244 Microscopical Essays. 



M. Mufchenbrock inclofed the pupa of a -moth in a glafs tube, 

 nearly of the fame fize with the moth itfelf. 



The end A of the tube was drawn out into a capillary form, 

 the other end was covered with a piece of wet bladder, to exclude 

 the air ; the capillary end was then plunged in water, which rofe 

 to D. He placed the capillary part of the tube before a micro- 

 fcope, on a fmall micrometer, in order to obferve any motion or 

 change in the fituation of the water ; as it is evident the exfpira- 

 tiori or inspiration of air by the infecl would make it rife or fall 

 alternately. 



In the firft experiment he obferved a fmall degree of motion at 

 diftant intervals, not above two or three times in an hour; in a 

 fecond experiment on another fubjecl;, he could obferve no 

 motion at all. He then placed fome pupas under the receiver of 

 an air-pump, in water which he had previoufly purged of it's air ; 

 on exhaufting the air from the receiver,' he obferved one bubble 

 to arife in a part near the tail, and a few near the wings. The 

 pupa did not fwell under the operation ; on the contrary, on 

 letting in the air, it was found to be diminifhed in a fmall degree, 

 but in lefs than a quarter of an hour it recovered it's former 

 figure. Mr. Martinet publifhed at Leyden, in 1753, a diflerta- 

 tion, in which, it is faid, he has clearly proved, by a number of 

 experiments, that the pupa of the caterpillar and, fome other 

 infe&s do not refpire : I have not feen the work, 



Among.; 



