410 THE COMPLETE GRAZIER. BOOK in. 



this stage into any discussion of these diseases, scheduled as trans- 

 missible from parent to offspring, it will nevertheless be appropriate to 

 indicate here the seat of each of the disorders which have been named. 

 The following brief notes may be read in connection with, though they 

 are given independently of, the foregoing anatomical details. 



Roaring is a complaint arising from some injur}' to the respiratory 

 passages, and usually to the larynx. In the front of the neck can be 

 felt the ringed trachea or windpipe, leading from the large cavity (the 

 pharynx) at the back of the mouth to the lungs. The larynx, at the 

 upper end of the trachea, is a complicated cartilaginous box, which 

 contains the membranes called the vocal chords, the passage of air 

 through which causes the vibration that results in the production of the 

 voice. The vocal chords are usually under the control of the animal ; 

 they can be approximated to each other, or allowed to remain apart. 

 In the former case, sound is produced when the air from the lungs is 

 forced between the chords. If the control over the muscles which 

 govern the vocal chords is lost, as in paralysis, respiratory sounds will 

 continually accompany the breathing, and this may be a common 

 symptom of roaring. The larynx occupies the same relative position 

 in a man as in a horse, and in some people it becomes greatly developed 

 into the protuberance known by the name of Adam's apple. It is 

 instructive to watch the motion of the larynx when a person is singing, 

 the transition from high to low notes being accompanied by the move- 

 ments associated with the different adjustments of the vocal chords. 

 Whistling is a modified roaring, and its seat may be either in the 

 larynx or in some other part of the trachea. 



Unsound feet, ringbone, navicular disease, and spavin are all dis- 

 orders of the bones, or joints, of the limbs. 



Ringbone is an exostosis, that is, an abnormal bony outgrowth, in 

 the region of the pastern bone, and its presence is noticeable either at 

 the joint of the cannon bone with the pastern, or at the joint of the 

 pastern with the coronet. If the exostosis should arise upon the 

 body of the pastern or coronet bone instead of between the joints, this 

 is known as false ringbone. The bones of the hind foot are more 

 frequently the seat of ringbone, o, disease which the reader will perceive 

 is in the region of the fetlock. 



Navicular disease is likewise associated with the foot. Behind the 

 junction of the coronet with the coffin-bone is a curiously- shaped bone 

 extending across from side to side. To this bone veterinarians have, 

 as has already been stated, given the name of the navicular, though 

 the bone so named by anatomists is in quite another region (the 

 tarsus, or hock). The navicular bone is, as it were, boxed up between 

 the coronet and the hoof; this bone is the seat of navicular disease, 

 which, as it progresses, may spread to the tendon for bending the foot, 

 which passes beneath the navicular bone. 



Lastly, as to spavin, by which, presumably, bone-spavin is meant. 

 The seat of this disorder is that region, halfway up the hind-leg, which 

 is popularly termed the hock, and is called by anatomists the tarsus. 

 There are six bones in the horse's hock, below which is the cannon 



