PREFACE. 



The following pages were originally arranged as a series of exercises to 

 be carried out by the class in the University of Texas under the guidance of 

 an assistant, the hours of work of the several classes so overlapping that it 

 was impossible for the writer to give his personal attention to the class in 

 this laboratory, for the work in which he was, however, responsible. The 

 exercises were outlined daily upon the blackboard, and verbal instructions as 

 to their purpose and the manner of procedure given, as required, to the class. 

 The arrangement being found well adapted to systematic work, it has been 

 continued, with changes from and some additions to the original scheme, 

 for several years ; and recently, at the request of some of his students and 

 with the thought that perhaps others might find some such definite ar- 

 rangement of work of use in teaching, the writer has written out these exer- 

 cises for publication. It has seemed advantageous that in their published 

 form there should accompany the v^ractieal, exercises such explanatory 

 matter as would adapt the book as a student's laboratory outline guide. 

 It would be beyond the writer's intention to make the work a compendium 

 of methods, and the instructions, although forming a considerable bulk of 

 the volume, include only such as from his experience he has adopted as best 

 suited in class work. 



There are arranged blank pages upon which notes of the outcome of the 

 various experiments and record of special instruction as to technique may 

 be added ; and as an appendix a blank form is printed, following which as a 

 form at the close of the work should be recorded the data ascertained in 

 connection with the more important forms of microorganisms which have 

 been studied in the exercises.* It has been the writer's custom to have 

 each student carry along with the regular class work during the last two or 

 three weeks some simple independent task, as the bacterial analysis of a 

 water-supply, of milk, soil, or air, in which an enumeration of the bacteria 

 found in a definite quantity of the substance examined is required, together 

 with the identification of one or more forms of the organisms encountered, 

 and such study of their pathogenic influence as time permits. The records 

 of such work also may well be made after the blank form in the appendix. 



* Copies of this form maybe obtained from P. Blakiston's Son & Co., Philadelphia. 



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