1888.] MICROSCOPICAL JOURNAL. 67 



3. The longitudinal muscular layer must be studied chiefly from a longi- 

 tudinal section ; a bit from such a section has been represented in figure 4. It 

 is seen to be made of bands or bundlesof protoplasm, granular-stained material, 

 bearing, scattered through the bundles, oval nuclei. The sides of the bundles 

 are often parallel for a distance, sometimes terminating in a triangle. The 

 bundles, also, sometimes break away from the principal mass of this kind of 

 tissue and extend into the submucous space, retaining, however, the charac- 

 ters just noted. The bands exhibit one peculiarity very conspicuous though 

 not as yet mentioned. They are crossed by transverse marks which seem 

 something like ripples on the surface of water. These transverse marks will 

 defy the observer equipped with only the ^-in. objective, and the section pre- 

 pared as above to explain them, and they have puzzled, and are still puzzling, 

 the biologists. Upon the ends of some of the bundles the protoplasm does 

 not stop short, but is, as it were, ' frayed out,' and in some of the bundles it 

 can be seen that, besides the transverse ' striae,' the protoplasm is also arranged 

 in longitudinal ' fibrillge.' This longitudinal and transverse striping of 

 the substance of the muscle tissue is found in so many places and so very 

 plainly that there can be no room for doubt that it is characteristic of the 

 entire longitudinal layer. 



The striped substance is not all that can be found in the longitudinal layer. 

 Fine lines, which run parallel v^ith the markings in the protoplasm and ^vhich 

 resemble cell w^alls, are seen bounding the bands ; they have received the 

 name of ' sarcolemma,' and they are parts of a membrane which encloses the 

 active or protoplasmic part of muscle. Besides, there are frequent nuclei 

 which careful study will show to be always close to the sarcolemma. 



These appearances, if carefully put together, appear to indicate that the 

 muscle layers of the sort we are now examining is composed of bodies whose 

 protoplasm has been considerably changed, at least as regards arrangement 

 in the cell, from the protoplasm in gland cells; for instance, those of the 

 mucous membrane, or even the circular muscle cell. It has, in fact, been 

 disposed in bands, both lengthways and crossways, in a manner which has 

 received very much study. It would be too lengthy for our present purpose 

 to consider this arrangement, or the cause of the ' striae ; ' those who would 

 follow the matter further will find it well treated in Huxley's ' The Cray-fish.' 

 The cellular structure of the mviscle tissue is obscured by the change which 

 took place during the development of the muscle, but the facts seem to be, 

 briefly, that the cells are very long, and set end to end their end walls oblit- 

 erated, and their side walls modified to form the sarcolemma. In short, the 

 longitudinal muscles of the cray-fish intestine are unlike the cells of the cir- 

 cular muscle layer, being cylinders placed end to end in parallel rows, their 

 side walls, the sarcolemma, encloses protoplasm so symmetrically arranged 

 inside the cell as to give an appearance of longitudinal and cross striping. It 

 is scarcely necessary to add that the ci'osscuts of the intestine will cut the 

 cylinders of the intestine muscle crossways, and they will appear as circles 

 modified in shape from contact with other circles. 



4. The sub-mucous layer contains, besides the blood which wanders 

 freely through it, bathing both the mucous membrane and the muscular coats, 

 certain cells which serve as padding or packing. They are called connec- 

 tive tissue cells, and are figured in fig. 4 at C. T. In the sections these can 

 hardly be clearly understood ; they seem as if blood coi"puscles, well stained, 

 the nuclei inside a space bounded by very fine lines. In many places one 

 cannot positively determine how to interpret the appearance, but in some 

 places he sees very plainly, somewhat large, nearly empty cells, each with its 

 nucleus. In other places such an interpretation is not consistent with the ob- 

 served facts, and the sub-mucous layer is crossed and recrossed by fine threads 

 which form a network extending (though not traceable) into and among the 



