68 



CONNECTIVE TISSUE. 



it constitutes the fenestrated membrane of Henle, found in the coats 

 of the blood-vessels. A remarkable character which elastic fibres ex- 

 hibit in many specimens, is their singular tendency to curl up at their 



broken ends; and these ends are not 

 Fig. 40. pointed, but abruptly broken across. 



Their size is very various ; the largest in 

 man are nearly ^^\j^th of an inch in 

 diameter, the smallest perhaps not more 

 than ^^Jy-j^th. In some varieties of the 

 tissue the larger sized fibres prevail ; 

 this is the case "R'ith the ligamenta 

 subflava, where their general diameter 

 is about -if ^Vo^^^ of an inch ; in other 

 instances, as in the cliordjB vocales, they 

 are exceedingly fine. In some animals 

 elastic fibres are met Avith TjVoth of 

 an inch in thickness. Acetic acid pro- 

 duces no change on the elastic fibres, 

 while it speedily alters the wavy areolar 

 fibres that are usually intermixed with 

 them in greater or less number. They 

 also withstand boiling for a short time 

 in solutions containing ten to fifteen 

 per cent, of caustic potash or soda, by 

 which the white fibres and the corpus- 

 cles of connective tissue are speedily 

 destroyed. 



Chemical Composition. — The elastic tissue, of course, contains 

 Avater. and loses much of its weight by drying ; but the proportion 

 is said not to be so great as in most other soft tissues. By very long 

 boiling it yields a substance in some points resembling gelatin, while 

 a portion, equal to rather more than the half, remains undissolved. 



The gelatin, no doubt, comes from the intermixed areolar tissue ; but the dis- 

 solved matter is not pure gelatin, for it is precipitated by acetic acid, and by- 

 some other re-agents which do not distiirb a solution of pure gelatin. The nature 

 of the substance which remains undissolved has not been determined. Caustic 

 potash and soda have little effect on elastic tissue in the cold, and in weak solu- 

 tions even when hot. unless the ai:)plication is long continued ; boiling in concen- 

 trated solutions speedily dissolves it. It is soluble with the aid of heat in dilute 

 hydrochloric acid. 



Vessels and Nerves. — The yellow ligaments, which contain this 

 tissue in its purest form, are but scantily supplied with vessels ; and no 

 nerves have been traced into them. We are not aware of any experi- 

 ments or observations as to their sensibility, but there is no reason for 

 supposing it to be greater than that of ordinary ligaments ; nor has 

 it been shown that structures containing this tissue possess vital con- 

 tractility, unless they also contain contractile fibres of another kind. 



Fig. 40. — El.\sxic Fibres from 

 THE Ligamenta Subflava, mag- 

 nified ABOUT 200 DIAMETERS. 



SPECIAL VARIETIES OF CONNECTIVE TISSUE. 



1. Jelly-like connective tissue or mi/ro//s fis.^-tfc. At an early 

 period of development connective tissue consists of a pellucid jelly 

 and nucleated corpuscles. The soft watery jelly contains the 

 chemical principle of mucus, or mucin, and, in much less proportion. 



