Excretion. 67 



organs of srnell, are also distributed in the nasal mucous 

 membrane. This mucous membrane is a pale delicate 

 rose color, the color and condition of the mucous mem- 

 brane are valuable aids in the recognition of diseases. 

 The sinuses of the head communicate with the nasal 

 cavities, evidence of which can be seen in cattle just after 

 removing the horns. The pharynx, just behind and below 

 the nasal cavities, is common to both respiratory and di- 

 gestive tracts and has already been described. The 

 larynx or voice box has been termed a mnsculo- cartila- 

 ginous valve, being made up of muscles, cartilages seven 

 in number, ligaments, and the vocal chords, the organs 

 of voice. Mucous membrane lines the entire- respiratory 

 tract. The muscles of the larynx have control of its 

 movements, such as widening or narrowing its capacity 

 by tightening or relaxing the vocal chords. In the dis- 

 ease known as Bearing there is wasting of the muscles 

 that control the chords, consequently the calibre of the 

 tube is smaller than required when the horse is put to 

 severe exertion, such as racing or drawing heavy loads. 

 One of the cartilages of the larynx acts as a lid to the 

 voice box, ar,d thus prevents food particles falling into 

 the larynx when on the way to the gullet. This being 

 the case it will at once be seen why when drenching ani- 

 mals only small quantities and plenty of time should be 

 given; if large amounts are poured down rapidly the lid 

 becomes raised to allow the animal to breathe and the 

 fluid passes down "the wrong way," that is, into the 

 windpipe 5 this will also occur if the tongue is pulled for- 

 ward during drenching, as such pulling tends to raise the 

 lid up and thus open the larynx, with the result quite 

 often of the death of the animal. 



