44 ELEMENTS OF HISTOLOGY. [Chap. v. 



connected into networks within the bundle, are to 

 be found in large numbers in the walls of the 

 alveoli of the lung, in the ligamenta flava, in the 

 ligamentum nuchae of the ox (in which the fibres 

 are exceedingly thick cylinders), in yellow elastic car- 

 tilage (see below), in the endocardium and valves of 

 the heart, and in the vascular system, particularly the 

 arterial division. In the latter organs the intima, 

 and also to a great extent the media, consist of elastic 

 fibrils densely connected into a network. 



52. The following are special morphological modi- 

 fications of the elastic fibres : (a) elastic fenestrated 

 membranes of Henle, as met with in the intima 

 of the big arteries ; these are in reality networks 

 of fibres with very small meshes, and the fibres 

 unusually broad and flat. (b) Homogeneous elastic 

 membranes, which surround, as a delicate sheath, the 

 connective tissue trabeculse in some localities, e.g., 

 subcutaneous tissue, (c) Homogeneous-looking elastic 

 membranes in the cornea, behind the anterior epithe- 

 lium as Bowman's anterior elastic membrane, and at 

 the back of the cornea as elastica posterior, or 

 Descemet's membrane ; in the latter bundles of minute 

 fibrils have been observed. (d) Elastic trabeculae 

 forming a network, as in the ligamentum pectinatum 

 iridis. In the embryonic state the elastic fibres are 

 nucleated, the nuclei being the last remnants of the 

 cells from which the fibres develop, one cell generally 

 giving origin to one fibre. These nucleated fibres are 

 called Henle's nucleated fibres. 



53. Special varieties of fibrous connective tissue 

 are these : 



(1) Adenoid reticulum. This is a network of fine 

 fibrils, or plates, forming the matrix of lymphatic or 

 adenoid tissue. (See Lymphatic glands.) The reticulum 

 is not fibrous connective tissue nor elastic tissue ; it 

 contains nuclei in the young state, and is derived from 



