380 



NATURE S TEACHINGS. 



-quite enough and examined, it will be seen that there are 

 some large tracheae, just like those of the Dragon-fly larva, 

 on each side of the proboscis, and that, where the end is 

 widened and flattened into a sort of disc, their place is taken 

 by a set of very much smaller tracheae, coming nearly to a 

 point, and each being supported internally by a series of 

 incomplete rings, shaped very much like the letter C. A 

 slide containing this object well mounted can be purchased at 

 any optician's for a shilling. 



THE trachea, or windpipe, as we call it, of all vertebrate 

 animals, man included, is formed on exactly the same principle, 

 as any one may see by going to a butcher's shop, and looking 



PIG. GOOSE. 



at the trachea, or windpipe, by which the lungs, or " lights," as 

 they are called, are suspended. Were it not for this structure, 

 we should not be able to bend our necks or turn our heads. 



The accompanying illustration shows the tracheae of three 

 well-known creatures. The left-hand figure is the trachea of 

 an Ox, the central figure that of a Pig, and the right-hand 

 figure that of a Goose. Mr. Tufien West, who made the 

 drawings, sent with them the following remarks : 

 - "The tracheas of animals furnish some very interesting 

 examples of variation in the form and arrangement of the 

 rings. Their purpose, perhaps, one can but guess at in some 

 cases ; but doubtless, as being works of the Master Builder, 

 careful study would be repaid. 



