7«>0 SUMMARY OF OUEEENT RESEARCHES RELATING TO 



tain from each other, arc placed two drops of a fp.c. salt solution 

 containing the material in the desired state of dilution; these are 

 known as the "material drops"; besides these is also placed one drop 

 of sterilised \ p.c. salt solution. The isolating glass needles are now 

 sterilised ; this is done by taking away the loose side pieces of the 

 isolation chamber, and by turning off the screw with which N is fixed 

 int<> ( t : \" is drawn carefully away from the apparatus ; the points of the 

 glass needles are then held in a flask of strong sulphuric acid, and 

 afterwards in a flask of ammonia ; they are then returned to the plate, 

 the movable side pieces replaced, and the side slits closed with thick 

 olive oil. A drop of water has been previously placed on the floor of 

 the isolation chamber. The cover-glass is seen to be studded with small 

 rounded drops, indicating that the chamber is saturated with steam. 



Under a low power the points of the needles are dipped into the drop 

 of sterile £ p.c. salt solution. By a movement of the Microscope, the 

 loop of the left-hand needle, now full of salt solution, is brought, under 

 a high power, exactly into the middle of the field ; the right-hand needle 

 being about three screw-turns beneath it. By means of the movable 

 stage and a low power the isolation chamber is so placed that the left- 

 hand loop rests almost on the margin of a material drop, that is on the 

 margin that lies nearest to the culture drops. With a high power the 

 margin of the drop is searched for a bacterium to isolate, a part of 

 the margin being chosen where there are not many other bacteria ; then 

 the outer end of the loop of the needle is brought into contact with the 

 margin, whereby a little fluid will be withdrawn from the drop ; the 

 isolation chamber is then moved a little, so that the small drop of fluid 

 containing the bacterium is separated from the material drop. The 

 isolated bacterium has now to be transferred to one of the culture drops. 

 Using a low power, the chamber is moved so far to the right, that the 

 loop of the left-hand needle when raised, arrives between two culture 

 drops and near to the margin of one of them ; then under a high 

 power, the loop is brought against the cover-slip, where it deposits a 

 drop that probably contains the isolated bacterium ; several drops are 

 deposited until this is made certain. To bring the isolated bacterium 

 into the culture drop, the pointed end of the right-hand needle is used ; 

 under a low power the lei t hand needle is drawn three screws'-rings 

 down, and the right hand needle is raised and brought by the sliding 

 arrangement of B, exactly under one of the drops in which there is an 

 isolated bacterium ; then under a high power the point of the right- 

 hand needle is made to rest on the cover-slip in the drop, and by 

 moving the isolation chamber the point of the needle carries the drop 

 with the bacterium into the culture drop, the bacterium being kept in 

 sight during the process. Diagrams illustrating the stages of this 

 manipulation accompany the description. The'author gives minute 

 details for carrying out these processes, for correcting errors, and for 

 avoiding possible difficulties, and refers to the modifications required 

 when dealing with various micro-organisms, and especially when the 

 method is employed for testing the favourableness of any particular 

 Minn. He considers that the method is especially useful for studying 

 variability and pleomorphism. 



