428 ABSORPTION. 



creased or diminished at will. With, the flexible tube is con- 

 nected the capillary tube of glass, which is to be introduced 

 into the part to be injected. In the case of the skin, the fine 

 glass point is introduced just below the cuticle at so acute an 

 angle as to be almost horizontal. A stop-cock, which is con- 

 nected with a tube into which the glass point is fitted, is then 

 turned, and the pressure of the column of mercury forces in 

 the injection. The puncture in the skin is to be very super- 

 ficial, otherwise the mercury will pass into the blood-vessels. 

 "When the operation has been successful, the mercury will be 

 seen to " cover the skin with a silvery net-work." The tube 

 should remain in place for from half a minute to a minute 

 only. To demonstrate that this plexus really consists of 

 lymphatic vessels, one of 'them may be denuded and punc- 

 tured with the glass point, when the lymphatic will become 

 instantly distended as far as the nearest gland, in which the 

 injection is always arrested. 1 



Lymphatics have not been actually injected and demon- 

 strated in all the tissues of the body ; but in some parts in 

 which it has been thus far impossible to inject them, we are 

 not justified in assuming positively that they do not exist. 

 For example, in the intestinal villi, according to Sappey, these 

 vessels have never been seen, though their existence is al- 

 most certain. The most generally received views with regard 

 to the ordinary mode of origin of the lymphatic vessels is 

 that they commence by a closed capillary plexus, which does 

 not communicate with either the small arteries, veins, or the 

 capillary blood-vessels, and is always situated externally to 

 the blood-vessels. It does not appear that the vessels compos- 

 ing this plexus vary much in size. They are very elastic, 

 and after distension by injection, they return to a very small 

 diameter w T hen the fluid is allowed to escape. It is prob- 



1 For full details for the performance of these exceedingly delicate manipula- 

 tions, the reader is referred to the work of Sappey. ( Traite d'Analomie Descrip- 

 tive, Paris, 1853, tome i., p. 639 et seq.} This author has been peculiarly suc- 

 cessful in his researches into the minute anatomy of the lymphatic system. 



