STRUCTURE OF STRIATED MUSCLE. 551 



on this subject may answer the questions that arise more de- 

 cisively than is possible from researches upon Vertebrata and 

 Arthropods. As I have made no personal observations upon 

 the subject, I must base my account upon the latest published 

 researches, those, namely, of Schwalbe,* to which I would also 

 refer all those that are desirous of becoming better acquainted 

 with the present state of our knowledge and with the litera- 

 ture of the subject. I extract from this work the following 

 statements which are of general importance. In the first place, 

 that the lowest animals in which striated muscular fibres 

 are met with are the Ccelenterata. Max Schultze, Briicke, and 

 Virchow have seen distinct transverse striationin the muscular 

 fibres of the swimming disk of Aurelia aurita, and Kolliker 

 in that of Pelagia and Agalmopsis. Further, it is to be re- 

 marked that, according to the observations of Schwalbe, in 

 Ophiothrix fragilis (Echinodermata) the muscle cells between 

 the ambulacral plates in the first place possess a sarcolemma, 

 and, secondly, the muscular substance appears doubly striated. 

 Such systems of lines, according to his statement, had already 

 previously been observed by Mettenheimer in the muscles of 

 Arenicola piscatorum and Nereis succinea. The same ap- 

 pearance has also been observed in Mollusks. The circum- 

 stance that the fibre cells of the muscles of Nematodes and 

 Hirudinese are composed of a medullary substance surrounding 

 the nucleus, and of a cortical substance splitting into fibrils, 

 also seems to me to be of importance. This observation was 

 made by G. Wagener in transverse sections of the dried mus- 

 cular fibres of Aulosdoma nigrescens, and it was corroborated 

 by Schwalbe in the Hirudo medicinalis. These observations 

 seem to me of importance, because they correspond to a certain 

 stage of development of muscle in the Vertebrata. Lastly, I 

 shall adduce the fact that Weissmannf has divided the mus- 

 cular fibres into muscle cells and primitive fasciculi, which 

 division has been opposed by Wagener.J Wagener regarded 

 the fibrils as the primitive elements of the muscular fibres. 



* Schultze's Archiv, Band v. 



+ Zeitschrift fur rationelle Medizin, 1862 and 1864. 



I Archiv von Reichert, etc., 1863. 



