415 



tion, possessing a roundish nucleus, whose longer diameter lay across 

 that of the containing mass. Between these bodies and the long 

 and delicate fibre-cells every possible gradation could be traced, 

 and it was therefore pretty clear that the former were but the ex- 

 tremely contracted form of the latter. That the appearances in 

 question were due to contraction of the fibre-cells, was proved by 

 their disappearance when a portion of the tissue was strongly 

 stretched. 



The bearings of these observations on the main question, respect- 

 ing the structure of involuntary muscular fibre, are obvious and im- 

 portant. In the first place, if the short substantial bodies were mere 

 contracted fragments of rounded fibres of uniform width, we should 

 expect them to be as thick at their extremities as at the middle ; 

 instead of which they are always more or less tapering, and often 

 present a very regular appearance of two cones applied to each other 

 by their bases. 



Secondly, the uniform central position of the nuclei in the con- 

 tracted fibres, proves clearly that the former are no accidental ap- 

 pendages of the latter, to which it seems difficult to refuse KoUiker's 

 appellation of cells. 



In conclusion, the author makes the following remarks : — 



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

 above mentioned, 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 cylindri- 

 cal nucleus imbedded in its substance. 



Professor KoUiker's account of the tissue being thus completely 

 confirmed in these two instances, and the description here given of 

 its appearance in the arteries of the frog's foot being an independent 

 confirmation of the general doctrine, there seems no reason any longer 

 to doubt its truth. 



It further appears, from what has been seen in the pig's intestine, 

 that the muscular elements are, on the one hand, capable of an ex- 

 traordinary degree of extension, and, on the other hand, are endowed 

 with a marvellous faculty of contraction, by which they may be re- 

 duced from the condition of very long fibres to that of almost globu- 

 lar masses. In the extended state they have a soft, delicate, and, 



2 M 2 



