X. SPECIAL COLLECTIONS. 959 



pagation of waves is further shown, and by means of two little springs on 

 adjoining places of the tube the velocity of propagation of the wave is demon- 

 strated, and if desired registered (also with different pressures indicated by a 

 manometer). The tube at the same time offers an opportunity for ausculta- 

 tion before and behind a dilatation. (Compare Bonders, Physiologic des 

 Menscheu. Leipzig, B. I, p. 78. Zweite Ausgabe, 1859.) 



3958. Scheme of the relations of Pressure in the mechanism 

 of Respiration. Prof. Donders, Utrecht. 



A glass cylinder (thorax), closed underneath by an elastic membrane (dia- 

 phragm), at the top by a stopper with three openings: 1st, for a tube (trachea) 

 with india-rubber bladder (lungs) ; 2nd, for a manometer, communicating with 

 the space in the cylinder ; 3rd, for a tube to regulate the pressure of the air in 

 the thorax. This pressure is made negative, as it is in reality ; which causes 

 the air to enter the india-rubber bladder, and the diaphragm to become 

 convex upwards. By pulling the diaphragm down (inspiration) the pressure 

 in the thorax decreases and the lung is more distended ; the resistance of the 

 lung is the negative pressure indicated by the manometer, Instead of an india- 

 rubber bladder a fresh lung of a dog or of a rabbit may be used. The space 

 in the cylinder outside the bladder is of no consequence, as not modifying the 

 pressure on the inner surface of the wall. 



d. PHYSIOLOGY OF MUSCLES AND NERVES. 



3959. Electrodes, with moist chamber for physiological re- 

 searches. P } ' f- Donders, Utrecht. 



a. Non-polari sable, consisting of glass tubes, at the thin bent end having 

 an aperture closed by moist salt-clay, continued in the lower part of the tube ; 

 on this clay the nerve is spread. The tube is further filled with a solution of 

 sulphate of zinc, wherein is a rod of amalgamated zinc. 



1. Four of these electrodes on a stand between a vice reaching into a moist 



chamber of glass, two for a polarising current, two for a stimulating 

 current on the extended nerve. (Compare Bonders, Onderzoekingen 

 gedaan in het physiologisch laboratorium, Ser. III., I. p. 1, 1873, and 

 Pfliiger's Archiv fur Physiologic, Bv., p. 1.) 



2. Four coupled with changeable distances. 



b. Ordinary. A set of rods of zinc or platinum of various forms fitting into 

 the same insulating glass tubes. 



3960. Small round Muscle-Chamber, with non-polar i sable 

 electrodes and registering lever. -Prof. Engelmann, Utrecht. 



Bottom, an ebonite disc 50 mm. diameter. Lid, a glass shade perforated 

 at the top, consisting of two halves, one furnished with a handle. 



Electrodes, two bent glass tubes ; the vertical arm perforates the bottom of 

 the chamber, and is at the top filled with clay impregnated with a solution of 

 sulphate of zinc. Through the horizontal arm an amalgamated zinc rod soldered 

 to a conducting wire is pressed into the clay. The openings of the tubes in the 

 chamber are covered with salt-clay. Between them the preparation (heart, 

 gastrocnemius, etc.) is put, whose contractions (increase in thickness) can be 

 registered by a lever attached by its axis to a lead wire, and resting on the 

 preparation by means of a vertical pin passing through the central opening 

 in the lid of the chamber. The whole movable on a stand. 



