IV. CHEMICAL. 795 



The purpose of the instrument is to obtain these two measurements simul- 

 taneously. 



It consists of two laths of wood fixed at a certain angle against a wall. 

 Down the centre of each lath is a groove in which slides an index to show 

 the required measurements. The third index below is for the purpose of 

 ascertaining with great nicety the law of growth. 



IV. CHEMICAL APPARATUS USED IN PHYSIO- 

 LOGICAL RESEARCH. 



3742. Closed Flask for Experiments in Abiogenesis, &c. 

 Professor D. Huizinga, Director of the Physiological 



Laboratory of the University of Groningen. 



The neck of the flask is surrounded by a glass cylinder closed below so 

 that a circular groove is formed. When the liquid in the flask has been 

 raised to boiling temperature, the flask is closed by the previously heated iron 

 cylinder, the under surface of which, as well as the mouth of the flask, have 

 been carefully ground so as to fit accurately. The circular grooves at the 

 top and bottom of the cylinder are then filled with heated mercury. The 

 stedrn now escapes through the axis of the cylinder. When ready for closing, 

 after sufficient boiling, the lateral silver tube is heated by a pair of gas burners, 

 and the bell-shaped iron cover is also heated and placed on the top of the 

 cylinder so as to dip into the mercury of the upper groove. The flame under 

 the flask is then removed. ' The air which now enters the flask must neces- 

 sarily pass through the continually heated silver tube. If judged necessary, 

 the inner width of this tube can be reduced by passing through it a platinum 

 wire. 



In abiogenetic experiments a hatching apparatus is then applied to, but 

 without touching, the flask, so that during the whole experiment the silver 

 tube remains exposed to the flames of the burners. 



The lateral iron bar with the movable weight serves for equilibrium, so as 

 to secure a firm position for the whole on the mouth of the flask. 



3743. Dialyser. 



Professor D. Huizinga, Director of the Physiological 



Laboratory of the University of Groningen* 

 A piece of parchment is glued on both sides of an ebony frame, and strips 

 of the same material are glued about the edges, and thus is formed a 

 perfectly tight bag. The whole is then exposed to diffused daylight, the super- 

 fluous bichromate removed, and the dialyser is ready for use. The glue 

 used is a mixture of gelatine and bichromate of potash. 

 The dialyser can be tested thus : 



1. When the paper is dry and water poured in, no perceptible drops of 



moisture, even after long standing, ought to appear on the outer 

 surface. 



2. Afresh solution of hsemoglobine (diluted fresh blood) being poured in, 



and the dialyser placed in water, should the red hsemoglobine appear 

 in the water the apparatus is defective. 



.For further particulars respecting this apparatus see " Archiv fur 

 Physiologic," Vol. xi. p. 392. 



3744. Two Self-acting Filtering Glasses, for microscopi- 

 cal reagents. P ro f- Jessen, Eldena, in Pomerania. 



