ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 



877 



Since liis first experiments Dr. Regnard has invented an inge- 

 nious method by which he can see, notwithstanding the great pressure, 

 what goes on inside the apparatus. Hitherto the operator simply 

 placed the animals on which he experimented in the iron block of the 

 Cailletet pump, and subjected them to the pressure corresponding to 

 a given depth ; he then released them, sometimes very slowly (after 

 several days), sometimes rapidly and even instantly, and examined, 

 physiologically and microscopically, the effects produced. But all 

 the intermediate stages between the introduction of the animals and 

 the time they were taken out escaped the observer. Now, however, 

 the apparatus shown in figs. 208 and 209 allows him to follow each 

 minute the effects. 



Two holes are pierced through the lower part of the Cailletet 

 block M (fig. 208). In these are inserted two tubes at r and r'. 

 These are hollow, and in each of them is solidly fixed a cone of 

 quartz B, the end of which comes as far as the edges of the hole which 

 is pierced in the screw-nut. A ray of light thrown in at the orifice r 

 will thus traverse the apparatus and emerge at r'. Experiments have 

 shown that the apparatus will resist easily a pressure of 650 atmo- 

 spheres, which represents that of the greatest depths that have been 

 dredged — about 6500 metres. Through one of the quartz cones are 

 sent the concentrated rays of an electric lamp. These rays cross the 

 block (full of water), and emerge on the opposite side, where they are 

 received by an achromatic object-glass which projects them on a 

 screen. The observer therefore works at a distance from the appa- 

 ratus, where he is sheltered from all 

 danger. The arrangement has an- 

 other advantage. The orifice pierced 

 at r is hardly'half a centimetre in 

 diameter, and small organisms can 

 be experimented with in the Vessel 

 immersed in the block M, which are 

 invisible to the naked eye. By pro- 

 jecting them with a lens they are 

 so enlarged, and appear with such 

 transparency, that we can follow on 

 the screen the movements of their 

 branchia, and even of their heart, 

 during the experiment. In the ex- 

 periment represented in fig. 209, one of the operators is occupied 

 in regulating the electric lamp and in setting the Projection Micro- 

 scope, while the other applies the pressure. 



Dr. Regnard is pursuing his studies on life under high pressures. 

 He showed last year that the unequal comjiressibility of the liquids 

 and solids of the organisms caused the latter, after a long pressure, to 

 be B(jakcd with water, become turgid, and consequently lose their 

 functions. But with the apparatus here described, he has been able 

 to follow the phenomena which precede this. At the pressure of 1000 

 metres (about 200 atmospheres) the object shows inquietude; at 

 2000 metres it falls to the bottom of the vessel struggling ; towards 



Fig. 208. 



