THE DIGESTIVE TRACT OF KLASMOBRANCHS. 2: 
twenty-four hours. When a small quantity of a 1 per cent sodium carbonate solu- 
tion was added to the oil mixture a permanent emulsion was formed in every case. 
When olive oil alone was treated with water and sodium carbonate the emulsion was 
not permanent. 
(b) A neutral ethereal solution of butter was made and litmus added to a distinetly 
blue tint. This was placed in contact with a teased bit of fresh pancreas, as recom 
mended by Gumgee (1893, p. 213). In ashort time the liquid bathing the pancreas 
became faintly pinkish in spots, showing that a slightly acid reaction had developed. 
(c) Aqueous extracts of the pancreas separated a small amount of butyrie acid 
from a dilute solution of ethyl butyrate, 
From these experiments it is to be concluded that lipase is secreted by the pan- 
creas of Mustelus canis, Carcharias lUittoral/s, and Raja erinacea, though its activity 
as demonstrated in vitro is not very great. 
RECTAL GLAND, 
Blanchard (1882) studied the function of the rectal gland, or digitiform gland, in 
Acanthias vulgaris, Mustelus canis, Seylliun catulus, Seyllium canicula, Raja pune 
tatu, and Raja maculata, \n every case he found that extracts of the gland emulsi- 
fied oil and conyerted starch to sugar, but had no action on white of egg or cane 
sugar. Extracts made by me of the rectal gland, or processus digitiformis, of Car- 
charias littoralis, Carcharhinus obscurus, Lanna cornubica, Mustelus canis, and Paja 
erinaced Wad no digestive action on fibrin or starch, nor did they hydrolyze ethyl! 
butyrate. In the secretion of the gland I found considerable mucin, To the struc- 
ture and physiology of the rectal gland I shall return ina later paper, At present, 
however, I should decide that the rectal gland has no digestive activity. 
SUMMARY. 
The results of the histological work in the present investigation may be sum- 
marized as follows: 
1. The mucous membrane of the bucal cavity of Mustelus canis and Carcharias 
Uittoralis consists of stratified epithelium, with goblet and cylindrical cells, but no 
glands. 
2. The mucous membrane of the esophagus possesses ciliated cylindrical cells 
and goblet cells, but no glands. 
3. Gastric crypts exist in the stomachic sac of the elasmobranchs. There is no 
differentiation into chief and parietal cells. The epithelium of the crypts consists of 
cylindrical cells and polygonal cells. 
4. The pyloric tube has the same kind of superficial epithelium as the stomachie 
suc and similar crypts. The polygonal cells, however, are absent. 
5. The epithelium of the intestines from pyloric tube to clouca consists of 
cylindrical cells and goblet cells. 
6. The rectal gland is a compound tubular gland. 
The physiological study and experiments produce the following conclusions: 
7. In the elasmobranchs examined, neither the buccal mucous membrane nor the 
mucous membrane of the esophagus has any digestive activity. 
