108 



MICROSCOPIC METHODS 



the worker himself. Cabot states that Wright's stain can be obtained 

 from the Harvard Co-operative Society, Boylston Street, Boston, U.S.A. 

 Neisser's Stain. Neisser introduced the following stain as an aid to 

 the diagnosis of the diphtheria bacillus. Two solutions are used as 

 follows : (a) 1 grm. methylene-blue (Griibler) is dissolved in 20 c.c. of 

 96 per cent alcohol, and to the solution are added 950 c.c. of distilled 

 water and 50 c.c. of glacial acetic acid ; (&) 2 grins. Bismarck-brown 

 (vesuvin) dissolved in a litre of distilled water. Films are stained in 

 (a) for 1-3 seconds or a little longer, washed in water, stained for 3-5 

 seconds in (&), dried, and mounted. The protoplasm of the diphtheria 

 bacillus is stained a faint brown colour, the granules a blue colour. 

 Neisser considers that this reaction is characteristic of the organism, 

 provided that cultures on Loffler's serum are used and examined after 

 9-24 hours' incubation at 34-35 C. Satisfactory results are not always 

 obtained in the case of films prepared from 

 membrane, etc. , but there is no doubt that here 

 also the method is one of considerable value. 



SPECIAL BACTEKIOLOGICAL METHODS. 



Wright's Methods of measuring small 

 amounts of Fluids. In ordinary work fine 

 calibrated pipettes may be used for measur- 

 ing small quantities of fluids, but such 

 pipettes are not always available, and by 

 Wright's technique if a Gower's 5 c.mm. 

 haemocytometer pipette be at hand any 

 measurements may be undertaken, in fact, 

 once the pipette now to be described (see 

 Fig. 45) is made we are independent of 

 other means of measurement. A piece of 

 quill tubing is drawn out to capillary 

 dimensions, and the extreme tip of it is 

 heated in a peep flame and then drawn out 

 till it is of the thickness of a hair though 

 still possessing a bore. If the point be 

 c mm pipette A broken off this hair and mercury be run 

 Casing of quill tubing'; into the tube the metal will be caught 

 B, rubber nipple ; C, where the tube narrows and will pass no 

 wax luting ; E to F f urt her in fact, though air will pass, 



E, hair capillary. this tube 5 c.mm. of mercury, measured 

 from a Gower's pipette, is run down till 



it will go no further. A mark is made on the tube at the 

 proximal end of the mercury, which is now allowed to run out, 

 and the tube is carefully cut through at the mark. A piece 

 of ordinary quill tubing is drawn out and broken off just 

 below where its narrowing has begun, the capillary tube has 



