324 



Prof. G. Dreyer and Dr. E. W. A. Walker. 



the surface dose and time of death of animal 4, while the doses in per 

 cent, of weight differ by 14 per cent. Again, if we compare the three 

 animals which received equal doses, if the dose is expressed in per cent, 

 of weight (viz.. 2, 3, 5), the lightest one survives while the two heavier 

 ones succumb. The explanation is at once evident on comparing the size 

 of the doses expressed in relation to surface. 



In Table IV is given another series of observations by Morishima where 

 the injection was made intravenously. This method is, of course, likely to 

 yield more precise results than subcutaneous inoculation, and it is seen that 

 the effects of the doses, when the latter are expressed in relation to body 

 surface, are remarkably regular and striking. On the other hand, when the 

 dose is given in percentage of body weight, as was done by Morishima himself, 

 the time to death varies very widely in animals which received equal dosage 

 with the drug on his method of calculation. Morishima's results might be 

 taken to indicate great individual differences in susceptibility in different 

 individual animals. But such individual differences do not appear when the 

 dose is calculated in relation to blood volume and body surface. 



Table IV. — Arsenic (As 2 3 ) in Eabbit, Morishima's Experiments 

 (intravenous injection). 



No. 



Weight 

 of animal, 

 in grm. 



Actual dose 

 (d), in mgrm. 



Dose (D) in 

 relation to surface, 

 in mgrm. 

 D = rf/W -' 2 . 



No. 

 of hours to 

 death. 



Dose in per 

 cent, of weight, 

 mgrm. 

 per 100 grm. 



... 



1 



1135 



6 81 



4-30 



ao 



60 



2 



1190 



7-73 



4-71 



432 



-65 



3 



970 



6-79 



4 -81 



48 



0-70 



4 



1155 



8 -08 



5 -04 



21 



0-70 



5 



1952 



13 66 



5 -82 



8 



70 



Similar facts can readily be made out from various other experiments which 

 have been carried out with arsenical compounds by a number of observers. 



In the case of another heavy metal, cobalt, the same results hold good 

 when the dosage is expressed in relation to surface instead of in the usual 

 manner as a'percentage of the body weight. This fact has been determined 

 by an analysis of Meurice's experiments (9) on pigeons injected into the 

 breast muscles with cobalt nitrate, Co(N0 3 )2. This is of special interest in 

 view of the fact that it has already been shown in the experiments which we 

 carried out in association with H. K. Fry, referred to elsewhere (10), that 

 the blood volume of birds (like that of mammals) is proportional to their 

 surface area. 



