if we except fome effays in Dr. Hunter's Medical Commentaries, Dr. Monro's firft publication at Berlin, and Mr. Hewfon's fhort account in the Experimental Enquiries, we have yet received little information on the fubject. We mean not to neglect Mr. Sheldon; but he has not yet exceeded the limits of what was formerly known, and has been frequently defcribed. The lymphatic fyftem, in its ftricter meaning, will be the fubject of his fucceeding volumes. Dr. Hunter, we find, always intended to have published a particular account of the lymphatics; and, when we recollect with what elegance and accuracy he has illuftrated the only fubject which he has explained by plates, the gravid uterus, we must regret that he did not accomplish his defign. If Mr. Sheldon proceeds with the fame precifion and elegance which diftinguish his first engravings, we fhall have fuftained little lofs. Mr. Cruikshank does not endeavour to attract attention in this way, yet the three plates with which this volume is illuftrated, are executed with no little care.

In this work Mr. Cruikshank gives not only a hiftory of the discovery, but he traces the doubtful hints, and uncertain language of former anatomists, who fometimes faw what they did not fully comprehend. A flight attention, and in attention the ancients were by no means deficient, would have fhown that effufed fluids difappear, and were in reality abforbed. The organs, for this purpose, they supposed were the red veins; and indeed the arguments were fo ftriking, and feemingly fo conclufive, that the earlier fupporters of distinct absorbent vessels were almost compelled by the force of evidence to allow, that red veins fometimes abforbed, or that lymphatics terminated very foon in these vessels, without paffing the tedious circuit of the thoracic duct. More careful enquiries have at last demonstrated, that the arguments which seemed so strong are really fallacious; and it appears now to be well established, that the absorbents, as a fyftem, are independent of the veins, till their united contents pass slowly into the fubclavian. In this whole enquiry, Mr. Cruikshank examines the fentiments and experiments of different authors, with precifion and candour. He appears well acquainted with what others have faid, and capable of deciding on intricate fubjects of this kind.

After having fhown how to difcover the lymphatics, he defcribes their coats, their valves, the glandular bodies which they pass through, their ramifications, anastomoses, number, and fize. The coats, he thinks, are irritable and mufcular; and the fluids are propelled by their contractions, while the valves prevent any regurgitation. Whatever be the power, while

6

while the body is in health, fluids circulate through them with great rapidity.

Anatomifts have differed in defcribing the ftructure of the lymphatic glands. While experiments were uncertain and contradictory, we thought that reafoning might be allowed to affift them; and when we perceived the great caution with which nature endeavours, in animal bodies, to prevent any substance that may be injurious from mixing with the general mafs; while many bodies, apparently mild, are found to be highly fo, we were led to confider the glands as receptacles for the new nourishment, in which it is to be mixed and blended with fluids already animalized, previous to its admiffion into the red veins. This was fupported by finding the vessels which brought the fluids to the gland minutely divided, as if it were to distribute the new fupplies to their several cells; and the veffels that carry them away equally minute, seemingly for the fame reafon. But there was this effential difference: the vafa efferentia foon joined to make larger veffels than those which entered the gland; and the veffels united into larger trunks the nearer they were to the thoracic duct. So far went reason; let us now attend to experience.

From what has been faid, it will appear, that it is no eafy matter to unravel the ftructure of the lymphatic glands. I fhall faithfully relate what has occurred to me, having been very much occupied in injecting these glands with quickfilver. If the glands are completely injected with quickfilver, and then examined in the microfcope, it is certainly true, as profeffor Mekel has obferved, that nothing but convolutions of lymphatic veffels are to be seen in many inftances; but it is as true, that after the most fuccefsful injections of thefe glands, the cells have been seen perfectly diftinct. I have injected many glands, where there was not the least appearance of a convoluted vessel, and where the radiated branches of the inferens and efferens, with intermediate cells only, were to be found; but I never injected a lymphatic gland, where I did not fee fome cells, particularly if I was attentive to the mercury just as it entered the gland, Accordingly, one of the best methods of fhewing thefe cells, is ftopping the injection after the gland is half filled; the cells are then exceedingly evident. But if the injection goes on, the cells are covered over with ramifications of finer veffels, entering thofe cells, and injected contrary to the valves. I have injected thefe into the furrounding cellular membrane itfelf, in the human fubject. In quadrupeds it is very easy to demonftrate the cellular structure: both in affes and horfes the glands on the mefentery are most distinctly cellular, as will be feen in the annexed engravings. In the former, the cells are diftinct, without any other diffection or preparation of the glands than merely injection; but in horfes it is neceffary to

dry

dry them, and afterwards lay them open; the cells then appear like thofe of a honey-comb, and briftles may be paffed from one fet into another, by lateral perforations, as is feen in the plates. When there is but one vas inferens and one efferens, there is but one fet of cells; but when there are many, each appear to have their proper cells; and thefe cannot be injected from the other cells, but only by their own inferentia.

It has been alleged by fome, that cutting into a lymphatic gland, and obferving the appearance of cells, is no proof that it is actually fo. In this way the veficulæ feminales appear cellular; and yet Haller proved, by maceration and diffection of the cellular membrane only, that they could be drawn out into the form of small intestines, or ftraight tubes; and that it was convolution only, and connection of cellular membrane, which made them put on this appearance. Now, fay they, may not the lymphatic glands appear cellular, and yet really be convolutions of veffels? In the first place, it is not poffible to do the fame thing with these convolutions, fuppofing them to be fuch, as Haller has done with the veficulæ feminales. In the next place, though I allow that even in the lymphatic glands of the horse, which are here exhibited engraved, there is fomething of the appearance of a twisted veffel in the outfide view, yet it can never be fuppofed to be the entering veffel which is thus convoluted, as its diameter is fifty times that of the radiated extremities of the inferens. Again, no convolu tion of veffel only can ever account for the lateral communication of fome cells, and there being no connection between others.'

