in. OSMOSE, ETC. 139 



620a. Model of an Air Compressor, which may also bo 

 used as a water meter. M. Eugene Bourdon, Paris. 



621. Air Pomp for Double Exhaustion (Cabinet's prin- 

 ciple). L wizard, Paris. 



62 la. Model of Pneumatic Machine. 



M. Loiseau, jun., Paris. 



627. Pick's Spring Manometer. Weber, Wurzburg. 



628. Portable Pneumatic Apparatus. 



Prof. Waldunberg, Berlin. 



This apparatus serves for condensing and rarefying air for medico-therapeu- 

 tical and physiological purposes. It is possible by its means 



1. To inspire during its use compressed air whose degree of compression 



remains constant, but the compression of which can be varied to any 

 extent by means of a known weight lying on it. 



2. To exhale into rarefied air whose rarefaction is known and can be varied 



by means of the superimposed weight. 



3. To inspire rarefied air. 



These three methods of action not only produce a certain mechanical effect 

 on the organs of respiration, but also affect the heart and the circulation. The 

 apparatus is therefore adapted for studying the physiological action of com- 

 pressed and rarefied air on the circulation and respiration. 



Especially, however, it serves for medico-therapeutical objects, for which 

 its mechanical action renders it applicable ; as, 1, the inhalation of com- 

 pressed air ; 2, exhalation into rarefied air ; and, 3, inhalation of rarefied air. 

 As a remedy it is suitable for a series of lung and heart diseases ; as, for ex- 

 ample, the exhalation into a rarefied atmosphere has been ascertained to be 

 beneficial in many cases of emphysema of the lungs and asthma. The 

 inhalation of compressed air in the treatment of pleuritis, bronchitis, and 

 dyspnoea, &c. 



629. Fneumatometer. Prof, Waldunberg, Berlin. 



630. Air Pump, made by Spencer & Sons, Dublin. 



Prof W. F. Barrett. 



630a. Single Barrel Air Pump. 



James How and Son, London. 



III. OSMOSE, DIALYSIS AND DIFFUSION. 



631. Electric differential Osmometer. Engelmann. 



Prof. Engelmann, Utrecht. 



Two glass vessels of quadrangular section, possessing in the plane ground 

 surfaces facing each other a round aperture 30 mm. diameter, and each con- 

 taining an electrode ; a platinum disc 30 mm. diameter. Between the two 

 vessels the cell is placed, a plane parallel plate of ebonite, furnished with a 

 transversal perforation 30 mm. diameter, communicating with a short brass 

 top, upon which a rise-tube, manometer, etc. can be screwed. The niein- 



