Minimal Lethal Dose of various Toxic Substances. 



329 



would be proportional to body weight in the younger and smaller individuals 

 of the species. On the other hand Dilling (25) in a recent communication 

 proposes a formula which approximates roughly to a dosage per kilogramme of 

 body weight. This is a system of dosage the fallacy of which was emphasised 

 by Moore. In view more especially of the considerations brought forward 

 above, we venture to suggest that it should now be entirely abandoned. 



Conclusions. 



1. In warm-blooded animals of the same species but of different weights 

 dosage must be calculated in relation to the body surface. 



This result agrees with the conclusion already reached by Moore* though 

 on different grounds. 



2. This statement is to be explained on the ground that the concentration 

 in the plasma of any given substance administered is dependent on the 

 volume of the circulating blood, which is itself proportional to the body 

 surface in any given species of animal. 



3. It follows that in the accurate measurement and standardisation of 

 toxic substances and antitoxins it will now be possible to make use of animals 

 of different weights within a given species instead of using only animals of 

 an arbitrarily selected weight, as has hitherto been necessary. 



4. Results in dosage calculated from one species of animal cannot 

 directly be applied to another species merely by taking surface into 

 due consideration, since tolerance and intolerance are specific characters 

 which are shown to be in many cases independent of the size of the species 

 concerned. 



5. For the human subject dosage in relation to the surface works out very 

 simply as approximately : — 



At 21 years Full dose At 3-4 years -i dose 



, 15 „ | „ „ 1 „ J „ 



„ 9-10 „ i „ In the early months ... -py „ 



REFERENCES. 



1. Dreyer, Georges, and Walker, E. W. Ainley, "Observations on the Production of 



Immune Substances," ' Journ. Pathol, and Bacterid. ,' 1909, vol. 14, p. 28. 



2. Dreyer, Georges, and Walker, E. W. Ainley, "On the Difference in Content of 



Agglutinins in Blood Serum and Plasma," ibid., 1909, vol. 14, p. 39. 



3. Dreyer, Georges, and Ray, W, " Observations on the Relationship between Blood 



Volume and the Total Amount of Agglutinin recoverable from Actively and 

 Passively Immunised Animals," ibid., 1909, vol. 13, p. 344. 



* Moore's conclusions seem to rest in the main on a consideration of " substances 

 which act by stimulation or inflammation of surfaces." 



