152 SUPPURATION AND ALLIED CONDITIONS. 



From the cultures a coloured body pyocyanin can be extracted 

 by chloroform, which belongs to the aromatic series, and crystallises in 

 the form of long, delicate bluish-green needles. With the addition of 

 a weak acid its colour changes to a red. 



This organism has distinct pathogenic action in certain animals. 

 Subcutaneous injection of small doses in rabbits may produce a local 

 suppuration, but if the dose be large, spreading haemorrhagic oedema 

 results, which may be attended by a septicaemia, the organism occurring 

 throughout the body. Intravenous injection may produce, according 

 to the dose, rapid septicaemia with nephritis, or sometimes a more 

 chronic condition of wasting attended by albuminuria. 



Micrococcus Tetragenus. This organism, first described by Gaffky, 

 is characterised by the fact that it divides in two planes at right angles 



to one another (Fig. 44), 

 and is thus generally found 

 in the tissues in groups of 

 four or tetrads, which are 

 often seen to be surrounded 

 by a capsule which stains 

 faintly or not at all. The 

 cocci measure I /m. in dia- 



> meter. They stain readily 



with all the ordinary stains 

 and also retain the stain in 

 Gram's method. 



It grows readily on all 

 2 the media at the room 



temperature. In a punc- 

 ture culture on peptone- 

 gelatine a pretty thick 

 whitish line forms along 

 the track of the needle, 

 whilst on the surface there 

 is a thick rounded disc 

 of whitish-yellow colour. 



The gelatine is not liquefied. The colonies in gelatine plates are rounded 

 yellowish-white points, which under a low power show a granular or 

 slightly nodulated surface ; the superficial colonies appear as opaque 

 round drops of yellowish-white colour. On the surface of agar and 

 of potato the growth is an abundant moist layer of the same colour. 

 The growth on all the media has a peculiar viscid or tenacious 

 character, owing to the gelatinous character of the sheaths of the 

 cocci. 



White mice are exceedingly susceptible to this organism. Sub- 

 cutaneous injection is followed by a general septicaemia, the organism 

 being found in large numbers in the blood throughout the body. 





FlG. 44. Micrococcus tetragenus ; young 

 culture on agar, showing tetrads. 



Stained with weak carbol-fuchsin. x 1000. 



