the body, the vertex of the angle being turned towai-ds the head. 

 This caudal inclination of the myotome dinunishes towards the cor- 

 nua, so that the cornua are nearly normal to the surface of the 

 body. In consequence of this caudal inclination the myotomes over- 

 lap to some extent. This muscular overlapping \aries between ', and 

 "/a in the neighbourhood of the knee, diminishing towards the connia 

 on account of the decrease of the caudal inclination of that part of 

 the myotome. 



The position of the myotome in respect to the dorsoventral axis 

 is variable along the body. If AB (lig. II) is a dorsoventral axis, at 

 right angle to the sagittal axis, and .1/s a line tangent to the dorsum 

 of the myotiMue, then we have in the angle AFB a measure for the 

 ante- oi' retroversion of the myotome in respect to the dorsoventi-al axis. 



The lirst myotomes behind the last bram-hial cleft, show a little 



3* 



