416 MANUAL OF HISTOLOGY. 



The normal fluid contents of the vesicle coagulates with 

 heat and alcohol, without losing its transparency. Floating in 

 it are granules, cells, and occasional translucent, curiously 

 shaped bodies called sympexions (Robin). The cells come 

 from the vesicle- wall and the intervesicular tissue. Many of 

 them have lost their nuclei. The "sympexions," if they uni- 

 formly occur, have not been shown to have any significance. 



Baber has recently announced the very interesting fact that 

 large numbers of colored and colorless blood-corpuscles are to 

 be found in the vesicle-cavities of the thyroid of man and lower 

 vertebrates. The colored cells, which largely preponderate, are 

 in a state of partial disintegration. This explains the yellowish 

 color of the vesicle-contents, and the inference is drawn that the 

 thyroid has the function of destroying red blood-corpuscles. 



The blood-vessels of the thyroid are quite numerous. They 

 ramify in the capsule along the trabeculse, and finally form a 

 rich plexus about the vesicles, but do not penetrate the inte- 

 rior. The walls of the veins are united firmly to the fibrous 

 reticulum of the gland, so that when a section of them is made 

 they do not collapse. 



TJie lymphatics form large and numerous trunks, both on 

 the surface and in the interior of the organ. They originate 

 by coecal extremities lying in the tissue between the vesicles. 

 These unite to form trunks which surround the lobules, and 

 give off branches that pass to the capsule. TKere a thick, per- 

 ipheral network is formed, from which lymph-trunks pass to 

 the thoracic and right lymphatic ducts. They contain a viscid 

 substance like that in the vesicles themselves, and it seems 

 probable that they have something to do with carrying off this 

 fluid. 



The nerves are from the middle and inferior cervical gan- 

 glia, but not (Frey) from the pneumogastric. They enter the 

 gland along the trabeculse and pass between the vesicles. Gan- 

 glion-cells, either single or in groups, are met with in their 

 course. The mode of termination is not known, more than 

 that they seem to dwindle away into fine, terminal fibres, that 

 are lost in the connective tissue. 



