316 THE MICROSCOPICAL NEWS. 
points presented in Klein’s paper may be very briefly stated. 
Firstly, contrary to what has been stated by some correspondents, 
Klein does not in his paper record a single experiment performed - 
by him upon sheep; and he expressly declares that ‘‘the fact of 
his (Pasteur’s) success in producing what he calls a ‘vaccine’—a 
something which, when inoculated into sheep, produces some 
modified form of splenic fever (anthrax) that protects the sheep 
against the after-production of fatal splenic fever when the virulent 
material is inoculated into the sheep—may be taken as established.” 
But with this admission Klein records results obtained by himself 
which are apparently not in harmony with the general hypotheses 
which Pasteur and others have promulgated. These results, more- 
over, have a further peculiar interest of their own. Klein com- 
plains that Pasteur has not made known the precise details of the 
process by which he produces the anthrax vaccine, and states that 
he himself has not been able to discover that process. His own 
inoculation experiments have been performed on rodents—mice, 
guinea-pigs, and rabbits—and, as we have said, they have been 
mainly designed to throw light on the hypothesis of the mutual 
convertibility of saprophytes and parasites as represented by the 
harmless hay bacillus and the deadly anthrax bacillus. Klein’s 
experiments with rodents induce him to contradict, so far at least 
as the anthrax bacillus is concerned, the statements that (1) the 
oxygen of the air is the cause of the decrease of virulence, (2) that 
the cultivated bacillus does not form spores at a temperature of 
42 to 43 deg. Centigrade, and (3) that the attenuated virulence 
once obtained is transmitted to the cultivation derived from that 
attenuated form. ‘The last statement of course obviously bears 
directly upon the alleged possibility of artificially converting into 
each other the known harmless and deadly species. We need not 
describe in detail the modes of cultivation adopted by Klein ; it will 
be sufficient to record the very remarkable phenomena observed by’ 
him. He grew the bacilli in gelatine pork and in pork broth. If 
grown in shallow vessels near the surface of the material and there- 
fore in proximity to the air in the vessels, they formed spores ; if 
grown at the bottom of deeper vessels in the same material no 
spores were formed until the rods, in growing upwards, reached the 
surface, when spores began to appear on the superficial rods. 
Hence the presence of free oxygen is apparently necessary to spore 
formation. 
Klein further asserts that no spores are formed by the bacilli 
when in the bodies of animals. Now mice are peculiarly suscep- 
tible to anthrax ; but Klein finds that, taking a given and perfectly 
pure cultivation ‘of the anthrax bacillus, such a cultivation becomes 
decreasingly fatal to mice if prevented from forming spores by the 
absence of oxygen. It, however, exercises no protective influence 
