66 



On the Muscular Fibres of the Stomach. 



[June 20, 



being to throw the delicate fibres into strong relief. By adopting 

 those methods, the author has been able to show that the arrangement 

 of the fibres in the stomach remarkably resembles that found in the 

 heart* and bladder f. This is particularly the case in the human sto- 

 mach, where the fibres are most highly differentiated. In it the fibres 

 pursue complicated, but well-marked directions ; the most external and 

 most internal fibres maintaining a more or less longitudinal course, 

 the deeper or more central ones becoming more and more oblique as 

 the centre of the parietes is reached. 



The fibres cross each other with great regularity, both from without 

 and from within, the longitudinal intersecting the very oblique at nearly 

 right angles, the slightly oblique and oblique at more acute angles. The 

 slightly oblique, oblique and very oblique fibres are spiral in their 

 nature, and form, or tend to form, figure-of-8 loops. These loops are 

 directed towards the greater and lesser curvatures of the stomach, but 

 are also traceable on the great cul-de-sac or fundus, and on the lesser 

 cul-de-sac or antrum pylori. As a result of the looped distribution of 

 the fibres, the root of the oesophagus and the pylorus are invested with 

 oblique and very oblique spiral fibres, arranged symmetrically in two 

 sets. These fibres pursue opposite directions, and surround the entrance 

 into and exit from the stomach after the manner of sphincters. The 

 crossing and looping of the fibres extends also to the body of the viscus, 

 and shows that the so-called circular layer is in reality composed of very 

 oblique spiral fibres, intersecting at very obtuse angles. 



The fibres are arranged in difi'erent planes or strata, and may be 

 divided into external and internal sets. These are united to each other 

 by a mutual interchange of fibrous filaments ; and the fibres of the 

 several strata interweave to a slight extent, so that the term layer must 

 be used in a restricted sense. The layers ai^e indicated by the prevail- 

 ing direction of the fibres, and are something like seven in number, 

 three external and three internal, with an intermediate or central layer 

 between. 



The fibres having the same direction, are in some instances strongly 

 developed at one part of their course, and feebly at another. They even 

 become gradually attenuated, until they are no longer discernible. The 

 muscular coat of the stomach is thickest towards the pylorus;]: and root 

 of the oesophagus ; then along the lesser curvature on either side of the 

 mesial line ; then along the greater curvature. It is thinnest on the 

 anterior and posterior surfaces, and towards the cardiac end. 



* " On the Arrangement of the Muscular Fibres in the Ventricles of the Vertebrate 

 Heart, with Physiological Eemarks," by the author, Phil. Trans, part 3. 1864, p. 445. 



t " On the Muscular Arrangements of the Bladder and Prostate, and the manner in 

 which the Ureters and Urethra are closed," by the author, Phil. Trans, part 1, 1867. 



X In the stomach of the Bear the walls of the antrum pylori are fully a quarter of an 

 inch in thickness. 



