Mr. Ellis on the nature of the Involuntary Muscular Fibre. 457 



are at variance with those now generally received. The present 

 communication contains the results of these inquiries, which tend to 

 show that the voluntary and involuntary muscles resemble each 

 other very closely in the arrangement and constitution of their fibres. 



After adverting to the present state of opinion on the subject, the 

 author gives an account of his own obseiTations, and treats successively 

 of the interweaving of the fibres, their size, form, and ultimate 

 structure ; their mode of attachment at their extremities, their length, 

 and the corpuscles connected with them. He devotes a section also 

 to the question of the periodic formation and destruction of muscular 

 fibres in the uterus, in its different conditions ; and while he is led 

 by his own investigations to recognize an enlargement in size of the 

 individual fibres of that organ during pregnancy, followed by subse- 

 quent diminution, he is unable to confirm the doctrine of new forma- 

 tion. Moreover, he finds that durins; pregnancy a considerable 

 amount of granular matter, with round or oval grauular-cells, is 

 deposited among the fibres. Tie adduces reasons for believing that 

 this substance cannot be regarded as a blastema, nor its imbedded 

 cells as formative cells, for the production of new fibres ; and he is 

 disposed to ascribe the enlargement of the uterus in pregnancy prin- 

 cipally to the enlargement of the muscular fibres, and the addition of 

 this new deposit. 



The following is a summary of the conclusions which the author 

 has arrived at on the main subject of his inqiury : — 



In both kinds of muscles, voluntary and involuntary, there is an 

 interweaving of the fibres with the formation of meshes. 



The fibres in botli kinds are long, slender, rounded cords of uni- 

 form width, except at the ends, where they are fixed by tendinous 

 tissue ; and in both, the size of the fibres in the same bundle varies 

 greatly. 



In neither voluntary nor involuntary muscle is the fibre of the 

 nature of a cell, but in both is composed of minute threads or fibrils. 

 Its surface-appearance in both kinds of muscle allows of the supposi- 

 tion that in both it is constructed in a similar way, namely, of small 

 particles or " sarcous elements," and that a diiference in the arrange- 

 ment of these elements gives a dotted appearance to the involuntary 

 and a transverse striatiou to the voluntary fibres. 



The length of the fibres varies in both cases with the organ or 

 part examined, and the connexion with tendon always takes place 

 after the same manner, whether the fibre is dotted or striated. 



On the addition of acetic acid, fusiform or rod-shaped corpuscles 

 make their appearance in all muscular tissue ; these bodies, which 

 appear to belong to the sheath of the fibre, approach nearest in their 

 characters to the corpuscles belonging to the yellow or elastic fibres 

 which pervade various other tissues ; and, from the apparent identity 

 in nature of these corpuscles in the different textures in which they 

 are found, and especially in voluntary as compared with involuntary 

 muscle, it is scarcely conceivable that in the latter case exclusively 

 they should be the nuclei of oblong cells constituting tlie proper 

 muscular tissue. 



Phil. Mag, S. 4. Vol. 13. No. 88. June 1857. 2 I 



