70 THE DISEASES AND DISORDERS OF THE OX. 



and with those present in most of the bones of the cranium. 

 The nasal chambers communicate at the posterior nares below 

 the lower border of the vomer. Each contains a structure 

 entitled the canal of Jacobson, which communicates with the 

 mouth. These canals begin in the floor of the nasal chamber, 

 one at either side of the septum. They run forwards, and 

 come to an end behind the pad forming the front of the palate. 

 These canals contain a number of mucous follicles. 



The larynx is simple, the lateral ventricles and true vocal 

 chords being only slightly developed. 



The ox has the lower vocal chord more markedly developed 

 than the upper, and bellowing is due to the length of the lower 

 vocal chord. The giraffe has voice only during that season. 



The trachea varies in length in different ruminants. For 

 example, in the tragulus there are 50, and in the giraffe 100, 

 tracheal rings. These rings are never perfect as they are in 

 birds. A third bronchus is present. It passes to the right lung 

 to supply a separate lobe which is not met with in the horse. 



The thorax has a relatively small capacity in ruminants. In 

 regard to the pleuree it is to be remarked that the posterior 

 mediastinum is strong and not perforated. It completely 

 separates one pleural sac from the other. This arrangement 

 occurs in all domesticated mammals with the exception of the 

 solipedes. The left lung is divided into two lobes, the right into 

 four, and the anterior lobe curves over and nearly covers the 

 front of the heart. In the camel the left lung is only rarely 

 divided. 



The interlobular tissue is thick in ruminants, and hence the 

 separation between the lobules is distinct. The knowledge of 

 this arrangement renders intelligible the distribution of pneu- 

 monic lesions in the larger ruminants. 



THE UKINARY SYSTEM. 

 In some animals the kidney almost resembles a bunch of 

 grapes, each lobule (grape) being provided with its own blood- 

 vessels and excretory duct. This subdivision occurs in all 

 animals in early foetal life ; but in most kinds of animals the 

 outer parts of the lobules coalesce, and the organ becomes a 

 single mass. The kidney of the ox is intermediate in form, the 

 inner substance of the organ being united, while the outer sub- 



