7. =Vermes.= The _heads_, _proglottides_ and _ova_ are best examined in the fresh state, in physiologic saline or glycerin. Acetic acid may be used to bring out details. Berlin-blue or methylene-blue may be injected through the genital pore for the demonstration of the excretory and genital organs. _Scolices_ and _hooklets_ of _echinococcus_ may be obtained by scraping the cyst-wall; examine in glycerin. Permanent preparations of _cestodes_, _nematodes_ and _trematodes_ may be made by fixing in mercuric chloride, formol or Flemming’s, after-hardening in alcohol, staining in orange G, borax carmine, alum hæmatoxylin, hæmatoxylin and eosin etc., mounting in glycerin gelatin; or dehydrating, clearing in xylol and mounting in balsam. For sections imbed in paraffin or celloidin. _Trichinæ_ may be studied by teasing the fresh muscle; by digesting with pepsin and hydrochloric acid and examining the freed trichinæ on a warm stage; or by imbedding in paraffin or celloidin and staining with hæmatoxylin and eosin. Permanent mounts of the embryos of _filaria_ may be made by fixing cover-glass preparations of blood or chylous fluid by heat or mercuric chloride, and staining for a few seconds with Löffler’s or a 2 per cent aqueous thionin. CHAPTER XXVIII. THE STAINING OF SPECIAL ORGANS AND TISSUES. I. BLOOD AND BLOOD-FORMING ORGANS. The =blood= may be examined by means of _films_, _stained_ or _unstained_, or by _sections_, _celloidin_ or _paraffin_.