XXll PBESIDENTI.U. ADDRESS. 



retarded owing to the limited supply of oxygen, or at the surface, 

 where it has fi-ee access to oxygen in the form of a delicate 

 crinkled yellowish- Avhite liilm, which rapidly develops in a felted 

 mass. All cultures when they arrive at a certain stage of 

 development give ofi' a peculiar, somewhat unpleasant, flowery 

 •odour. Although the most favourable temperature for the culti- 

 vation of the tubercle bacillus is about blood heat (37 per cent, 

 centigrade or 98-6 per cent. Fahrenheit), recent experiments 

 have shown that it will grow quite readily at the ordinary tem- 

 perature of the room even on sterilised potatoes or beetroot, and 

 in honey, milk, and urine. Koch showed by his discoveries, 

 which. have been slightly modified by other observers, that the 

 tubercle bacillus behaves in a characteristic manner to some of 

 the aniline dyes, if fact, to demonstrate it a special method of 

 staining is necessary, which enables us at once to distinguish it 

 by means of the microscope from all other micro-organisms. 

 The most reliable and simple method for staining tubercle 

 bacilli is a modification by Zieh]-Neelsen. The preparation, 

 <iover-glass, or section, is placed in a Avatch-glass full of carbolised 

 Fuchsin for about five minutes, then washed in water to remove 

 the sui-plus stain, aftenvards plunged into a 33 per cent, 

 solution of sulphuric acid, or as some people prefer a 10 ]Xiv 

 cent, solution of nitric acid, until perfectly decolorised, the 

 staining process is then completed by immersion in an a<jueous 

 .solution of ^lethylene blue, afterwards the preparation is again 

 washed in water, dried, and finally mounted in Canada balsam 

 dissolved in xylol. AVhen such a preparation is examined under 

 -a suitable microscope, it will be found that the bacilli of tuber- 

 •culosis alone have retained the primary red coloration (Fuchsin), 

 while all other micro-organisms and any histological elements 

 which may be present are decolorised by the acid, but have taken 

 on the contrast or background stain methylene blue. This 

 invaluable method (which is practiced all over the world), is 

 almost in daily use in our Stock Institute at Brisbane, being 

 principally employed for detecting tubercle bacilli in sputum from 

 phthisical patients, milk of cows suffering from tubercular mam- 

 mittis, and various morbid specimens ; but its chief use is in 

 <ionnection with providing stockownaers in this and the neighbour- 



