WITH THE MICROSCOPE. 125 



or non-striated muscular fibre may be obtained from various situa 

 tions, both in man and also in the lower animals. These fibres are 

 most abundant in the alimentary canal, the uterus, the bladder, the 

 ducts of glands generally, and large vessels, but they are also found 

 dispersed amongst fibrous tissue in certain situations, particularly in 

 the skin. There are also bundles of pale muscle connected with the 

 hair bulbs, which may be demonstrated in some cases. The elon- 

 gated cells, of which this form of muscle is composed, are also to be 

 demonstrated in the small arteries, pi. XXIX, fig. 189, and veins, as 

 well as in the trabecular tissue of the spleen, and corpora cavernosa 

 penis, the urethra, &c. Involuntary muscle, which has hitherto been 

 described as consisting of flattened bands, has been demonstrated 

 by Professor Kolliker to consist of the elongated cells just referred 

 to. The contractile fibre cells usually appear as flattened bands, or 

 fusiform fibres, slightly wavy, and terminating at each end in a point. 

 These cells may be readily isolated by macerating small pieces of 

 the muscular coat of the alimentary canal, &c., in dilute nitric acid, 

 containing about twenty per cent, of strong acid. By a little teasing, 

 with the aid of fine needles, separate cells may be readily obtained. 

 Fig. 186, pi. XXVIII, represents some of the contractile fibre cells from 

 the small intestine. These cells may also be demonstrated in most 

 of the lower animals ; but it is worthy of remark that a portion only 

 of the alimentary canal of some fish is surrounded by involuntary 

 muscle, while it has been shown that the whole of the muscular fibre 

 of the intestine of the common tench is of the striped variety 

 (Weber). 



224. Examination of the Muscular Structure of the Heart ami 

 Tongue. The muscular fibres of the heart will be found to exhibit 

 the transverse striae characteristic of voluntary muscle ; but they are 

 arranged in long bands, and upon carefully examining a well-prepared 

 specimen, taken either from the heart of man or of most animals, 

 frequent and distinct anastomoses and branchings of the fibres may be 

 observed. The existence of sarcolemma is doubtful, but in many 

 cases a little connective tissue which corresponds to it may often be 

 detected. 



In order to exhibit these fibres, the heart of any small animal 

 may be taken, and after boiling it for a short time in water, small 

 pieces may be cut off, and carefully torn up with needles. The length 

 of time which the boiling should be continued, varies in different 

 cases. Half a minute is sufficient for the hearts of very small 

 animals ; sheep's hearts may be boiled for a quarter of an hour. Sec- 

 tions of the muscular substance of the tongue are readily made by 

 drying the organ when perfectly fresh, and removing a very thin sec- 



