214 



LYMPHATIC AND LACTEAL SYSTEM. 



fices on account of the material particles of 

 which this fluid is composed; the lymph they 

 suppose enters the vessels by imbibition through 

 their coats. 



Before alluding to the other opinions on the 

 subject of the origin of the lymphatic vessels, 

 it may be as well to premise the changes 

 which have taken place in our physiological 

 notions with respect to the function of ab- 

 sorption since the time of the Hunters and 

 their immediate successors. Magend^e has 

 proved by numerous convincing experiments, 

 that imbibition does take place in the living 

 as well as in the dead body, not only through 

 the coats of the lymphatics and bloodvessels, 

 but through all the tissues. It has been equally 

 well established by Magendie, Delille, Segalas, 

 Mayer, Emmert, and other physiologists, that 

 we can no longer exclude the veins from parti- 

 cipation in the important function of admitting 

 new and foreign matters into the animal sys- 

 tem. With respect to imbibition, I will select 

 one of many experiments instituted by M. 

 Magendie. lie exposed the external jugular 

 vein in a dog, and having separated it from its 

 cellular attachments, placed a piece of card 

 underneath the vessel so as to isolate it from 

 the surrounding parts. He now applied to the 

 centre of the vein a watery solution of the 

 spirituous extract of nux vomica. In four mi- 

 nutes the symptoms of poisoning made their 

 appearance. If then it be admitted that imbibi- 

 tion takes place in the living textures, there can 

 be no longer an absolute necessity for open 

 mouths to the origins of the absorbing vessels, 

 and it follows that the lymphatics cannot be the 

 sole agents in the process of absorption. 



I will now adduce some experiments con- 

 ducted by different physiologists, proving the en- 

 trance of various substances into the livinganimal 

 system by other channels than the lymphatics. 

 Magendie divided all the structures of the 

 hind leg of a living dog, with the exception of 

 the femoral artery and vein, through which the 

 circulation was carried on. He then inserted 

 the upas tieute poison into the foot of the 

 mutilated limb. The animal was poisoned in 

 the usual space of time required for this sub- 

 stance to take effect. He repeated the same 

 experiment with the additional precaution of 

 placing inert tubes into the artery and vein, 

 and afterwards dividing these vessels, leaving 

 the limb connected to the trunk by the tubes 

 only, through which the blood passed to and 

 from the limb ; the same effect followed on the 

 introduction of the poison. 



Mayer injected a solution of prussiate of pot- 

 ash into the lungs of an animal : in from two 

 to five minutes after the injection, the serum 

 of the blood, tested by a salt of iron, gave 

 evidence of the presence of the prussiate of 

 potash by the usual green or blue precipitate. 

 It was detected in the blood long before it 

 could be perceived in the contents of the tho- 

 racic duct, and in the left side of the heart be- 

 fore it appeared in the right. It was therefore 

 evident that the pulmonary veins and not the 

 lymphatics had first received the prussiate of 

 potash and conveyed it to the heart. Segalas 



included a piece of intestine between two liga- 

 tures in a living animal, and tied all the blood- 

 vessels leading to it excepting one artery ; the 

 lacteals were left uninjured and pervious ; an 

 aqueous solution of nux vomica was now in- 

 jected into the piece of intestine and there 

 secured for an hour without producing any 

 symptoms, but on removing the ligature from 

 one of the veins, the poison took effect in six 

 minutes. The converse of this experiment was 

 performed by Magendie and Delille. A por- 

 tion of intestine of a living animal was in- 

 cluded between two ligatures ; the lacteals pro- 

 ceeding from it were ligatured and divided, 

 the bloodvessels being left pervious. A so- 

 lution of nux vomica thrown into this piece of 

 intestine destroyed the animal in six minutes. 

 Emmert applied a ligature to the abdominal 

 aorta in a dog, and afterwards inserted prussic 

 acid into the foot of one of the hind legs; no 

 ill effects followed in seventy hours ; the liga- 

 ture was then removed, and in half an hour 

 symptoms of poisoning appeared. 



In addition to simple imbibition, Dr. Dutro- 

 chet has shewn that fluids situated in contact with 

 animal membranes permeate them in obedience 

 to certain laws. When two fluids of different 

 densities are in contact with the opposite sides 

 of a membranous septum, they both permeate 

 it, but with different degrees of rapidity. The 

 more rapid current takes place from the rarer 

 to the denser fluid; to this he applies the term 

 of Endosmosis : the slower current from the 

 denser to the rarer fluid he calls Exosmosis. 

 These remarkable powers must be continually 

 in action in the animal machine, composed as 

 it is of solids and fluids, and cannot for the 

 future be lost sight of in considering the sub- 

 ject of the absorption and deposition of fluids 

 in a living animal, or the arrangement of the 

 structures by which these important functions 

 are accomplished. Taking these facts into con- 

 sideration, and bearing in mind the experi- 

 ments above detailed, we are led to the con- 

 clusion, that the capillary bloodvessels and 

 even other tissues imbibe indiscriminately 

 fluids brought in contact with them, and appa- 

 rently in obedience to the physical or mecha- 

 nical laws regulating imbibition, rather than in 

 virtue of any new and essential agency with 

 which they may be endowed as living struc- 

 tures ; while the lymphatic system is left in 

 possession of a higher grade of absorption ac- 

 companied with an elective power (especially 

 manifest in the lacteals) existing only with life, 

 and if not entirely independent of mechanical 

 or physical laws, at any rate frequently at 

 variance with them ; by this elective power 

 they are enabled, to a great extent, to refuse 

 materials injurious to the economy of the 

 animal, and to select those alone which may 

 be made subservient to the nutrition of the 

 system. 



These physiological considerations will pre- 

 pare us better for the examination of the re- 

 maining theories on the mode of commence- 

 ment of the lymphatic vessels. We shall next 

 enter upon that which ascribes to them an 

 origin from the cellular tissue. Fohmann has 



