556 MR LISTER ON THE MINUTE STRUCTURE OF 



Hence it appears that the length of the most contracted fibre-cell is the same as 

 that of the nucleus of an extended one. The fibres vary somewhat in breadth, 

 independently of the results of contraction. Thus, one in the extended condition 

 which I sketched, but which is not here shown, measured only — - inch across. 

 The nuclei of the uncontracted fibres are very constantly of the same length, and 

 are good examples of the rod-shape to which Kolliker has directed particular 

 attention. They always possess one or two nucleoli, and have often a slightly 

 granular character ; occasionally, as in fig. 21, they present an appearance of 

 transverse markings. One frequently sees near the nucleus of a fibre that has 

 been artificially extended from the contracted state, an appearance of a gap in 

 the substance of the cell, forming a sort of extension of the nucleus, as if the fibre 

 generally had been stretched more completely than the nucleus : an example of 

 this is presented by fig. 7. Mr Ellis lays great stress on a dotted appearance 

 which he considers characteristic of involuntary muscular fibre. I must say I 

 agree with Kolliker in finding the fibre-cells, for the most part, homogeneous 

 when extended, or faintly marked with longitudinal striae.* No doubt dots are 

 present in abundance; but these, so far as I have observed them in the pig's 

 intestine, are distinctly exterior to the fibres, though adherent to their surface; 

 and I suspect them to be little globules of a tenacious connecting fluid. That 

 the fibre-cells do stick very tightly together, may be seen by drying a minute 

 portion of the tissue, after which they will be found shrunk, and slightly sepa- 

 rated from one another, but connected more or less by minute threads. 



To sum up the general results to which we are led by the facts above men- 

 tioned. It appears that in the arteries of the frog, and in the intestine of the 

 pig, the involuntary muscular tissue is composed of slightly-flattened elongated 

 elements, with tapering extremities, each provided at its central and thickest part 

 with a single cylindrical nucleus embedded in its substance. 



Professor Kolliker's account of the tissue being thus completely confirmed in 

 these two instances, and the description here given of its appearance in the arte- 

 ries of the frog's foot being an independent confirmation of the general doctrine, 

 there seems no reason any longer to doubt its truth. 



* The longitudinal striae above referred to, are probably due to a fine fibrous structure in 

 the substance of the fibre-cells. When in London, last Christmas, I had, through the kindness 

 of Dr Sharpey, the opportunity of examining a specimen of muscle from the stomach of a rabbit, 

 which he had prepared after Reichert's method. The nitric acid had not only detached the 

 fibre-cells from one another, but also brought out very distinctly in each muscular element the 

 appearance of minute parallel longitudinal fibres, which seemed to make up the entire mass of 

 the fibre-cell except the nucleus. In a plate accompanying the paper on the Iris, before re- 

 ferred to, I. gave figures of some fibre-cells with distinct granules arranged in longitudinal and 

 transverse rows. This appearance, which, however, so far as my experience goes, is exceptional, 

 and is hardly sufficiently marked to deserve the appellation " dotted," is probably caused by une- 

 qual contractions in the constituent material. — 2d April 1857. 



