THE MUSCULAR SYSTEM. 99 



than in the preceding. In several cases I even found 

 Nos. 1, 2, 3, and 4 entirely deficient. No. 5, on the 

 contrary, seems to be always present. There are, 

 indeed, two muscles marked thus. The one rises in 

 the third abdominal segment, as I have already 

 mentioned, and passes forwards, dividing into two 

 heads, which are attached to the anterior margin of 

 this segment. The other, which corresponds with it, 

 rises at the posterior end of this segment, at the edge 

 of the muscle just described, and, passing through the 

 present segment, is attached to the anterior margin of 

 the first abdominal segment. 



