AUSCULTATION. 501 



should be struck, and the blow must be perpendicularly to 

 the surface, otherwise the character of the sound will be mis- 

 leading. 



The pleximeter employed in mediate percussion, is generally 

 a flattened and oblong, oval, or circular piece of ivory, silver, or 

 caouchouc, the latter being the most suitable, from its making 

 little or no sound of its own when struck. A still more con- 

 venient pleximeter is the median finger of the left hand, firmly 

 applied over the surface to be examined. In using these 

 agents the following precautions are to be adopted : (a) The 

 instrument must be applied closely to the surface to prevent 

 any sound from air contained beneath it; (6) It must be 

 pressed somewhat firmly, where much superficial fat or mus- 

 cular tissues exist, in order to compress the latter and render 

 them more conducting, and bring it closer to the organ 

 to be examined; (c) in the case of an ivory or other un- 

 yielding pleximeter, the nails must be cut close, and the 

 blow made with the palmar aspect of the finger ends, to 

 prevent any clicking sound from the contact of the two hard 

 bodies. 



Palpation is the examination of a part by touch; succussion, 

 by shaking; and mensuration, by measuring. The modes of 

 applying these will be best considered when speaking of their 

 individual applications. 



In applying these various means of diagnosis in the lower 

 animals, we find that, notwithstanding all their advantages, 

 they are less useful than in the hands of the human physi- 

 cian. This is more especially the case in the maladies we 

 are about to consider, namely, those of the organs of 

 respiration. The chest of the human subject is almost 

 entirely exposed to examination, the mammae of the adult 

 female proving the chief obstacle to a thorough exploration. 

 Thoracic maladies can accordingly be traced through all 



