ANATOMY OF THE LACTEAL AND LYMPHATIC SYSTEM. 427 



after the consideration of certain points in the anatomy of 

 the lymphatic system. 1 



Physiological Anatomy of the Lacteal and Lymphatic 

 System. One of the most difficult problems in anatomy is 

 to determine the situation and mode of origin of the lymphat- 

 ics in different parts of the body. The tenuity of the walls 

 of these vessels, even in their course, and the presence of in- 

 numerable valves, render it impossible to study them by the 

 ordinary methods of injection. Since it has been ascertained, 

 however, that they originate in many parts by a rich anas- 

 tamosing plexns, their anatomy has been well made out in 

 certain situations by simply puncturing with a fine-pointed 

 canula the parts in which the plexus is supposed to exist, and 

 allowing a fluid, generally mercury, to gently diffuse itself in 

 the vessels of origin. Following the course of the vessels, 

 the fluid passes into the larger trunks, and thence to the lym- 

 phatic glands. The regularity of the plexus through which 

 the fluid is first diffused and the passage of the injection 

 through the larger vessels to the glands are positive proof 

 that the lymphatics have been penetrated, and that the ap- 

 pearances observed are not the result of mere infiltration. 

 This mode of investigation is best illustrated in the injection 

 of the lymphatics of the skin. The pressure employed is de- 

 rived simply from a column of mercury of sufficient height ; 

 the tube in which the mercury is contained being connected 

 with a flexible tube, by which the height may be readily in- 



1 One of the most successful of the early investigators into the anatomy of 

 the lymphatic system was the great anatomist, Mascagni. He demonstrated the 

 capillary plexus of origin of these vessels in many of the tissues of the body, 

 but was led into the error, in some instances, of supposing that fluid simply ex- 

 travasated in the substance of the tissue was contained hi lymphatic vessels. He 

 has therefore described lymphatics in situations where they have not been de- 

 monstrated by more recent investigations. However, the figures which he gives 

 of these vessels are copied into many of the recent works on anatomy. (MAS- 

 CAGNI, Dei Vasi Linfatid. Prodrcmo della Grande Analomia, Firenze, 1819, 

 pp. 3-54.) 



