oe PREFACE. 
the practising physician, in that it enables him to ob- 
tain an intelligent grasp of the nature of the infectious 
‘diseases. 
The methods used in the laboratory for the isolation 
and identification of the typhoid, tubercle, and diph- 
theria bacilli have been given with especial fulness, as 
bacteriological examinations of the discharges of per- 
sons suspected to have typhoid fever, tuberculosis, or 
diphtheria are now generally made for these bacteria 
in the laboratories of the health departments of even 
the smaller cities, because of the manifest importance 
to the public of knowing where such sources of infec- 
tion exist. . 
In preparing this book the best works have been 
freely consulted. Of these, those of Fliigge and 
Sternberg, on General Bacteriology, and those of 
Abbott and Mallory and Wright, on Technique, should 
perhaps be especially mentioned. 
My sincere thanks are due to Dr. Hermann M. 
Biggs, the Director of the Bacteriological Laboratory, 
and to my colleagues in it, who have so freely furnished 
me with the results of their original investigations. I 
wish also to especially acknowledge my indebtedness 
to Dr. A. R. Guerard, who has given me invaluable 
aid in the preparation of the book. The illustrations, 
with the exception of those on malaria and cholera, 
for which I am indebted to Drs. Welch and Dunham, 
