414 APPENDIX. 



c. Alum-Hsematoxylin (Bohmer). 



(1) Haematoxylin, crystals 35 gm. 



(2) Alcohol, absolute 10 c.c. 



(3) Potash-alum 10 gm. 



(4) Water, distilled 30 c.c. 



Dissolve i in 2 = A ; dissolve 3 in 4 = B ; A is added to B, drop by 

 drop, and allowed to stand in the light for several days before filtering. 



For staining sections, dilute with distilled water, several drops of 

 the stain to a watch-glass of water usually producing the requisite 

 rich bluish-purple solution. The sections remain in the diluted stain 

 until colored dark blue, this usually requiring 5-8 minutes, although 

 the exact time depends upon the condition of the tissue and the 

 strength of the staining fluid employed ; the sections are transferred 

 to distilled water and allowed to soak from 5 to 10 minutes, by which 

 time they have become a bright rich blue ; a too intense color and a 

 light lilac tint are alike to be avoided. 



The tissue having been stained in bulk with either borax-carmine 

 or Delafield's haematoxylin, it is now ready for the important manipu- 

 lation of embedding. 



4. Embedding. This may be simple or interstitial, the former 

 affording a general support to the tissue by grasping its surface with- 

 out penetrating the tissue, the latter supporting not only the surface, 

 but also, in consequence of the complete infiltration of the specimen, 

 every part of the object. For the purposes of hasty examination, 

 the simple embedding often answers perfectly, and is preferable on 

 account of economy of time and labor ; where, however, really fine 

 preparations are desirable, the additional labor involved by the more 

 elaborate process is amply repaid by the character of the resulting 

 preparations. 



The most satisfactory mass for simple embedding consists of 

 paraffin 2-3 parts -|- tallow i part ; the melted mass is poured around 

 the piece of tissue, which has been previously fixed in position by a 

 carefully-inserted pin within a paper mould. The mass should cool 

 slowly, and the sections should be cut with both knife and block 

 flooded with strong spirit. 



Interstitial Embedding, by which every portion of the entire 

 tissue-mass is held together and sustained, each isolated fragment 

 being retained in its relative position and preserved in the mounted 

 preparation, has given the histologist of to-day a command of his 

 tissues incomparably superior to anything that his predecessors pos- 

 sessed, and enables him to secure complete series of objects whose 

 minuteness and frailty precluded perfect preparations by the older 

 methods. 



