140 Lectures on Bacteria. [J xn. 



isolate it have been hitherto ineffectual. If the Bacilli in the 

 blood of an infected animal are separated from the fluid of the 

 blood by nitration through porous earthenware, the fluid when 

 injected does not produce anthrax. In these negative results 

 lies the gap in the foregoing line of argument. If we still stand 

 by our previous assumption, it follows that the poison is ex- 

 creted and is operative in very minute absolute quantities, or 

 merely that it decomposes rapidly outside the living blood and 

 loses its efficiency, or both of these suppositions are true. 



The analogies, which may be brought forward in support of 

 the assumption here made that a poison excreted by the Bacillus 

 is the exciting cause of the disease, are drawn partly from the 

 fact that bodies which in extremely small quantities exert a 

 virulent poisonous effect, the poisons of dead flesh, ptomaines, are 

 produced by other Bacteria, though it is true out of dead organic 

 substances, partly and chiefly from Pasteur's observations on 

 fowl-cholera, a disease running a parallel course to that of 

 anthrax and caused by a parasitic Bacterium, of which we will 

 now proceed to give an account. 



But before doing so I have one more remark to make on the 

 attenuation of virulence. If we consider that Bacillus Anthracis 

 is a distinct species, it seems highly remarkable according to our 

 usual experience that it should have a poisonous effect at one 

 time and not at another. Yet similar phenomena are not 

 altogether rare. It will be sufficient to mention one example, 

 that of the sweet and bitter almond to which attention was first 

 called by Nageli, if I am not mistaken, in connection with the 

 subject which we are considering. The bitter almond is 

 poisonous from the amount of amygdalin which it contains, 

 though it is not very dangerous to human beings ; the sweet 

 almond contains no amygdalin and is not poisonous. The 

 sweet almond tree does not differ specifically from the bitter ; a 

 tree with bitter seeds may be produced from a sweet seed ; bitter 

 and sweet seeds may even be borne on the same tree in flowers 

 and fruits not morphologically distinguishable from each other. 



