is 



ing that in size and contour Schmidt's crystal and Koch's 

 bacillus were similar, would that justify the assertion of 

 their identity ? Evidently not to an individual whose 

 conception of a Bacterium comprises something more 

 than size and shape. The crystal cannot be made to 

 absorb and retain aniline dyes, as Dr. Schmidt expressly 

 states ; the bacillus, like other bacteria, is readily stained 

 by any one of several aniline colors. The crystal, we 

 way assume, does not grow nor reproduce ; the bacillus 

 elongates, divides, and produces in its substance two or 

 more globular bodies, which in turn grow into rods. 

 Dr. Schmidt fails to appreciate these vital differences ; 

 ignores the absorbent and reproductive powers of the 

 true bacilli, attested by a score of competent observers. 

 For him size and shape are enough, and upon this fan- 

 cied resemblance of his crystals, in outline, to bodies 

 that he has never seen, he assumes their identity. I shall 

 consider Schmidt's paper in the discussion of tuberculosis, 

 and make this allusion here because it illustrates admir- 

 ably the fact that even in these latter days publications 

 about bacteria, by men of experience in other departments 

 of medicine, even in pathology, evince a failure to appre- 

 ciate the first principles of mycological investigation. 



To ascertain the relation to a disease of bodies whose 

 bacterial nature is thus recognized, and which are found 

 in the blood or tissues of a diseased animal, it is evident 

 that the first step must consist in the perfect isolation of 

 the bacteria from the enclosing tissue ; since otherwise 

 the possible effect of inoculation may not be ascribed 

 to the bacteria rather than to the accompanying unor- 

 ganized substances. 



The isolation of bacteria from the blood and tissues of 

 an animal has been attempted chiefly in two ways : by 

 simple filtration through papet, clay, or other porous sub- 

 stance, and by artificial cultivation. Filtration is evidently 

 a very unsatisfactory attempt at isolation ; the separation 

 of the smaller bacteria, especially micrococci, is practi- 

 cally impossible ; and since other ingredients of blood or 

 tissue are or may be retained on and in the filter, the 



