Section 1.
OP TUB LYMPHATrc VESSELS.
The lymphatic vessels, which arc also termed from their office absorbents, form an important part of the vascular system ; they are more especially connected witli tlie veins, of which, indeed, they may be consi- dered as forming an appendage. These vcissels, in con- 8C(|uence of their tenuity and of the transparency of the 6uid they contain, ore more difficult to perceive than U)c arteries or veins. This indistinctness was doubtless the cause of the lymphatics remaining during a long period unknown ; so that their existence was only first satisfactorily ascertained about two hundred years ago, although it is certain that the ancients knew sumethiog of absorption, which tliey thought was accomplished by the veins and arteries. Tlie important discovery of this
3)0
U IMSCOVBftV. ar.LYMPHATtCa.
sjritco) was commenced br AscUi, an Ilalina anatomUt; who accitlentnlly observed in a dog the lympUalig* yfJ the mesentery, which he named, on account of the white-{ coloured 6uid they contained, vena laetm., He,B{ only discovered these rosiecls, but he uUo poiitt«d out] their use, by stating that tlwy abMirl>ed the ch)k fxoipj :the intestines. The Inctealn were subsequently d«tcct<w| in the human body. The c<immon lymphaticR of the] body were discovered some years afterwards by Rud^i or, according to some authorities, by Joliffe or tfao]ine. A.S these 'es8cls contained a thin watery fluid, they were supposed to be different from the lacteal tolie&H aud to distinguish them, they were called vasa aquogaJ ■ rasa lymphatica, &c. This distinction between the] lymphatic and lactiferous vessels, has been generaHyj retained, and it is even adopted by most anatometsi tlie present day. There is, however, no suHicientrcosonj to justify the division, for the lacteaU ar^- nothing morel than the lymphatics of the intestines, which sometimvij contain chyle, and at other times lymph. .. ,„(
The lymphatic vessels collectively possess an arborts-l cent arrangement, but it is not so striking as in tbel other divisions of the muscular system. In the limbs and in the parietcs of the trunk, they are distributed like tlie veins, in a superficial and dccp-seattd plane. The vea»els | which belong to the former class, are placed under tjiej skin in company with the subcutaneous veins. Tliel deep and larger lymphatics are lodged principally in tlifl' | interstices of tlie muscles, where they surround the trunkal and branches of the arteries. A simiW disposition is J al.so observed in the internal organs, as the lungs, { stomach, liver, &c. ; in these \T8Ccni, one set is mtuat
DtSPOSITIOK AND ANASTOMOSIS.
imme^Iintely lieacath the peritoneal coat, and the other more deeply on the mucous membrane.* -■•"'The principal lymphatic vessels generally obsen-ea Straight course ; in the extremities, for example, they run in the form of long purullcl tubes, which sometimes pftj* Wo or thretf feet, or even more, without presenting 'any mmifieations. It has, however, been truly remarked l>y Oniikshnnk, that the absence of communications ts in most instances only apparent, depending- on the ditfi- dilty of injecting the branches in consequenco of the nuiubcr of tlieir valves. In many parts of the body, as the stomach, intestines, &c., the lymphatics nunil^' in the manner of the arteries ; and in other placciJ, as on the surface of the liver, and still more distinctly on tne luBgs, they form a large network, the areohe of which are filled up with liner and more intricate net- works of smaller lymphatics.
These vessels anastomose withcaeii other most freely. not merely by their small branches, but by iniiiks of large size, which frequently unite and sepamtc again, SO as to form in many places distinct plexuses. It is ''Worthy of remark that when two of these vessels join, the tube which proceeds from them is seldom larger than cither of thum separately. Another peculiar fact con- nected with the anastomosis of the lymphatics, is tliat, "filler they have united to form a trunk, they again "■ttparate into branches, which ramify and subsequently ' ' end in other trunks ; these alternate unions and divisions ' 'occur several limes before the vessels ultimately ter- 'Iminate. The superficial absorbents are particularly dis-
- Thccfuincandnnangi-nieatof UielymplislicvMwUgLii! vay beauliruliy n<pi7s:[itM] lu MdK'»gni'i ii]>lciidid woik, Vasot. Lyinpb. Corp. Hum. TlitL cl khnoginphia.
