SPECIAL VARIETIES OF 



ends are not pointed, but abruptly broken across. Their size is very 

 various ; the largest in man are nearly ^oV^th of an inch in diameter, the 

 smallest perhaps not more than -3-^0 o tn - In some varieties of tne tissue the 

 larger sized fibres prevail ; this is the case with the ligamenta subflava, 

 where their general diameter is about -y^o o th of an incl1 5 in otaer instances, 

 as in the chord so vocales, they are exceedingly fine. In some animals elastic 

 fibres are met with fj-^^i^ of an inch in thickness. Acetic acid produces 

 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 corpuscles of connective tissue are speedily destroyed. 



The elastic tissue, of course, contains water, 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 reagents which do not disturb 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 solutions even when 

 hot, unless the application is long continued ; boiling in concentrated solutions 

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

 acid. 



Little is known respecting the blood-vessels and nerves of this texture. 

 The yellow ligaments, wliich contain it in its purest form, are but scantily 

 supplied with vessels ; and no nerves have been traced into them. I am 

 not aware of any experiments or observations as to their sensibility, but 

 there is no reason for supposing it to be greater than that of ordinary liga- 

 ments ; nor has it been shown that structures containing this tissue possess 

 vital contractility, unless they also contain contractile fibres of another 

 kind. 



SPECIAL VARIETIES OF CONNECTIVE TISSUE. 



1. Jelly-like connective tissue or mucous tissue. In the early embryo the 

 areolar tissue consists of a pellucid jelly and nucleated corpuscles. The soft 

 watery jelly contains the chemical principle of mucus, or rnucm, and, in 

 much less proportion, albumen, but no gelatin. In the general course of 

 development of the tissue, fibres, both white and elastic, are formed in the 

 soft matrix, and finally this substance entirely or in a great measure dis- 

 appears. But in certain cases the course is different. The cells may dis- 

 appear, only the jelly remaining, as in the vitreous humour of the eye; or 

 the corpuscles may branch out and join together in form of a network in 

 the jelly, with the persisting nuclei at the spot whence the threads 

 diverge. Such a condition is seen in the enamel-organ of growing teeth. 

 The areolar tissue surrounding and imbedding the vessels in the umbilical 

 cord consists of fusiform and ramified corpuscles associated with white 

 fibrillar bundles and elastic fibres, along with much of the soft matrix, 

 which is persistent at the time of birth and constitutes the jelly of 

 Wharton. 



