LYMPHATIC AND LACTEAL SYSTEM. 



211 



Fig. 50. 



A 



B 



C 



Exhibits three fortns of valves of very frequent occur- 

 rence in the lymphatics, especially in the neighbour- 

 hood of glands, and which are not described in 

 works on Anatomy. ( Taken from specimens pre- 

 pared for the microscope.) Magnified ten diameters. 



A. a, the interior of the vessel. b, b, the 

 valvular flaps composed of the lining membiane 

 only. The attached, the unattached edges, as well 

 as the surface of these flaps, are on the same plane ; 

 they do not perfectly close the vessel. 



B. a, the interior of the vessel, b, the valvu- 

 lar flap of a circular form, resembling the dried 

 pyloric valve of the stomach ; apparently com- 

 posed of the fibrous as well as the inner tunic. 



C represents a combination of the two former. 

 a, the interior of the vessel, b. valvular flaps re- 

 sembling those of A. c, a third fold resembling 

 the circular fold of B. 



in diameter they are frequently not more than a 

 line apart, while in others of half that magni- 

 tude there may be an interval of an inch between 

 them. It has been observed that they are more 

 frequent and closer together in the larger lym- 

 phatics than in the smaller ; this is not always 

 the case ; for instance, the lymphatics of the 

 upper extremity, which are much smaller than 

 those of the lower, have less intervals between 

 their valves ; and in the neck, where the vessels 

 are still smaller, the valves are less distant apart. 

 It appears to me that the valves are much more 

 approximated to each other in the neighbour- 

 hood of the glands, and this observation applies 

 to the vasa afferenlia as well as to the vasa eft'e- 

 rentia, but especially to the latter; from which 

 circumstance the notion may have arisen, that 

 the valves are more frequent the larger the 

 vessel. The valves recur less frequently in the 

 thoracic duct than in any other part of the 

 system. It is not uncommon to find in this 

 vessel an interval of two or three inches in 

 extent without a valvular fold. 



Mode of origin of the lymphatics. The 

 plan I have hitherto adopted in describing 

 the lymphatic vessels has been to present to 

 the reader, first, that which is most readily 



understood, because easily recognizable by our 

 senses, and about which there could be little 

 difference of opinion; but I have now to direct 

 attention to a part of our subject which has 

 hitherto baffled the efforts of all inquirers, viz. 

 the mode of origin of the lymphatic vessels, 

 concerning which the sight, aided by the most 

 powerful glasses, has failed to supply us with 

 satisfactory and demonstrable information. The 

 numerous opinions and conjectures on this sub- 

 ject, only present us with so many instances, of 

 the vain struggles of the human mind, to ad- 

 vance in a strict science of observation, beyond 

 the limits assigned to our senses, and of the 

 unwillingness, even in the philosopher and man 

 of science, to acknowledge the weakness and 

 limited range of his faculties. 



When we consider the transparency of the 

 coats of the lymphatic vessels, as well as of their 

 contents, the small size of their secondary 

 branches, and the numerous valves they every 

 where present, we cannot feel surprised that 

 their precise origin should be involved in 

 much obscurity. From the opaque natuie of 

 the chyle, it might be imagined that while the 

 vessels were distended with this fluid, the 

 anatomist would be enabled to trace them to 

 their commencing branches, but unfortunately, 

 it is almost impossible to prevent the onward 

 motion of the chyle in the vessels first re- 

 ceiving it, while the valves offer a complete 

 barrier fo any retrograde movement. Added to 

 which, the opacity of the coats of the intestine 

 renders it extremely difficult to follow these 

 vessels from the peritoneal surface of the outer, 

 to the villous surface of the inner tunic, even 

 when distended with chyle. Transparency of 

 the coats of the intestine may be obtained by 

 drying, but the chyle becomes transparent at 

 the same time. Various modes of investigation 

 have been adopted by anatomists to overcome 

 these difficulties, the principal of which it mav 

 be necessary here to mention. Injections of 

 quicksilver or coloured fluids have been thrown 

 into the arteries, by which means the injection 

 has occasionally made its appearance in the 

 lymphatic vessels : this result occurs, accord- 

 ing to Panizza, in a particular organ in an 

 animal of one species, while in another the 

 experiment will succeed, not in the same, but 

 in some other organ. Thus he succeeded in 

 filling the lymphatics from the arteries, in the 

 intestines of the dog and pig; in the liver of 

 man, the horse, and dog ; in the testicle of the 

 dog and bull; in the penis and spleen of the 

 horse. lie was unsuccessful in the intestines 

 of man, the horse, birds, the salamander, and 

 the tortoise ; in the liver of reptiles ; in the 

 spleen of man, the dog, and the pig ; in the 

 kidneys of mammalia and birds; in the penis 

 of man and the dog. 



Breschet is of opinion that injections by the 

 veins pass more readily into the lymphatic sys- 

 tem. I have now in my possession two prepa- 

 rations where the lymphatics have been acci- 

 dentally injected from the veins ; one in the 

 mesentery of the turtle, the other in the kidney 

 of man ; and I have undoubtedly observed 

 this occurrence much more frequently after in- 



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