MORPHOLOGY 619 



If the staphylococcus be only slightly virulent or the dose injected be small, 

 a suppurative arthritis is produced which may either prove fatal or end in 

 recovery (Courmont). Bezancon and Griffon described a staphylococcus 

 which invariably produced articular lesions. 



Occasionally death does not take place for a long time : in such cases 

 lesions of myelitis will be found and the animal will suffer from paralysis 

 and convulsions. 



Guinea-pigs, Rats, Mice and Dogs. These animals are not so constantly 

 susceptible as rabbits. In them, sub-cutaneous inoculation produces an 

 abscess ; intra-peritoneal inoculation may terminate in a fatal septicaemia. 



Geese. Lucet, by inoculating staphylococci isolated from a case of the 

 peculiar osteo-myelitis of young geese, was able to reproduce the characteristic 

 lesions of the disease in geese. Feeding experiments and sub-cutaneous 

 inoculation were without result, but inoculation of broth cultures or of pus 

 from the bone into the vein of the wing proved fatal in 3-4 days. Post 

 mortem, a multiple osteo-myelitis was found, and the liver was very much 

 enlarged : the organism was isolated from the bone marrow, the pus in the 

 bone, and from the spleen. 



SECTION II. MORPHOLOGY. 

 1. Microscopical appearance. 



The staphylococci are spherical cocci measuring O6-1//. in diameter, non- 

 motile, generally arranged in irregular-shaped masses of five to thirty cocci 

 which are often compared to bunches of grapes, 

 and rarely occurring singly or in pairs or in *,* 



short chains composed of quite a few cocci. , 



Staining methods. The staphylococci stain 



readily with the basic aniline dyes and are Jf *. m fy **; 

 gram-positive. **?$V *X %** 



These characteristics are common to all varie- "/**> . 



ties of the pyogenic staphylococci. v * * ., 



F 



2. Cultural characteristics. .;, 



Physical conditions. The staphylococci grow :* ^ ..^. n 



at any temperature between 10 and 44 C., *& : ff ' 



on all culture media, aerobically as well as FlQ , 28Q ^ staphylococcuspyogenes 

 anaerobically : the optimum temperature is aureus. Film from a broth culture. 

 about 35-37 C. The most favourable tern- ^h^SlT 1 ^ 01 ^ (0c<m ' obj ' 

 perature for pigment production lies between 



20 and 25 C. ; the colour does not appear when the cultures are grown 

 in vacuo. 



Staphylococcus pyogenes aureus. 



Broth. At 37 C. the medium becomes cloudy in 12-24 hours, after which 

 an abundant white precipitate is thrown down but the broth still remains 

 cloudy. Later on, the precipitate assumes a yellowish tint and may become 

 bright orange in colour. Sometimes the pigment is slow in making its appear- 

 ance and may never be very marked. In old cultures, the Staphylococcus 

 aureus often loses its power of producing pigment and then cannot be dis- 

 tinguished from the Staphylococcus albus. 



Gelatin. Stab culture. At 20 C. in 24-36 hours a granular growth appears 

 along the line of sowing : towards the fifth day it forms a funnel-shaped 

 liquefaction filled with a turbid liquid and at the bottom a yellowish- white 



