ELEMENTS OF HISTOLOGY. 



[Chap. IX. 



lines. These lines gradually increase in number, and 

 to join that ultimately they form a dense network. 

 Thus a more or less regular pattern of small polygonal 

 fields is produced, which are styled Cohnheim's areas or 

 fields (Fig. 41). Each corre- 

 sponds to the end-view or 

 optical section of a sarcous 

 element prism, and is granu- 

 lar, as if composed of a 

 bundle of minute fibrils. 

 If this be the case, each 

 sarcous element will have to 

 be considered as a bundle 

 of rods. The bright lines 

 producing the Cohnheim's 

 fields are the interstitial 

 substance. When a muscle 

 fibre shrinks, after death 

 or after some hardening re- 

 agents, Cohnheim's fields 

 shrink into small circular areas, separated by a rela- 

 tively large amount of the interstitial substance. 



88. During contraction the cross striation is much 

 narrower, the dim disc becoming shorter in the long 

 diameter of the fibre, but broader in the transverse 

 direction. 



The broader the lateral disc in a fibre, the more 

 apart from one another are the dim or contractile 

 discs. 



On the surface of the substance of the muscle 

 fibres, but within the sarcolemma, are seen isolated 

 oblong nuclei, which belong to small protoplasmic, 

 more or less branched corpuscles the muscle cor- 

 puscles. In the adult fibres these are few and far 

 between ; in the young and growing fibres they are 

 numerous and large. Their protoplasm is the sub- 

 stance which, becoming converted into the muscular 



Fig. 41. Striped Muscular 

 Fibres in Cross Section. 



Each fibre is limited by the sarco- 

 lemma; the muscular substance 

 is differentiated into Cohnheim's 

 areas. (Atlas.) 



