360 The Development of the Connective Tissues 



within the ground substance midway between tlie cells. At no point is 

 the diameter of the fibers as great as that of the granules in the aryte- 

 noid cartilage of the adult. Furthermore, there are absolutely no 

 granules of elastic tissue in the cartilage in which the elastic fibers 

 have appeared and are growing. The same pictures, only more ad- 

 vanced, are seen in the arytenoid cartilages of pigs' embryos up to 24 

 cm. long. I have been unable to obtain specimens between embryos 

 24z cm. long and the adult, so cannot contribute anything regarding 

 the development of the elastic granules. It is probable that they appear 

 as minute specks and gradually grow larger and larger, for where they 

 are in clumps granules of all sizes are seen. 



Mucous Membrane of the Intestine. — The reticulum of the mucosa and 

 the prefibrous tissue of the submucosa form a single layer in the intes- 

 tine of the embryo pig 24 cm. long. At this time no elastic fibers 

 whatever can be demonstrated in any of the layers of the intestine by 

 Weigert's method. Unfortunately the succeeding stages were not at 

 my disposal, but from the examination of the intestine in the adult 

 it is shown that the bundle of white fibers of the submucosa are sur- 

 rounded with numerous elastic fibers which form a dense network 

 throughout the muscularis mucosa and the stratum fibrosum. From 

 this point a few fibrils extend between the crypts but not into the villi. 

 Spalteholz " has followed them throughout the mucosa, showing that 

 they accompany the muscle bundles of the villi. At any rate there is 

 considerable reticulum in the mucosa of the intestine which has no 

 accompanying elastic fibers, as is also the case in the ground sul)stance 

 of cartilage. 



Lymph Nodes. — Frozen sections of lymph nodes Avhich have been 

 stained by Weigert's method show beautiful networks of elastic fibers 

 throughout the trabeculfe and the follicles. Within the trabecular the 

 elastic fibrils are very numerous and from there they pass at regular 

 intervals along tlie bands of reticulum through the sinus to the peri- 

 phery of the follicle. Their course is quite direct towards the center 

 of the follicle wh'^re they anastomose to form an irregular network. If 

 the section is macerated for a few days in a solution of bicarbonate of 

 soda to soften the cells, the sections can be cleared pretty well, leavin*j 

 only the reticulum and the elastic fibers. When specimens thus ob- 

 tained are stained by Weigert's method it is found that not all the 

 reticulum fibrils are accompanied with elastic. At the periphery of the 

 follicle about every second fibril, while more towards its center, about 

 every fifth reticulum fibril is accompanied by an elastic fiber. 



'■'Spalteholz, Arch. f. Auat., Supplement Band, 1897. 



