QUALITATIVE BACTERIOLOGICAL ANALYSIS. 123 



gnarled and convoluted thread-like masses. Surface colonies 

 exhibit a faint and transparent expansion. Under a low power 

 the colony is seen to consist of a mass of long threads, sometimes 

 throwing out processes into the surrounding gelatine, which is 

 not liquefied. 



Gelatine Tubes. Produces a faint transparent film almost 

 invisible to the naked eye. 



Agar. Growth resembles that on gelatine. 



Potatoes. Growth inappreciable. 



Broth. In forty-eight hours a fine mass resembling delicate 

 cotton-wool collects at the bottom of the tube and the broth 

 above remains perfectly clear. 



Microscopical Characters. Streptococci forming very long 

 chains. The individual cocci are 0'4 /* thick. It is not motile. 



Three other varieties of streptococci have been described, 

 which differ from the above in that they liquefy gelatine. They 

 were not very fully investigated by their discoverers, so that it 

 is difficult to follow the descriptions. They are as follows : 



The Streptococcus Albus. This organism was isolated by 

 Maschek from water. On gelatine plates it forms flat expansions 

 with a white periphery ; under a low power a small dark yellow 

 cloud is visible in the centre. Liquefaction proceeds rapidly. 

 In gelatine tubes it forms a flat expansion, which rapidly liquefies 

 the gelatine and produces a white deposit. On potatoes it grows 

 rapidly, producing a slimy expansion. 



The Streptococcus Vermiformis. This organism was also 

 isolated from water by Maschek. On gelatine plates it forms 

 yellowish- white centres, which sink into the gelatine. The 

 centre is light, whilst the periphery is composed of a dark ring. 

 Under a low power the contents of the colony are granular, 

 whilst the rim exhibits a radiated structure. It liquefies the 

 gelatine very rapidly. On potatoes it forms a dirty yellow 

 expansion, which grows very rapidly. The individual cocci 

 are almost always arranged in filaments which show a slow 

 vermiform movement. 



The Streptococcus Coli Gracilis. This streptococcus was 

 found by Escherich in the intestinal canal and faeces of flesh- 

 eaters. It consists of cocci with an average diameter of 

 0*2-0'4 fj. ; in recent gelatine cultures it shows S-shaped forms 



