EMPYEMA OF THE FACIAL SINUSES. 311 



fever and influenza, and in cattle in malignant catarrhal fever ; it also affects 

 both the head and neck as the result of wounds in these regions. Where 

 the head is held low for considerable periods, as after bruising or sprain 

 of the muscles of the neck or disease of the cervical vertebrae, marked 

 oedema may develop, completely transforming the appearance of the 

 animal, while swellings affecting the nasal mucous membrane and adjacent 

 structures induce difficulty in breathing. A photograph of such a case 

 is presented in Fig. 306. 



This condition demands attention, as, being often accompanied by 

 fever, it may, on superficial investigation, be mistaken for a symptom of 

 certain infectious disorders. Such an error is, however, avoided by con- 

 sideration of the history of the case and the condition of the neck muscles, 

 or the cervical vertebrae. Marked dyspnoea may necessitate tracheotomy. 

 As soon as possible the head should be raised and so maintained by 

 slinging the horse and employing '"a headrest. The result is often 

 astonishing ; a large swelling of this kind disappearing in a few hours. 

 Massage is useful to promote resorption of the transudation. 



(D) DISEASES OF THE FRONTAL AND SUPERIOR 



MAXILLARY SINUSES. 



Although in cases of empyema of the facial sinuses of the horse, 

 the frontal and superior maxillary are chiefly involved, the other 

 or smaller sinuses (inferior maxillary and sphenoid) are sometimes 

 implicated. The superior maxillary sinus communicates with the 

 middle meatus of the nasal chamber by a curved slit-like opening, 

 which is very unfavourably situated and too small to give free exit 

 to the usual purulent collection in the sinus. The inferior maxillary 

 compartment in 3 r oung horses is very small, and though larger in 

 old animals it seldom contains pus. Normally it is separated from 

 the superior or larger sinus by a transverse bony partition, which, 

 in a few horses, is imperfect or perforated. This small sinus com- 

 municates with the nasal passage by a portion of the curved slit 

 already mentioned. The frontal sinus has no direct outlet to the 

 nasal chamber, but it communicates by a large opening with the 

 superior maxillary sinus, so that impaction or disease of the frontal 

 sinus nearly always affects the large maxillary sinus. In oxen the 

 frontal sinus opens directly into the nasal chamber. 



The mucous membrane of the frontal and maxillary sinuses is 

 continuous with that of the nasal passages. In the sinuses it is 

 closely attached to the bone, to which it acts as periosteum, and 

 contains numerous small mucous glands. From its sheltered position 

 this membrane is seldom primarily diseased. But when nasal infec- 

 tion or catarrhal inflammation arises, the disease readily extends 

 and becomes chronic, and the exudate, finding no direct outlet 4 



