652 APPENDIX. 



a methodical and systematic procedure is always requisite. So 

 many unknown objects, so many strange and unusual forms, so 

 many structural peculiarities are revealed to the eyes of the tyro 

 in microscopy, that he is at once plunged into profound con- 

 fusion, from which he can extricate himself only by adopting 

 the most laborious and rigid system of observation. He should 

 examine with the utmost care the physical appearance and cha- 

 racter of the ultimate structures ; he should note the exact shape 

 of the object, whether round or oval, globular or flat, &c. ; the 

 peculiarities of its edge or border, whether fine and brilliantly 

 illuminated, or dark and abrupt, whether smooth or rough, re- 

 gular or irregular, serrated or beaded, &c. Peculiarities of color 

 produced by strong and faint, and by reflected and transmitted 

 light, should next claim his attention. The size of the object 

 should, in all cases, be obtained by actual measurement, and all 

 variations in diameter noted. The transparency must also be 

 observed, — whether the body be opaque or diaphanous. If 

 opaque, the degree of opacity must be stated, its causes, and the 

 effects upon the transmission of the luminous rays. The 

 superficial and deep-seated layers, and in the case of cellular and 

 tubular bodies, the contents should also be investigated ; and 

 lastly, the effects of various reagents upon these physical pro- 

 perties must be ascertained with the same care and patience. 



It will thus be seen that the successful application of the micro- 

 scope to the diagnosis of disease, requires a very considerable 

 acquaintance with the healthy appearance and structure of both 

 the animal and vegetable tissues. Armed with this preliminary 

 knowledge, the student will be surprised at the facility with 

 which he will be enabled to distinguish from each other the 

 various animal solids and fluids, different morbid products, the 

 matters constituting food, &c., whether these be unchanged, or 

 in a state of disintegration from the processes of mastication, 

 digestion, ulceration, &c. 



In view, however, of the great difficulty experienced in demon- 

 strating accurately the histological character of the healthy 

 tissues, and the still greater difficulty of making out the charac- 

 teristics of morbid growths, the student should exercise great 

 caution and deliberation in pronouncing an opinion upon the 

 nature of any morbid tissues examined by him. 



The student shoiild early acquire the habit of recording all his 

 observations in a note-book kept expressly for the purpose. He 

 should exercise himself also in making drawings, as exact as 

 possible, of all the objects he examines. Such a practice, though 

 laborious, will leave upon his mind a more vivid and lasting im- 

 pression of the various objects of his research, and gradually 

 render him a very close and reliable observer. 



