EXPERIMENT STATION BULLETINS. 579 



hoppers had risen to 8.3% even, the nitrogen-volume was only O.Oo c. c. 

 less at the end than the estimated amount for the sample. 



PROOF BY ACTUAL VOLUME MEASUREMENT THAT GASES AND VAPORS MAY 

 BE ABSORBED INTO THE BODY-TISSUES OF INSECTS. 



In the first part of the paper evidence was given that the tissues of 

 insects may absorb gases and vapors confined with them. Proof by 

 actual volume measurement may most conveniently be given here. 

 Briefly, the general method used was as follows: An accurately meas- 

 ured amount of the air-vapor mixture (or of the pure gas, in some in- 

 stances) was transferred from the burette (Fig. 4.) to insects in a con- 

 tainer from which pure air had just been expelled by mercury. Then 

 after an interval of time, the whole amount was returned to the burette 

 and again accurately measured. The difl'erence in volume between the 

 readings showed whether gas had been given off, or taken up, by the 

 insects. By transferring back and forth at intervals and measuring in 

 this manner, something could be learned of the rate of absorption. In 

 order to determine whether an absorbed gas may be given off or exhaled 

 again, the manipulation just described was reversed. That is, insects 

 were placed in a respiration container with the gas (vapor) or air- 

 gas mixture for about thirty to sixty minutes. This gas was then all 

 pushed out of the container and a measured amount of pure air intro- 

 duced from the measuring burette. After various intervals of time the 

 gas was again measured. Table VIII, (p. 50) records the result of some of 

 these absorption and exhalation experiments. Besides the gases given 

 in the table, formaldehyde gas,* ammonia, hydrogen and the vapor of 

 ether were tried with similar results. 



As may be seen from the table, when a measured amount of one of 

 these gases or air-gas mixtures was transferred to' insects that had been 

 in air, the volume of the transferred gas qusickly decreased. The great- 

 est decrease came in the first three to five minutes. After ten minutes 

 any decrease could be accounted for by respiration — except in case am- 

 monia, sulphur dioxide or hydrocyanic acid gas had been used. These 

 three gases continued to be absorbed while the insects remained alive. 



The exhalation which was given off to pure air from insects saturated 

 with some gas-mixture was slower than the absorption. With gasoline, 

 carbon disulphide, nitrogen, hydrogen, carbon dioxide and formalde- 

 hyde, however, all (or all but a trace) of the measured amount of vapor 

 absorbed could be finally recovered. When ammonia, sulphur dioxide, 

 or hvdrocvanio acid gas was used, verv little could be recovered bv ex- 

 halation ; and if it were transferred once more to the insects, it would be 

 slowly taken up again. Oxygen, once taken up by the tissues, could 

 Dot be recovered as such — at least, not in appreciably measurable 

 amounts. It seemed to reappear only in combination, as carbon dioxide 

 and moisture. The fate of the greater part, at least, of the ammonia 

 absorbed has already been explained in this paper. Sulphur dioxide 

 and hydrocyanic acid gas seemed to become fixed in some non-volatile 

 combination within the insect tissues. 



*Beetles confined in formaldehyde-gas-air-mixture which was obtained by allowing 100 c.c. of air 

 to become saturated above 10 to 15 c.c. of a 40 per cent solution of formaldehyde at 2.3° C. were scarcely 

 able to move after two hours. The largest, strongest specimens became quiet only after about 3* 

 hours. When removed to fresh air after being so deeply affected, the heart-beats might improve for 

 a time but the insects did not recover fully and died after 6 to 8 hours. Formaldehyde gas had to 

 be present in high percentages to kill and even then its action was slow. 



