19 



45. Caustic potash dissociator. [8] Formula: Caustic 

 potash, potassium, hydroxid (in sticks), 35 to 40 grains; distilled 

 water, 65 or 60 c. c. This solution will be used for the isolation of 

 cardiac muscle 'cells', although it may be used for striated or plain 

 muscular tissue, or as a general dissociator. It may also be employed 

 for isolating the cells of hair, horn or nail, either full strength or 

 diluted. 



Ten to fifteen minutes or longer will be enough for the isolation 

 of heart muscle ( 189 6) ; 2 to 3 days may be required for the ade- 

 quate maceration of cornified epithelial cells. 



SECTIONING. 



46. In addition to the examination of tissue by the separa- 

 tion of the component elements isolation it may be examined 

 microscopically after cutting very thin slices or sections of it. This 

 may be done free-hand or by means of a special machine, a micro- 

 tome, and with or without an imbedding and supporting mass. 



For the finer work an imbedding mass and a microtome must 

 be used. Free-hand sectioning without an imbedding mass, and 

 even without previous fixing is, however, necessary or advisable 

 when economy of time is a desideratum, as in clinical examinations 

 of tissue, when one wishes to study the part alive or fresh (i. e., 

 not treated with reagents), or if the reagents necessary for fixing 

 and imbedding destroy or alter the structural features to be investi- 

 gated. 



The ability to recognize tissues and organs unaffected by re- 

 agents and without the employment of methods involving the ex- 

 penditure of time and effort is very desirable, especially in patho- 

 logical work, when haste often forbids the employment of the finer 

 methods, were facilities for their use available, as in some cases 

 they are not. Great skill in the use of simple tools may be gained 

 and counts for much. It should be remembered also that the greater 

 one's knowledge of a structure the less the need to resort to special 

 methods of preparation for its recognition. 



IMBEDDING METHODS. 



47. When the consideration of time is not so important and 

 finer results are more to be desired, the sections should be prepared 



