THE WIND-PIPE. 159 



other by so many channels, and in such various ways, that it is impossible 

 by the closure or loss of any one of them materially to impede the flow of 

 the vital current. If the jugular be destroyed, the blood will circulate 

 through other vessels almost as freely as before. 



THE WINDPIPE., 



In the fore part of the throat (6, p. 68) is placed a curiously constructed 

 tube, extending from the back part of the mouth to the lungs, and designed 

 for the conveyance of air to and from these organs. The windpipe of 

 the horse is composed of nearly sixty rings of cartilage, connected together 

 by strong and elastic ligaments. The rings are broad in front, narrowing 

 behind, and there overlapping each other, so as to be capable of consider- 

 able extension and contraction ; and across the posterior part run strong 

 muscular fibres, which give to that portion of the tube a power of action, 

 depending not indeed on the will, but on sympathy with other parts 

 concerned in breathing. 



This singular and beautiful mechanism deserves serious attention. It is 

 necessary for the comfort, and even the existence of the animal, that this 

 air-tube should be free from compression, and always open ; and it is 

 attached to the neck, long, and capable of the most varied motion. Would 

 any tube composed of an uniform substance, however elastic, maintain its 

 form and size amidst all these complicated motions? When the horse is 

 browsing, the windpipe is an inch or more longer than when the neck is 

 arched ; there is, therefore, the ligamentous substance between the circular 

 rings, which will lengthen the tube when required, and immediately con- 

 tract to its former dimensions when the force that caused the elongation is 

 removed. When the head is bent^ and the neck is arched, and in various 

 positions of the neck, a portion of the windpipe is violently pressed upon ; 

 therefore there are the cartilaginous rings — cartilaginous that they may 

 yield to pressure, and immediately recover their form when the pressure is 

 removed ; and lapping over each other, that the difference of calibre or size 

 in the tube may be as great as the necessities of the animal may occa- 

 sionally require, and muscular at the back, that all these powers of elasti- 

 city may be exerted to the fullest extent. The cartilaginous rings, again, 

 are broad and strong in front where danger may threaten, and softer and 

 more yielding behind, where the bones of the neck afford secure protection. 



The windpipe is lined by a membrane, likewise curiously contrived. It 

 is smooth and plain in front under the broad cartilaginous rings, and where 

 little change of dimension can take place ; but behind, it is puckered into 

 several folds, running down the windpipe, and not across it, and adapting 

 itself easily to any change in the size of the tube. 



Then it is easy to imagine that the windpipe of a good horse should be 

 large to admit the passage of a greater quantity of air ; and in horses from 

 which speed is required, as in the blood-horse, the windpipe is compara- 

 tively larger than in other breeds devoted to slower work. 



The windpipe should project from the neck. It should be as it were 

 detached from the neck, for two important reasons ; first, that it may easily 

 enter between the channels of the jaw, so that the horse may be reined up 

 without suffering inconvenience ; and, next, that being more loosely attached 

 to the neck, it may more readily adapt itself to the changes required, than 

 if it were enveloped by fat or muscle, to a certain degree unyielding : there- 

 fore, in every well-formed neck, and it will be seen in the cut, (p. 154,) 

 it is indispensable that the windpipe should be prominent and loose pn the 



