104: PRACTICAL HISTOLOGY. 



agent ; but it may be employed during the later 

 stages, especially in conjunction with the chromic 

 acid, since the latter reagent has, by its peculiar 

 coagulant action upon the animal tissues, so altered 

 their constitution that their structure is no longer 

 rendered indistinct by diluted nitric, acetic, and 

 the ordinary acids, which produce swelling and 

 maceration of the fresh tissues, and especially of the 

 connective tissue. 



The process of decalcification being completed, the 

 pieces are placed in water for a few hours to get rid 

 of the excess of chromic acid imbibed, and are then 

 transferred to spirit; or sections may be made at once 

 without placing the piece in spirit at all. In cutting 

 them, if the bit of bone is too small to be held in the 

 fingers, it may be placed in a split piece of cork. The 

 sections should be very thin, but it is not necessary 

 that they should be large or include the whole thick- 

 ness of the bone; they are to be stained in the log- 

 wood solution, washed in water, and finally mounted 

 in glycerine. The corpuscles within the lacunae, or 

 at all events their nuclei, are beautifully shown, and 

 all the soft parts are more or less stained, but the 

 actual substance of the bone is very slightly colored. 

 At the same time, any lines of demarcation which 

 may be present indicating successive deposits of 

 osseous matter in the formation of the bone, or 

 absorption at any part and subsequent redisposition, 

 with the characteristic scalloped edge which such a 

 junction almost always possesses, are very clearly 

 shown by a difference in the coloration. Moreover, 

 if in the section there happens to be any portion 

 remaining of the (ossified) matrix of the original 

 embryonic cartilage, this, like cartilage matrix gene- 

 rally, is intensely "stained by the logwood. 



Preparation 5. Instead of chromic, picric acid 

 may be used for the decalcification. A saturated 

 solution of the acid is employed, and care is to be 

 taken constantly to supply fresh crystals of picric 

 acid to take the place of that which is used up in 



