THE GROUSE DISEASE 



fowl and pigeon. Specimens made of cultivations in 

 broth, on gelatine, or on Agar show, besides the char- 

 acteristic oval rods, also numerous dumb - bells or 

 chains of four. 



If a drop of blood of an animal dead of the 

 disease, or of a recent culture, be examined in the 

 fresh condition, the bacilli are not possessed of active 

 motility, all appearing non-motile or only showing 

 Brownian molecular movement. A trace of a droplet 

 of the heart's blood of a fowl, pigeon, or rabbit dead 

 of the disease, used for a gelatine plate cultivation or 

 rubbed over the slanting surface of nutrient gelatine 

 and kept at 20° C, yields innumerable colonies. The 

 first indications of the colonies visible to the unaided 

 eye do not appear before 48 hours are over, though 

 with a magnifying-glass they can be just discerned 

 after 36 hours. When easily visible to the un- 

 aided eye, that is, during the third and fourth days, 

 and even later, they appear as minute dots, greyish- 

 yellow in reflected light. Under a lens they are 

 round, sharply outlined, and somewhat prominent, 

 brownish and granular in transmitted light. The 

 colonies growing on the surface are a little larger 

 and have a slightly uneven outline, recognisable as 

 such under a glass, those in the depth remain very 

 small spherical dots (Fig. 35). In gelatine streak 

 culture, after an incubation at 20" C, there is visible, 



