22 NORMAL HISTOLOGY. 



in absolute alcohol to the absolute alcohol used for 

 the final dehydration of the specimen, before laying 

 it in oil of origanum. We thus complete the dehy- 

 dration and stain with eosin at one operation. 



Hydric acetate is sometimes used to render tissues 

 transparent. This it does by causing the albumi- 

 noid materials and particles within them to swell and 

 become actually more transparent, differing in this 

 from glycerin and balsam. It produces, however, 

 very considerable changes in the form and character 

 of many tissue elements, so that although very 

 valuable for special purposes, as will presently be 

 seen, it is now much less frequently employed than 

 formerly. 



The chemical agents which the histologist uses, 

 and the manipulative devices to which he has re- 

 course in the study of the tissues, are very numer- 

 ous, and we have considered here only a few of the 

 more important and typical. The preparation of 

 each tissue presents to the worker in histology a 

 separate problem, and in few departments of science 

 is careful attention to technical minutiae of more 

 importance than in that which is now to engage us. 



