212 



LYMPHATIC AND LACTEAL SYSTEM. 



jections by the veins than by the arteries. 

 Every anatomist who has had much experience 

 in injecting the lymphatic vessels has been in- 

 commoded by the injection passing unex- 

 pectedly into some large vein, and on looking 

 for the communication, he has found the veins 

 from a lymphatic gland conveying the injection 

 into one of the nearest large venous trunks. 

 Tliis has occurred to me frequently in the 

 human subject, where the common iliac veins 

 and the cava inferior have received the quick- 

 silver from the veins of the neighbouring 

 lymphatic glands. I have also seen the same 

 occurrence lately in the horse, and have the 

 specimen shewing the fact now in my museum. 

 It was these veins conveying the injection from 

 the lymphatics into the venous trunks, which 

 Lippi mistook for the vasa efferentia of the 

 glands, and which induced him to publish his 

 work describing many terminations to the 

 lymphatic system in mammalia, hitherto un- 

 known to anatomists. This error was the more 

 excusable, inasmuch as his opinion appeared 

 to be confirmed on the investigation being 

 pursued by himself and others in the remain- 

 ing classes of vertebrate animals, where various 

 communications do actually take place between 

 the lymphatic trunks and the veins. 



Coloured fluids have been thrown into the ca- 

 vity of the pleura and peritoneum in living ani- 

 mals for the purpose of bringing the lymphatic 

 vessels into view, and of tracing if possible their 

 extreme branches after absorption had taken 

 place. In this way it is said that minute vessels 

 anastomosing with each other, and forming a 

 delicate net-work, may be made apparent on the 

 surface of the serous membrane, and that the 

 trunks of the neighbouring lymphatics may be 

 seen filled with the coloured fluid. In post- 

 mortem examinations also, the absorbent vessels 

 have been observed distended with a fluid of a 

 yellow or red colour, where effusions of pus 

 or blood had taken place during life. In all these 

 instances we probably first notice the injection 

 in the larger lymphatic vessels which are easily 

 recognized by their numerous valves, and on 

 tracing these back to their commencing branches 

 we only discover an intricate net-work of mi- 

 nute vessels apparently continuous with each 

 other. It is exceedingly difficult to distin- 

 guish these from equally small branches of 

 artery and vein, filled probably with the same 

 coloured injection. You look in vain for the 

 channel by which the injection has entered 

 these vessels; no continuity of lymphatic with 

 the minute twigs of the other sets of vessels 

 can be detected ; no open orifice belonging to 

 either can be distinguished. Many anatom- 

 ists have endeavoured to fill the commencing 

 branches of the lymphatic system by forcing 

 the injection, thrown into them, in a retrograde 

 direction, and in fishes where there are no 

 valves, with the effect of shewing very nume- 

 rous lymphatic vessels destitute of orifices, but 

 not so universally distributed as has been 

 imagined. 



Fohmann, Breschet, and others have simply 

 made a puncture in the tissues, and by forcing 

 quicksilver into the wound, have occasionally 



succeeded in filling a minute net- work of lympha- 

 tics. Cruickshank and Hewson employed liga- 

 tures to the thoracic duct, to the larger lympha- 

 tics, or simply round the limb immediately pre- 

 vious or subsequent to the death of the animal, 

 for the purpose of distending the radicles of the 

 system. Lastly, the microscope has been had 

 recourse to by most observers. But the pre- 

 vailing physiological opinions of the day have 

 had more influence than all our anatomical in- 

 vestigations in determining our notions of the 

 mode of origin of the lymphatic vessels. In- 

 deed, so much lias this been the case, that I shall 

 find it convenient, in treating the subject of the 

 origin of these vessels, to refer to the physio- 

 logical views of the periods during which the 

 successive opinions have been broached. The 

 only other observation I shall make on entering 

 upon this difficult and still obscure subject is, 

 that the chyle seen on the coats of the in- 

 testine, contained in its proper vessels, so near 

 to the villous tunic, has tempted anatomists to 

 confine their observations perhaps too much 

 to this one-absorbing surface, with the fixed 

 intention of applying the information thus 

 gained, to the whole system ; whereas the fluid 

 contained in the chyliferous vessels differs so 

 much from that of the rest of the system, that 

 it is not very improbable that the former which 

 admit particles of matter should possess ori- 

 fices, while the latter should receive its con- 

 tents by imbibition without perceptible orifices, 

 which, in fact, is the opinion held by two emi- 

 nent physiologists, who have paid considerable 

 attention to the subject, Magendieand Cruveil- 

 hier. The first opinion with respect to the 

 mode of origin of the lymphatic vessels which 

 I shall consider is that by open orifices. 



Many investigators at various periods have 

 attributed open orifices to the radicles of the 

 lymphatic vessels; indeed, this has been the 

 prevailing opinion till within the last few 

 years. Asellius, the discoverer of that part of 

 the system which is connected with the intes- 

 tines, imagined that his " vasa lactea " com- 

 menced by open mouths from the interior of 

 the intestine. His words are, " ad intestina 

 instar hiant spongiosis capitulis." The first dis- 

 coverers of the rest of the system, the " vasa 

 lymphaticu," did not attribute to them the func- 

 tion of absorption, but regarded them as destined 

 to assist the veins in returning the circulating- 

 fluids to the heart. They supposed them, there- 

 fore, to be continuous with those arteries which 

 admitted a colourless fluid only, while the 

 veins in a similar way received their contents 

 from the arteries conveying the red blood. The 

 lymphatics properly so called were not consi- 

 dered to possess open orifices at their origin, 

 until they were generally recognized as sharing 

 with the lacteals, the important office of absorb- 

 ing fluids, as well as conveying them towards 

 the heart. It was not fairly established until 

 the time of the Hunters, that these vessels 

 formed part of the absorbent system, although 

 Glisson and Hoffmann had expressed their 

 opinion to this effect, a few years after the dis- 

 covery of the lymphatic vessels. But to do 

 justice to this part of our subject, it will be 



