56 MASTITIS OF THE COW 



In stab cultures in gelatin-agar and agar at 38° C. it 

 forms a nail-like growth (Fig. 12). The nail-like growth 

 in the stab is wedge-shaped and most vigorous near the 

 top. The head of the nail or surface growth is thick and 

 glistening and covers the greater part of the surface. In 

 gelatin stab culture at 20° C. the growth is similar, the 

 medium is liquefied more or less quickly (ca. 3 days) in 

 goblet or funnel shape ( Fig. 13 ) . The liquefied medium is 

 diffusely turbid and has a dense bacterial deposit on the 

 floor against the unliquefied medium, but at the expense of 

 the surface growth. 



In streak cultures upon agar, potato and coagulated 

 Fig. 12. Fig. 13. blood scrum at 38° C. they form elevated 

 beaded round colonies which coalesce and 

 produce a thick band along the streak. 



In bouillon the organism grows with dif- 

 fuse turbidity of the medium and forms 

 ^/ II dense bacterial deposits on the bottom of the 



Fio. 12.— Culture of tubc. It docs uot prcscut a surface growth. 

 lMum^g°e!atfn-agar^. t! Milk at 38° C. Is usually somewhat 

 Fig:' 13.— Culture of slowlv coaffulatcd, a condition which en- 



stapnylococci. fetab in *' *-" 



fodaye. Horn^-shap^d ^^^^^ ^^r from scvcral days to a week, 

 liquefaction. usually thrcc to five days. 



In media which contain sugar, i.e., glucose, maltose, lac- 

 tose, and saccharose, it forms acid but no gas, so that the 

 medium finally contains ca. 2 per cent, normal acid. 



Resistancy. — The staphylococcus does not form 

 spores, although it is very resistant. It resists light and 

 drying in a sealed culture tube for a year or probably 

 longer. It endures daylight very well. 



Pathogenicity. — The virulence varies greatly. There 

 are pathogenic staphylococci which produce no alterations 

 when injected subcutaneously, others which only cause local 

 necrosis and abscess formation and again others which cause 

 death rather quickly. 



