190 now TO WORK 



to err from the natural deterioration in structure of the organs upon 

 which the observation of his facts entirely depends. 



2^1. Of Recording the Result of Microscopical Observations. 



Taking notes of microscopical observations is a subject of great 

 importance. The observer must endeavour to acquire the habit of 

 describing in words the appearance of objects under the microscope. 

 This is probably not so easy as would at first be supposed, although 

 undoubtedly many persons are able to describe what they see much 

 more correctly, and with greater facility, than others. Accuracy in de- 

 scribing microscopical specimens can only be acquired by practice, 

 and I think it a most excellent rule at first, for a student to take notes 

 of the appearances of every object submitted to examination. The 

 time is well spent, and much of what is so described is retained in the 

 memory. The notes should be short, and should consist of a simple 

 statement of points which have been observed. Inferences should be 

 carefully avoided, and nothing should be stated without the observer 

 being thoroughly satisfied of its accuracy. If he is not quite certain 

 of any observation, he should express his doubts, or place a note of 

 interrogation after the statement. The use of indefinite terms should 

 be avoided as much as possible, and whenever any particular word is 

 used, a definite meaning should be attached to it. Much confusion 

 has arisen from the use of terms which have not been well defined. 

 Thus the word "granule" is applied by many authors to a minute 

 particle which appears as a small speck even when examined by the 

 highest powers, as well as to a small body with a perfectly clear centre, 

 and with a well-defined sharp outline, which would be more correctly 

 termed a small "globule" So, again, the term " molecule'''' has been 

 employed in some cases synonymously with "granule" but it would 

 obviously be wrong to speak of a small globule as a molecule. It 

 seems to me very desirable to restrict the terms "granule" and 

 " molecule " to minute particles of matter which exhibit no distinct 

 form when examined by the highest powers at our disposal, and 

 and the term " globule " to circular or oval bodies of all sizes which 

 have a dear centre with a well-defined dark outline. Other examples 

 of the use of insufficiently defined terms might be pointed out. If 

 an observer makes use of a term which is generally employed without 

 any definite meaning being attached to it, he should describe at 

 length the meaning which he assigns to it, and should, of course, use 

 it only in this one sense. 



Exactness of Description should always be aimed at, and we must 

 remember that with a little trouble this exactness may be obtained 

 with the use of a small number of words. That appearance of precision 

 which is often aimed at by those who give long useless descriptions 



