334 DISCOVERY REPORTS 



by Schulte with the rectus capitis anticus major muscle. The deeper and more dorsal 

 portion was identified with the longus colli and is restricted to the bodies of the 

 vertebrae. In both the foetuses dissected the scalene and rectus capitis anticus major 

 were found to converge and unite somewhat anterior to the first rib (which is attached 

 to the 7th cervical vertebra) at about the level of the 5th and 6th cervical vertebrae. 

 Caudally the rectus capitis expands to a considerable belly opposite the first rib, and 

 then diminishes to be inserted into the ventral surfaces of the first three or four dorsal 

 vertebrae as far back as the point of contact of the dorsal aorta with the vertebral 

 column. Fig. 1 shows the relations of these two muscles and the Y formed by them 

 embracing the anterior extension of the thorax. It is seen that rostrally the two fused 

 muscles, scalene and rectus, passing somewhat inwards and ventrally to their insertions 

 into the skull, give place in the fore part of the neck to a complex of muscles composed 

 of the splenial mesially and the trachelo-mastoid laterally (d). The former runs from 

 the cervical neural spines to the squamosal bone and the latter from the dorsal parts of 

 the first ribs to the squamosal. 



Fig. 1 also shows the heart turned aside to show the dorsal aorta (/), the ductus 

 arteriosus (m) and the pulmonary artery. The lungs and most of the vessels on the 

 left side of the neck have been omitted for the sake of clarity. The left subclavian, 

 brachial and axillary arteries (p) are shown. The venous system is drawn somewhat 

 displaced by the turning aside of the heart, but the " axillary venous plexus" is drawn 

 in its normal position. 



The whole fork of the Y formed by the scalene (a) and the rectus capitis anticus (b) 

 is occupied by the main mass of the rete mirabile (Fig. 1, dotted) which thus forms an 

 irregular triangular mass. In Fig. 1 the pecked line (s), running through the dotted 

 area representing the rete, marks out the extreme anterior limit of the pleural dome. 

 Around its anterior aspect runs the posterior thoracic artery (q) and the posterior 

 thoracic vein, which has been omitted for the sake of clearness. 



One side of the triangle formed by the rete between the rectus and the scalene 

 muscles — the mesial side — rests dorsally against the vertebral column (cv) and ventrally 

 against the rectus anticus muscle. Where the rete lies against the vertebral column it 

 extends between the heads of the ribs and between the transverse processes, coming 

 into contact at these points with the overlying dorsal musculature. It is found extending 

 up into the neural canal through the intervertebral foramina, as was noted by Turner. 

 The laterally directed side of the retial triangle lies against the scalene muscle, while 

 behind it overlies the first intercostal space. The caudally directed side lies against the 

 anterior extremity of the dome of the pleural cavity underneath the pleural lining 



(Fig- 1 )- 



The mesial relations of the rete to the vertebral column and the rectus capitis 



muscle and the lateral relations to the scalene are further shown in Fig. 2. This 



schematic diagram represents a transverse section through the posterior neck region. 



In section the scalene muscle (c) is shown to be somewhat arched for its insertion upon 



the ribs so that in front of the ribs its ventral face is nearly in contact with the rectus 



