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Show 86 Ramg'firaiiom, Anastomoses, Number, and Size, this way the vesicula: seminales appear cellular; and yet Haller proved, by maceration and dissection of the cellular membrane only, that they could be drawn out into the form of small intestines, or straight tubes; and that it was convolution only, and connection of cellular membrane, which made them put on this appearance. Now, say they, may not the lymphatic glands appear cellular, and yet really be convolutions of vessels? In the first place, it is not possible to do the same thing with these convolutions, supposing them to be such, as Haller has done with the vesiculae seminales. In the next place, though I allow that even in the lymphatic glands of the horse, which are here exhibited engraved, thereis something of the appear- ance of a twisted vessel in the outside View, yet it can never be supposed to be the entering vessel which is thus convoluted, as its diameter is fifty times that of the radiated extremities of the inferens. Again, no convolution of vessel only, can ever account for the lateral communication of some cells, and there being no connection between others. (y tbs Lymp/mtics mzd Lactmls. 87 and even in the dead, previous to any dissection, or removal of the con- neeting substance, the cellular membrane, which in many instances so evi- dently determines the shape of parts, they would always be found forming acute angles :--though this is not always the case, it is very frequently so. The lymphatics ramify pretty much in the same manner as the arteries. The veins ramify as the arteries do, to meet their extremities, to re- ceive their blood. The lymphatics lie on the trunks, and branches, of the arteries, to receive protection and support from the stronger vessels : but though this is frequently the case, there are great exceptions to this rule, and what Haller says of the nerves, is also true here: " Anguli omnigeni." Their branches in some parts are vastly more numerous, and closer together, than those of the blood-vessels. This appearance is frequently to be met with on the external surfaCe of the liver. On the ex- tremities they run in the form oflong parallel tubes, apparently without ra- mifying; on more careful examination, however, I find that this is a de- ception; that they certainly do ramify, though not so much as on the liver ; and the reason why they appear not to ramify is, that a pair of valves are almost always placed at the beginning of every branch, which hinders the injection from passing down. I formerly observed, that this appearance was to be found in the thoracic duct, the trunk ofthe system itself. LymC H A P. XV. phatic vessels, however, frequently do run a long way without i'amifying at 'l‘bu Ramifications, Armslomosas, Number, and Size, (ft/ac LyInp/Jatics (Ind Lacteals. all; sometimes two or three feet, or more. This is different from any thing we find in arteries or veins. The carotids run six or eight inches some- times, and the iliacs nearly as much, without ramifying: but except the ar- teries and veins of the umbilical cord, there is no other instance of the Tue common appearance of arteries and veins, is that oftrees sending off blood vessels running so far without branches. branches ; and the term anatomists employ to express this appearance, is rami- seatcd and a superficial set; these last are very irregular in their course, and fication. Every body knows that the branches Ufa tree are commonly sent The lactcals form a deep- seldom appear to ramify; the former in their mode of ramilying, are not to off, at acute angles, to the trunk; so are the branches of the trunk ofan arte- be distinguished from the arteries and veins, and run exactly parallel to ry: and the reason of this seems to be, that in making an acute angle, they deviate less from the straight line ofthe trunk, and of course less opposition is made to the current ofthe blood. Dr. Hunter would not allow that the branches of arteries made a right, much less an obtuse, angle: they sometimes seemed to do so, but this was a deception that in the living body, and them. 'I‘lielarger lymphatics ofthe lungs have something very peculiar in their appearance, and in general resemble a fishing-net: the areolafi of this larger net-work are filled up with a finer and more intricate net-work of smaller lymphatics; so that the whole external surface of the lungs may, in a very successful injection, be seen covered with lymphatics. In general, we 0an |