190 THE TISSUE OF THE ORGANIC MUSCLES, BY J. ARNOLD. 



slightly serrated, and the former are sometimes uneven, 

 appearances which, like the curving of the ends, must be 

 regarded as consequences either of manipulation in the prepara- 

 tion of the specimen, or as post-mortem changes. 



Another explanation must, however, be given of the trans- 

 verse strise, which occur in considerable numbers, and at regu- 

 lar distances, on one or both sides of the fibres. These, from 

 the concordant results of the observations of Meissner* and 

 Heidenhain,-f- are probably to be regarded as phenomena of 

 contraction. 



The length of the fibres varies from G'045 0'230 milli- 

 meters ; the mean length is from 0'048 0'089 millimeters ; the 

 breadth 0'004 O'Ol miUimeters. 



STRUCTURE OF THE SMOOTH MUSCULAR FIBRES. 



The substance of the muscular fibre cells examined in serum 

 whilst perfectly fresh has a dull appearance, except at the 

 edges, which are frequently somewhat clearer. In many speci- 

 mens no further indications of structure are perceptible, but in 

 others there is a more or less distinct longitudinal striation, 

 which is often particularly obvious near the extremities, and is 

 rendered still clearer by the addition of a few drops of a O'Ol 

 per cent, solution of chromic acid, or of solution of gold con- 

 taining O'l per cent. (fig. 31, a). In many fibres, dark, highly 

 refractile granules are imbedded in various parts, apparently 

 without any definite arrangement. These, which disappear on 

 the addition of alcohol, are not to be confounded with the 

 granules that are commonly found at the two ends of the 

 nucleus. The latter form pyramidal rows extending for a 

 greater or less distance from the poles of the nucleus to which 

 their bases are applied towards the ends of the fibres to which 

 their apices point. These granules are imbedded in a substance 

 which has likewise the form of a pyramid, and is differentiated 

 from the adjoining material by its greater transparency when 

 examined by transmitted light. In many fibres a second line 

 is to be observed, which lies at some distance from, and not 



* Zeitschrift fiir rationale Medicin, Band ii., 1858. 

 t Studicn des Physiologischen Institute, 1861. 



