SMOOTH MUSCLES. 



FIG. 25. 



are approximated, whilst the intervening substance be- 

 comes shorter and, at the same time, broader. 



Compared with this, the structure of the smooth, or- 

 ganic, or, although this is a less expressive term, invo- 

 luntary muscular fibres, appears much more simple. On 

 examining any part of those organs in which smooth 

 muscular fibres are contained, we find in the majority of 

 cases, first of all, just as was the case with the transversely 

 striated muscles, little fasciculi as, for example, in the 

 muscular coat of the urinary bladder. Within these 

 fasciculi, upon further investigation, a series of distinct 

 elements can be distinguished, of which a certain num- 

 ber, six, ten, twenty, or more, are held together by a 

 common connective substance. According to the notion 

 which universally prevailed 

 until quite recently, every 

 one of these elements was 

 analogous to the primitive 

 fasciculus of striped muscle. 

 For as soon as we succeed 

 in separating these fasciculi 

 of smooth muscle into their 

 more minute constituents, 

 we find their ultimate ele- 

 ments to consist of long, 

 spindle-shaped cells, which 

 usually contain a nucleus in 



their centre (Fig. 5, b). According to the view on the 

 contrary, which, especially in consequence of the impul- 

 sion given by Leydig's investigations, has quite lately 



Fig. 25. Smooth muscular fibres from the parietes of the urinary bladder. A. 

 Fasciculus still coherent, out of which at a, a single isolated fibre-cells protrude, 

 whilst at b their simple divided ends appear. B. A similar fasciculus after being 

 treated with acetic acid, whereby the long and narrow nuclei have become evident 

 a. and 6, as above. 300 diameters. 



