ACK^^^OWIiEDGMEKT. 
As this standard is based upon the one established by Ehrlich, the 
principles involved and the methods employed are practicall}^ a repro- 
duction of his work. First of all, I have to acknowledge not only the 
debt I individually owe, but the debt that all the world owes, to the 
I remarkable genius of Ehrlich, who has done more, perhaps, to forward 
the problems of serum therapy than anyone else, not excepting 
Behring and Roux, the discoverers of the practical uses of diphtheria 
I antitoxin. It is therefore evident that in the following pages no 
S' claim to originality can be made. In a few instances some improve- 
,1 ments in the methods of testing, leading to increased accurac}", have 
jj been introduced. I have naturall}" drawn heavily upon the published 
^ literature on the subject, particular! 3’ the writings of Ehrlich, also 
Morgenroth, von Dungern, Madsen, Arrhenius, Marx, Smith, and 
i Welch. 
A bibliography of all the articles consulted in writing this Imlletin, 
; as well as in the work of standardizing the serum, will l)e found 
I on page 85 . 
! It is a pleasure to acknowledge particularh^ the assistance I have 
! had from m3" colleague. Dr. Reid Hunt, Chief of the Division of Phar- 
! macology, whose deep insight into ph3"siological chemistiw has helped 
me to a better understanding of some of the problems involv"ed in 
making the imniunit3" unit. 
I also wish to acknowledge the assistance especialh^ of Passed 
Assistant Surgeons John F. Anderson, the assistant director in this 
' laboratoiy, and also Passed Assistant Surgeon R. von Ezdorf, and 
T. B. McClintic, and Assistant Surgeons Edward Francis and A. M. 
Stimson, who have faithfull3" carried out maiy details of the work 
under 1113" supervision. 
The inception of the law and the benefits that have alreadv resulted 
from its administration are properW credited to tlie Surgeon-dein'ral 
of the Public Health and Marine-Hospital Service. It is therefore' 
Pa pleasant duty to acknowledge this as one of the manv debts our 
countiy owes to the public health work of Walter A^Amall, 
( 5 ) 