Our author's obfervations on the ramifications of lymphatics, and the termination of this fyftem in the jugular and fubclavian veins, are very correct and ingenious. We defer enlarging on these subjects only on account of their making our article too extenfive.

Of the origin of the lacteals we have not spoken in the proper order, because the subject is'in fome degree connected with their offices. We have explained Lieberkuhn's opinion in our Fifty-fifth Volume, p. 103. That author's ampullula, the veficle, mentioned in our article, and the spongy body, in the following extract, relate to the fame appearance. Mr. Cruikshank's obfervations are comprifed under the fubfequent heads.

1. Many of the villi were fo full of chyle, that I saw nothing of the ramifications of the arteries or veins; the whole appeared as one white veficle, without any red lines, pores, or orifices whatever.

2. Others of the villi contained chyle, but in a small proportion; and the ramifications of the veins were numerous, and prevailed, by their redness, over the whiteness of the villi.

3. In

3. In fome hundred villi, I faw a trunk of a lacteal, forming or beginning by radiated branches. The orifices of thefe radii were very diftinct on the furface of the villus, as well as the radii themselves, feen through the external furface, paffing into the trunk of the lacteal, they were full of a white fluid. There was but one of these trunks in each villus.

4. The fpongy cavity, which Leiberkuhn fpeaks of, appeared clearly to be the common cellular membrane, connecting all the arteries, veins, nerves, and lacteals together.

5. The orifices on the villi of the jejunum, as Dr. Hunter himfelf faid (when I afked him, as he viewed them in the microscope, how many he thought there might be) were about fifteen or twenty on each villus; and in fome I saw them ftill more numerous. I have, on a former occafion, described thefe orifices as appearing in a bulbous extremity of the lacteal; but repeated examinations of the villi, under fimilar circumstances, have now taught me the real ftructure of their orifices and primary branches. They arife out of the lymphatic glands exactly in the fame way, that is, by fmall orifices belonging to radiated branches, which prefently unite to form one veffel. Every effort I have made to detect the orifices of the lymphatics, has hitherto been ineffectual. I have looked for them on the villi of the lips, villi of the toes and fingers; but we have not there the opportunity of finding them filled with a white fluid, as in the inteftines. This circumftance, however, when it is confidered that lacteals and lymphatics are the fame veffels, is probably of no confequence. There may be fome little variety, but the orifices and beginnings we may confider, from fo great analogy in other refpects, as very much refembling each other.'

Mr. Cruikshank does not fuppofe that these vessels act in absorbing, on the principle of capillary tubes, because their action is neceffary, uniform, and conftant; while lacteals may be immersed in chyle, and lymphatics in ferum, without any abforption taking place. From the obfervations which we have juft felected, we think this fubject may be easily explained. The apparatus of an artery, a vein, and a nerve, feems to fhow that the veffel must be in different ftates, depending on the condition of the vital and animal powers. From what we perceive in the villi of the tongue, it is probable, that the extremity of the lacteal must be raised, to perform its office; and we shall want few arguments to fhow that, if the lacteals act by capillary attraction, it cannot be in the state of pendulous veffels. Each lacteal must be erected for that purpofe, its orifice must be expanded, and all this will depend on the state of the animal economy; fo that the action cannot be conftant and indiscriminate. We fhall allow that there is a power of felection in the lymphatics. If the body is immerfed in falt

8

water,

water, the aqueous particles will be abforbed, and the falt excluded: fome poisons are also innocent by being taken into the ftomach. We cannot well explain these subjects, but they are as confiftent with capillary attraction as with any other hypothefis, except that of an intelligent power refiding in thefe orifices. In the case of falt-water, we may lean fo far towards the corpufcular philofophy as to fuppofe the particles of falt too large to pass through the orifices of the lymphatics, though they undoubtedly are admitted, when in a very dilute ftate, through the lacteals. Other bodies, we may fuppofe, produce a strong contraction in their mouths by excefs of ftimulus, or may render the nerve inactive by a contrary power. We have not a fingle proof that bark, in the finest substance, or opium unchanged, enters the blood-veffels. Though very ftimulating fubftances are sometimes abforbed, it is only after they have been at least diluted, probably changed in the ftomach.

Mr. Cruikshank feels a difficulty in explaining how folids are abforbed. We cannot affift him; but we fufpect that, in the greater number of inftances, it is dead folid matter that is taken up, and we can then easily suppose it gradually diffolved, while the parts in folution are continually absorbed, We know that there is a conftant regular circulation of the subftance of the folids; but, as new matter is neceffarily depofited in a fluid form, a menftruum is provided for that which is to be abforbed.

Our author's obfervations on dropfies are particularly valuable, but they are too long to be inferted. We fhall felect a fhort paffage, which is clear, and we believe correct, as it relates to the depofitions laiteux, mentioned in one of our foreign articles, and elucidates that fubject.

• After a woman has lain-in fome days, fhe is sometimes taken with shivering, and other symptoms of fever; her milk difappears, the fever goes on, and fhe dies. On opening the body, the cavity of the abdomen has on fuch occafions been found full of a whey-coloured fluid mixed with laminæ of coagulated white matter. The fever, by many, has in this cafe been attributed to the abforption of the milk from the breaft, and its being carried into the blood-veffels; believing the appearances they faw in the abdomen to be from the milk, they have given it the name of dépôt du lait. I do not contend that the milk, in this cafe, is not abforbed; but I believe that milk would do no mischief in the blood-veffels. The appearances in the abdomen are peculiar to the peritoneal inflammasion and would have taken place if the patient had been a male instead of a female. The whey-coloured fluid is the fluid

of