ABSORPTION. 



23 



exists between them during their course, and 

 we are not aware of any physiological cause of 

 this arrangement. 



With respect to the mouths or origin of the 

 lymphatics there is even more uncertainty than 

 with respect to that of the lacteals ; no anato- 

 mical investigation has hitherto been able to 

 detect them, and although numerous facts of 

 constant occurrence would seem to prove that 

 their capillary extremities are distributed over 

 all the surfaces of the body, it is from various 

 pathological observations and from the analogy 

 of the lacteals that we arrive at this conclu- 

 sion.* 



The thoracic duct is a vessel of considerable 

 size, which is situated near the spine, and 

 which extends from about the middle of the 

 dorsal vertebrae to a short distance above the 

 left subclavian vein ; here it assumes an arched 

 form, and is bent down until it enters the vessel 

 near its junction with the jugular vein of the 

 same side.-f The duct, in its passage along 

 the spine, is deflected in various ways, and 

 proceeds in a somewhat irregular or tortuous 

 course. For the most part it consists of a 

 single trunk, but occasionally there are two 

 trunks, either of the same or of different sizes, 

 and we have not unfrequently partial appen- 

 dages, which are added to the main trunk in 

 different parts of its course. J Besides what is 

 properly considered as the thoracic duct, in 

 which all the lacteals and the greatest part of 

 the lymphatics terminate, a portion of these 

 latter, especially those which proceed from the 

 upper part of the body and from the superior 

 extremity of the right side, are generally col- 

 lected into a separate trunk, named the great 

 right lymphatic vessel, or right thoracic duct, 

 which is connected with the right subclaviau 

 vein." These irregularities in the disposition 

 and form of the thoracic duct may be consi- 

 dered as in no respect affecting its physiological 

 uses, and to be no more than an anatomical 

 variation of structure, probably depending 



* Sec Magendie, Physiol. t. ii. p. 175. Watson, 

 however, conceived that he had detected their open 

 mouths on the surface of the bladder, Phi). Trans, 

 for 1769, pi. 16. Monro, in speaking of the lym- 

 phatics of fishes, remarks that there is ' no doubt 

 that they begin by open mouths," p. 30. 



t For descriptions and plates of the thoracic duct 

 the following works may be referred to; Haller, 

 Prim. Lin. c. xxv, 565 ; Op. Min. t. i. p. 586 

 et seq. tab. 11, 12 ; and El. Phys. xxv. 1. 10 . . 3 : 

 Albinus, Tab. Vas. Chylif. ; Bolius and Saltzmann, 

 in Haller, Disp. Anat. t. i. ; Cheselden, Anat. 

 pi. 26; Portal, Mem. Acad. pour 1770; Sabatier, 

 ibid, pour 1786 ; Haase, De Vas. Cut. et Intest. 

 Abs. tab. 2. and tab. 3. fig. I ; Mascagni, ps. i. 

 sect. 7. art. 8. tab. 13, 15, 19; Sheldon, pi. 5; 

 Cruikshank, p. 166 . . 176 ; Magendie, Physiol. t. ii. 

 p. 160; Meckel, Manuel, $ 1698. 



J In Mascagni, tab. 15, we have an example of 

 this irregularity. 



Phis is said to have been discovered by Stenon 

 in 1664; Meckel, Manuel, $1703. See Haller, 

 Prim. Lin. $ 766 and Hewson's Enq. pt. 2. p. 61 . . 3, 

 pi. 4. Cruikshank, p. 176, 7, conceives that Hew- 

 son was the first who described the lymphatics of 

 tho right side as being collected into one trunk. For 

 the figure of this part, see Mascagni, tab. 19. nos. 

 185, 187. 



upon some mechanical cause. It is, however, 

 a circumstance of considerable importance in 

 respect to the pathological conclusions that 

 have been sometimes drawn from the obstruc- 

 tions of this organ, as well as from the experi- 

 ments that have been performed upon it.* The 

 structure and properties of the thoracic duct 

 appear to be similar to those of the large trunks 

 of the lacteals and lymphatics; its coats are 

 comparatively thin and transparent, yet it is 

 possessed of considerable strength, and is ca- 

 pable of being distended much beyond its 

 ordinary bulk ; it is furnished with numerous 

 valves, and exhibits a great degree of con- 

 tractility. 



The lymphatic or conglobate glandsf com- 

 pose a very important part of the absorbent 

 system, if we may judge from their number 

 and their general diffusion over every part of 

 the body. They are of various sizes, and are 

 grouped together in various ways; occasionally 

 they are single, but more frequently connected 

 together in masses of considerable extent. They 

 are found in almost every part of the body, 

 always connected with the lacteals and lympha- 

 tics, and it is asserted that each one of these ves- 

 sels, in some part of its course, passes through or 

 is connected with one or more of these glands.]; 

 There are certain parts of the body in which 

 they are more numerous, and are connected in 

 larger masses ; the lacteals are furnished with 

 numerous glands in their passage along the 

 mesentery, while the glands that belong to the 

 lymphatics are found in the greatest number 

 and largest masses in the groin, the axilla, and 

 the neck. It is necessary to remark that this 

 account of the distribution of the lymphatic 

 glands applies only to the animals which belong 

 to the class of the mammalia; in birds they are 

 much more rare, and still more so in fish, while 

 among the lower animals, where we have suffi- 

 cient evidence of the existence of an absorbent 

 system, the glands have not yet been satisfac- 

 torily demonstrated. 



With respect to the structure of these glands, 

 as well as that of glands of other descriptions, 

 a controversy has long existed among anato- 

 mists, whether they consist of a series of cells 

 or follicles, as they have been termed, or whe- 

 ther they are composed simply of a congeries 

 of vessels. The question may be regarded as 

 still at issue ; but it may be remarked that 

 whereas the older anatomists generally leaned 

 to the opinion of the follicular structure of the 



* See on this subject Sir A. Cooper, in Med. 

 Rec. and Res. p. 86 ct seq., and Magendie, 

 Journ. t. i. p. 21. 



t Some of the late French physiologists prefer 

 the term lymphatic ganglions, upon the principle 

 that the term gland more properly belongs to an 

 organ of secretion. 



Mascagni, ps. 1. sect. 4. p. 25: but this h s 

 been doubted by some anatomists; see Hewson, pt.2. 

 p. 44, 5. 



See Fleming's Zool. t. i. p. 338 ; Blumenbach's 

 Comp. Anat. by Lawrence, ch. xiii. p. 256 ; Diet, 

 des Sc. Med. art. " Lymphatique," par Chaussier 

 et Adelon, p. 249; Breschet, art. " Lymph. 

 Syst.," Diet, de Med. t. xiii. p. 397. Hewson in- 

 forms us that birds have lymphatic glands in the 



