386 GENERAL MICROSCOPIC TECHNIQl 



glass slide and is covered over with a cover glass and examined. 

 Thin membranes also (e. g., omentum, mesentery, fasciae) may 

 be examined in the fresh condition by spreading them out over 

 a glass side and keeping them moist by means of an indifferent 

 fluid, such as blood serum, physiological salt solution, etc. In 

 investigating larger organs we must separate the morphological 

 units from one another or cut the tissue into thin sections. 



(a) Isolation and Teasing of Tissues. 



By means of two sharp needles fresh tissue may be torn 

 apart so that its elements are isolated. It is best to have the 

 tissue immersed in a drop or two of normal salt solution. 

 Such tissues as tendon, muscle, and nerves can be studied in 

 this way to advantage. The elements of many tissues, however, 

 cannot be isolated so easily. In such instances the cement 

 substance which binds the elements together should be dis- 

 solved out by means of maceration. The most useful fluids 

 for this purpose are the following : 



(a) Ranvier's Dilute Alcohol (33 per cent.}. This may be 

 made by adding 65 cc. of distilled water to 35 cc. of 96 per 

 cent, alcohol. This is a specially good fluid for isolating 

 epithelial cells. Small pieces of tissue which have been left in 

 the alcohol from six to twenty-four hours may easily be teased 

 out. 



(b) Potassium or sodium hydrate is most useful in a solution 

 of 33 per cent., for the isolation of muscle elements (twenty 

 minutes) and the elements of nails (three to five hours). For 

 the study of hairs a 4.6 per cent, solution is used for three or 

 four days. The elements should be examined in a solution of 

 the same strength as that in which they have been macerated. 

 Water should not be added. Care should be taken not to let 

 the lens of the objective touch the fluids. 



(c) Very dilute formalin (0.25 per cent.) or potassium bi- 

 chromate (0.1 per cent.) may be used for the isolation of epithe- 

 lial cells. Tissues should be left in these fluids one to two days. 



(d) Hydrochloric acid is useful in isolating the kidney 

 tubules. It should act for from ten to twenty-four hours. 



