810 SEC. 18. BIOLOGY. 



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.' 



3959. Electrodes, with moist chamber for physiological re- 

 searches. , Prof. Donders, Utrecht. 



a. Non-polarizable, 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 polarizing current, two for a stimulating 

 current on the extended nerve. (Compare Donders, 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-polarizable 

 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 w,ire, 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. 



3961. Gas Chamber for electro-physiological experiments 

 particularly with living membranes. Prof. Engelmann, Utrecht. 



The bottom of the chamber is an ebonite disc, diameter 13 cm., thickness 

 13 mm., resting on three small feet. Lid, a glass shade, height 12cm., diameter 

 11 ena., with a broad flat ground rim resting in a groove of the ebonite disc ; 

 through the perforated neck a thermometer can be introduced. 



On the bottom of the chamber 6 binding screws, each separately in electri- 

 cal connexion with corresponding binding screws on the outside of the 

 chamber. 



Inside the chamber, between the binding screws, the object-support is 

 placed, an ebonite plate furnished with : 



1st. A central vertical vice to fix a horse-shoe cork frame upon which the 

 animal membrane is spread. 



2nd. On each side a glass pillar to fasten the electrodes. 



To conduct the electric currents from the preparation small tubular non- 

 polarizable electrodes are used ; they are attached to lead wires and each 

 connected by a very thin wire with one of the screws. 



The other screws are to conduct electric currents, either to stimulate the 

 object or to warm it by galvanism. 



Two bent glass tubes, conducting through the bottom into the chamber, for 

 the entrance and outlet of gases. 



(Onderzoekingen gedaan in het physiologisch laboratoriun der Utrechtsche 

 Hoogeschool. Derde Reeks, II. 1873, p. 9, &c., PI. I.) 