¥ft
d^W. A*#. «"««»»•
tii^utshed by the freedom of (hMr oomTDiintention : it is .indt-ed ao great, tliul it" all ihoaf vvsftds whicli arci F|iJl^ced .betwe^Q Uie' skin and the cxtiTtuil npoDeuru»M. { cpuld.b^ u^t«dia oneisubject, the body would appear surrounded by a great I)Tnphatie network. ,, The (lispoKitinn of this sy&t^m renders it impnsiuble to mdce an accurate cstiinata of Its total capacity. Tbe difficulty ariiies from tbe circutnstanoc of the lymphatic vc&suls biung dispcTKcd in an tnHnitc number of bmnche*. which bvor no regular proportion to the size uf the trunk in which they terminate; thus Mr. CruikRhank has mentioned several instances in wluch he found branches pqual to, or even surpassing the thoracic duct in magnitude. Without, however, altemplinp any very exact calculation, it may be affirmed that the coUectirc size of the lymphatics is about double that uf tbet arteries.
For the reason just stated, the number of the lym-i phatic ve&seltt is much greater than that of the siteriea^l and veins. This excess is very Ktriking' in the supi-rticial parts of the body, where from ten to twenty, or even 1^ thirty lymphatics m«y be counted accompanying one subcutaneous rein. There arc at least two deep lympha- lies with each artery, and frequently tiierc are four, six, or n)<Hv.
The number of these tubes is subject to cousidvrablei v-ariation in the different organs. They arc extremely numerous in the skin, and in the mucoas membranes, i especially of the small intestines, where they are termed i; lacteals ; also in the testicle, Uver, spleen, luugs, &c • Tbctr number is less in the serous membranes, in the i muBclca, and bones ; and there are yet fewer in cartilap". ■ lif^nent, and tendon. In certain parts of the IxKly, '
OniGlN OP LYMPnATICS.
ai3
although the most careful investigations have been made,' no lymphaticti have been satisfiictorily discovcretl. TTiey' have not been traced in the globe of the eye, in the sub-' stance of the brain or spinal cord ; a few are represented ' in the plates of Mascagni, on the dura mater, and also' on the pia mater. It i^ also generally admitted that the j^Mentu is not provided with lymphatics.
oft'TOk ORimN AND TERMINATION OK THE LYMPHATIC
ltd timi;.' 1 1.
Sbction II.
VKSSBLS.
I
M;:!' ■■■■> '!■ I !
Tns^B vessels arc so extrcmelv minute at their com' ' mencumcut. that it is impossible to stale any thing with ' certainty respecting the manner in which they actually" uiseut IC was formerly thought that the absorbents, like the veins, were directly continued from small artories, : which were therefore called lymphatic arteries. This hypothesis was supported by the (act, that fluids thrown ( into the arteries readily pass into the IjinphaticB. It> has, however, been objected to this statement, that the " injected fluids do not reach the lymphatics immediately ' from the arteries ; but that they are either extravasatcd into the cellular membrane, and thence absorbed, or that they enter the lymphatic tubes by transudation. The majority of anatomists, since the time of Drs. Himtei and Monro, believe that the absorbing vessels begin by open D>ouths or orifices, which are placed on the aur- ' faces of the differeol membmncs, and in the substance '* of tbe various oi^ns. This theory is rendered probable ■ by the observations of Cniikshank, who saw on the villi'
'314
TBRMWATION OrXVMPHATlC*;'"*
l^^fhesniaTl'iritestines.^with the' atrf' cif th* riilci'oftSJj)*,
' 'some hundreds of httle openinffs, which were the arigiBB
I 'of lacteal vessels. It is true that neither. Cruilubiok
I 'hor any«f his succejssors, have been able to pereeive
['orifices of the common tym|>lintics ; but n.s the lacteals
I 'are merely tlie ab«irbents of tlie inlvsUtii's, it bus ham
''contenderl that what is pro%'ett with respect to them
must be admitted of the other partB of the syatenij THi
'widence which has been brought forward on iHrth
of this (jucstion, is so forcible and at the same time so
contradictory, that it is impossible to form a salislactor}'
conclumoii ; and therefore I believe that the miirato oi^nt
of ihc Ijinphatics is one amongst the many points o
minute anatomy, which yet remain to be discox-ered.
