JUGULAR LYMPH SACS AND CHANNELS — NECK OF PIG 59 



mastoid muscle and along its ventral border is the superficial cer- 

 vical plexus. This is now one large gland. Its efferent vessels 

 are the group of ducts to the apex of the sac and a large group to 

 the sac stalk not injected in this specimen. They show well in 

 other specimens connecting the cervical plexus with the stalk of 

 the sac. They follow the external jugular vein and join the sac 

 near the valve into the vein. The specimen shows some of the 

 afferent vessels of the cervical plexus. Along two of the groups of 

 afferent vessels namely the submaxillary vessels and along the 

 facial vessels are developing lymph glands. This figure may 

 well be compared with the injection of the lymph glands in the 

 neck of a new born given as fig. 30 by Bartels in Das Lymphge- 

 f asssystem, in Bardeleben' s Handbuch der Anatomie des Menschen, 

 p. 103, 1909. 



Injections of pigs 7 cm. long show the same structural lines in 

 the lymphatics as the pig measuring 5 cm., with a few modifica- 

 tions. The relations of the jugular sacs are practically the same. 

 One thing must, however, be noted, that the size of the sac has not 

 changed much from that of the 5 cm. pig. Consequently, the 

 relative size of the sac being decreased, it does not occupy as 

 extensive an area in the neck. The anterior curvature instead 

 of being placed below the basi-sphenoid is below the atlas, and the 

 apex lies in the plane between the third and fourth vertebrae 

 instead of extending back to the fifth or sixth. 



Another important morphological change is in the marked 

 development of the lymph glands. The region of the sac between 

 the anterior curvature and the apex having probably lost its 

 function, more or less, as a line of drainage, has become consider- 

 ably reduced in size, with three or four distinct constrictions. 

 The beginning of this change was seen in the pig 5 cm. long. 



The third marked change in the sac is the shifting of the 

 cross connection, which in earlier stages passes directly from the 

 apex to the stalk. Instead of connecting by a short vessel with 

 the stalk it passes parallel to it, a connection being finally estab- 

 lished near the point where the stalk connects with the vein. 



In embryos 8.5 cm. long the sac stalk passes forward external 

 to the internal jugular vein to terminate in a single large node 



