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MIDDLETHIRD OVA-EXTBACTOK. 97 



an inch or two beyond outwards, and about half an inch inwards. 

 The diameter of this tube should be three-eighths of an inch. 

 I quote Mr. Francis' own words, explaining the mode of using it : 

 " The thumb is placed on the top of the implement ; the nozzle is 

 then plunged into the water, and placed before the ova or small 

 fry it is desired to extract, and the thumb being suddenly with- 

 drawn, the ova is drawn up into the body of the vessel, and can 

 be dropped out at the thumb end if required, or examined in the 

 bowl of the instrument. This is a useful implement if it is wished 

 to examine ova or fry without damage, but it is a clumsy affair to 

 remove dead ova with, as it draws up everything that comes 

 within its influence, and often more than the operator requires." 

 Mr. Francis further writes, as to tweezers of various shapes : 

 "These also are clumsy, and disturb the surrounding ova more 

 than is necessary, and often crush the ova and scatter the con- 

 tents, which speedily putrefy all over the tray." 



He then refers to a fine needle stuck on the end of a stick and 

 used as a spear ; but from the toughness of the shell of the ovum 

 it is very slow, and on glass grilles, where the ova lie in rows, 

 would be impracticable. The last implement referred to is one 

 invented by Mr. Francis himself, and, until the invention of the 

 ova-extractor, was by far the best thing out. It is simply a fine- 

 pointed handle to which is attached a piece of brass wire, twisted 

 into a loop, and bent to any convenient angle. Mr. Francis justly 

 praises it as follows : " Softly introduce it between the ova and 

 under the one you wish to withdraw, and fetch it out swiftly but 

 steadily. No disturbance is created, and the method is almost 

 infallible, if quickly and neatly done, while the rapidity which can 

 be exercised after a little practice is astonishing. A dexterous 

 operator can pick the ova up almost as quickly as a fowl can pick 

 up barley." 



One dark afternoon in December, while I was ordering some 

 glass tubes to experiment on grilles, my eye fell on a pipette for 

 measuring drops. Why not reverse the principle, and use the 

 suction caused by the air expelled from the bulb to hold an 

 egg against the end of the tube ? I went home and measured 



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