630 THE LYMPHATICS. 



to reach the submaxillary cavity, where they enter the ganglia situated to 

 the right and left of that space. 



The majority of anatomists admit the presence of lymphatic plexuses in 

 the splanchnic or synovial serous membranes. M. Sappey, however, denies 

 this ; he considers the vessels that can be so easily injected by pricking the 

 external surface of a viscus, as belonging to its proper tissue, and not to the 

 serous membrane covering it. Those on the inner face of the walls of the 

 splanchinc or synovial cavities, and which are sometimes filled with mercury, 

 do not, according to him, come from the serous tunic, but from the sub- 

 jacent tissues. 



The lymphatics do not exist in vessels, although some modern anatomists 

 have admitted them to be present in the inner layer of the circulatory 

 apparatus. The lymphatic sheaths discovered by His, Eobin, and Tomaso, 

 around the blood-capillaries of the frog, and those of the brain and spleen 

 of Man, ought not to be considered as the lymphatics of vessels, as they 

 merely surround the ultimate vascular ramifications, and do not arise in the 

 substance of their waUs. 



In the nervous tissue lymphatics have not been discovered, though they 

 are present in the meninges. 



Their existence is doubtful in hone tissue and in the muscles ; but they are 

 abundant in the glands and glandiform organs of the animal economy, 

 forming the finest, richest, and most easily demonstrated plexuses. 



It has been stated above that the lymphatics commence by capillaries 

 arranged in networks. Are these networks the real, or only the apparent, origin 

 of the lymphatics ? This is a question that has been, and is still, warmly 

 discussed. It is, however, believed that the plexuses are fed by very minute 

 radicles lodged in the substance of the tissues. 



But how do these radicles originate ? In the epithelium, says Kiiss ; in 

 the plasmatic cells of the connective tissue, asserts Virchow ; in the serous 

 membranes, states Eecklinghausen, since he observed fatty matters pene- 

 trate the lymphatics by the abdominal face of the diaphragm. The opinion 

 of Virchow is overthrown at present by the researches of Eanvier, which 

 have modified the descriptions given of the connective tissue. According to 

 this authority, plasmatic cells do not exist in that tissue ; what have been 

 described as such by Virchow have been only radiating spaces limited by the 

 fasciculi of coimective fibres, in which elements analogous to lymph globules 

 circulate. It may be added that these fasciculi are covered by large flat 

 cells, which give these spaces the appearance of a serous cavity with septa at 

 close intervals. These conclusions of Eanvier, then, should afBrm the 

 hypothesis of the Wurzbourg professor, and tend to prove that in the connec- 

 tive tissue of the economy there is an infinite number of minute serous cavities 

 into which the lymphatic vessels open, in which the lymph circulates, and 

 which are m communication, on the other hand, with the great splanchnic 

 cavities. _ It must be mentioned, however, that these deductions are only 

 hypothetical, particularly at the period of scientific evolution through 

 which we are now passing. 



Course of thk Ltmphatio Vessels.— The lymphatics follow the track 

 ot the veins and are divided, exactly like them, into superficial and deep 

 vessels. Ihe latter, running parallel to each other, are grouped immediately 

 around the corresponding veins, on which they are generally superposed. 

 -Ihe hrst, although situated in proximity to the superficial veins, are widely 

 spread on each side and on the surface of the superficial aponeuroses, by 

 forming parallel fasciculi, like the deep lymphatics. 



