4 BIOLOGICAL LECTURES. 



disease is not inconsiderable, and we may safely say that only 

 with such bacteria as produce toxins of great potency, which 

 are easily yielded by the cells to the surrounding medium, 

 would it be possible in a given disease for the toxic chemical 

 substances by themselves to give rise to the same phenomena 

 as those which are due to the action of the living bacteria. 



The study of the nature and action of these toxins, or, as 

 they are now generally called toxalbumins, has added not a 

 few interesting facts to our knowledge of poisons in general ; 

 but, at the same time, it must be understood that the forms 

 with which we are dealing have not at this time been isolated 

 in a state of absolute purity, although they have been obtained 

 in a condition of great potency. Their exact nature is not as 

 yet well understood. They are believed by most bacteriolo- 

 gists and chemists to be of an albuminous nature, many 

 authorities claiming them as enzymes. They are amorphous 

 bodies and differ essentially from the crystallizable ptomaines, 

 with which substances they are sometimes confused. Perhaps 

 the one best studied, certainly the one possessing the greatest 

 potency, is the toxalbumin produced by the tetanus bacillus. 

 In the still impure state in which it has been obtained, its 

 activity has been found to be simply appalling. A single dose 

 of 0.000.000.05 grm. suffices to produce death after tetanic 

 convulsions in a mouse weighing 1 5 grams, and it is estimated 

 that the fatal dose for an adult human being does not exceed 

 0.23 mg. You will appreciate this fact better if you remember 

 that the fatal dose of atropine is 130 mg., and of strychnia 

 from 30 to 100 mg. It should further be mentioned that this 

 toxalbumin, unlike many of the others, is capable of giving rise 

 to the same symptoms as the bacillus which produces it. 



Another extremely virulent, although less active, toxalbumin 

 is that obtained from the cultures of the diphtheria bacillus. 

 Of this 0.4 mg. suffices to kill eight guinea pigs, each weighing 

 400 grams. 



In contradistinction to the tetanus toxin, that produced by 

 the diphtheria bacillus does not reproduce the entire series of 

 phenomena of the disease to which it belongs, since the in- 

 jection of it does not produce at the point gf inoculation an 



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