76 GENERAL ANATOMY OF THE TISSUES. 



titious coat of the arteries, and the endocardium, consist of a loose 

 connective tissue not altogether dissimilar to that of the fibrous 

 membranes, and of finer or coarser elastic fibrous networks, with 

 which in the veins smooth muscles are also partly mixed. 



h. The so-called vascular membranes [tunica vasculosis), 

 to which belong the pia mater, with the plexus choroidei, the 

 choroid coat and the iris, all contain very numerous vessels, 

 which, however, appear to have less reference to the membranes 

 themselves than to the nutrition of other organs. Supporting 

 these vessels we have either a common connective tissue, in 

 which there are no elastic fibres (iris, pia mater), with parallel, 

 matted, and anastomosing bundles, or a homogeneous con- 

 nective tissue (plexus choroidei, choroidea), to which, as in the 

 choroid, peculiar elements, namely, anastomosing cells, gene- 

 rally filled with more or less pigment, may be added. 



i. The homogeneous connective tissue. — In many organs we 

 find membranes whose chemical nature agrees with that of 

 connective tissue, but which contain neither distinct bundles 

 nor fibres, and appear to be more homogeneous. Such is the 

 homogeneous tissue which often invests the bundles of the 

 arachnoid singly, or in a number together ; the coats of the 

 Malpighian corpuscles of the spleen, and of the glandular 

 follicles of the intestine (tonsils, lingual-follicles, the solitary 

 and Peyerian glands), certain of the so-called membranae 

 propria of the glands appear to come under this head also; yet, 

 since some of them do not belong here, and consist of a very 

 different substance from connective tissue, as, for example, that 

 of the kidneys, and since we have no thorough investigation 

 of these structures, for the present nothing decided can be 

 said upon the subject. 



k. Loose or areolated connective tissue (" amorphous con- 

 nective tissue" of Henle), consists of a soft meshwork of 

 reticulated, or variously interwoven bundles of connective 

 tissue, which in larger or smaller quantity constitute a filling 

 up and uniting mass between the organs and their parts, and 

 appear under two forms : 



1. As adipose tissue, when numerous fat-cells are contained 

 in the meshes of an areolated tissue which is usually very 

 poor in elastic fibres. 



2. As common lax connective tissue, when the latter are 



