C. THE (ESOPHAGUS, BY E. KLEIN. 533 



form a continuous layer, as in Man, but first makes its appearance in 

 the middle of the upper fourth, in the form of isolated longitudinal 

 fasciculi, which, in the lower half, surround at various points the 

 acinous glands, and sparingly accompany their excretory ducts nearly 

 to the epithelium. The glands throughout the whole length of the 

 oesophagus form a continuous layer, the thickness of which consider- 

 ably increases in its lower part. 



In the loose submucous tissue, nodal points are scattered, consist- 

 ing of stellate plexuses of elastic fibres which present a remarkable 

 yellowish-green colour. 



The outer muscular layer of the oesophagus in the Dog is arranged 

 in a much more complex manner than in Man. It is only in the 

 upper half of the first fourth that it is composed of an external 

 longitudinal and of a stronger internal circular layer. In the lower 

 half of the first and the upper half of the second fourth, both layers 

 are equally well developed, and are composed of fibres decussating 

 obliquely, and at right angles. In the lowest part of the second, and 

 throughout the whole of the third fourth, the inner layer is thinner, 

 and becomes longitudinal, whilst the external is thicker, and is now 

 circular. In the upper half of the inferior fourth, three layers are 

 constantly present : an internal longitudinal ; a middle, which is the 

 strongest, circular ; and an internal, which is the thinnest, longitu- 

 dinal. The latter is derived from the internal, but chiefly from the 

 middle, which proceeded above from the external layer. In the lower 

 half of the inferior fourth, three layers are constantly present : an 

 internal oblique ; a middle, which is the strongest, transverse ; and 

 an external, which is the weakest, longitudinal. The fasciculi of 

 the outer muscular layer do not, therefore, pursue a rectilinear, but 

 a well-marked spiral course. 



Smooth muscular fibres first make their appearance at about the 

 commencement of the lowermost fourth of the external muscular 

 layer, but even there they are confined exclusively to the innermost 

 portion, which, immediately above the cardia is composed of smooth 

 muscular fibres alone. The remaining layers are composed of striated 

 muscular fibres up to the point of entrance of the oesophagus into 

 the stomach. 



The nerves are arranged in the same manner as in Man, but they 

 are more numerous. They lie between the internal longitudinal and 

 middle circular layers, and present ganglion cells which are either 

 scattered or are arranged in series one behind the other. 



In the Rabbit the mucous membrane of the oesophagus resembles 



