142 THE AMERICAN MONTHLY [May, 



coat. In the optical section tlie edge of the tube appears 

 to be bordered by cubical cells, this is the optical effect 

 of the muscle cells, obtained by the view of their optical 

 section. In the centre of some of these, the nucleus is 

 seen, but others are not cut in its plane and hence do not 

 how it. The capillary is seen as a thin parallel walled 

 tube, with enlargements at regular intervals due to the 

 position of the nuclei of the endothelium cells. 



The (ESOPHAGUS, exhibits the three coats with great 

 distinctness, on the surface it presents a layer of epider- 

 mis, in character like that on the tongue, but not thrown 

 into papillae ; beneath the epidermis is the dermis, the 

 vascular and connective tissue portion of the first coat, 

 this is a compact mass of fibrous matter, penetrated here 

 and there by smaller vessels and in places by the duct of 

 the mucous glands which lie in the submucous coat. At 

 the bottom of the layer is some muscular tissue. The 

 middle coat is composed of loosely arranged connective 

 tissue, in which the chief blood-vessels lie, in this layer 

 also are situated the glands, which, known as the oeso- 

 phagaeal glands, secrete the mucous secretion needed to 

 moisten the surface of the organ, so as to reduce friction 

 in swallowing. The vertical section accompanying this 

 shows the duct leading down into the submucous coat, 

 where it dilates to run to the various portions of the gland, 

 no section will ever be found to show the full length of 

 the duct, as this semi-diagrammatic drawing does. Fully 

 half of the wall of the oesophagus is composed of muscu- 

 lar tissue, this is arranged in two portions one circular 

 and one longitudinal, these when cut are seen, one cut 

 lengthwise, the other, cross-wise, out side of the muscular 

 coat is a denser layer of connective tissue forming a 

 sheath for the tissues beneath. 



The examination of the different parts of the section 

 with the high power will demonstrate the following points, 

 the epidermis is composed of cells which lie in several 



