162 MICROBES AND TOXINS 



produced differed from the pure tetanic symptoms. It is not 

 yet possible to believe in the existence of pro-toxins analogous 

 to the pro-diastases such as the pro-fibrin-ferment. 



The toxins act in extremely minute doses, like the diastases, 

 of which a very small quantity can determine a chemical 

 change in a very large mass of material. But there are 

 alkaloid poisons which also act in a very small dose : a man 

 dies after absorbing the five-millionth part of his weight of 

 aconitine or digitalin. The mere fact of possessing an action 

 produced by very small doses is not equivalent to being a 

 diastase ; it may be an ordinary chemical phenomenon ; an 

 artificial catalyst such as colloidal platinum is " inactivated " 

 by one thousand-millionth part of hydrocyanic acid; Graham's 

 solution of ferric hydrate under certain conditions is sensitive 

 to the presence of i/5,ooo,oooth of ferrocyanide of potassium.^ 

 Finally, the phenomena produced by toxins are phenomena 

 taking place in living creatures, which makes it all the more 

 difficult to determine whether they are diastasic in nature or 

 simply due to ordinary chemical reactions. It is true that the 

 toxins of diphtheria and tetanus can "kill" 20 to 100 

 million times their weight of living animal, but these figures 

 must not be allowed to produce this illusion : the quantitative 

 relationship is complicated by a qualitative element whose 

 importance cannot be exaggerated. When a horse is killed 

 by i/8o,oooth of its weight of tetanus toxin, the toxin is not 

 acting on the whole mass of the horse : to produce death it 

 is sufficient for it to act on the medullary nucleus of the 

 vagus nerve, a group of cells scarcely weighing two grams. 

 The diphtheria toxin similarly acts in an elective fashion on a 

 group of cells in the medulla or in the cardiac ganglia. To 

 take facts of another order, the fixation of carbon monoxide 

 on the haemoglobin of the blood is not a diastasic phenomenon 

 (on the contrary it arrests a vital diastasic function of the 

 first importance), yet the toxic power of carbon monoxide in 

 proportion to the weight of the body is certainly more than 

 100,000. 



^ J. Duclaux — La chimie de la matiire vivante, Chapitre X. 



