162 



STRUCTURE OF MUSCLE. 



Fig. 79-* 



facility, the longitudinal lines are indistinct, or scarcely perceptible. 

 " In fact," says Mr. Bowman, " the primitive fasciculus seems to con- 

 sist of primitive component segments or particles, arranged so as to 

 form, in one sense, fibrillae, and in another sense, discs ; and which of 

 these two may happen to present itself to the observer, will depend 

 on the amount of adhesion, endways or sideways, existing between 

 the segments. Generally, in a recent fasciculus, there are transverse 

 striae, shewing divisions into discs, and longitudinal striae, marking 

 its composition by fibrillae." 



Mr. Bowman has observed that in the substance of the ultimate 

 fibre there exist minute " oval or circular discs, frequently concave on 

 one or both surfaces, and containing, somewhere near the centre, one, 

 two, or three minute dots or granules." Occasionally they are seen to 

 present irregularities of form, which Mr. Bowman is inclined to regard 

 as accidental. They are situated between, and are connected with 

 the fibrils, and are distributed in pretty equal numbers through the 

 fibre. These corpuscles are the nuclei of the nucleated cells from 

 which the muscular fibre was originally developed. From observing, 

 however, that their "absolute number 

 is far greater in the adult than in the 

 foetus, while their number, relatively to 

 the bulk of the fasciculi, at these two 

 epochs, remains nearly the same," Mr. 

 Bowman regards it as certain, that 

 " during development, and subsequent- 

 ly, a further and successive deposit of 

 corpuscles" takes place. The corpus- 

 W&JII 'HUM 'HhlfMiJl c ^ es are brought into view only when 

 WMI 'will the mu scular fibre is acted upon by a 



tj ,' | solution of " one of the milder acids, 



as the citric." 



According to my own investiga- 

 tions^ the ultimate fibril of animal life is cylindrical when isolated, 

 and probably polygonal from pressure when forming part of an ulti- 

 mate fibre or fasciculus. It measures in diameter 2o ^ 00 of an inch, 

 and is composed of a succession of cells connected by their flat sur- 

 faces. The cells are filled with a transparent substance, which I 

 have termed myolim. The myoline differs in density in different 

 cells, and from this circumstance bestows a peculiarity of character 

 on certain of the cells ; for example, when a fibril in its passive 

 state is examined, there will be seen a series of dark oblong bodies 

 separated by light spaces of equal length ; now the dark bodies are 



* Mass of ultimate fibres from the pectoralis major of the human foetus, at 

 nine months. These fibres have been immersed in a solution of tartaric acid, 

 and their " numerous corpuscles, turned in various directions, some presenting 

 nucleoli," are shewn. From Mr. Bowman's paper. 



t These were made on dissections of fresh human muscle, prepared with 

 great care by Mr. Lealand, partner of the eminent optician, Mr. Powell. 



