34 ANATOMY OF THE LYMPHATIC SYSTEM. 



In the lumen of the lymphatic there swim a number of lymph- 

 corpuscles of various sizes, exhibiting amoeboid movements. How 

 easy it is to fail to see the lymphatics in the fresh omentum is shown 

 by the circumstance that, if the membrane is subjected to only a very 

 slight stretching, the lymphatics collapse completely, and appear as 

 nothing else than rows of spindle-shaped elements, between which 

 migratory cells lie here and there. Even in silvered preparations the 

 same source of error exists. I have seen it happen, in a considerable 

 number of silver preparations in which the lymphatics were plainly 

 visible, although their endothelium was only faintly coloured, that, on 

 removing the preparation from one object-glass to another (necessitated 

 by an accident), the lymphatics were no longer to be seen. It is only 

 in the rarest cases that a lymphatic will be seen, unless the omentum 

 be treated in situ with the proper reagents. And, in my opinion, 

 this will not appear astonishing, when it is borne in mind, on the one 

 hand, how delicate and flaccid the lymphatics in this situation are, and 

 on the other hand, how tender and thin is the ground-substance itself. 

 How easily, therefore, ^he lymphatics collapse when the membrane is 

 cut out and the circulation of lymph has ceased. Thus, as regards 

 the mesentery, there is no possibility of failure in the demonstration 

 of the large lymphatics running from the intestine to the mesenterie 

 glands and accompanying the blood-vessels, and which possess muscular 

 walls ; for in their case, collapse to the extent of their disappearance 

 cannot occur. On the other hand, demonstration of the lymphatic 

 proper in the mesentery invariably fails if the mesentery is not 

 treated in situ with the greatest care. In like manner, it is hard to 

 fail in demonstrating the lymphatics of the pleural side of the centrum 

 tendineum, because here the serous membrane is prevented from 

 shrinking too much by the subjacent tendinous tissue. On the other 

 hand, want of success in demonstrating the lymphatics of the medias- 

 tinal pleura is easily intelligible on the same grounds as in the case of 

 the omentum. 



From the circumstances just now mentioned, it follows that one 

 should be very careful in asserting the existence, in an omentum 

 whose lymphatics are not apparent, of spindle-shaped elements and 

 among them a greater or less number of migratory cells ranged 



