PREFACE TO THE THIRD EDITION 



IN the preparation of the third edition of this laboratory manual it 

 soon became evident that the new material to be added would increase 

 the size of the book beyond that which would permit its being readily 

 carried in one's pocket. It has, however, been possible to keep the 

 size of the book within the limits considered desirable by the use of a 

 smaller type in a considerable proportion of the paragraphs so that in 

 this way and by increasing the number of lines on each page it has been 

 possible to add extensively to the subject matter and with only an in- 

 crease of about sixty-five pages. 



The advantage attaching to more ready reference obtained by the 

 alternation of different sizes of type would appear to make this plan an 

 improvement over the old. 



While the chapters dealing with bacteriology have been added to 

 and made to include more recent advances it will be noted that in the 

 section on animal parasitology the subject matter has been greatly 

 increased. 



In the revision of the chapter on protozoa I am greatly indebted to 

 Professor Minchin's recent work on the Protozoa and in those relating 

 to arachnoids and insects to the very practical volume of Colonel 

 Alcock entitled "Entomology for Medical Officers." 



The illustrations have" been added to and many which did not seem 

 to bring out sufficiently details of anatomy have been replaced by others 

 more satisfactory in that respect. 



The three plates of the cestode, trematode and nematode ova were 

 drawn by Mr. L. Avery under the supervision of P. A. Surgeon Garrison, 

 U. S. N. and it is believed that they will be found more satisfactory 

 than similar plates contained in works on animal parasitology. 



Several new tables have been added among which special attention 

 is called to the one on urinary findings in various diseases of the genito- 

 urinary system and also to the key to the intestinal bacteria attached 

 to the inside of the board cover. 



A chapter on "Disinfectants and Insecticides" giving the practical 

 application of methods of carrying out these important Public Health 

 questions has been added. 



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