TRACHKffi. 



381 



" In the Ox the rings are very strong and close, and in form 

 like a horse- shoe with the ends approximated. 



" In the Pig the incomplete rings are broad at one part, and 

 narrow on the opposite side, with a tendency to spiral arrange- 

 ment. I imagine that this would make a very rigid tube, and, 

 indeed, it feels so in the hand. 



" Then, in the Goose, the narrowed lower part is that which 

 is figured just before the trachea reaches the sternum. The 

 (complete) rings are twice as broad in one half as in the other, 

 and by the alternate disposition of these differing widths, a 

 tube is formed of great flexibility fore and aft, but almost 

 absolutely rigid in the lateral direction. This seems to be so 



BINGED TISSUES OF SDGAB-CASE VEGETABLE SPIBAL TISSUES TENDJSG TO BDTGS, 



marked an evidence of design as to be calculated to greatly 

 raise our admiration." 



WE have seen several examples of ringed tissues tending to 

 the spiral form, and it is but natural that we should expect to 

 find spiral tissues tending to the ring. 



In the accompanying illustration the two left-hand figures 

 represent the curiously modified ringed tissue which is to be 

 found in the sugar-cane, the left-hand figure being much more 

 magnified than the other. 



The other figures represent four examples of vegetable spiral 

 tissues, in which it will be seen that there is a tendency to form 

 rings, and that if a number of rings were substituted for the 



