272 Illinois State Laboratory of Natural History. 



small glass tubes, about a quarter of an inch in diameter, 

 pipettes were made in the flame of an alcohol lamp by drawing 

 out each end to a capillary filament, the tips being closed by 

 melting at the time of making. To charge these pipettes, the 

 end of a proleg of a caterpillar was usually cut off with steril- 

 ized scissors, the point of the capillary tube broken off with for- 

 ceps just flamed in an alcohol lamp, one of these points pushed 

 into the cavity of the proleg, and the pipette partially filled by 

 exhaustion of the air from the other end. To introduce the 

 droplet of fluid so obtained into the test tube we invariably, re- 

 moving first the beaker and the cap of cotton contained within 

 it, carefully forced down through the cotton plug the capillary 

 tube of the pipette containing the infection material, without 

 loosening at all the plug itself. Sometimes the tip of the tube 

 containing the fluid was broken off inside the test tube before 

 the withdrawal of the pipette, at other times the contents were 

 carefully forced out with the breath, pains being taken not 

 wholly to expel the fluid contents of the pipette. After with- 

 drawal of the tube, the cotton plug was grasped with sterilized 

 forceps and slightly twisted within the mouth of the test-tube 

 to close effectually any small opening through the plug which 

 might have been made by the introduction of the pipette. 

 After this the cap of cotton and the beaker glass were restored, 

 and the tube was set aside with a companion precisely like it in 

 all respects, except that it had not been infected. During the 

 latter part of our investigations these check tubes were them- 

 selves operated upon with capillary pipettes, distilled water only 

 being introduced, at the time that the experimental tube was 

 infected. 



In withdrawing portions of the products of the culture for 

 inspection a similar process was used, the freshly made pipettes 

 being introduced as for infection and partially filled by exhaust- 

 ing the air from the upper end. After withdrawal, the cot- 

 ton plug was again twisted as already described and the cap 

 returned. The cover glasses used in the examination and prep- 

 aration of the material, whether this was derived directly from 

 the larvae or from artificial cultures, were flamed with an alco- 

 hol lamp immediately before using, after being thoroughly 

 cleaned by rubbing with a linen cloth. Slides were similarly 



