THE ANATOMY OF THE THYEOID GLAND 185 



but tapers from the postero-lateral angle of the thyroid gland 

 outward to the tissue surrounding the hyoid sinus. The vessels 

 form perivascular lymphatics about the venous sinuses. Ink or 

 a colored fluid injected into the connective tissue about the hyoid 

 and thyroid sinuses readily fills the anastomosing vessels forming a 

 sheetlike mass of peculiar form (fig. 2, thyr. sn.) . Ink thus injected 

 can also be traced into the perivascular lymphatics of the hypo- 

 branchial arterial vessels (fig. 8) as far backward as the walls of the 

 coronary arteries; it can likewise be found in small perivascular 

 lymphatics in the walls of the thyroid arteries and to some extent 

 in the broad venous spaces between the vesicles of thethja'oid gland, 

 indicating that the lymphatic vessels to some extent may open into 

 the veins of the thj^roid. The vessels of the lymphatic plexus in 

 the cervical fascia are apparently connected with the blood-vessels 

 of the thyroid sinus, for excessive pharyngeal contraction in the 

 living fish forces blood into areas which otherwise appear to be 

 occupied only by lymphatic vessels. The blood-vessels may with- 

 out doubt be classed as ''venae lymphaticae" and the lym- 

 phatics as vasa lymphatica" after the terminology of Favaro 

 ('06), who says that the same vessel may in fishes carry either 

 blood or lymph at the same or different times so that these vessels 

 may in this sense be either vasa or venae lymphaticae. Fluid 

 injected into the lymphatics spreads so rapidly over so great an 

 area that it seems almost impossible to trace a connection with 

 the blood sinus by means of injections; the fluid enters the blood- 

 vessels so readily that one is unable to exclude the possibility of 

 an intra- venous injection. 



The statement by Baber ('81) that he was able to demonstrate 

 no lymphatics in the thyroid gland of Elasmobranchs led me to 

 pay special attention to the study of these vessels by injection 

 methods. As I have already pointed out, Baber states that ''in 

 both the skate and the Conger-eel an extensive system of vessels 

 lined with epithelium becomes injected by the method of punc- 

 ture." He then injected the blood vessels of a Conger-eel with 

 Berlin blue through the "efferent branchial vein" and"dorsal 

 aorta and thereupon states that "in the Conger-eel at least, there 

 is no evidence of any system of lymphatic vessels," emphasising 



