THE MUSCULAR SYSTEM. 97 



completely tlirougli it, to the anterior edge of the 

 second, where it is inserted, partly below, and partly 

 at the side of, the muscle No. 1 of that segment. 



PI. LIX. — 6, 7. These two muscles correspond to 

 those which I have indicated by the same numbers in 

 the fourth abdominal segment. They rise, side by 

 side, at the lateral edge of No. 5, and not very far 

 from the anterior margin of the segment. They are 

 largest at their dorsal extremity, and pass straight 

 downwards. 



Pis. LIX and LXI. — 8. This powerful muscle rises 

 at the anterior margin of the antepenultimate segment, 

 at the side of No. 5, and passes downwards and 

 forwards, dividing into two branches, which, at their 

 lower and anterior extremity, are intimately connected 

 with the neighbouring portions of Nos. 6 and 7, as 

 well as of the muscle No. 16, which has not yet been 

 described. The lower branch terminates in the third 

 segment before arriving at its anterior margin ; but 

 the upper branch is longer, and penetrates into the 

 next segment. 



No. 9 rises below, and close to. No. 8. It has the 

 same general course, but diverges somewhat, and ends 

 at about the middle of the segment. It will be seen, 

 from the figure, that the end lies under the muscle 

 marked No. 16, and over that marked No. 15. It 

 cannot, therefore, be directly attached to the skin in 

 this position, because the muscle No. 15 comes 

 exactly in the way. The true attachment of this 

 end of the muscle, like that of Nos. 6 and 7, and the 

 posterior branch of No. 8, with all of which it is closely 

 connected, is not easy to make out. I believe, how- 

 ever, that a delicate membrane passes from its lower 

 extremity, both backwards and forwards, over No. 15, 

 and that, by thus acting on the centre of that mem- 

 brane, the same effect is produced as if the muscle 

 were actually attached to the skin at the point where 

 it terminates. 



PI. LIX. — No. 10 rises under the posterior termina- 



7 



