The MicKoscoPE. o<);j 



entirely distinct, as he says that toward the inferior extremity of the 

 canal they inter-cross in an almost inextricable manner. 



In 1868, Klein (11) described an exceedingly complex arrange- 

 ment of the fibres in the dog. In the pharyngeal eighth, he said, 

 there is an external longitudinal and an internal circular layer; in 

 the next two eighths the fibres of both layers decussate obliquely 

 and at right angles; in the next three eights there is an inner 

 longitudinal and an external circular layer; in the next eighth there 

 are three layers: an internal longitudinal, a middle circular and an 

 external longitudinal, the last mentioned layer being derived from 

 the other two. In the last, or gastric eighth, there are also three 

 layers: an internal oblique, a middle transverse and an external 

 longitudinal. Klein does not say how these results were obtained, 

 but from the figure it is evident that his conclusions were drawn 

 from the study of transections. 



Gillette (7) made a study of the " muscular tunic of the 

 oesophagus in the animal series," and these briefly were his 

 conclusions : In the dog there is no longitudinal layer. The 

 superficial or ectal layer is composed of circular or elliptical fibres 

 that cross on the dorsal wall in such a way as to represent a raphe. 

 The second layer is subadjacent to the first, and is composed of 

 fibres that have a direction opposite to the first, which they cross at 

 an acute angle. A third very thin coat is mentioned. In the cat 

 there are two layers, and the longitudinal arrangement is shown only 

 in the caudal or gastric end. In the sheep there is no longitudinal 

 layer, and the muscular tunic is composed of an entanglement of fibres 

 that present no regularity. In the ox the arrangement is similar to 

 that found in the sheep. In the horse there are two thick longi- 

 tudinal bands of fibres extending one on each side, from the 

 pharynx to the junction of the middle and gastric thirds. Between 

 these longitudinal bundles, and springing from them are annular 

 bundles that cross at a " raphe " on the dorsal wall and become 

 mixed on the ventral wall. In the caudal third the regularity has 

 disappeared. Two internal columns were seen, corresponding to 

 those on the surface. 



Franck (5), in 1883, described another system as existing in the 

 horse. He says, in substance, that there are two lateral bundles, as 

 above, and from these the oblique spirals take their origin. Upon 

 the ventral and dorsal wall is a scarcely noticeable seam where the 

 spirals come together. This constitutes the ectal layer. The ental 

 layer is thinner, and its spirals cross those of the ectal at an acute 

 angle. In ruminants the muscular arrangement is in reality as it is 



