161 



of the body with the thoracic, we will find these five elements 

 abundantly represented ; and we find also that their representatives 

 constitute the only true endo -skeletal trunk muscles. For each of these 

 we have a corresponding muscle on the neural aspect, an antithesis ; 

 and with a little care we will find that the complex muscles of the back 

 can be resolved into a series of repetitions of these five types more accu- 

 rately. We may call these elements: — 1. External Interhsemapophysial, 

 or Interneurapophysial ; 2. Internal ditto ; 3. Spino-hsemapophysial or 

 neurapophysial ; 4. Basio-hsemapophysial, or neurapophysial ; 5. In- 

 terspinal. In the dorsal region proper we can represent these antitheses 

 thus : — 



External intercostal type, 

 Internal ,, 



Transversus thoracis, anterior type, .... 



,, ,, posterior type, 



Rectus ,, . . . . 



= Splenius and serrati. 



= Iliocostals, Longissimus dorsi, Transver- 

 salis colli, Trachelo-mastoid, Cervicalis 

 ascendens. 



— Multifidus spinse, Semispinals colli and 



dorsi, Obliquus superior, Complexus. 

 = Rotatores spinse. 

 = Interspinals, spinalis dorsi. 



The trapezius we leave out of account, because properly it has a 

 place in the great limb system of muscles. 



If we follow out the same idea, we will find the same five elements 

 to enter into the composition of the abdominal wall ; and referring 

 these, as we may do with great facility, to their thoracic representatives, 

 we may tabulate them as follows : — 



External intercostal type, == External oblique. 



Internal intercostal type, = Internal oblique. 



Transversus thoracis posterior type, = Transversalis diaphragm. 

 Transversus thoracis anterior type, = Pyramidalis. 

 Rectus anterior type, = Rectus abdominis. 



In each of these muscles we have the combined representative of 

 several muscles of each series ; thus the internal oblique frequently ex- 

 hibits a tendinous intersection corresponding to the first lumbar rib. 

 I have also seen the line of the cartilage of the eleventh rib continued 

 forwards to the rectus by a tendinous interspace in its fibres. A similar 

 tendinous rib index has been described in the transversalis by Sommer- 

 ring. The rectus muscle, likewise, by its linese transversa?, exhibits a 

 tendency towards costal intersections, which in the crocodile arrive at 

 their fullest development in the form of abdominal ribs on either side 

 of the prolonged sternum. • Of these, in man the numbers are generally 

 three, rarely four ; but in other animals they are more numerous. The 

 hare, for instance, presents us with eight or nine such "inscriptions." 

 On the posterior wall of the abdomen, or more correctly, in the lumbar 

 region of the spine, we have these same muscles antithetically repre- 

 sented, as follows. (In all these tables I use the names of the thoracic 

 muscles as the nearest or clearest representatives of the typical arrange- 

 ment) : — 



