THE ARTERIAL SYSTEM. 43 



96. The subolavians lie, at first, ventral to the carotids, 

 and, diverging, embrace in the angle between them the 

 reddish thyroid body; on being traced, each will be 

 found to give ofiE : 



a. A minute thyroid artery, distributed to the or- 

 gan of that name. 



b. The ascending cervical, which is distributed on 

 the ventral surface of the neck and throat. 



c. Farther on, the subclavian passing forward 

 and outward gives ofE a short trunk, which 

 soon divides into branches distributed to mus- 

 cles about the shoulder and pectoral arch. 



d. ' Then turning dorsally, the subclavian gives off 

 the superior cervical, which runs to the side of 

 the neck near its base, and there breaks up. 



e. Next, a branch, which runs to the side of the 

 vertebral column, and there passes in between 

 the first costal plate and the first rib. 



/. Then it gives ofE the axillary artery, which, 

 crossing dorsal to the large cords of the bra- 

 chial plexus, turns round the subscapularis 

 muscle, and becomes the brackial artery, which 

 is distributed to the forelimb. 



g. The remainder of the subclavian continues as 

 the internal mammary artery, which runs out- 

 ward to the edge of the carapace, and runs 

 back along it, in the hollow of the marginal 

 plate, to anastomose with the epigastric, which 

 passes forward from the posterior portion of 

 the dorsal aorta (no, c). 



97. The carotid arteries, first dorsal and then external 

 to the subclavians, cross dorsal to the latter and reach 



