1903 Reptile Studies 299 



case is it ever changed so long as it remains there. As I 

 have said, there is nothing remarkable in this fact. Hut on 

 one occasion I caught an adder which was very heavy 

 in the region of the throat, evidently full of food, and on 

 expressing the contents out of the mouth I found that the 

 first object to appear was a water-vole, with no signs at all 

 of digestion upon it. This was followed by a second, 

 which was quite perfect until the head appeared (the vole as 

 usual having been swallowed head first). The head, how- 

 ever, was partially digested. I argued that if the vole had 

 been passed on entire into the digesting part of the 

 alimentary tract, it would show evidence of the process 

 over the whole body, not merely at one point. The 

 question that remained then was to get a specimen in 

 which I could observe the position of food in the act of 

 digestion, so as to ascertain the exact mechanism. It was 

 a long time before I got such a specimen ; indeed, it was only 

 when working at this subject quite recently. Last year 

 (1902) my collectors sent me two specimens which clearly 

 demonstrated the whole process. The first of these was a 

 specimen of Vipera aspis, sent to me from near Bordeaux 

 in France. I felt by external examination that it had 

 food in it, so opened the alimentary tract in situ. The 

 result was most interesting. A full-sized green lizard, 

 Lacerta viridis, was lying half in the gullet and half in the 

 mid-gut, the former half unchanged, the latter part 

 absolutely disintegrated by digestion except the bony 

 parts. It was firmly gripped by the constriction at the 

 entrance to the mid-gut, marking off at a definite point the 

 digested from the undigested part. The lizard had been 

 swallowed head first, and digestion had got to the length of 

 destroying the head, thorax, and part of the abdomen of 

 the lizard, leaving the tail and hind limbs untouched. The 

 stomach wall of the lizard was dissolved, revealing in turn 

 the food of the lizard, in the shape of a large number of 

 beetles. 



The second specimen, which I happened to receive 

 shortly afterwards, was an Australian black snake over 

 3 feet long. On opening this in the same way I was 

 very gratified to find an analogous state of things. The 



