SECT. 22.] CONNECTIVE TISSUES. 4 1 



packing or connecting material between individual organs and 

 parts of organs (adipose tissue, medulla of bone, loose areolar 

 tissue, vitreous humour, tendons). With regard to the genetical 

 connection between the different tissues of connective substance, it 

 is not to be considered as if oue of these tissues were the 

 highest which, during its development, runs successively through 

 the form of all the others ; on the contrary, this connection rather 

 lies in the circumstance that they are developed from a similar 

 genetic matter, in several parallel series, of which the members 

 can be transformed into each other. If we start from the em- 

 bryonal cellular tissue, from which the connective substance is 

 developed, we obtain three members of the first series, viz., mucous 

 tissue, cartilage, and connective tissue, including elastic tissue. In 

 the two former, the embryonal cells have proceeded uniformly in 

 their development, in the one case to cartilage-cells, in the other 

 to cells of mucous tissue, an intermediate substance having at 

 the same time arisen between them ; whilst in connective tissue, 

 they become transformed essentially according to two types, and 

 are converted, firstly, into connective tissue corpuscles, and, 

 secondly, into the proper cells of connective tissue; the latter 

 of which pass into the fibrous matrix of this tissue, whilst the 

 other either persist as cells, or are converted into elastic fibres. 

 Now these three tissues are intimately related in so far as, 

 firstly, cartilage and mucous tissue, as comparative histological and 

 pathological facts ( Virchow) more especially prove, present tran- 

 sitions, and may probably even be, in certain cases, converted into 

 one another ; secondly, they are also capable of becoming trans- 

 formed into connective tissue, which is evidently the highest form, 

 as the phenomena seen in the formation of the medulla of cartilage 

 seem to prove. With regard to connective tissue, on the other 

 hand, it cannot, owing to its complex structure, be directly trans- 

 formed into cartilage and mucous tissue; but it very frequently 

 happens that, firstly, its corpuscles assume all the characters of 

 cartilage-cells, as in fibro-cartilage, and, secondly, that together 

 with its fibrous substance arising from the cells, a homogeneous 

 substance, containing mucus and albumen, develops itself, as in the 

 gelatinoid embryonal connective tissue, which, perhaps, also occurs 

 as a gelatiniferous substance, or is converted into such in certain 

 cases, so that the affinity of connective tissue with cartilage and 

 mucous tissue is not to be mistaken. It is in no way inconsistent 

 with tins intimate connection of the tlnee tissues in question, that 

 each of them, in the further course of development, may arrive at 



