1893.] MICROSCOPICAL JOURNAL. 37 



microscope, aiui with the elements of microscojiical moimtin<j^. 



TlIK Tit ANSI. ATOK.] 



P.\u I I. — Gknkual Methods. 



The tissues ami organs wliose structure and texture — that is, the 

 nature and the arrangement of whose constituent anatomical 

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

 anatomical methods which we shall describe by showin<^ how to 

 make and to use the reaj^ents. 



I. — A first method allows of the separating of the orj^ans into 

 thin slices to be exaiuined by transmitted bj^ht ; this is -srr//V^;/ 

 cutting-, which we place at the head of <;eneral methods, since its 

 discussion permits nearly all the reaj^ents to be passed in review. 



2. — When orj^ansare membranous thev can be examined flat on 

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

 this is the method of extension of membranes^ 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 jilace last the examination of living objects, because 

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

 employed only after one has become familiarized vvith 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 l)e subjected to the action of reagents. Fixing 

 should be done witii 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 shoukl not be made more than 

 twenty-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 osmic acid. 



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

 large ijitantity. 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 amuKjnia, osmic acid. We cannot too 

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



