﻿IX, B, 4 Barber: The Pipette Method 357 



human blood. Some work has been done by me on the effect of 

 poisons and other substances injected into the cells of Nitella.^^ 



In making a new capillary point, the pipette may be removed 

 from the holder, the old point broken off, and a new one made 

 from the same capillary. When the capillary is used up, a new 

 one may be made from the end of the straight portion of the 

 pipette, and the process may be continued until all is used back 

 to the loop. If a capillary point remains in good condition after 

 use, the pipette may be removed from the holder and kept for 

 later use ; but it must be placed in a refrigerator, else the expand-, 

 ing mercury is apt to burst it. 



In certain kinds of work it is of advantage to use two pipettes 

 simultaneously. This makes necessary the use of a second 

 holder for another pipette (fig. 15). With this modification, 

 one may inject two different substances into the same cell 

 at the same time, or by varying the pressure inject with one 

 pipette and withdraw with the other. One pipette may be 

 used simply as a probe or dissecting instrument, or it may be 

 attached to a rubber tube and used as an isolating pipette while 

 the other is arranged for injection. In one experiment, a 

 rotifer was held by the blunted point of one pipette while mer- 

 cury was injected into the body with the other. Points may be 

 made fine almost to invisibility, with sufficient stiffness for 

 piercing the wall or even the membrane of the nucleus of a cell. 



It has seemed to me that this inoculation technique in its 

 different forms may assist in the solution of various problems 

 in the biology of microscopical plants and animals. The in^ 

 troduction of foods, poisons, stains, and fixatives is made pos- 

 sible, and cells may be probed or dissected under high power — 

 methods which may be of use in the study of the structure, 

 chemistry, and physiology of cells. Finally, materials may be 

 withdrawn from one cell and injected into another, and it is 

 possible that investigations on fertilization and heredity may 

 be extended by this technique. 



In conclusion, it may be stated that this paper aims to give 

 the principle on which the pipette technique is founded and 

 only a part of its applications in detail. Experienced laboratory 

 workers, especially in fields less familiar to me, may make new 

 applications of the method or changes in the details of those de- 

 scribed here. I believe that the method may be much further 



'"Journ. Infect. Dis. (1911), 9, 117. 



