ON THE DEVELOPMENT OF THE ANIMAL TISSUES. 177 



cent observations of Rosenthal, the nuclei are still present in the mus- 

 cular fibre of adult animals. The proper substance of the muscular 

 fibres is produced by a deposit taking place within the tube. (The 

 structureless sheath of the primitive muscular fasciculus, which I ob- 

 served long since in insects, appears to be the remains of the tube 

 formed by the united walls of the primitive cells.) 



According to the late observations of Valentin,* there are first visible 

 in the blastema of muscle nuclei with nucleoli, which soon become sur- 

 rounded by extremely delicate cells. These cells assume an oblong 

 figure and arrange themselves in linear forms like filaments of Confervse. 

 On the inner surface of the membranous walls of the tubes, or secon- 

 dary cells formed by the coalescence of the primary cells, longitudinal 

 striae or fibres are deposited, while the septa dividing the tube into 

 compartments are absorbed. The muscular fasciculus then has the form 

 of a tube, with proportionally thick walls which are composed of perfectly 

 transparent longitudinal fibrils. The nuclei of the primary cells are 

 contained in the cavity of the tube. 



[ Mr. William Bowman's Observations "On the Minute 



Structure and Movements of Voluntary Muscles," read before the 

 Royal Society, June 18th, 1840, not having been referred to by Pro- 

 fessor Miiller, we consider, now that we are detailing the labours of 

 philosophers on this subject, we should be committing an act of injus- 

 tice to this talented observer, did we not quote the abstract of his 

 paper published in the Proceedings of the above named Society, and 

 refer those of our readers still further interested in details, to the entire 

 paper in the Philosophical Transactions for 1841, where the excellent 

 illustrations bear out to the letter the facts brought forward : 



" The objects of the author, in this paper, are the following, 1st. 

 To confirm, under some modifications, the view taken of the primitive 

 fasciculi of voluntary muscles being composed of a solid bundle of 

 fibrillse. 2dly. To describe new parts entering into their composition. 

 And 3dly. To detail new observations on the mechanism of voluntary 

 motion. 



" He first shows that the primitive fasciculi are not cylindrical, but 

 polygonal threads ; their sides being more or less flattened where they 

 are in contact with one another ; he next records, in a tabular form, the 

 results of his examination of their size in the different divisions of the 

 animal kingdom. It appears that the largest are met with in fish ; they 



* Muller's Archiv., 1840, p. 179. 

 VOL. II. N 



