C. THE (ESOPHAGUS, BY E. KLEIN. 535 



smooth fibres do not merely replace the transversely striated, but 

 occur in great numbers as a new formation, so that these external 

 layers in the vicinity of the cardia exceed the two others in breadth. 



Ravitsch* has found the following arrangement of the smooth 

 muscular fibres to obtain in the Horse, Calf, Pig, Cat,' and Rabbit. 



In the Horse the muscular layers of the oesophagus are entirely 

 composed of transversely striated fibres as far as the thickening that 

 is found about 2025 centimeters above the cardiac orifice ; below the 

 thickening, smooth fibres make their appearance in the inner layer, 

 whilst they do not present themselves in the external layer till near 

 the cardia. 



In all the above-named animals the transversely striated elements 

 extend in both layers of the oesophagus to a variable distance from the 

 cardia, always ceasing sooner in the inner than in the outer layer. 

 This last statement is, however, opposed to that which, as mentioned 

 above, I have found to occur in the oesophagus of the Rabbit. 



Ganglion cells are here still more frequently met with than in the 

 Dog ; not only scattered amongst the fibres of the nerves running 

 in the external muscular layer, but also in the lower fourth, in the 

 form of microscopic ganglia, situated between the middle and external 

 muscular layers. 



The mucous membrane of the oesophagus of the Hat is precisely 

 similar to that of the Rabbit, in regard to all its parts epithelium, 

 papillae, and mucosa as well as in the distribution of the muscular 

 layer of the mucosa. The external muscular layer generally divides 

 into a stronger internal and circular, and a thinner external longi- 

 tudinal layer. Here and there the external muscular layer exhibits 

 in its lowest portions an internal, strongest, oblique ; a middle, 

 circular ; and an external, thinnest, longitudinal layer. All .the 

 layers are free from smooth muscular fibres as far as the cardia. 



The oesophagus of Birds presents many points of difference from 

 that of Mammals. In the fowl the mucous membrane is from O5 to 

 O8 of a millimeter thick, and is covered with laminated pavement epithe- 

 lium, the uppermost cells of which are tabular, and separated from each 

 other by a broad, remarkably sinuous, intervening substance ; those 



* J. Ravitsch, Ueber das Vorkommen quergestreiften Muskelfasern im 

 (Esophagus der Haussaiigethiere, " On the presence of transversely striated 

 muscular fibres in the (Esophagus of domestic Animals ;" Virchow's 

 Archiv, Band xxvii., p. 413. 



