ANIMAL STRUCTURES— MODE OF INVESTIGATING. 387 



saw, file, and hone ; by dissolving out the grease, the lacunse and 

 canaliculi show up very much better. A lapidary's wheel will be a 

 most useful article for grinding and polishing sections of bone or teeth. 



Having thus briefly examined a few of the more important struc- 

 tures of the animal economy, and imperfect in a. detailed point of 

 view though that examination be, we trust it may be found to smooth 

 the way, or in some degree assist the investigations of the student to a 

 better and more general sui-vey of the whole fabric. Such a survey will 

 not be unattended with its difficulties and disappointments ; nevertheless, 

 it will fully reward him for any amount of labour he may bestow. 



The importance of being thoroughly familiar with the structure and 

 microscopical characters of any particular organ in a healthy condition, 

 cannot be too strongly urged upon the attention of the student ; as to a 

 want of this knowledge must be attributed many erroneous descriptions 

 of morbid appearances. All who wish to use the microscope success- 

 fully, with reference to the examinations of organs in disease, will do 

 well to become acquainted with minute anatomy generally, not only of 

 the human subject, but of the lower animals ; without such knowledge 

 it will be found impossible to prosecute pathological inquiries with any 

 degree of success. 



To the medical student, desirous of obtaining further information 

 in this especial department of microscopy, we can recommend a very 

 valuable little book by Dr. Beale, on The Microscope, and its Applica- 

 tion to Clinical Medicine. Also Dr. Bennett's Lectures on the Study of 

 Clinical Medicine, where some excellent hints will be found on the 

 proper mode of investigating animal structures. 



The principal physical characters to be regarded in microscopic 

 examinations may be summed up as follows : 



1. Shape. — Accurate observation of the shape of bodies is very neces- 

 sary, as many are distinguislied by this physical property. Thus the 

 human blood-globules presenting a round biconcave disk, and are in this 

 respect different from the oval corpuscles of birds, reptiles, and fishes. 

 The distinction between round and globular is very requisite. Human 

 blood corpuscles are round and flat ; but they become globular on the 

 addition of water. Minute structures seen under the microscope may 

 also be likened to the shape of well-known objects,^ such as that of a 

 pear, balloon, kidney, htart, &c. 



2. Gohwr. — The colour of structures varies greatly, and often difiers 

 under the microscope from what was previously conceived regarding 

 them. Thus the coloured corpuscles of the blood, though commonly 

 called red, are, in fact, yellow. Many objects present different colours, 



