PREFACE. 



This modest manual has been prepared by the writer for his 

 classes in Histology and Bacteriology. The condensed statement of 

 many important facts of these subjects will be appreciated by those 

 who have a limited amount of time for their study. The absence 

 of diagrams may be a disappointment to some and, at first thought, 

 appear as a disadvantage; but the study of nature is primarily the 

 study of objects, and not of books and diagrams, though these are ad- 

 mitted helps. Its end should be the interpretation of facts and the 

 demonstration of truth, and this is accomplished by going direct to 

 nature, the source of facts and the embodiment of truth. A fact 

 is any reality, and truth is the correspondence between a proposition 

 and a reality a quality rather than an essence, the substantive sug- 

 gested by the adjective true. Not every proposition is true, but 

 every reality in nature embodies a truth. When we prove the agree- 

 ment between a proposition and the real thing at issue we demon- 

 strate the truth. The same thing is accomplished,, and doubt- 

 less a higher discipline attained, when we accurately observe a re- 

 ality of nature and then frame a proposition that truthfully ex- 

 presses that reality. One of the highest acts of the human mind is 

 correctly to observe a fact and accurately state the truth embodied 

 in that fact. A diagram may embody the truth. When a student 

 correctly interprets nature and then prepares a diagram that truth- 

 fully represents that interpretation, he has performed an act of the 

 highest disciplinary and practical value. Nothing will convey to the 

 mind of the teacher a student's conception of a subject so fully as 

 an effort on the part of that student to represent by a diagram that 

 which he observes. It is well, therefore, to encourage students 

 to copy nature rather than the conceptions of others, even though 

 their delineations may at times appear crude. The motto of the 

 teacher should be : " Nothing goes in this laboratory without draw- 



ings." 



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