114 SUMMARY OF CURRENT RESEARCHES RELATING TO 



the middle; suppose the lid cut away so as to leave au opening - 08 ra. 

 in length and ■ 023 m. in height. This opening is closed by soldering a 

 pieco of lead b in such a way that the box is divided into two com- 

 municating portions, one c lower than the other d (fig. 18). 



On the floor and roof of tho flatter half two opposite circular openings 

 e are made. These are covered with a cemented glass. The whole is 



Fi«. 18. 



arranged on a metallic circle beneath so that the lower glass is not 

 rubbed or injured by moving the apparatus on the stage. 



On the roof of the deeper half a large hole is made for pouring in 

 water and inserting ice fragments. A smaller hole receives a thermo- 

 meter. Finally, just above the floor of the higher portion, the end of a 

 tube 7* is inserted. The free end i of this tube, which is about the 

 size of a goose-quill, is curved so that water cannot flow out. 



Before use, the apparatus is half-filled with water poured in by the 

 large hole, air-bubbles under the glass are got rid of, and a drop of fluid 

 medium containing the object to be observed is placed on the upper glass, 

 and carefully covered in familiar fashion. 



The projecting tube is then warmed by a spirit-flame till the 

 thermometer in h indicates the desired temperature. A glass should 

 be placed below the free end to receive expelled drops. 



For cooling purposes the apparatus is filled a third full with water 

 at the temperature of the room or higher, and ice particles are inserted 

 at the opening g. An overflow can be emptied out, via the long tube, 

 by inclining the Microscope and without disturbing the arrangements. 

 The layer of water between the two glass plates is quite thin, so that 

 the strength of the light is but slightly altered. 



Apparatus for determining Sensibility to Heat.* — An apparatus for 

 the investigation of the heat sensibilities of the cockroach is described 

 by Prof. V. Graber. A trough of tin is divided into two end chambers 

 and a middle chamber whose floor is of wood, and which can be separated 

 from the end chambers by sliding doors. All three are covered by 

 sliding lids of glass or of tin at pleasure, and the whole is surrounded 

 by water-baths, two lamps placed underneath these enabling the end 

 chambers to be kept at temperatures differing by any wished amount. 

 The lamps are prevented from interfering with each other's action by a 

 wooden block under the middle chamber, which serves also as a stand 



* Arch. f. d. Gesammt. Physiol. (Pfluger), xli. (1887) pp. 241-3. 



