EXPLANATION OF THE PLATES. 



PLATE XL. 



STRUCTURE OF FIBROUS TISSUE. 



Fig. 1. Example of elastic fibrous tissue in its ordinary 

 form, taken from the crico-thyroid membrane, and 

 magnified 670 diameters. 



2. Form of elastic tissue, constituting the elastic coat of 



many blood-vessels of medium calibre. 670 di- 

 ameters. 



3. This figure illustrates various stages in the develop- 



ment of blood vessels. At first a transparent and 

 tubular membrane is surrounded by a single coil of 

 elastic tissue, subsequently other coils and filaments 

 appear, the filaments principally take a longitudinal 

 direction on the tubular membrane, but some also 

 pass circularly around this ; these threads- are nu- 

 cleated, and belong to the second form of elastic 

 tissue, and which is elsewhere encountered in the 

 human organisation, as in tendons, the dartos, &c. 

 350 diameters. In h the threads are shown sepa- 

 rately. 



4. A peculiar areolar form of mixed fibrous tissue mag- 



nified 130 diameters, and principally encountered in 

 the great omentum. 



5. Blood vessels from the pia mater. All the smaller 



vessels present a similar structure, their coats being 

 formed of nucleated filaments of elastic tissue. 350 

 diameters. 



r 4 



