THE BASICRANIAL RETE 351 



a broad fibro-muscular attachment to the palate and to the hamular processes at the 

 root of the tongue. It thus separates the rete and the cavity it occupies from the 

 posterior nares. Immediately posterior to the nares is a large cavity with fibro-muscular 

 walls — the naso-pharynx — in the formation of which the palato-glossus muscle takes 

 a large part. The naso-pharynx contains the larynx and associated structures. Two great 

 constrictor muscles, of which the largest is the middle constrictor, run from the wall of 

 the naso-pharynx to the stylo-hyoid cartilage. Both this cartilage and the middle 

 constrictor muscle are shown cut through in Fig. 9. In the posterior half of the rete 

 the middle constrictor muscle forms its mesial boundary. Anteriorly the mesial boundary 

 is formed by the palato-glossus as already mentioned. The middle constrictor also forms 

 a large part of the posterior boundary of the rete. 



There is thus a space, bounded by the squamosal bone and the tympanic bulla dorsally, 

 by the mandible and the masseter and pterygoid muscles laterally, by the belly of the inter- 

 nal pterygoid muscle ventrally and by the palato-glossus and middle constrictor mesially 

 and posteriorly. Here the rete is found, forming a large crescent-shaped highly vascular 

 mass, exactly similar in appearance to the thoracic rete already described. It resembles 

 the latter in that it is invested in its own fibrous integument, and is easily dissected away 

 from neighbouring cartilages and muscles, with which it appears to have no intimate 

 relation. The thoracic rete, however, is very much more diffuse. The basicranial rete 

 completely surrounds and envelops the external pterygoid muscle, which runs through 

 the midst of it from the external pterygoid plate of Schulte (Fig. 9) to its attachment to the 

 mandible. It also surrounds Meckel's cartilage, which forms a narrow cartilaginous rod 

 within a fibrous sheath running from the bulla to the mandible across the space occupied 



by the rete. 



RELATION TO BLOOD VESSELS 



Like the thoracic rete the basicranial rete is composed of intimately related arteries and 

 veins. The external carotid artery, cervico -facial of Turner, which passes from the com- 

 mon carotid along the lateral part of the face towards the orbit and maxilla, traverses the 

 centre of the basicranial rete dorsal to Meckel's cartilage (Figs. 3 and 9). During its 

 course through the rete it repeatedly gives off short many-branched arteries to the retial 

 substance. A branch runs to the lower jaw from the cervico-facial shortly before that 

 artery reaches the rete. Opposite the orbit the cervico-facial splits into an orbital and a 

 maxillary branch. A vein, the pterygo-maxillary, runs from the palatine border of the 

 maxilla diagonally across the attachment of the internal pterygoid muscle to the palate. 

 It passes external to the hamular process, and runs closely adherent to the fibro-muscular 

 wall of the pharynx, around the inner and posterior surface of the tympanic bulla, to 

 join the jugular vein. Its course over the attachment of the internal pterygoid muscle is 

 plexiform, and it receives a network of veins at this point from the mesial and ventral 

 parts of the rete. The main body of the rete is drained by a pair of veins having a rostral 

 direction and joining up with the orbital vein to enter the pterygo-maxillary behind the 

 orbit. From the mandible a plexus of small veins breaks up among the capillaries of 

 the rete. 



