TRANSACTIONS OF THE SECTIONS. 77 



lifies it for this office better than any now inuse ; this is the bugle or trumpet-end, 

 the edges of which being made very thin, and fitting flat on the walls of the chest, 

 are most readily affected by their vibrations. The instrument thus constructed, if 

 tried with a test-sound, will be found for most purposes superior to those now inuse. 



But most stethoscopes are provided with a perforated stopper, the object of which 

 is to shut out diffused sounds, and transmit by the central canal the sound from a 

 spot only. I find that the same object can be pretty well attained with the new ste- 

 thoscope by reversing it, applying the ear-end, which is made of dense wood, to the 

 chest, and the hollow end to the ear ; and, from its flatness, this pectoral end fits 

 the ear very well, without hollow enough to give the conchal sound. 



An inconvenience early found in this instrument was its fragility in the pocket. 

 This was readily obviated, and a convenient portability obtained, by taking off the 

 ear-end and fitting it into the hollow" end, which is thus supported in its thin part. 



Percussion. 



Since I explained the principle of percussion in 1835, I have had almost daily op- 

 portunities of proving its accuracy, and of deriving advantage from the varied modes 

 of percussion which a clear understanding of that principle suggested. So delicate 

 do I now find this test, that in many instances it discovers disease when other signs 

 are negative. 



The principle is briefly this, that the sound on percussion is derived from the 

 bodies which the impulse of the stroke reaches ; and the character of the sound de- 

 pends on the conjoint vibration of these bodies. Thus gentle and flat percussion 

 reaches, and is toned by, superficial parts only ; forcible percussion reaches, and is 

 toned by, deep-seated parts also. 



The character of the stroke-sound differs not only in loudness and clearness, but 

 also, and most remarkably, in pitch ; the deepest tones being the healthiest in all 

 cases except a few of pneumothorax and flaccid emphysema. In some instances the 

 stroke-sound is much louder on the diseased than on the healthy side. This is re- 

 markably the case where the sound is tubular, from condensation or compression of 

 the upper lobes of the lungs from pneumonia, pleurisy, or tubercle ; but in all these 

 cases the morbid character of the sound is proved by its note being higher than on 

 the healthy side. 



In percussion of the abdomen, different degrees of pressure with the pleximeter or 

 the hand struck on, will often afford useful results. The gentlest filliping percussion 

 without pressure may sometimes detect the superficial dulness of a layer of serum, 

 too thin to be discoverable by fluctuation : strong pressure, on the other hand, dis- 

 places the superficial parts, and brings the pleximeter within striking distance of the 

 deep-seated parts. 



For general purposes I consider the fingers the best instruments for percussion ; 

 and the various ways in which they may be used constitute one of their best recom- 

 mendations. There are, however, a few cases in which a little instrument for per- 

 cussion will give more accurate indications ; and I will mention one which is very 

 simple as well as efficient. Percussion plates generally are too large to be applied 

 closely between the ribs : when made of hard materials they cause too much clack- 

 ing on their own surface. The hammers recommended by Drs. Burne and Bennett 

 are liable to the objection, that their strokes may not fall in the same direction ; and 

 thus the sound may vary from the mode of the stroke. 



To obviate these objections, I have a firm narrow slip of whalebone slightly bent, 

 so that one end forms a handle, while the other is applied to the chest : this last is 

 covered with leather and velvet, to deaden the clack of the surface. The hammer is 

 made of a lenticular spheroid of lead, also covered with leather and velvet, with a 

 small rod of whalebone for its handle. The pleximeter fits like a finger between or 

 on the ribs : the hammer head being circular, can scarcely vary in the direction of its 

 stroke, and both being elastic as well as firm in their handles, they may be used with 

 much ease and precision. 



Observations on the Therapeutic Application of Air- Tight Fabrics. 

 By Professor Williams. 

 The use of oiled silk the author stated to be now of frequent practice, as a preventive 



