340 THE AMERICAN MONTHLY [Nov., 



of any kind are present. Mucous is however abundantly 

 secreted by single cells of various shapes and sizes which 

 occur among the other cells in the mouth and esophagus. 

 In most of these respects, however, it does not differ 

 from other Amphibia. 



In the stomach, two kinds of glands are found, as is 

 the case with the majority of vertebrates, though their 

 homology with the glands occupying the cardiac and 

 pyloric portions of the stomach in mammals is doubtful. 



The cardiac glands are far the more numerous and the 

 arena occupied by them is clearly demarcated from the 

 pyloric region by the greater opacity of the mucosa, due 

 to the granular cells of these glands. 



The structure is that characteristic of these cardiac 

 glands in Amphibia. The surface epithelium dips down 

 forming the neck of the gland, below which are several 

 large mucous cells, which are in turn followed by a 

 tubule formed of the secreting cells. In mammals pep- 

 sin is now thought to be secreted by the chief cells of 

 the cardiac glands, while the parietal cells produce the 

 hydrochloric acid of the gastric juice. In Amphibia no 

 parietal cells are present and the secreting cells seem to 

 perform both functions. They contain numerous gran- 

 ules which embody the precursor of the pepsin, and their 

 abundance has been shown by Langley in investigation 

 on the frog to depend directly upon the state of diges- 

 tion. These granules may be clearly seen by hardening 

 the tissue in a 1 per cent aqueous solution of osmic acid, 

 which stains them a light brown. In the pancreas of 

 Necturus also' the zymogen granules of trypsin may be 

 beautifully demonstrated. 



Leucocytes of white blood corpuscles occur in all por- 

 ti<»ns of the alimentary canal in the connective tissue and 

 in the epithelium, where they are sometimes of enormous 

 size, and greatly distort the epithelium cells surrounding 

 them. In the stomach epithelium they are to be found 



