210 QUEENSLAND AGRICULTURAL JOURNAL. [1 Mar., 1899. 
even now frequently sings praises of the valuable assistance which the micro- 
scope rendered in saying the life of what is at the present time a champion 
animal of his class in Australia. 
TUBERCULOSIS. 
There is no known disease which has a wider distribution than tuberculosis. 
The study of this disease in all its manifestations has claimed the attention of 
the greatest scientific minds throughout the world; the original manuscripts 
alone of these investigators would more than fill this room, and yet, although 
so much information has been elucidated in connection with this disease, there 
still remains practically an inexhaustive field for experimental research work 
for the most persevering and painstaking of investigators. Not only is 
tuberculosis the most common disease in mankind, but there is no other disease 
in existence which attacks so many different kinds of animals. Not one of our 
domesticated animals is completely refractory to it; they simply vary in their 
degree of susceptibility. The first person to claim the honour of having 
demonstrated the contagiousness of the disease was Villemin in 1865, whose 
experiments were subsequently confirmed by Cohnheim. In the year 1882 that 
celebrated bacteriologist, Robert Koch, as a result of his masterly and extremely 
delicate researches with the microscope, announced the discovery of the 
tubercle bacillus, which he succeeded in isolating and cultivating outside the 
animal body on artificial nutrient media; further, by inoculating guinea-pigs 
with small portions of the cultivations, he invariably produced tuberculosis, 
which caused the death of the animal ; and last, but not least, he again found 
unmistakable evidence of the presence of tubercle bacilli in all the lesions of the 
disease. ‘These investigations justified Koch in expressing the opinion that 
“¢ without the tubercle bacillus there could be no tuberculosis’ —a fact which has 
been maintained up to the present day. For many years it was general 
believed that the blood-serum media as used by Koch was the only one on whic 
the tubercle bacilli could be cultivated, but Roux, of the Pasteur Institute, 
found thata more favourable medium could be found in nutrient agar-agar 
with the addition of about 6 per cent. of glycerine. On this the bacillus grows 
abundantly and rapidly ; the growth stands out from the surface of the solid 
medium and takes the form of small yellowish-white lichenoid grains, which are 
dry, dense, and difficult to crush, each grain containing hundred of thousands 
of bacilli. In the case of liquid media, the growth takes place either at the bottom 
of the vessel in the form of extremely small yellowish-white grains, development 
being retarded owing to the limited supply of oxygen, or at the surface, where 
it has free access to oxygen in the form of a delicate crinkled yellowish-white film, 
which rapidly develops in a felted mass. All cultures when they arrive at a 
‘certain stage of development give off a peculiar, somewhat unpleasant, flowery 
odour. Although the most favourable temperature for the cultivation of the 
tubercle bacillus is about blood heat (87 degrees Centigrade or 98°6 degrees 
Fahrenheit), recent experiments have shown that it will grow quite readily at 
the ordinary temperature 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—in 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 
Ziehl-Neelsen. ‘The preparation, cover-glass, or section is placed in a watch- 
glass full of carbolised fuchsine for about five minutes, then washed in water to 
remove the surplus stain, afterwards plunged into a 33 per cent. solution of 
sulphuric acid, or, as some people prefer, a 10 per cent. solution of nitric acid, 
until perfectly decolorised ; the staining process is then completed by immersion 
in an aqueous solution of methylene blue; atterwards the preparation is again 
washed in water, dried, and finally mounted in Canada balsam dissolved in 
xylol. When such a preparation is examined under a suitable microscope,tit 
