THE THORACIC DUOT. 721 



CHAPTER II. 



THE LYMPHATICS IN PARTICULAR. 



We will commence with the examination of the thoracic duct and all its affluents, 

 and terminate by studying the great lymphatic vein (dmtm If/mphatirm ilcxter). 



In this description the glands and principal lymphatic vessels will be only 

 referred to, the arrangement of the networks being already noticed when speak- 

 ing of the different organs, and they will be further alluded to when treating of 

 the nervous system, the organs of sense, and those of generation. 



Article I. — The Thoracic Duct (Fig. 389, t t). 



Preparation. — Tie the jugulars and axilbiry veins near their termination, as well as the 

 anterior vena cava about the middle of its length ; expose the thoiacic duct by removing the 

 ribs on the right side : open that vessel near the pillars of the diapliragua, and tlirow into its 

 interior two injections of tallow, one forward, the other backward from the incisiim. Tlie first 

 injection will till the canal and the venous reservoir which is intersected between the ligatures 

 applied to the above-named vessels; the second, although directed in opposition to the valves, 

 oveicomes the resistance nffered by them, and passes into Pecquet's cistern and the principal 

 branches wliich open intn that confluent. 



Or we may sel-ct one of these branches in the abdominal cavity — for example, one of those 

 which lie beside the colic arteries near tlieir origin — and inject the entire thoracic duct from 

 its origin to its termination. But this proceeding requires more practical ability than the first, 

 in order to find the vessel which is to receive the cannula; if the animal is very fat, it is 

 impossible. 



The thoracic duct is the general confluent for all the lymphatics of the body^ 

 with the exception of those which come from the right anterior limb and the 

 right moiety of the head, neck, and thorax. 



Extent. — It extends beneath the vertebral column, from the first lumbar 

 vertebra to beyond the entrance to the thorax. 



Origin. — Its origin is marked by a very irregular dilatation, described as the 

 snhlumbar reservoir, or cistern of Peccjuet {receptaculum or cysterna chyli), into 

 which open the principal affluents of the canal. 



This reservoir is divided, internally, by lamellae into several incomplete com- 

 partments, and may be more or less voluminous and circumscribed, as well aa 

 very variable in shape. 



It is placed above the abdominal aorta and the posterior vena cava, at the 

 anterior mesenteric artery, or more frequently a little behind it. 



Course. — To this receptacle succeeds a tulje, the caHbre of which is very 

 irregular, and appears singularly slender when compared with the diameter of 

 the commencing dilatation, or that of the affluent vessels composing it. This is 

 the thoracic duct. It enters between the two pillars of the diaphragm {hiatus 

 aorticus), along with the posterior aorta, deviating more or less to the right side 

 of that vessel, and accompanies it to about the sixth dorsal vertebra, in passing 

 to the outside of the right intercostal arteries, which it crosses, and beneath the 

 vena azygos, beside- which it lies. Sometimes, however, we find it carried in this 

 first part of its course directly above the thoracic aorta, between the double 

 series of intercostal arteries, and to the left of the vena azygos, which is then 

 found immediately in contact with the right side of the aorta ; or it may even 



