1893.] MICROSCOPICAL JOURNAL. 37 



microscope, and with the elements of microscopical mounting. 

 — The Translator.] 



Part L — General Methods. 



The tissues and organs whose structure and texture — that is, the 

 nature and the arrangement of whose constituent anatomical 

 elements are to be determined, should be subjected to a series of 

 anatomical methods which we shall describe by showing how to 

 make and to use the reagents. 



I. — A first method allows of the separating of the organs into 

 thin slices to be examined by transmitted light ; this is section 

 cuttings which we place at the head of general methods, since its 

 discussion permits nearly all the reagents to be passed in review. 



2. — When organs are membranous they can be examined flat on 

 the object-carrier, without the use of the preceding method ; 

 this is the method of exte/zs/ofz of mcvibranes^ which, as we 

 shall see, is of great importance. 



3. — Having learned the arrangement of cells, it is necessary 

 to study their form and structure by dissociation, which allows 

 the anatomical elements to be separated from one another. 



4. — We place last the cxaDiinatiofi of livifig objects^ because 

 this is delicate work, productive of many errors, and to be 

 employed only after one has become familiarized with microscop- 

 ical observation. 



Method by Section Cutting. 



This comprises a number of manipulations. The object is to 

 be fixed and hardened before being cut ; the sections are then 

 stained and mounted in the proper preservative. 



Fixation of Tissues. 



The purpose of this is to kill the anatomical elements, and to 

 coagulate the living material so that, fixed in its natural form, it can 

 without change be subjected to the action of reagents. Fixing 

 should be done with great care 



1. Use material perfectly fresh, alive if possible, under penalty 

 of fixing cadaveric changes which might be mistaken for normal 

 structure. This rule should be strictly observed in pathological 

 observations, which in general should not be made more than 

 twentv-four hours after death. 



2. Place only small fragments in the fixing liquids If 



a good fixation is desired the size should not exceed a square 

 centimetre with alcohol, and a millimetre with psmic acid. 



3. Make a judicious choice of the fixative, and use it in very 

 large quantity. A fixative that will act well on one organ may 

 act badly on another. If without previous experience, one should 

 place portions of an organ in several fixatives, selecting preferably 

 alcohol, bichromate of ammonia, osmic acid. We cannot too 

 often repeat that an amount of the fixative should be used equal 



