A MICROMANIPULATOR FOR THE ISOLATION OF BACTERIA AND TE DISSECTION OF CELLS

I have recently described (Chambers, 1922, b) an apparatus for the manipulation of micro needles and micro pipettes under the highest magnifications of the microscope. This apparatus is an improvement on Barber's Pipette Holder (Barber, 1914) because of its simpler construction and the greater accuracy with which one can control its movements. An additional advantage consists in the existence of certain devices for bringing the pipette or needle, quickly into position before starting actual operation. The working principle of the apparatus (which is being pat-ented) is imustrated in figure 1. It consists in the use of bars of rigid metal connected at their ends to form a Z like figure by resilient metal acting as spring hinges. The bars are forced apart by screws and return when the screws are reversed. By these means arc movements are imparted to the tip of a pipette which is attached to one of the bars. As the radius of each arc is about two and a half inches, the fine movements imparted to the tip of the pipette are practically in straight lines because the excursion never exceeds one millimeter. The instrument can be used by itself for one needle or pipette, or with a companion apparatus when two needles, or a needle and a pipette are to be used simultaneously. When a pair is used, one is a left handed and the other a right handed appara-tus, both being clamped to the front of the microscope stage. For the isolation of bacteria, one instrument is sufficient. It may be clamped on the left side of the microscope stage, figure 2, so that the pipette projects into the moist chamber from th