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LYMPHATIC AND LACTEAL SYSTEM. 



Syn. Absorbent system.) The lymphatic sys- 

 tem is composed, in the fust place, of the 

 vessels which collect and convey the lymph 

 from all parts of the body and the chyle from 

 the intestines, and ultimately deposit them in 

 the veins. Secondly, of the small fleshy bo- 

 dies called conglobate, lymphatic, or absorbent 

 glands, which are found connected with this 

 system of vessels in various parts of their 

 course. 



The lymphatic system is confined to the 

 class Vertebrata. It is the least complicated 

 in Fishes, and consists in them simply of pel- 

 lucid valveless vessels. In Reptiles, also, it 

 is composed of these vessels only, but which 

 are armed with more or less perfect valves. In 

 the two higher orders of Vertebrata, Birds and 

 Mammalia, to the vessels containing very nu- 

 merous and perfect valves, the conglobate 

 glands are superadded : in all, however, the ter- 

 mination of the system is in the veins, and its 

 origin and general arrangements are probably 

 in all essentially the same. 



The different parts of the lymphatic system 

 had escaped the notice of anatomists until the 

 middle of the sixteenth century, and the entire 

 system was not discovered till the middle of 

 the seventeenth. I must here except the lym- 

 phatic glands, which from their large size must 

 have been observed by the earliest anatomists, 

 and we accordingly find them alluded to by 

 Hippocrates, who classed them with the other 

 glandular organs. 



The first isolated discovery in the vascular 

 part of this system was made by Eustachius in 

 1563, who saw and described accurately the 

 thoracic duct in a horse. He called it the 

 vena alba t.'ioracis, and traced it downwards 

 from the left subclavian vein to the lumbar ver- 

 tebrae, where he noticed the dilatation now 

 called the receptaculum chyli ; he however had 

 no conception that it formed the trunk of a se- 

 parate system of vessels, but conceived it to be 

 a vein of a peculiar kind. Fifty-nine years af- 

 terwards, in the year 1622, Asellius was fortu- 

 nate enough to discover the lacteal vessels on 

 the mesentery of a dog ; and although on the 

 following day he was much disappointed in not 

 being able to see them in another dog in- 

 spected for the purpose, by continuing his re- 

 searches he soon convinced himself of their ex- 

 istence in most animals. He also attributed to 

 them their proper function, having remarked 

 that whenever there was chyle in the intestines, 

 these vessels also contained a white fluid, and 

 could then only be seen. He failed, however, 

 to connect the vena alba thoracis, the discovery 

 of Eustachius, which had probably been for- 

 gotten, with his own, and mistaking the lym- 

 phatics of the under surface of the liver for the 

 continuation of his vessels, was led into the 

 error of supposing them to terminate in the 

 liver. Asellius, who died in 1626, had not 

 seen the lacteals in man, but inferred and as- 

 serted their existence. According to Haller, 

 Veslingius was the first who saw these vessels 

 in the human subject, in the year 1634; but 

 Breschet informs us, in his Systeme Lympha- 

 tique, page 4, that, "en 1628, les lympha- 



tiques du me"sentere furentaperpus pour la pre- 

 miere fois chez 1'homme. Peiresc, Senateur 

 d'Aix, informe par Gassendi de la decouverte 

 qu' avail faite Aselli, distribua plusieurs exem- 

 plaires de 1'ouvrage de ce proffesseur aux me- 

 decins de sa connoissance, et leurabandonna un 

 criminel condamne a mort, pour verifier le fait 

 sur son cadavre. On fit hien manger cet 

 hornme avant de le conduire au supplice, et 

 une heure et demie aprbs sa mort, 1'ouverture 

 du bas ventre montra le mesentere tout cou- 

 vert de vaisseaux lacts pleins de chyle." 



The thoracic duct was rediscovered in the 

 year 1649, by Pecquet, who published a de- 

 scription of it in 1651. Haller ascribes this 

 discovery to Veslingius : " Idem Veslingius, 

 nisi plurimum fallor, primus post Eustachium, 

 contra omnes coEetaneos, rectius anno 1649, 

 vidit vas lacteum grande, in pectus adscendere ; 

 cum reliqui incisores, partim ab Asellio per- 

 suasi, et partim a lymphaticis vasis hepatis se- 

 ducti, chyliferos ductus ad hepar ducerent." 



It now became evident that the thoracic duct 

 was the trunk of the vasa lactea, and that the 

 chyle was not conveyed to the liver, as Asellius 

 supposed, but was poured into the venous sys- 

 tem at the union of the subclavian and internal 

 jugular veins of the left side. The lymphatics 

 of the under surface of the liver were soon after 

 shewn by Glisson and Veslingius to have their 

 valves so arranged as to convey their contents 

 from, and not to this organ. 



In the two or three following years the rest 

 of the lymphatic system was discovered by 

 Rudbeck in Sweden, by Bartholin in Den- 

 mark, and by Jolyffe in this country ; nor was 

 it long before the function of absorption was 

 ascribed to it by Glisson, in 1654, and by 

 Hoffmann. Since this period, we have been in- 

 debted for various details of the arrangement of 

 this system of vessels in man and other Mam- 

 malia, in Birds, in Reptiles, and Fishes, to 

 numerous investigators, Nuck, Ruysch, Albi- 

 nus, Meckel, Hunter, Monro,Hewson, Cruick- 

 shank, Sremmerring, Mascagni ; and in the pre- 

 sent day to Fohmanu, Lauth, Lippi, Rossi, 

 Panizza, and other continental anatomists. 



The lymphatic vessels in the human subject 

 are exceedingly delicate and transparent tubes, 

 numerous but small, existing in most if not 

 in every part of the organism, crowded 

 with valves, and terminating, after passing 

 through the glandular bodies, in two princi- 

 pal trunks, through which the contents of the 

 whole system are emptied into the circulating 

 venous blood at two corresponding points not 

 far distant from the heart, viz. at or close to the 

 angles of union between the subclavian and 

 internal jugular veins. The two trunks of the 

 lymphatic system are by no means symme- 

 trical. That which enters the veins on the left 

 side measures as much as sixteen or eighteen 

 inches in length in the adult human subject. 

 It commences in the abdominal cavity by 

 a slightly marked dilatation, the receptaculum 

 chyli, into which the chyliferous vessels pourtheir 

 contents ; it then passes through the thorax to 

 reach its termination in the neck. This trunk 

 is usually termed the thoracic duct ; it may 