The absorbent vessels, as noon b-s they are suffi- ciently large to be perceived, are observed to oom- ' municnte witli each other in the manner alrvady tle- scribetl ; and subsetiueiitly, aftir u longer or shorter course, they appear to terminate in the l)Tnpha(ic glands. Minute inspection shews tnat they do not end in Uiese bodies ; but that, having ramified within them, tJiey;
- still continued onwards, and either pass toother gluiMlSi '' or to the trunks which are supposed to form the com*' ' nion termination of the lymphatic system. Tin} prin- ' cipal trunk is called the tfioraric rfMrf, which receives the nlisorbent-s from the lower half of the body, Uie intt-- rior of the chest, the left upper extremity> and the left ' side of the head and neck. This canal heginn oppnsi ■ to tlic third or second wrtcbra of the loins ; it
upwards on the spine till it reaches the superior part ' Ihc chest; it then crosses obliquely to the left Bide, an eventually empties itself into tlie angle formed hy thel union of the left internal jugular and the left KUbt'lavimt
FRBB COMMUNICATIONS WITH VBINS. 3|5
veins. Iliere ts ronsiderable irregularity in the thomcic duct'i it oft«u dindes into two or roori; large branches, whilst it i^ pluccU in the posterior mediastinum, and 1 have sometimes seen it form a very intricate plexus of Un&ll tubes. The remniniu^ l)'mphatics end in a smaller iirutik on the right side of tlie body, which corresponds in its icrmination to the thoracic duct. It gcnerully happens that there are on each side two or tliree lesser Ijinphatics, which open into the jugular and t^uhdavi&n
-')' The oommiinieations between the lymphatic and vc-
iintnis trunks, which I have just described, were gcnerully
imipposed, until late years, to be the only connexions
existing between the two systems. TTie recent invest!-
puions of several anatomists have, however, proved that
the ahGorl)ent» communicate with the veins in many
Other situations.* It has, for example, been observed
by Fohovinn, thcit meny of the lacteal vessels end in the
Teiiwt of the Mscera ; and Lippi has shewn, that the ab-
eorbents of the abdomen open freely into the neighbour-
. tog venous trunks and branches. According to a late
-writer, t the lymphatics terminiite in three different
mtwles:— 1, They empty themselves, whilst in the very
substance of the different organs, and still being of a
capillary size, into the venous branches. 2. They end
in the small %-eins within the lymphatic glands. 3. They
open by great trunks into tlie large veins of the neck.
These intinuite connexions will explain, as we shall lind
faenoftcr, Uiu cause of many of the discrepancies which
I, . r 'I ■ '
I * It ii ptoptt to Uaic, Ilint Mr. Brncty Cliickc diieovcred, wmc yean ago,
(oraimiiiiciiiiotii IwiBceii the thorocie duel dni! the lumbar vaina in the hone,
— Rrti'f CvrlapwJia, nnicle Anattmy. Vrirrinitrii.
\ idutli, Kiui tur Ics VAiwcatu Lyinpli. Sirtitiovg, iSZi,
M
«t
•<■ (flULTBS.
have occurred in the experimcoto-.on lymphatic ami
yeaouii absorptiun. n jm . >.
Mi> rrttlinrm-i ■ lutl