LATERAL FACES OF THE HEAD. 61 



ceptible in normal conditions and at rest. They dilate slightly during 

 inspiration and become relaxed again during expiration. It is not 

 thus during exercise ; their movements are accelerated in proportion to 

 the efforts executed. Other circumstances, as the age, the temperature, 

 and the seasons of the year, modify their frequency and often their 

 rhythm. The causes of irregular dilatations of the nostrils or of ex- 

 cessive rapidity of their movements should be carefully determined. 

 These are always symptomatic of pulmonary emphysema or of some 

 other grave affection of the respiratory organs. The examination in 

 this case will, therefore, include that of the lungs, the trachea, the 

 larynx, and, if need be, that of the other organic apparatus, if the accel- 

 eration be due to their diseased condition. 



Examination of the Interior of the Nostrils. The exam- 

 ination of the interior of the nostrils is made as follows : Let us sup- 

 pose the animal to be held by the bridle or simply by a halter whose 

 strap is passed through the mouth. Taking, for example, the nostril 

 on the right side (Fig. 24), the inferior lip is seized with the left hand 

 and the bulb of the right thumb is placed under the internal wing in 

 order to remove it from the external, which is separated by means 

 of the index finger. With this simple manoeuvre it is usually suffi- 

 cient to inspect the state of the mucous membrane over a large part 

 of its area. If it do not suffice, an assistant will hold the head, and 

 both hands are used ; the internal ala is seized by the right hand and the 

 external by the left hand, the head being so held towards the light as 

 to expose the largest surface of the nasal fossa. In some cases reflected 

 light from a mirror may be utilized. 



It is necessary to recall certain normal anatomical dispositions : 



The skin which covers the alse of the nose, preserving its characteristics, is 

 reflected into the nostrils to form a cul-de-sac known under the name of the 

 false nostril, and becomes continuous with the pituitary mucous membrane. The 

 hairs with which its free surface is provided are destined to arrest particles of 

 dust held in suspension in the air, which are obnoxious to the respiratory organs, 

 and which, when inhaled into the more sensitive portions of the apparatus, 

 cause irritation. 



At the inferior part of the* nostril', on the floor and a little anterior to the 

 point of continuity of the skin and the mucous membrane, is found the external 

 orifice of the lachrymal duct, giving exit to the tears in their passage through 

 excretory apparatus and offering such characteristics that it cannot be mistaken 

 for a pathological alteration. It is ordinarily single, but may be double and 

 even triple. Its form is round, its edges perpendicular, commonly called punched- 

 out, and the liquid which exudes is limpid and transparent. 



A cartilaginous septum, the septum nasi, separates the nasal fossae into right 

 and left. It is covered by the mucous membrane and is related to a lamina 



