THE CONNECTIVE TISSUES. 13! 



cells. The ground substance may be specifically colored by certain 

 reagents, safranin producing an orange and hematoxylin a blue stain. 



On treating cartilage by certain methods, systems of lines 

 appear in its ground substance, possibly indicating a canalicular sys- 

 tem in the cartilage. In order to make these structures visible, Wolters 

 recommends staining thin sections for twenty-four hours in a dilute solu- 

 tion of Delafield's hematoxylin (violet blue). They are then treated 

 with a concentrated alcoholic solution of picric acid. 



The capsules are seen to best advantage if small pieces of car- 

 tilage are treated with a i% solution of gold chlorid. 



Connective -tissue and elastic fibers in cartilage are easily 

 demonstrated by staining the specimens with picrocarmin. The con- 

 nective-tissue fibers are colored a pale pink, the elastic fibers yellow. 

 The latter may also be stained with a i /o aqueous solution of acid 

 fuchsin. 



If a section of fresh cartilage be placed in a weak solution of 

 iodo=iodid of potassium (Lugol's solution), glycogen can sometimes 

 be seen in the cartilage-cells, stained a peculiar mahogany brown. If 

 elastic fibers be present, they also are stained brown, but of a different 

 shade. 



Thin bone lamellae, such as occur in the walls of the ethmoidal 

 cells, can be cleaned of all the soft parts and examined without further 

 manipulation. If larger bones are scraped with a sharp knife, pieces 

 suitable for microscopic examination are sometimes obtained. 



Microscopic Preparation of Undecalcified Bone. A long bone 

 is thoroughly freed from fat and other soft parts by allowing it to macerate, 

 after which it is thoroughly washed and dried, thus freeing it from its 

 organic material. Then, by means of two parallel cuts with a saw, as 

 thin a disc as possible is cut out. The section is now ground still thin- 

 ner, either between two hones or upon a piece of glass covered with 

 emery. One surface of the bone is then polished and fastened by means 

 of heated Canada balsam to a thick square plate of glass with the 

 polished side toward the glass. Care should be taken that no air-bubbles 

 are inclosed between the section and the glass. As soon as the specimen 

 is firmly adherent, the other side is ground upon the emery plate or hone, 

 during which manipulation the glass to which the bone has been fastened 

 is held between the fingers. As soon as the section is sufficiently thin 

 and transparent, it is polished. In order to remove the Canada balsam 

 and powdered bone from the section, the glass and bone are dried and 

 placed in some solvent of Canada balsam, such as xylol. This loosens the 

 specimen from the glass, after which it is immersed in absolute alcohol, 

 thoroughly washed, and dried in the air. On examining the bone 

 through the microscope, its lacunae will appear black on a colorless back- 

 ground. The reason is, that the air has taken the place of the evapo- 

 rated alcohol and the spaces appear black by direct light. Sections 

 thus prepared may be permanently mounted as follows : Small pieces 

 of dry Canada balsam are placed both upon a slide and a cover- 

 glss and warmed until they have become fluid, then allowed to 

 cool until a thin film forms over the balsam ; the bone disc is then 

 placed upon the balsam on the slide and quickly covered with the 

 cover-glass. A firm pressure will evenly distribute the balsam, and if 



