THE DIGESTIVE TRACT OF ELASMOBRANCHS. 15 
because in natural digestion the products are rapidly carried off, the stomach is in 
constant movement, and the pepsin and hydrochloric acid are constantly being 
renewed. 
In no ease, whether the solution was acid, neutral, or alkaline, did I tind that 
glycerin extracts of the mucous membrane of the stomachic sac of the various 
elasmobranchs had the power of converting starch to sugar. In concluding that the 
mucous membrane of the stomachic sac of elasmobranchs does not produce a diastatic 
enzyme I should be in exact agreement with Richet (1882), who studied Seyl//win 
and Acanthias, and with Yung (1899), who extended his studies further—to Galeus 
and Lamna cornubica. Upon ethyl butyrate, likewise, 1 found that the watery 
extracts had no effect whatever. 
MUCOUS MEMBRANE OF THE PYLORIC TUBE. 
Peptic glands are absent from the pyloric tube. To study the physiology of 
this tube, I took 10 smooth dogfish (Justelus canis) and 10 sand sharks ( Carcharias 
littoralis). After carefully washing the inner surface of the pyloric tube I scraped 
off the mucus and macerated it in elycerin and 0.5 per cent hydrochloric acid solution. 
After twenty-four hours the liquid was filtered. To the filtered liquid small pieces 
of fibrin were added. In twelve hours the digestion mixture was tested and showed 
syntonin, but no peptones. Contrary to Krukenberg’s (1877) results from work on 
selachians, we must conclude with Yung that the formation of pepsin is limited to 
the cardiac end of the stomach or the stomachie sae. 
The pyloric tube has likewise no action on starches or fats. 
Conclusion: The only active ferment secreted by the stomach of elasmobranchs 
is pepsin. 
CONTENT OF THE STOMACH. 
The study of the content of the stomach is really the study of the content of the 
stomachic sac. The content of the stomach varies greatly. Sometimes it is strongly 
acid and viscid; sometimes it is liquid and holds in suspension alimentary débris, 
more or less recognizable, oil, fish in various stages of decomposition, chitin, ete. 
An analysis was made of the contents of the stomachic sac of Mustelus canis, 
Carcharhinus obscurus, Carcharias littoralis, Squalus acanthias, Tetronarce occi- 
dentalis, Raja erinacea, Lamna cornubica, and Galeocerdo tigrinus. The acid content 
of the stomach was neutralized and an abundant precipitate of syntonin occurred. 
The filtrate was boiled, and if a precipitate occurred was again filtered. The solu- 
tion was boiled and again treated with an excess of ammonium sulphate. The 
precipitate showed albumoses. The filtrate was then tested with the biuret reaction. 
As a rule syntonin, proteoses, and peptones were found in the stomach content. 
Occasionally, however, no peptone could be found in the stomach content of J/ustelus 
canis and Carcharias littoralis. 
Conclusions: The stomach of J/ustelus canis, Carcharias littoralis, Squalus acan- 
thias, Tetronarce occidentalis, Carcharhinus obscurus, Raja erinacea, Lamna cornubica, 
and Galeocerdo tigrinus secretes pepsin and converts proteids partly to antipeptone. 
