LYMPHATICS, ETC., OF THYROID GLAND OF THE DOG. 209 



guish the nucleated membrane forming the wall of a capillary 

 blood-vessel from that of a lymphatic. 



Contents of the Lymphatics. — On examining a specimen 

 injected with Berlin blue and stained with picrocarminate 

 of ammonia, by far the greater part of the cavity of the 

 lymphatics is seen to be filled with a granular material of a 

 more or less bright yellow colour. The blue injection occu- 

 pies the peripheral portion of the lumen, forming bands of 

 colourinsr matter betvveen the wall of the vessel and its 



• • • T 



contents (see fig. 1, b). On examining the lymphatic tubes 

 some of them are seen to contain this granular material ; the 

 greater part, however, in a well-injected specimen, are filled 

 with blue injection. It is probable that the injection first 

 entering the smaller tubes forces their contents, or at least 

 a part of them, onwards into the larger tubes and lym- 

 phatic vessels. From the relation existing between the in- 

 jection and the contents of the vessels I am led to the 

 conclusion that during life the contents are of a viscid con- 

 sistence ; for if, at the time of the injection, the contents were 

 fluid, the injection on entering the vessels would either force 

 the contents of the same before it or would mix with them. 

 The injection, however, being performed immediately after 

 death, the contents could not have had time to coagulate, and 

 as the blue does not mix with the contents, but forms a sepa- 

 rate layer between them and the wall of the vessel, it follows 

 that the contents must during life have been more or less 

 viscid in character. 



In sections stained with logwood the contents of the 

 lymphatics usually present a uniform appearance, but are 

 sometimes finely granular. They stain of a greyish-violet 

 colour. 



In addition to this material the lymphatics sometimes 

 contain a few hyaline drops. 



II. Parenchyma. 



Besides the stroma, lymphatics, blood-vessels, &c., between 

 the vesicles, there is another tissue, to which, as far as I am 

 aware, no reference is made by authors on this subject. To 

 this tissue it is proposed to give the name of "parenchyma," 

 on the supposition that it is possibly analogous to the 

 parenchyma of the testis described by various authors. 



Characters of the Parenchyma. — On examining with a 

 high power sections of the gland stained with haematoxylin 

 and mounted in balsam, numerous cells are seen differing 

 markedly in size and shape from the epithelial cells amongst 

 which they lie. These cells are usually more or less rounded 



