OP THE RUMINANTIA. 59 



all the fibres of the inner layer, when traced round in the outer 

 layer, become non-decussating at the first decussation at which 

 they arrive after having entered the outer layer*. I have cal- 

 culated that, were this last theory true, the decussating bundle, 

 at a decussation, would be ten times as large as the non-decus- 

 sating ; because a spiral running from the one end of the oeso- 

 phagus to the other would cross it nine or ten times. 



Now, what is the use of this remarkable and beautiful arrange- 

 ment of the fibres ? Is it to enable the animal to ruminate ? It 

 would be difficult to conceive why so elaborate and ingenious a 

 structure should be required to bring the food lach from the 

 stomach ; for the simpler human oesophagus, with its longitudinal 

 and transverse layers, ought to be just as able to carry the food 

 up from the stomach as to take it down ; and that it is so is 

 shown by the act of vomiting. And further, the idea that it is 

 a special provision for rumination is proved to be erroneous by 

 the fact (as I have ascertained) that the oesophagus of the dog 

 has the same structure as that of the Buminant. I have not 

 examined the oesophagus of any of the other Carnivora ; but the 

 above is true of the dog's, at any rate. 



The advantage gained by a structure such as this, seems to be, 

 1st, rapidity of transmission. A body at a, if pulled by two 

 oblique strings, will be advanced to B more rapidly than if these 

 strings were puUed directly before the body, supposing the power 



moves at the same rate in both cases. When the strings are ob- 

 lique, however, although rapidity of transmission is gained, there 

 is a loss of power. 



A bundle of fibres of the inner and outer layers, when viewed 

 in, relation one to another, form a parallelogram (mie Fig. 11). 



* I have frequently used the term "layer" both in the singular and plural 

 numbers : e. g. the term " inner layers " refers to the internal layers of both of the 

 symmetrical halves into which the oesophagus may be longitudinally divided, 

 while " inner layer" refers to the internal layer of one of these halves. * 



