716 THE LYMPHATICS. 



always to choose that animal. The operation is simple and always successful, 

 and we are astonished that in the hands of some mdividuals it should fail. Not 

 only can the two networks of the membrane be filled, but also the trunks 

 arisin<i: from them, and which are directed towards the entrance of the nasal 

 cavities, collect in several thick branches around the nostril, and curve up 

 towards the face to reach the submaxillary space, where they enter the glands 

 situated to the right and left of that region. 



The majority of anatomists admit the presence of lymphatic plexuses in the 

 splanchnic or synovicil serous memhranes. Sappey, however, denies this ; he con- 

 siders 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 splanchnic or synovial 

 cavities, and which are sometimes filled with mercury, do not, according to him, 

 come from the serous tunic, but from the subjacent tissues. 



The lymphatics do not exist in vessels. The lymphatic sheaths discovered by 

 His, Robin, and Tomaso, around the blood-capillaries of the Frog, and those 

 of the brain and spleen of Man, and recognized by Rusconi, Milne-Edwards, as 

 well as demonstrated by Ranvier around the vessels of the mesentery, ought not 

 to be considered as the lymphatics of vessels ; they merely surround the ultimate 

 vascular ramifications, and do not arise in the substance of their walls. 



In the nerve 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, Sappey admits that 

 they are exceeded by smaller capillary networks and spaces. 



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 Recklinghausen, since he observed fatty matters penetrate the lymphatics 

 by the abdominal surface of the diaphragm. The opinion of Yirchow is upset 

 at present by the researches of Ranvier, which have modified the descriptions 

 given of the connective tissue. According to this authority, plasmatic cells do 

 not exist in that tissue ; and what have been described as such by Virchow, have 

 been only radiating spaces hmited by the fascicuh of connective-tissue fibres, in 

 which elements analogous to lymph corpuscles circulate. The researches of 

 Ranvier tend to support the hypothesis of Recklinghausen, and show that in the 

 connective 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 in communication, on the other hand, with the great splanchnic 

 cavities. 



Course of the Lymphatic Vessels. — The lymphatics follow the course 

 of the veins, and are divided, exactly like them, into superficial and deep vessels. 

 The latter, running parallel to each other, are grouped immediately around the 

 corresponding veins, on which they generally lie. The first, although situated 

 in proximity to the superficial veins, are widely spread on each side and on 



