94 



THE SURGICAL ANATOMY OF THE HORSE 



and profuse hasmorrhage into the spinal canal with a fatal result, 

 is a liable sequel. 



Any fracture of the sixth or seventh vertebra? is serious on account 

 of the liability to injury of the phrenic nerve, in which case paralysis 

 of the diaphragm would most probably result. This nerve derives 

 its fibres from the inferior primary divisions of the fifth, sixth and 

 seventh cervical nerves, though the contribution from the fifth 

 is inconstant. 



Fracture through the oblique processes of the third or fourth 

 cervicals may be favourably treated when there is not much dis- 

 placement. When such a fracture is suspected, a cradle should be 

 applied to the neck, the head tied to the rack, and all precautions 

 taken to prevent the animal moving its head. 



THE SINUSES OF THE SKULL 

 These are large irregular spaces formed in the skull, the size of which 

 they materially increase without providing any addition to its weight. 

 The sinuses are placed chiefly in the region of the face, but some are 

 deeply seated and extend towards the cranium. 



Four pairs of sinuses are described, namely, the sphenoidal, frontal, 

 superior maxillary, and inferior maxillary. 



The Superior Maxillary Sinus. — This is much the most extensive and 

 it is placed on the lateral aspect of the face, being bounded, as is 

 gathered from its name, chiefly by the superior maxillary bone. 

 Superiorly it communicates with the frontal sinus, the division between 

 the two being a thin plate of bone, which stretches obliquely between 

 the ethmoidal lateral mass and the osseous tube placed on the inner 

 aspect of the superior maxilla through which the lachrymal duct passes. 

 The communication between the frontal and superior maxillary sinuses 

 is in this plate, and is in the form of a large elliptical foramen, the 



