306 THE LYMPHATIC SYSTEM, BY F. v. RECKLINGHAUSEN. 



lary lymphatics at least, in those organs in which they have 

 been investigated with special reference to this point, as the 

 serous membranes, the walls of the intestine, the diaphragm, 

 both in its muscular and tendinous portion, and the membrana 

 nictitans of the Frog are lined by a single layer of flattened 

 epithelium. They also possess a special membrane, though 

 not completely homogeneous and structureless, as was formerly 

 maintained, nor entirely closed, as we shall hereafter have oc- 

 casion to see. 



I was formerly of opinion, after I had satisfied myself of the pre- 

 sence of an epithelium in the lymphatic capillaries, that I had by this 

 means discovered an essential distinction between them and the blood 

 capillaries ; but, as subsequently it has been shown by experiments 

 with silver that the wall of the capillary bloodvessels, in some organs 

 at least, consists of epithelial cells, the distinction fails. 



The lymphatic capillaries are, in fact, constructed on the same type 

 as the blood capillaries (see the section on the bloodvessels). The ex- 

 istence of such an analogy has been contested, because the blood capil- 

 laries can be easily isolated in portions of considerable length in some 

 organs, as the brain, whilst it is very difficult to exhibit such de- 

 tached portions of the capillary walls of the lymphatics. Very re- 

 cently Frey has been led to the conclusion* that, "whilst in the 

 blood capillaries the walls maintain a perfect independence in regard 

 to surrounding tissues, in the lymphatics they fuse with them." I be- 

 lieve that we must beware of admitting that the blood capillaries are 

 so completely isolable in all organs, or form such independent tubes, 

 as in the brain. In many glands as the liver, for example, not to 

 mention the spleen the wall of the capillary bloodvessels is not 

 capable of being isolated. 



And now arises the question, do the lymphatic capillaries 

 possess a special wall or not ? Admitting an answer in the 

 affirmative, are the above-mentioned phenomena taking place 

 in the resorption of chyle consonant with it ? They would 

 appear to demand that the lumen of the chyle capillaries 

 should not be closed towards the free surface of the mucous 

 membrane. But these appearances can be equally well ex- 

 plained, if we suppose that the wall is not everywhere formed 

 of a continuous solid layer, or, in other words, that it possesses 



* Handluch, p. 427. 



