560 



THE MICROSCOPE. 



The muscular fibre, known as the non-striated, or invo- 

 luntary, consists of a series of tubes presenting a flattened 

 appearance, without the transverse strisB so characteristic 

 of the former : elongated nuclei immediately appear upon 

 the application of a little dilute acetic acid. Professor 

 Wharton Jones first demonstrated this structure in his 

 lectures at Charing Cross Hospital, about 1843: he was 

 led to infer, from appearances in very young fibre, that 

 the striped muscular fibre is originally composed of 

 similar elements to the unstriped, or plain muscular tissue, 

 which, in the process of development, becomes enclosed 

 in a sarcolemma (simple membrane) common to many of 

 them; the fibres then split into smaller fibres (fibrillw). 

 Thus accounting for the nuclei of striped muscular fibre ; 

 which, according to his views, are "the persistent nuclei 

 of the primitive muscular-fibre cells." 



The non-striated fibre is beautifully seen in connexion 

 with the skin surrounding the hairs of the head, a few 



Fig. 299. A portion of involuntary muscular fibre surrounding the hair. 



fibres of which are separately shown in fig. 299. Professor 

 Kolliker originally described these muscles of the skin, of 

 which there appear to be one or two in connexion with 

 each hair-follicle, arising from the more superficial parts of 

 the outer skin, then passing down to the root of the hair, 

 close behind the fat-gland, and there embracing it. It is 

 indeed most remarkable that skin, when covered with 

 hair, should alone be provided with these muscular 

 fibres; the effect of the contraction of which must be 

 to thrust up the hair-follicles and depress the inter- 

 mediate portions of skin, and thus produce that peculiar 



