36 Emil Goetsch. 
fuscus belongiwg to the Chiroptera and according to Oppel the mar- 
supial species, Trichosurus vulpecula, Aepyprymnus rufescens, and 
Phascolarctus cinereus. 
B. Mammals in which the glands are few in number. ‘To this 
group belong Erinaceus, Scalops and Lutreola in which a few mucous 
glands with demilunes occur in the upper end of the cesophagus, and 
Mephitis in which a few glands of similar nature are to be found 
at the. lower end of the cesophagus. 
C. To the third class belong a small group of mammals belonging 
to different orders in which the glands are present in considerable 
numbers. These are Didelphys, Proeyon, Canis familiaris and C. 
vulpes. Meles taxus and Nasua rufa, in which glands occur in 
considerable numbers throughout the whole extent of the cesophagus, 
Sus scrofa domestica in which they are abundant in the upper half 
of the cesophagus and few in number in the lower half. 
In structure the cesophageal glands are compound tubulo-alveolar 
glands, consisting, except in those of man, of two kinds of cells, 
mucous cells and serous cells. The latter elements, which have been 
overlooked by previous observers with the exception of Klein (79), 
Renaut (97) and Helm (07) are aggregated in the form of 
demilunes such as we find in the submaxillary gland of the dog, and 
like the demilunes of the salivary glands are provided with well 
defined intercellular secretion canaliculi. In the glands of the lower 
end of the csophagi of Procyon and Didelphys these serous cells 
are so numerous that in many cases they form sessile alveoli on the 
sides of the mucous tubules with an independent lumen from which 
the secretion-canaliculi branch off. In man no demilunes could be — 
found, thus confirming the observations of Schaffer. 
A survey of the distribution of glands makes it apparent that the 
occurrence of cesophageal glands is the exception rather than the 
rule in mammals and that their presence bears no relation whatever 
to the mechanical qualities of the food nor to the completeness of 
mastication. Purely vegetable feeders are uniformly devoid of glands 
in the esophagus and in many flesh feeders they are either few in 
number or wholly absent. Ranvier it is true explains the absence of 
glands in rodents on the basis of the thoroughness of mastication, 
