vol.i.] Esterly. — Poison Glands of Plethodon. 2.">1 



secretion from the glands, as does Phisalix-Picot ('()()). Eberth 

 and Bunge ('92) have described free nerve fibres which seem to 

 end with knobs outside the epithelium of the ball of the thumb 

 of the male frog. Loeb ('96) has also shown how closely the 

 glands of Amblystoma are connected with the central nervous 

 system. In 1S98 Herrick and Coghill were able to show the 

 existence an intimate connection of nerve fibres with the walls 

 of the glands, but were unable to discover the exact relation 

 of the fibres to the gland cells. They also described the 

 plexus of nerves beneath the corium as being composed of two 

 sorts of fibres; larger ones connected with the nerve bundles 

 of the central system, and smaller ones which in part, at least, 

 originate in ganglion cells in the corium. Schuberg ('03) has 

 criticised the results of these authors, contending that many or all 

 of the nerve bundles described are really connective tissue 

 bundles, and that the ganglion cells are the "Mastzellen" he 

 himself figures. 



Massie ('99) continuing the work of Herrick and Coghill, 

 considers the same arrangement of fibres beneath the corium, 

 and also shows that nerves end on the muscles of the "ental" 

 glands. He finds that nerve fibres passing from the nerve bundle 

 plexus under the corium are intimately connected with the ental 

 glands, and seem distinct from the nerves supplying the muscles. 

 "It seems, therefore, that there are two groups of nerves passing 

 to the glands of the ental series; the one attaching by the typical 

 endings to the enveloping muscle cells, the other ramifying 

 promiscuously over the surface of the gland." (p. 59.) 



In the study of the nerves of the poison glands of Plethodon, 

 three methods have been relied upon; namely, the silver nitrate- 

 pyrogallic acid method of Cajal, and Mallory's phosphotungstic 

 acid haematoxylin and fuchsin- orange G-anilin blue methods. 

 The last named gave most excellent results, while of the other 

 two Cajal's was only indifferently successful. 



The haematoxylin of Mallory stains only the sheaths of the 

 nerves and so it is of no value in tracing the axis cylinders, since, 

 as is well known, the nerves lose the medullary sheaths on pass- 

 ing into the corium. Beneath the corium. however, the nerves 

 can readily be followed by this method. In some instances fibres 



