210 



MANUAL OF HISTOLOGY. 



Tims the yellow ligaments of the vertebral column are uncommonly 

 rich in elastic fibres of 0-0056-O0065 mm., which are usually met with 

 bent or arched, and giving off a tolerable number of branches, which are 

 also hooked or like tendrils, and frequently attain a remarkable degree of 

 fineness. In the infant such fibres have still but a small diameter, and 

 it is not before a certain amount of maturity of the mammal body has 

 been attained that the formation of these broader fibres takes place. 

 Smaller individuals only show the finer examples. 



The amount of fibrillated connective-tissue found amongst these is 

 subject to great variation. Though in many localities tolerably abundant, 

 it becomes in others rather scanty, and often excessively diminished in 

 amount. It was in such cases as this that earlier investigators were 

 accustomed to speak of elastic tissue. 



There could hardly be a more suitable object for the study of an elastic 

 tissue of this kind in all its peculiarities, than the 

 walls of the larger arteries, especially those of the 

 larger mammals. 



Here we meet with thin elastic membranes (fig. 

 201, a), in which is seen a network of very fine 

 elastic fibres embedded in homogeneous intermediate 

 matter; or this membranous ground-substance may 

 bo pierced with holes of various kinds (fig. 201, &), 

 (the fenestrated tunic of Henle}. We likewise 

 encounter very simple elastic tunics without em- 

 bedded fibres (fig. 202, 1), which are also studded 

 with apertures (a), the whole of the substance 

 presenting the appearance of bands and broad irre- 

 gular fibres (b, c). Between such and a dense in- 

 terlacement of broad elastic fibres (fig. 202, 2), it is 

 often difficult to distinguish with certainty. Those 

 dense networks which have a homogeneous inter- 

 stitial substance, as in fig. 203, afford still better 

 objects. 



In those localities where the elastic fibres are very 

 broad, their edges may be here' and there jagged like a saw. Again they 

 are frequently pierced with very minute holes. This is seen very gene- 

 rally in the external coat of the aorta of the whale, where the fibres may 

 measure 0-0056 or even '00.75-0 -0088 mm. 



128. 



Having now made ourselves acquainted with the ordinary bearings of 

 elastic fibres and nets, we must turn to the consideration of the limiting 



Fig. 203. A. very dense 

 network of broad elas- 

 tic fibres from the mid- 

 dle coat of the aorta of 

 an ox. The fibres are 

 connected by a homo- 

 geneous intermediate 

 substance of a mem- 

 branous structure. 



FIR. 204.-A connective-tissue bundle from the base of the human brain, treated with acetic acid. 



layers of many connective-tissue bundles, which have spruncr f rom 

 metainorphosis mto elastic substance of some matter situated arold 



