TISSUES, ORGANS, AND SYSTEMS. 93 



3. Similar muscular tubes with a trausverscly striated 

 cortical layer without distinct fibrils. (Many muscular fibrils 

 of the Hiradi/iidce, and of the muscles of Fishes enumerated 

 under 2). 



4. Muscular fibres without any internal cavity, with a 

 sarcolemma and transversely striated contents, which do not 

 break up into fibrils, but frequently into discs (Bowman), 

 Salpa, some Radiata, many Articulata. 



5. Similar muscular fibres, which readily break up into 

 fibrils. (Most Vertebrata, certain muscles of Insects). 



6. Simple isolated cells, whose contents are changed into a 

 transversely striated substance, which either fills the whole cell 

 or forms only a thin layer upon its membrane. Here my 

 observations lead me to place the peculiar cartilaginous striae, 

 which Purkinje (Mikr. neurol. Beobachtungen, in Mull. f Arch./ 

 1845) found in the endocardium of Ruminants. They consist 

 of large polygonal cells with beautiful nuclei, which internally, 

 but as it seems only upon their wall, contain a transversely 

 striated substance, which is not distinguishable from that in 

 the muscular fibres. 



All these forms are readily comprehended, if the genesis of 

 the true transversely striated muscular fibres in the higher 

 vertebrata be properly understood (see the special part, 

 Muscles); and I cannot agree with the supposition of Stannius 

 (Gott. Nachr., 1851, p. 17), that the transversely striated mus- 

 cular fibrils are developed according to many, essentially different 

 types. Even the gap which has hitherto separated the smooth 

 from the transversely striated muscles becomes less, when we 

 remember that the so-called transversely striated muscular 

 fibrils may also have homogeneous non-striated contents, and 

 also that even when transversely striated they may appear as 

 isolated cells} 



Muscular fibres of the same description as the transversely 

 striated muscles, and in part actually striated, are very widely 

 distributed. In the Vertebrata such muscles are found in the 

 oesophagus of some Mammalia and of the plagiostome fishes, in 

 the intestine of Tinea chrysitis, in the stomach of Cobitis 



1 [The muscles of the Medusae consist of flat, fusiform bands, whose ends are inter- 

 laced like those of smooth muscle, but which present the most distinct transverse 

 striae. — Eds.] 



