398 Prof- Marshall Ward. Experiments on the [Dec. 15, 



prepared with spores from a very vigorous and virulent agar tube of 

 anthrax. The spores, which were quite mature, were not subjected 

 to heat, but simply shaken in sterile water to wash and separate them 



thoroughly. 



The three gelatine plates were made at 35 C., the agar plates at 

 60 C., neither of which temperatures could injure the ripe spores. 



The three gelatine plates were labelled pi, p2, and p 3, and the 

 agar plates p 4 to p 8 in order. 



Immediately after making the plates, all were exposed to the 

 December sun, except plates p 4, p 5, and p 6, and this was done as 

 follows : In each case the plate had a stencil plate with a cut-out 

 letter on its lower face, and arranged as described above (p. 396). 



p\ t a gelatine plate with a large letter M, was exposed, face down, 

 to the light reflected from a mirror (see fig. 1) for three hours on 

 December 7, and for four hours on December 8, the interval being 

 passed in a cold room (t about 8 9 C.), and then incubated at 20 

 in the dark. 



pS was treated in exactly the same manner. But this was an 

 agar plate with a large W. 



p 2, a gelatine plate with a large H, was exposed and heated in the 

 same way, except that no mirror was used, the latter being upwards 

 towards the sun. 



p 3, a gelatine plate with a large B, was similarly exposed, face up, 

 but a plane mirror arranged to reflect light down upon it. 



p 7, an agar plate with a large E, was treated exactly as the last. 



There now remain the three agar plates, p 4, p 5, and p 6, to 

 account for. 



p 4 was placed forthwith in the dark incubator at 20 C. 



p 5 and p 6 were kept for eighteen hours in a drawer, the average 

 temperature' of which is almost 16 C., and were not exposed till next 

 day (December 8), when they lay for five hours, face upwards, and 

 with a mirror above them, p 5 had a small E, and p 6 a broad but 

 email I, to let the light in. 



After exposure, these also were put in the same incubator with the 

 others. 



Nothing was visible to the unaided eye on these plates (except p 4) 

 until the llth instant, though the microscope showed that germina- 

 tion was proceeding on the 10th. The plate p4, however, had a 

 distinct veil of colonies all over it on the 9th, and this had developed 

 to a dense typical growth by the llth. 



On December 11, at 10 A.M., the state of affairs, as regards the 

 exposed plates, was as follows : 



p$ &nd p6 showed each a sharp transparent letter E and I 

 respectively of clear agar in a dull grey matrix of strong anthrax 



lomes, which covered all the unexposed parts of the plate 



