44 ELEMENTS OF HISTOLOGY. [Chap.v. 



connected into networks within the bundle, are to be 

 specially found in considerable numbers in the walls 

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

 the ligamentum nucha3 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, found behind the anterior 

 epithelium as Bowman's elastica anterior, and at the 

 back of the cornea as elastica posterior, or Descemet's 

 membrane; in this latter bundles of minute fibrils 

 have been observed, (d) Elastic trabecula3 forming a 

 network, as in the ligamentum pectinatum iridis. 

 In the embryonal 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. Such 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, being derived from 



