TISSUES OF THE BODY. 



207 



city of the fi'bre often gives rise to a peculiar delicately wavy or undulating 



course in the fasciculi of the tissue, which gives to many parts the appear- 



ance, recognisable even without the microscope, of being made up of bands, 



or transversely ribbed. The interlacement of the bundles is besides 



liable to variation. They frequentl} 7 pass through the same plane along- 



side of one another, in which case there usually appears a considerable 



amount of homogeneous residual interstitial matter, as a pale thin lamella, 



through which the several fasciculi 



are connected with one another. 



In other cases, again, the bundles 



are arranged parallel to one an- 



other, and at the same time rather 



densely, so that the residue of un- 



changed intercellular substance is 



greatly diminished, as, for instance, 



in a tendon. Finally, the bundles 



may be woven together more con- 



fusedly, though at times also with 



a certain amount of regularity and 



rectangular arrangement, but so 



that no particular direction in their 



course appears to be the predomi- 



nant one as, for instance, in the 



sclerotic coat of the eye. From 



this we see that parts formed of 



Connective-tissue may differ most 



,. 1-, . . 



essentially in appearance, consist- 

 ence, &c. 



Connective-tissue bundles possess, according to the number of fibril.s 

 contained in them, a greater or lesser diameter. And as these may again 

 be associated to form thicker cords, they can be distinguished as primary, 

 secondary, and tertiary fasciculi. 



An important question now arises, namely, whether these aggregations 

 of fibrillae are naked and without any envelope, or whether the whole 

 strand is not encased in a homogeneous sheath of condensed substance. 

 The first of these may be looked upon in general as the most probable 

 state of the two. And yet we may distinguish in many places bundles 

 which arc enclosed in an envelope, sometimes thick, and sometimes of 

 great delicacy. These occur especially where the connective-tissue is 

 loosely arranged, as, for instance, in subcutaneous cellular tissue, or, more 

 distinctly still, at the base of the brain. The membranes so formed, 

 moreover, may have preserved the ordinary glutin-yielding nature, or have 

 undergone subsequently a metamorphosis into elastic matter (see below 1 ). 



Acetic acid has come greatly into use as an important reagent in the 

 investigation of the tissue in question. The fasciculi of connective-tissue, 

 namely, which, owing to their nature as collagenic structures, are to a 

 certain extent remarkable for their insolubility, lose very rapidly their 

 fibrous appearance under the action of the acid, and become clear and 

 transparent, swelling up at the same time very considerably. In tissue 

 rendered clear in this manner, which is not unfrequently marked by a 

 transverse striping together with the puffing out of the bundles, the 

 elastic fibres and networks now make their appearance in the most beauti- 

 ful way, beside which we are also able to recognise the changed connective- 



g- 199. Bundles of connective-tissue lyinp in an 

 abundant interstitial matter. To the left are seen 



a f ew isolated flbriiise. 



