42 TOXINES AND ANTITOXINES. 



As already mentioned, the dose L ? is equal to 100 in the case 

 of most toxines in the fresh condition. Thus, EHRLICH found 

 that one of his freshly-prepared diphtheria virus solutions was 

 of such composition that one I.E. (Immunity Unit) neutralised 

 0'31 c.c. of the poison. Hence, it followed that the lethal dose 



0*31 



of the poison solution had to be = O'OOSl c.c., and this 



10U 



was found to be actually the case. Thus, with this poison, too, 

 L = 100. After three-quarters of a year the poison showed 

 the same neutralisation value in c.c., but the single lethal dose had 

 risen to 0-009 c.c., so that L ivas equal to about 38 i.e., that 

 33 toxic units (contained in 0*31 c.c.) corresponds to the dose 

 L . The toxic value and L dose then remained constant. 



Other poisons decompose in such a way that L is equal to 50, 

 while others, again, become finally constant with an L dose of 

 25, &c. 



It would seem, then, that the toxines either decompose in 

 such a manner that half of them becomes inactive, or that they 

 undergo a tripartite change so as to consist of two parts of toxoid 

 to one of unaltered toxine. 



EHRLICH'S chief endeavour has been to establish the absolute 

 value of an I.E. (Immunity Unit) i.e., to determine to how 

 many saturation units the I. E. corresponds in poisons consisting 

 of toxines, toxones, and toxoids, or, to express it quite crudely, 

 how many haptophore groups correspond with the number in one 

 I.E. He is strongly inclined to fix their number at 200, and 

 he bases this conclusion on the following premises : The value 

 L is usually equal to 100 in the case of fresh poisons, and these 

 subsequently decompose in such a manner that their L values 

 stand in a very simple proportion to 100. From this he con- 

 cludes that the absolute force of combination must also stand 

 in some very simple relationship to the number 100. Now, 

 no poison has yet been prepared, in spite of all attempts at 

 purification, with a value L exceeding 200, the highest observed 

 being 160 in the case of a poison which was certainly not per- 

 fectly pure (MADSEN). Hence, EHRLICH concludes that every 

 toxine bouillon must contain 200 saturation units i.e., that 

 the I.E. is equivalent to 200 saturation units. An absolutely 

 pure toxine (without toxones) would thus, in the fresh condition 

 (i.e., without toxoids), show an L value of 200 and an L + value 

 of 201. 



In this case x 4 y + z, in the general formulae given above, 

 is equal to 200, and from this it is possible to calculate the 

 quantity of toxones by the aid of the values a and /3, where 



