ORGANS OF THE BODY. 



473 



dinal layer of muscular fibres, as well as its fine internal transverse tunic, 

 shows a gradual substitution of contractile fibre cells for the striped tissue, 

 of which the upper portion of the tube is composed. In the superior 

 third of the latter the first species of muscle alone is to be found. Then, 

 on the entry of the oesophagus into the thorax, contractile fibre cells begin 

 to make their appearance, either scattered or in groups, first among the 

 transverse bundles, and later, in the longitudinal tunic. After this they 

 become more and more numerous, so that from about the middle of the 

 tube on the muscle tissue usually appears to be made up entirely of the 

 smooth variety of cells (Welcker and Schweigger-Seidel) remaining so 

 throughout the whole of the digestive tract. 



The mucous membrane loosely adherent to the muscular tunic beneath 

 is thrown into a multitude of rugae, and contains numerous simple papilla? 

 covered by strongly laminated epithelium. In the upper part of the 

 oesophagus large numbers of isolated bundles of vertically arranged con- 

 tractile fibre cells are scattered through it, and lower down a continuous 

 longitudinal Muscularis mucosce presents itself, occupying the deeper 



Fig. 452. (Esophageal glands from the human subject. 



portion of the membrane (Koettiker, Henle, Klein). The latter (at least in 

 the new-born child) is formed of distinct lymphoid tissue (Klein). 



The glands of the oesophagus (fig. 452 and 453) occurring, it would 

 appear, in varying numbers, sometimes scanty, sometimes abundant, are 

 of the small racemose species, two or three of their excretory ducts 

 frequently joining to form one common canal. At the extreme end of 

 the human oesophagus, about the cardiac opening, are to be found small 

 structures, extending not quite down to the sub- 

 mucosa ; these are the cardial glands of Cobelli. 

 Here they form an elevated ring about 2 mm. in 

 height. 



The blood-vessels are arranged in a moderately 

 loose network of capillaries, and the lymphatics 

 also in a retiform interlacement with small meshes, 

 the tubes measuring about 0-0200 or 0-0699 mm. 

 in diameter, and lying for the most part parallel 

 with the axis of the oesophagus. These latter are 

 situated in the deeper strata of the mucosa, and in 

 the submucous 'connective-tissue. The arrangement 

 of the nerves here appears to be similar to that in the pharynx. 



251. 



"VVe now come to the description of the stomach (ventricvlus), which, 

 on account of the physiological importance of the organ, must necessarily 

 be more minute than that of the last mentioned parts, its mucous mem- 

 brane calling for our special attention. 



The serous covering of the viscus presents the ordinary structure of 



Fig. 453. A small racemose 

 cesophageal gland from 

 the rabbit. 



