TUBERCULOSIS. 383 



author found there was only a slight increase in the number of bacilli 

 inoculated, but milk with glycerine in the proportion of 5 per cent, 

 forms a more favourable medium. The author has also cultivated the 

 bacillus on sterilised urine and glycerine, and ordinary nutrient 

 gelatine with 5 per cent, of glycerine. On potato the growth of 

 the bacillus is extremely slow. Beevor succeeded in obtaining 

 cultures at the ordinary temperature of the room. 



Examination of Cultivations. — To examine the bacilli in these 

 various preparations the author prefers to use Neelsen's method, 

 floating the cover-glasses for from five to ten minutes on warm 

 carbolised fuchsine, and passing them through dilute sulphuric acid. 

 In some cultures the bacilli are shorter and thicker than is commonly 

 observed in human sputum, and they are for the most part without 

 the beaded appearance. In old cultures on glycerine agar-agar the 

 number of granular or beaded bacilli increases, and there are also 

 numerous peculiar forms. There are bacUli, sometimes two or 

 three times the length of an ordinary bacillus, provided with a 

 club-shaped enlargement at one or both extremities, and in rare 

 cases with lateral branches. They are no doubt identical with the 

 bacilh with swollen extremities and the branched forms observed 

 by Nocard and Roux. 



In milk the appearance is very striking, many bacilli attaining 

 in old cultures a great length, and all are more uniformly beaded 

 than in any other cultivations. Staining preparations by the method 

 of Gram in all cases exaggerate this appearance. 



The important part played by the environment is shown by the 

 morphological differences observed in artificial cultivation under 

 varying conditions, and by the fact that by successive cultivation 

 the bacillus can be educated to grow upon a medium which is un- 

 suitable for obtaining primary cultures. 



Impression preparations of the growth of the bacillus on the 

 surface of glycerine agar-agar in capsules show a tendency to the 

 formation of serpentine colonies, composed of bundles of more or 

 less parallel bacilli. 



Spore-formation. — In old cultivations true spore-formation can 

 readily be observed, both in stained and unstained preparations. In 

 the latter case they are recognised in the form of one or two highly 

 refractive bodies in individual bacilli. 



Toxic Products of Cultures. — The poisonous substances found in 

 cultures, and the composition and use of tuberculin, have already 

 been described (p. 43). 



Inoculation Experiments.— A relatively small portion of a culti- 



