G. ST. HILAIRE ON THE FAHAKA OF THE NILE. 115 



simple was to employ a sac within reach of the cavities of the mouth 

 and of the gills, and of which there was only wanting an increase of 

 capacity, we shall be less astonished that this modification, however 

 wonderful it may seem, should have fallen upon the stomach, and 

 that this organ should acquire so prodigious a volume. 



It is, moreover, a fact established by observation. If the interior 

 of the air pouch (poche aerienne) of the fahaka be examined, two 

 openings will be found in it, one of which corresponds with the neck 

 of the gullet (oesophagus), and the other with the commencement of 

 the intestinal canal. 



The thinness of this sac leads us, at first sight, to suppose that it 

 cannot be the stomach j but this thinness is incidental to its dis- 

 tended condition, inasmuch as it is formed of as many coats as all 

 other stomachs, and is covered in the same manner with the 

 muscles and skin of the abdomen. It is known, and this is the 

 answer to this kind of objection, that when an organ is dispropor- 

 tional to the limits which are, as it were, marked out for it, it is 

 always at the expense of its mass : thus a glass-blower makes, with 

 a given quantity of matter, globes of greater or less capacity, 

 according as he is required to make the sides thicker or thinner. 



This large stomach, situated more inferiorly, covers nearly all the 

 other abdominal organs. Taking its origin from the fauces (arri&re- 

 bouche), it covers the liver, the swim-bladder, the intestines, to which 

 it adheres by means of a very thin cellular tissue ; then, returning 

 upon itself, it covers all the abdominal muscles, which are enlarged 

 in the same proportion as itself, and then passes to the last portion 

 of the breast-bone (sternum,) where we saw its point of departure. 

 There all is adherent, the several coats of the stomach, the muscles 

 of the abdomen, and the skin so that, in order to study the struc- 

 ture of these parts, it is necessary to take the trouble to separate all 

 the layers of which this portion of the great sac is formed. 



We easily comprehend then how the abdominal muscles, forming 

 an intermediate layer between the coats of the stomach and the 

 skin, expel the air which produces the enlargement of the fahaka. 

 This is effected by the contraction of thin muscular fibres, seconded 

 by the non-activity or the restitution of the muscles of the chest. 



These muscular fibres, in contracting still more, force as well the 

 membranes of the skin without, as those of the stomach within, to 

 fold themselves : and the stomach, compressed, as it were, and re- 

 duced to dimensions which are more in harmony with the other 

 organs of the animal, returns to its ordinary functions. 



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