vol.l] Esterly. — Poison Glands of Plethodon . 247 



to iron haematoxylin. That is, both the mucous cells and those 

 of the replacement glands slain blue in Mallory, red or pink in 

 Van Gieson, and both have a fibrillar structure. The mucous 

 reaction is also given with mucicarmine. And finally, the nuclei 

 of the ingrowing gland fundaments always stain intensely black 

 in iron haematoxylin, as do the nuclei of the mucous elands. 



The facts just related have been gained entirely from a study 

 of preparations made from material taken from unstimulated 

 animals, that is those not irritated prior to immersion in killing 

 fluids. The evidence along this line is stronger and more con- 

 vincing in the case of an animal which, without stimulation of any 

 kind other than such as might have occurred in nature, got rid 

 of a great deal of the secretion in the glands of the tail and then 

 cast that organ off, as if it could be of no further use. The 

 animal in question, when first observed, was seen to be entangled 

 head down betweeu some pieces of bark in the terrarium in 

 which it was confined. This seemed to irritate the salamander 

 very much, for when it freed itself it began moving quickly 

 about, swinging its tail from side to side like an angry cat. The 

 tail, during this time, became covered with a very abundant 

 white secretion, After about five minutes of such behavior on 

 the part of the animal, when I merely touched the tail it was 

 suddenly thrown off, the break being in the constriction back of 

 the cloaca. 



The tail was put into Zenker's fluid after about fifteen min- 

 utes, and sections made later. Here the likeness between the 

 fundaments in the empty poison glands and the mucous glands 

 could not be more complete. In all the stains used the appear- 

 ances are exactly the same. The cells of the mucous glands are 

 much higher than in other animals seen, stain a lighter blue in 

 Mallory, and have a vesicular structure approaching granular, 

 rather than the filar structure usually seen. Even so. the 

 replacements glands cells are their exact counterparts, and show 

 the same reactions to Van Gieson, mucicarmine, and iron haema- 

 toxylin, as well as Mallory's stain. 



It seems hardly possible that the cells of the mucous glands 

 could have so changed their structure and appearance in fifteen 

 or twenty minutes, though the increase iu height and consequent 



