THE RESPIEATOEY APPAEATUS. 315 



tion with the hyoid bone is less direct than in the 

 horse. 



Pkaryngotomy. — After giving an account of an '^epi- 

 demic affection of the upper air-passages_,^^ which is evidently 

 the disease we have mentioned as diphtheria^ Youatt says : 

 "When there is no great external enlargement and yet 

 much difficulty of breathing exists and suffocation is 

 threatened, there is reason to apprehend that the pharynx, 

 or some factitious pouch which nature has suddenly formed 

 for the fluid, or (yet very rarely, for they are small in the 

 ox) the guttural pouches (?), or the commencement of the 

 communication between the mouth r.nd ear, are filled with 

 pus/^ In such cases he recommends the performance of 

 an operation similar to that known as hyovertebrotomy in 

 the horse. In the present day we would operate through 

 the mouth for this condition. 



TuMOUES OF THE Larynx duc to scrous accumulations 

 beneath the glottal mucous membrane, cancerous growths, 

 &c., are not frequent in the ox. They prove serious 

 impediments to respiration. 



Fractures of the Laryngeal Gartilage may take place 

 from injury ; union ensues, the earthy deposit uniting the 

 fractured edges sometimes forms a tumour projecting 

 beneath the laryngeal mucous membrane. Tumours of 

 neighbouring parts or impactions in the oesophagus may 

 impede respiration by pressure on the air-passages. 



The trachea has more numerous rings and differs from 

 that of the horse, in that the ends of the cartilages meet to 

 form an acute angle posteriorly. There is a small special 

 bronchus given off from the right side of the tube some 

 distance before its termination. Though the dorsal 

 vertebrae and ribs of the ox are much less numerous 

 than those of the horse they are larger, and the posterior 

 ribs are longer, and therefore the differences between the 

 size of the thorax in the two animals is not so great as 

 might be expected. The most essential reduction depends 

 on the way the diaphragm bulges in the ox, so that 

 it extends to opposite the sixth and seventh ribs. The 

 flat sternum of the ruminant allows him to comfortably 



