46 MUSCLES. 



a 



seem to correspond always with their narrow or con- 

 tracted intervals, or, as it is still described by some, 

 with the tapering points of the fibre-cells. A cir- 

 cumstance which has doubtless served to perpetuate 

 this erroneous view is that these fibres break very 

 easily when an attempt is made to isolate them, and 

 as the rupture always -takes place at one of the con- 

 stricted portions of the fibre, which tapers off as it 

 breaks, in consequence of its elasticity, it results that 

 each fragment thus detached presents a regular spin- 

 dle shape. (PL XIV. fig. VIII.) But if a section is 

 made across the course of the fibres, polygons are 

 brought into view, varying very considerably in dia- 

 meter (jioth to lioth of a line), but never of a size 

 so small as to be recognisable as the terminal point 

 of a spindle-shaped corpuscle. (PI. IX. fig. II.) The 

 same section shows also the mode in which these 

 fibres are grouped together so as to form fasciculi of 

 muscle. Between the fibres which are thus in imme- 

 diate contact with each other, forming fasciculi, there 

 is no intervening substance whatever ; but they are 

 surrounded by an investment, or sheath, of connecting 

 tissue which also includes the blood-vessels and ner- 

 vous filaments by which they are supplied. (PI. IX. 

 fig. II. 4.) 



contractile ceiiB. The contractile fusiform element, or fibro- cellular 

 corpuscle, is found only in those organs whose nor- 

 mal condition is one of imperfect development as 

 for example, in the smallest arteries, of a diameter of 

 from 7V th to ?Vth of a line. In vessels of this class 

 the middle or muscular coat consists of this element 

 in its purest form. It is not difficult to demonstrate 



