PERCUSSION. 81 



sounds, and, in consequence, Delafond after many trials relinquished this 

 — as well as another somewhat similar contrivance of his own — for the 

 use of the hands simply. The parts to be sounded may be struck back- 

 handed, with the knuckles ; or both hands may be employed, one serving 

 as the mediator. In fact, in animals, mediate percussion has advantages 

 over immediate, not only on account of the external soft parts being 

 thereby compressed, and themselves contributing to the sound, but also 

 because we are able with more precision to test certain places where 

 sound is but very indistinct, as around the cartilaginous borders of the 

 ribs. Notwithstanding this, for the common purposes of practice, 

 Delafond prefers immediate percussion, to be practised with one hand 

 alone ; and in performing it, he recommends attention to these rules, viz. 

 First : Let the shock or stroke be given perpendicularly to the surface to 

 be sounded : an oblique stroke would deaden the sound. Secondly : The 

 ribs themselves are to be struck, and not the intercostal spaces, bones 

 being better producers and conductors of sound than soft parts. Thirdly : 

 In striking or tapping, the same force should be employed against every 

 part. Fourthly: The same practice, in regard to manner and place, 

 should be strictly observed on both sides of the chest, in order that any 

 comparisons made may be correct. 



Pectoral sounds will be found to vary according to the region of the 

 chest percussed, the age of the animal, its condition, the full or empty 

 state of its bowels, audits peculiar conformation and organisation. Even 

 when all these circumstances appear alike, resonance may be considerably 

 greater in one animal than another. The chest of the horse admits of 

 being percussed either upon the right or the left side, from behind the 

 shoulder as far as the last rib : with a view, however, of rendering the 

 different sounds and their modifications distinguishable, it will be best to 

 make some division of this space. Suppose we draw an ideal line, corres- 

 ponding with the posterior border of the shoulder, and another in the 

 direction of the last rib : the interval between these two fixed boundaries 

 we divide by three horizontal lines into three equal parts, which we 

 designate regions^ superior, inferior, and middle. The superior region 

 extends from the scapular line to the last rib, along the border of the 

 longissimus dorsi, and includes the superior third of the superficies of the 

 ribs. The inferior region is marked by a line running from the elbow 

 along the superior border of the pectoralis magnus, the insertion of the 

 external oblique muscle and cartilages of the false ribs, and comprehends 

 the inferior third of the said space. The middle region comprises the 

 middle third, between these two lines. 



A DirrERENCE IN THE RESULTS OF PERCUSSION ofthe chcsts of men and 



quadrupeds, arises from the circumstances of the one being horizontal, the 



other vertical, in position, and of that of the horse in particular having 



those large intestines, the caecum and colon, as well as the stomach, conti- 



II. 6 



