ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 715 



Simple and Rapid Method of Producing Romanowsky Staining 

 of Blood-Films.* — Dr. W. B. Leishman prepares the stain in the fol- 

 lowing way. Solution A : A 1 p.c. solution of medicinal ruethylen-blue 

 (Grubler) in distilled water is alkalised by the addition of 0*5 p.c. 

 sodium carbonate. Solution B consists of aO'l p.c. solution of extra 

 B A eosin (Grubler) in distilled water. Equal volumes of the two solu- 

 tions are mixed in a large open vessel and allowed to stand for from 

 6-12 hours, being stirred from time to time with a glass rod. The 

 precipitate is then collected on a filter, washed with distilled water, and 

 the insoluble residue collected, dried, and powdered. The powder pig- 

 ment is dissolved in methyl-alcohol in the proportion of 0*15 p.c, and 

 the solution kept in stoppered glass bottles. 



Three or four drops of the solution are deposited on a blood-film 

 prepared in the usual way. In about ^ minute 6 or 8 drops of distilled 

 water are added and allowed to mix with the staining solution. After 

 allowing it to act for about 5 minutes, the stain is washed off with dis- 

 tilled water. The preparation may now be examined either wet or after 

 drying without heat, and mounting in balsam. 



Neutral Red for Detecting Bacillus coli in Water. — Dr. R. H. 

 Makgill f concludes from his experiments" that neutral red media afford 

 a rapid and delicate test of the presence of Bacillus coli in water. By 

 using varying quantities of water a rough estimate can be obtained of 

 the number present, allowance being made for the influence of inhibit- 

 ing organisms. Where a fair sample of water is examined, a negative 

 result may be taken as evidence of the absence of B. coli. Further 

 investigation is needed to decide whether or not a positive reaction 

 always indicates the j)resence of B. coli ; but the writer has not ob- 

 served any case in which this bacillus was absent from a sample of 

 water which gave a typical positive reaction. 



Dr. W. G. Savage, J who has also investigated the same subject, finds 

 that a positive neutral red reaction obtained by the method adopted, 

 while not absolutely diagnostic of B. coli, yet in the vast majority of 

 cases points to the presence of that organism. A negative neutral red 

 reaction does not certainly exclude B. coli, but renders its presence 

 highly improbable. The test is readily applied, and is of great value 

 in the routine examination of water. 



(6) Miscellaneous. 



New Centrifuge for Bacteriological Work. § — Dr. J. W. H. Eyre 

 has devised a machine (fig. 161) which is easy of manipulation and 

 fulfils the following requirements. The tubes are of such capacity as 

 will enable from 250-500 ccm. of milk to be manipulated at one time. 

 It has a rate of 2500-3000 revolutions per minute. The gearing is so 

 arranged that the requisite speed is obtained by 40 or 50 revolutions of 

 the crank-handle per minute. The handle is provided with a special 

 clutch, so that, on ceasing to turn, the machine is not stopped. The 

 tube-bearing portion of the machine is a metal disc of sufficient weight 

 to ensure good " flank " movement. 



* Brit. Med. Journ, 1901, ii. pp. 757-8. 



t Journ. Hygiene, i. (1901) pp. 430-0. J Tom. eit, pp. 437-50. 



§ Brit. Med. Journ., 1901, ii. pp. 773-4 (1 fig.). 



