The frontal sinus, then, occupies all the supero-lateral portion of the cranial box, which is thus provided with a double wall. At one point, however, over a lozenge-shaped area, the cranial cavity is only protected by a single wall. It is in this region that the slaughterman strikes the animal when killing it. The frontal sinus may be examined by inspection and palpation. Inspection sometimes reveals deformity of the external wall of the sinus. Such deformity, however, is rare, and Moussu has only observed it in two cases of tuberculosis of the bones forming the cranial wall. By percussion one detects abnormal sensibility, and partial or complete dulness over certain areas. [Illustration: $1] _Maxillary sinus._—The maxillary sinus occupies the whole lateral region of the face, from the inferior extremity of the maxillary spine as far as the sub-orbito-palatine region. In front its external wall is very solid, but behind, below the orbit, is extremely thin. Externally the sinus is largely protected by the anterior insertion of the external masseter muscle, a fact which explains how rarely it is injured. =Larynx.= In consequence of its deep situation, the larynx can scarcely be examined except by inspection, external palpation, internal digital palpation, and auscultation. External examination presents no difficulty, and enables one to detect lesions around or near the larynx. Palpation reveals the existence of œdematous swellings, enlargements of the retro-pharyngeal lymphatic glands, inflammatory engorgements, etc. Internal digital examination, like examination of the pharynx, can only be performed after very firmly fixing the animal in position, and inserting a gag in the mouth. [Illustration: $1] The hand is introduced, palm downwards, and passed as far as the pharyngeal cavity. The index finger can then easily be slipped into the glottis. Exploration must be effected rapidly and without violence. It reveals the condition of the glottis, the presence, position and form of growths like myxomata and of new tissues, due to the presence of actinomyces, as well as tuberculous vegetations or ulcerations. By auscultation we discover the presence of normal or abnormal laryngeal sounds—roaring, whistling, or bubbling sounds, etc. =Trachea.= The trachea may be examined by palpation and auscultation. Palpation reveals the degree of sensitiveness, abnormalities in position or form, the presence of peripheral inflammations, fractures of rings, etc. Auscultation indicates whether the tracheal sound be normal or otherwise, or accompanied by abnormal sounds, like mucous _râles_, or by pathological sounds conveyed from the chest. =Thorax.= The thorax can be examined by inspection, palpation, percussion, and auscultation.