HARDENING OF TISSUES. 47 



Fresh sections may be treated as already described (§ 31, p. 45), 

 but it is well to pass them through a saturated solution of bichloride 



Fig. II. — His's method of washing off extra stain from dried films 

 in which there is no coagulable albumen. See description in text. 



of mercury, by which the protoplasm of the tissues is fixed ; they then 

 may be transferred to a three-quarter per cent, saline solution, and 

 stained and mounted. 



Hardening of Tissues. 



33. Although such examination in the fresh condition should always 

 be made where possible, the results obtained are never so satisfactory 

 as where the tissues in which the micro-organisms are embedded are 

 slowly and carefully " fixed," and where a more deliberate examination 

 may be made. 



