VOL. i.] Kstfrhj. Poison Glands of Plethodon. 241 



color is as a whole yellow with a tinge of red. In iron haema- 

 toxylin some granules stain (I'l. XXII, Fig. 1<S) black: but at 

 times one can detect in sonic granules a clear outer portion 

 which takes the counter stain (erythrosin, etc.), while the central 

 part stains dark black, and others which take only the counter 

 stain. 



The mucous secretion, on the other hand, reacts very differ- 

 ently, as does the cytoplasm of the mucous cells, which can be 

 easily distinguished from their secretion. Here the reactions are 

 typically those of mucus. Mallory's stain, which colors mucus in 

 the sublingual of a cat a clear blue in two minutes, stains in the 

 same wiiy both the cells and the secretion of the small glands. 

 This same stain beautifully differentiates the mucus in the goblet 

 cells of the oesophagus and intestine of Plethodon. I have not 

 been able to obtain the reaction in these gland cells with thionin , 

 in which Nicoglu places so much confidence as a mucous stain. 

 Hubbard ('03) has had the same difficulty. However, inucicar- 

 mine, a specific mucous stain, gives the mucous reaction after 

 twelve or twenty-four hours in both the glands of Plethodon and 

 the sublingual of the cat. The use of Van Gieson's stain clearly 

 differentiates the small gland from the large ones. In the former 

 the cells and the secretion are stained a clear red or pink, 

 without a trace of yellow as in the poison glands. Orcein also, 

 which has been described as a mucous stain, colors the cytoplasm 

 of the mucous gland cells a deep brown, and has absolutely no- 

 effect on the granular secretion of the poison glands. The iron 

 haematoxylin is of little use in revealing the mucous nature of the 

 small glands, since they take only the counter stain except for 

 the nuclei. These become a deep black as already said. But 

 this method at least serves to distinguish the two sorts of glands 

 aside from the nuclear staining, in that the secretion of the small 

 glands never takes the haematoxylin, as do the granules of the 

 large glands. 



From these distinctions as to the primary character of the 

 two classes of glands, we are led to consider the histogenesis of 

 the secretion. It has been generally held that this process is not 

 the same in the mucous and poison glands. Seeck ('91), p. 55, 

 holds that the secretory cells are of two sorts, "solche die als. 



