120 Proceedings of Royal Society of Edinburgh. [sess. 
virulent plague in Bombay or its vicinity, and there has not, there- 
fore, arisen any necessity to have recourse to cultivation in animals 
to obtain plague microbes of a suitable potency. 
A little of the juice of a plague bubo is asperated out by means 
of a sterilised glass tube drawn out to capillary size at one end, 
and known as a Pasteur’s pipette. When this juice is withdrawn 
with suitable precautions, it is found to yield in almost every case 
a pure culture of plague bacilli when sown on agar jelly. If the 
resulting culture appears to be pure, then portions of it are removed 
Fig. 3. — The Steam Steriliser. 
to small trial flasks of bouillon prepared exactly as the large ones 
are. These are placed in the dark and kept at a suitable tempera- 
ture, and in forty-eight hours thereafter, if the growth sown in them 
has been pure, an abundant crop of stalactites makes its appearance 
in the hitherto perfectly clear bouillon, forming, when viewed by 
transmitted light, one of the most curious and beautiful sights a 
bacteriologist could wish to see. The stalactites have been likened 
to silk threads hanging down into the bouillon from the surface. 
Having proved the absolute purity of the growth in this way, the 
operator may proceed with confidence to transfer the contents of 
