THE REVERSED SPIRAL 



239 



simply a convenient way of coiling a tube which has 

 greatly increased in length while its ends were fixed. 

 The intestine of the Tadpole is at first straight. 

 Afterwards it grows very long, to suit the vegetarian 

 diet of the young animal. This 

 long tube must needs be coiled, 

 for the space into which it has 

 to be crowded is small. Being 

 fixed at both ends it cannot 

 be coiled continuously in one 

 direction. The watch-spring 

 coil, which represents the in- 

 testine of the Tadpole in 

 many standard books, is a 

 mechanical impossibility. 



The colon of a Ruminant 

 is extremely long, and having 

 lengthened while the ends were 

 fixed, it is coiled in a reversed 

 spiral. It lies nearly in one 

 plane, and winds inwards in a 

 regular spiral to the centre ; 

 then reverses its course, and 

 winds outwards between its 

 former turns. The pattern is 

 very characteristic, and im- 

 mediately recognised a second 

 time. I remember seeing it 

 depicted over and over again in Italian pictures 

 of the torments of the damned. At the Campo 

 Santo at Pisa and elsewhere, the entrails practised 

 upon by demons are shown with this Ruminant 



FIG. 62. Under- side of Tad- 

 pole showing the intestine 

 with its reversed spiral 

 through the transparent 

 body-wall. From Howes' 

 A Has of Biology. 



