126 THE TISSUES. 



this process many of the osteoblasts become inclosed in bone 

 matrix, forming bone-cells and the blood-vessels of the Haversian 

 spaces remain as the vessels found in the Haversian canals. The 

 spongy intramembranous bone not absorbed at the commencement 

 of the formation of the system of concentric lamellae, remains 

 between the concentric systems as interstitial lamellae. The circum- 

 ferential lamellae are those last formed by the periosteum. Calcifica- 

 ation of the osseous matrix takes place after its formation by the 

 osteoblasts. 



From what has been stated it may be seen that the shafts of 

 the long bones and bones not preformed in cartilage develop by the 

 process of intramembranous bone-formation, while the cancellous 

 bone in the ends of the diaphysis and in the epiphyses is endochon- 

 dral bone. Further, that long bones grow in length by endo- 

 chondral bone-development, and in thickness by the formation of 

 intramembranous bone. In the development of the smaller irreg- 

 ular bones, both processes may be engaged ; the resulting bone can 

 not, however, be so clearly defined. 



TECHNIC 



Ran vier's Method. One of the methods for examining connective- 

 tissue cells and fibers is that recommended by Ranvier ( 89) ; it is as follows : 

 The skin of a recently killed dog or rabbit is carefully raised, and a o.i'/ ( 

 aqueous solution of nitrate of silver injected subcutaneously by means of a 

 glass syringe. The result is an edematous swelling in which the connective- 

 tissue cells and fibers (the latter somewhat stretched) come into imme- 

 diate contact with the fixing fluid and are consequently preserved in their 

 original condition. In about three-quarters of an hour the whole eleva- 

 tion should be cut out (it will not now collapse) and small fragments 

 placed upon a slide and carefully teased. Isolated connective-tissue cells 

 with processes of different shapes, having the most varied relations to 

 those from adjacent cells, are seen. The fibers themselves either consist 

 of several fibrils, or, if thicker, are often surrounded by a spirally encir- 

 cling fibril. By this method numerous elastic fibers and fat-cells are also 

 brought out. If a drop of picrocarmin be added to such a teased prepa- 

 ration and the whole allowed to remain for twelve hour's in a moist 

 chamber, and formic glycerin (a solution of i part formic acid in 100 

 parts glycerin) be then substituted for twenty-four hours, the following in- 

 structive picture is obtained : All nuclei are colored red, the white fibrous 

 connective-tissue fibers pink, the fibrils encircling the latter brownish- 

 red, and the elastic fibers canary yellow. The peripheral protoplasm 

 of the fat -cells is particularly well preserved, a condition hardly obtain- 

 able by any other method. 



Connective tissue with a parallel arrangement of its fibers is best 

 studied in tendon, those in the tails of rats and mice being particularly 

 well adapted to this purpose. If one of the distal vertebrae of the tail be 

 loosened and pulled away from its neighbor, the attached tendons will 

 become separated from the muscles at the root of the tail and appear as 

 thin glistening threads. These are easily teased on a slide into fibers and 



