DIGESTIVE SYSTEM 125 



contains parts for the secretion both of mucus and albumen. 

 Besides these three great glands of the oral cavity many 

 mammals (among the rodents, insectivora, carnivora, cheiroptera 

 and ungulata) possess a mucus-secreting glandula retrolingualis 

 and a single excretory duct, namely, the duct of Bartholini. 

 Zumstein l doubts the occurrence of this gland in man, but as 

 it is found neither in the rabbit, hare, horse nor ass, its absence 

 in man can still not be reckoned among the specifically human 

 characters. 



Proceeding to the oesophagus and stomach we find the 

 separation of these two departments of the digestive system 

 hardly more than suggested in the ccelenterata and mollusca 

 (with the exception of the tunicata), and even in the vermes 

 and arthropoda but little developed. There are even mem- 

 bers of the vertebrate class (e.g., the amphioxus and cyclo- 

 stoma) whose first intestine shows no sign of the appearance 

 which characterises the organ in man and the other vertebrates. 

 In the higher fishes, the amphibians and the lower reptiles, the 

 oesophagus is completely subordinate to the sac-like stomach. 

 A distinct separation of oesophagus and stomach is first found 

 in the higher apes. In many of the birds a part of the 

 oesophagus is extended into a crop ; in all the stomach is 

 divided into an ante-stomach, abundantly provided with glands, 

 and an adjacent muscular stomach which is most highly de- 

 veloped in the granivora and least in the birds of prey. 



The most distinct separation of oesophagus and stomach, 

 and most closely resembling the human formation, is that of 

 the mammals. The muscular structure of the oesophagus in 

 the semi-apes is very similar to that of man. 



In the oesophagus of the Primates the numerous striated 

 muscles, together with non-striated, extend almost to the 

 Cardia, whereas in man the striated muscles are found without 

 exception nowhere but in the upper part of the oesophagus, and 

 the gradual transition from striated to non-striated muscles 



o 



commences at the limit of the upper and middle third or quarter. 

 Internal to these muscular strata are the non-striated fasciculi of 

 muscular fibre belonging to the muscularis mucosai, the numerous 

 mucous glands situated in the lower part, the longitudinal folds 



1 A. Oppel, loc. cit., part Hi., p. 571. 



